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If we detect that we recursively entered the debugger we should hack
our I/O ops to NULL so that the panic() in the next line won't
actually cause another recursion into the debugger. The first line of
kgdb_panic() will check this and return.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20200507130644.v4.6.I89de39f68736c9de610e6f241e68d8dbc44bc266@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Using kgdb requires at least some level of architecture-level
initialization. If nothing else, it relies on the architecture to
pass breakpoints / crashes onto kgdb.
On some architectures this all works super early, specifically it
starts working at some point in time before Linux parses
early_params's. On other architectures it doesn't. A survey of a few
platforms:
a) x86: Presumably it all works early since "ekgdboc" is documented to
work here.
b) arm64: Catching crashes works; with a simple patch breakpoints can
also be made to work.
c) arm: Nothing in kgdb works until
paging_init() -> devicemaps_init() -> early_trap_init()
Let's be conservative and, by default, process "kgdbwait" (which tells
the kernel to drop into the debugger ASAP at boot) a bit later at
dbg_late_init() time. If an architecture has tested it and wants to
re-enable super early debugging, they can select the
ARCH_HAS_EARLY_DEBUG KConfig option. We'll do this for x86 to start.
It should be noted that dbg_late_init() is still called quite early in
the system.
Note that this patch doesn't affect when kgdb runs its init. If kgdb
is set to initialize early it will still initialize when parsing
early_param's. This patch _only_ inhibits the initial breakpoint from
"kgdbwait". This means:
* Without any extra patches arm64 platforms will at least catch
crashes after kgdb inits.
* arm platforms will catch crashes (and could handle a hardcoded
kgdb_breakpoint()) any time after early_trap_init() runs, even
before dbg_late_init().
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20200507130644.v4.4.I3113aea1b08d8ce36dc3720209392ae8b815201b@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
In commit 81eaadcae8 ("kgdboc: disable the console lock when in
kgdb") we avoided the WARN_CONSOLE_UNLOCKED() yell when we were in
kgdboc. That still works fine, but it turns out that we get a similar
yell when using other I/O drivers. One example is the "I/O driver"
for the kgdb test suite (kgdbts). When I enabled that I again got the
same yells.
Even though "kgdbts" doesn't actually interact with the user over the
console, using it still causes kgdb to print to the consoles. That
trips the same warning:
con_is_visible+0x60/0x68
con_scroll+0x110/0x1b8
lf+0x4c/0xc8
vt_console_print+0x1b8/0x348
vkdb_printf+0x320/0x89c
kdb_printf+0x68/0x90
kdb_main_loop+0x190/0x860
kdb_stub+0x2cc/0x3ec
kgdb_cpu_enter+0x268/0x744
kgdb_handle_exception+0x1a4/0x200
kgdb_compiled_brk_fn+0x34/0x44
brk_handler+0x7c/0xb8
do_debug_exception+0x1b4/0x228
Let's increment/decrement the "ignore_console_lock_warning" variable
all the time when we enter the debugger.
This will allow us to later revert commit 81eaadcae8 ("kgdboc:
disable the console lock when in kgdb").
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20200507130644.v4.1.Ied2b058357152ebcc8bf68edd6f20a11d98d7d4e@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
With earlier commits, the API no longer discards the const-ness of the
sysrq_key_op. As such we can add the notation.
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-kernel@vger.kernel.org
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: kgdb-bugreport@lists.sourceforge.net
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://lore.kernel.org/r/20200513214351.2138580-9-emil.l.velikov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Kernel doc does not understand POD variables to be referred to.
.../debug_core.c:73: warning: cannot understand function prototype:
'int kgdb_connected; '
Convert kernel doc to pure comment.
Fixes: dc7d552705 ("kgdb: core")
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Here are 3 SPDX patches for 5.7-rc1.
One fixes up the SPDX tag for a single driver, while the other two go
through the tree and add SPDX tags for all of the .gitignore files as
needed.
Nothing too complex, but you will get a merge conflict with your current
tree, that should be trivial to handle (one file modified by two things,
one file deleted.)
All 3 of these have been in linux-next for a while, with no reported
issues other than the merge conflict.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'spdx-5.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx
Pull SPDX updates from Greg KH:
"Here are three SPDX patches for 5.7-rc1.
One fixes up the SPDX tag for a single driver, while the other two go
through the tree and add SPDX tags for all of the .gitignore files as
needed.
Nothing too complex, but you will get a merge conflict with your
current tree, that should be trivial to handle (one file modified by
two things, one file deleted.)
All three of these have been in linux-next for a while, with no
reported issues other than the merge conflict"
* tag 'spdx-5.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx:
ASoC: MT6660: make spdxcheck.py happy
.gitignore: add SPDX License Identifier
.gitignore: remove too obvious comments
Currently the PROMPT variable could be abused to provoke the printf()
machinery to read outside the current stack frame. Normally this
doesn't matter becaues md is already a much better tool for reading
from memory.
However the md command can be disabled by not setting KDB_ENABLE_MEM_READ.
Let's also prevent PROMPT from being modified in these circumstances.
Whilst adding a comment to help future code reviewers we also remove
the #ifdef where PROMPT in consumed. There is no problem passing an
unused (0) to snprintf when !CONFIG_SMP.
argument
Reported-by: Wang Xiayang <xywang.sjtu@sjtu.edu.cn>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Currently the code to manage the kdb history buffer uses strncpy() to
copy strings to/and from the history and exhibits the classic "but
nobody ever told me that strncpy() doesn't always terminate strings"
bug. Modern gcc compilers recognise this bug and issue a warning.
In reality these calls will only abridge the copied string if kdb_read()
has *already* overflowed the command buffer. Thus the use of counted
copies here is only used to reduce the secondary effects of a bug
elsewhere in the code.
Therefore transitioning these calls into strscpy() (without checking
the return code) is appropriate.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
This reverts commit bbfceba15f.
When DBG_MAX_REG_NUM is zero then a number of symbols are conditionally
defined. It is therefore not possible to check it using C expressions.
Reported-by: Anatoly Pugachev <matorola@gmail.com>
Acked-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Replace open coded single-linked list iteration loop with for_each_console()
helper in use.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
The point bp is assigned a value that is never read, it is being
re-assigned later to bp = &kdb_breakpoints[lowbp] in a for-loop.
Remove the redundant assignment.
Addresses-Coverity ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20191128130753.181246-1-colin.king@canonical.com
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
If you switch to a sleeping task with the "pid" command and then type
"rd", kdb tells you this:
No current kdb registers. You may need to select another task
diag: -17: Invalid register name
The first message makes sense, but not the second. Fix it by just
returning 0 after commands accessing the current registers finish if
we've already printed the "No current kdb registers" error.
While fixing kdb_rd(), change the function to use "if" rather than
"ifdef". It cleans the function up a bit and any modern compiler will
have no trouble handling still producing good code.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191109111624.5.I121f4c6f0c19266200bf6ef003de78841e5bfc3d@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Some (but not all?) of the kdb backtrace paths would cause the
kdb_current_task and kdb_current_regs to remain changed. As discussed
in a review of a previous patch [1], this doesn't seem intuitive, so
let's fix that.
...but, it turns out that there's actually no longer any reason to set
the current task / current regs while backtracing anymore anyway. As
of commit 2277b49258 ("kdb: Fix stack crawling on 'running' CPUs
that aren't the master") if we're backtracing on a task running on a
CPU we ask that CPU to do the backtrace itself. Linux can do that
without anything fancy. If we're doing backtrace on a sleeping task
we can also do that fine without updating globals. So this patch
mostly just turns into deleting a bunch of code.
[1] https://lore.kernel.org/r/20191010150735.dhrj3pbjgmjrdpwr@holly.lan
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191109111624.4.Ibc3d982bbeb9e46872d43973ba808cd4c79537c7@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
The kdb_current_task variable has been declared in
"kernel/debug/kdb/kdb_private.h" since 2010 when kdb was added to the
mainline kernel. This is not a public header. There should be no
reason that kdb_current_task should be exported and there are no
in-kernel users that need it. Remove the export.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191109111623.3.I14b22b5eb15ca8f3812ab33e96621231304dc1f7@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
As of the patch ("MIPS: kdb: Remove old workaround for backtracing on
other CPUs") there is no reason for kdb_current_regs to be in the
public "kdb.h". Let's move it next to kdb_current_task.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191109111623.2.Iadbfb484e90b557cc4b5ac9890bfca732cd99d77@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Currently if sequences such as "\ehelp\r" are delivered to the console then
the h gets eaten by the escape handling code. Since pressing escape
becomes something of a nervous twitch for vi users (and that escape doesn't
have much effect at a shell prompt) it is more helpful to emit the 'h' than
the '\e'.
We don't simply choose to emit the final character for all escape sequences
since that will do odd things for unsupported escape sequences (in
other words we retain the existing behaviour once we see '\e[').
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191025073328.643-6-daniel.thompson@linaro.org
Currently if an escape timer is interrupted by a character from a
different input source then the new character is discarded and the
function returns '\e' (which will be discarded by the level above).
It is hard to see why this would ever be the desired behaviour.
Fix this to return the new character rather than the '\e'.
This is a bigger refactor than might be expected because the new
character needs to go through escape sequence detection.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191025073328.643-5-daniel.thompson@linaro.org
kdb_read() contains special case logic to force it exit after reading
a single character. We can remove all the special case logic by directly
calling the function to read a single character instead. This also
allows us to tidy up the function prototype which, because it now matches
getchar(), we can also rename in order to make its role clearer.
This does involve some extra code to handle btaprompt properly but we
don't mind the new lines of code here because the old code had some
interesting problems (bad newline handling, treating unexpected
characters like <cr>).
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191025073328.643-4-daniel.thompson@linaro.org
Currently kdb_read_get_key() contains complex control flow that, on
close inspection, turns out to be unnecessary. In particular:
1. It is impossible to enter the branch conditioned on (escape_delay == 1)
except when the loop enters with (escape_delay == 2) allowing us to
combine the branches.
2. Most of the code conditioned on (escape_delay == 2) simply modifies
local data and then breaks out of the loop causing the function to
return escape_data[0].
3. Based on #2 there is not actually any need to ever explicitly set
escape_delay to 2 because we it is much simpler to directly return
escape_data[0] instead.
4. escape_data[0] is, for all but one exit path, known to be '\e'.
Simplify the code based on these observations.
There is a subtle (and harmless) change of behaviour resulting from this
simplification: instead of letting the escape timeout after ~1998
milliseconds we now timeout after ~2000 milliseconds
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191025073328.643-3-daniel.thompson@linaro.org
kdb_read_get_key() has extremely complex break/continue control flow
managed by state variables and is very hard to review or modify. In
particular the way the escape sequence handling interacts with the
general control flow is hard to follow. Separate out the escape key
handling, without changing the control flow. This makes the main body of
the code easier to review.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191025073328.643-2-daniel.thompson@linaro.org
Recent versions of gcc (reported on gcc-7.4) issue array subscript
warnings for builds where SMP is not enabled.
kernel/debug/debug_core.c: In function 'kdb_dump_stack_on_cpu':
kernel/debug/debug_core.c:452:17: warning: array subscript is outside array
+bounds [-Warray-bounds]
if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
~~~~~~~~~^~~~~
kernel/debug/debug_core.c:469:33: warning: array subscript is outside array
+bounds [-Warray-bounds]
kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
kernel/debug/debug_core.c:470:18: warning: array subscript is outside array
+bounds [-Warray-bounds]
while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
There is no bug here but there is scope to improve the code
generation for non-SMP systems (whilst also silencing the warning).
Reported-by: kbuild test robot <lkp@intel.com>
Fixes: 2277b49258 ("kdb: Fix stack crawling on 'running' CPUs that aren't the master")
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20191021101057.23861-1-daniel.thompson@linaro.org
Reviewed-by: Douglas Anderson <dianders@chromium.org>
In kdb when you do 'btc' (back trace on CPU) it doesn't necessarily
give you the right info. Specifically on many architectures
(including arm64, where I tested) you can't dump the stack of a
"running" process that isn't the process running on the current CPU.
This can be seen by this:
echo SOFTLOCKUP > /sys/kernel/debug/provoke-crash/DIRECT
# wait 2 seconds
<sysrq>g
Here's what I see now on rk3399-gru-kevin. I see the stack crawl for
the CPU that handled the sysrq but everything else just shows me stuck
in __switch_to() which is bogus:
======
[0]kdb> btc
btc: cpu status: Currently on cpu 0
Available cpus: 0, 1-3(I), 4, 5(I)
Stack traceback for pid 0
0xffffff801101a9c0 0 0 1 0 R 0xffffff801101b3b0 *swapper/0
Call trace:
dump_backtrace+0x0/0x138
...
kgdb_compiled_brk_fn+0x34/0x44
...
sysrq_handle_dbg+0x34/0x5c
Stack traceback for pid 0
0xffffffc0f175a040 0 0 1 1 I 0xffffffc0f175aa30 swapper/1
Call trace:
__switch_to+0x1e4/0x240
0xffffffc0f65616c0
Stack traceback for pid 0
0xffffffc0f175d040 0 0 1 2 I 0xffffffc0f175da30 swapper/2
Call trace:
__switch_to+0x1e4/0x240
0xffffffc0f65806c0
Stack traceback for pid 0
0xffffffc0f175b040 0 0 1 3 I 0xffffffc0f175ba30 swapper/3
Call trace:
__switch_to+0x1e4/0x240
0xffffffc0f659f6c0
Stack traceback for pid 1474
0xffffffc0dde8b040 1474 727 1 4 R 0xffffffc0dde8ba30 bash
Call trace:
__switch_to+0x1e4/0x240
__schedule+0x464/0x618
0xffffffc0dde8b040
Stack traceback for pid 0
0xffffffc0f17b0040 0 0 1 5 I 0xffffffc0f17b0a30 swapper/5
Call trace:
__switch_to+0x1e4/0x240
0xffffffc0f65dd6c0
===
The problem is that 'btc' eventually boils down to
show_stack(task_struct, NULL);
...and show_stack() doesn't work for "running" CPUs because their
registers haven't been stashed.
On x86 things might work better (I haven't tested) because kdb has a
special case for x86 in kdb_show_stack() where it passes the stack
pointer to show_stack(). This wouldn't work on arm64 where the stack
crawling function seems needs the "fp" and "pc", not the "sp" which is
presumably why arm64's show_stack() function totally ignores the "sp"
parameter.
NOTE: we _can_ get a good stack dump for all the cpus if we manually
switch each one to the kdb master and do a back trace. AKA:
cpu 4
bt
...will give the expected trace. That's because now arm64's
dump_backtrace will now see that "tsk == current" and go through a
different path.
In this patch I fix the problems by catching a request to stack crawl
a task that's running on a CPU and then I ask that CPU to do the stack
crawl.
NOTE: this will (presumably) change what stack crawls are printed for
x86 machines. Now kdb functions will show up in the stack crawl.
Presumably this is OK but if it's not we can go back and add a special
case for x86 again.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
I noticed that when I did "btc <cpu>" and the CPU I passed in hadn't
rounded up that I'd crash. I was going to copy the same fix from
commit 162bc7f5af ("kdb: Don't back trace on a cpu that didn't round
up") into the "not all the CPUs" case, but decided it'd be better to
clean things up a little bit.
This consolidates the two code paths. It is _slightly_ wasteful in in
that the checks for "cpu" being too small or being offline isn't
really needed when we're iterating over all online CPUs, but that
really shouldn't hurt. Better to have the same code path.
While at it, eliminate at least one slightly ugly (and totally
needless) recursive use of kdb_parse().
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
The kdb_bt1() had a mysterious "argcount" parameter passed in (always
the number 5, by the way) and never used. Presumably this is just old
cruft. Remove it. While at it, upgrade the btaprompt parameter to a
full fledged bool instead of an int.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
From doing a 'git log --patch kernel/debug', it looks as if DCPU_SSTEP
has never been used. Presumably it used to be used back when kgdb was
out of tree and nobody thought to delete the definition when the usage
went away. Delete.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Right now kgdb/kdb hooks up to debug panics by registering for the panic
notifier. This works OK except that it means that kgdb/kdb gets called
_after_ the CPUs in the system are taken offline. That means that if
anything important was happening on those CPUs (like something that might
have contributed to the panic) you can't debug them.
Specifically I ran into a case where I got a panic because a task was
"blocked for more than 120 seconds" which was detected on CPU 2. I nicely
got shown stack traces in the kernel log for all CPUs including CPU 0,
which was running 'PID: 111 Comm: kworker/0:1H' and was in the middle of
__mmc_switch().
I then ended up at the kdb prompt where switched over to kgdb to try to
look at local variables of the process on CPU 0. I found that I couldn't.
Digging more, I found that I had no info on any tasks running on CPUs
other than CPU 2 and that asking kdb for help showed me "Error: no saved
data for this cpu". This was because all the CPUs were offline.
Let's move the entry of kdb/kgdb to a direct call from panic() and stop
using the generic notifier. Putting a direct call in allows us to order
things more properly and it also doesn't seem like we're breaking any
abstractions by calling into the debugger from the panic function.
Daniel said:
: This patch changes the way kdump and kgdb interact with each other.
: However it would seem rather odd to have both tools simultaneously armed
: and, even if they were, the user still has the option to use panic_timeout
: to force a kdump to happen. Thus I think the change of order is
: acceptable.
Link: http://lkml.kernel.org/r/20190703170354.217312-1-dianders@chromium.org
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Feng Tang <feng.tang@intel.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The comment that says that module_event() is not static is clearly
wrong.
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
strncmp(str, const, len) is error-prone.
We had better use newly introduced
str_has_prefix() instead of it.
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Add SPDX license identifiers to all Make/Kconfig files which:
- Have no license information of any form
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The strncpy() function may leave the destination string buffer
unterminated, better use strscpy() instead.
This fixes the following warning with gcc 8.2:
kernel/debug/kdb/kdb_io.c: In function 'kdb_getstr':
kernel/debug/kdb/kdb_io.c:449:3: warning: 'strncpy' specified bound 256 equals destination size [-Wstringop-truncation]
strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: Wenlin Kang <wenlin.kang@windriver.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
The "whichcpu" comes from argv[3]. The cpu_online() macro looks up the
cpu in a bitmap of online cpus, but if the value is too high then it
could read beyond the end of the bitmap and possibly Oops.
Fixes: 5d5314d679 ("kdb: core for kgdb back end (1 of 2)")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
If you drop into kdb and type "summary", it prints out a line that
says this:
ccversion CCVERSION
...and I don't mean that it actually prints out the version of the C
compiler. It literally prints out the string "CCVERSION".
The version of the C Compiler is already printed at boot up and it
doesn't seem useful to replicate this in kdb. Let's just delete it.
We can also delete the bit of the Makefile that called the C compiler
in an attempt to pass this into kdb. This will remove one extra call
to the C compiler at Makefile parse time and (very slightly) speed up
builds.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
The strcpy() function is being deprecated. Replace it by the safer
strscpy() and fix the following Coverity warning:
"You might overrun the 129-character fixed-size string ks_namebuf
by copying name without checking the length."
Addresses-Coverity-ID: 138995 ("Copy into fixed size buffer")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
The strcpy() function is being deprecated. Replace it by the safer
strscpy() and fix the following Coverity warning:
"You might overrun the 1024-character fixed-size string remcom_in_buffer
by copying cmd without checking the length."
Addresses-Coverity-ID: 138999 ("Copy into fixed size buffer")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.
This patch fixes the following warnings:
kernel/debug/gdbstub.c: In function ‘gdb_serial_stub’:
kernel/debug/gdbstub.c:1031:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
if (remcom_in_buffer[1] == '\0') {
^
kernel/debug/gdbstub.c:1036:3: note: here
case 'C': /* Exception passing */
^~~~
kernel/debug/gdbstub.c:1040:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
if (tmp == 0)
^
kernel/debug/gdbstub.c:1043:3: note: here
case 'c': /* Continue packet */
^~~~
kernel/debug/gdbstub.c:1050:4: warning: this statement may fall through [-Wimplicit-fallthrough=]
dbg_activate_sw_breakpoints();
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/debug/gdbstub.c:1052:3: note: here
default:
^~~~~~~
Warning level 3 was used: -Wimplicit-fallthrough=3
Notice that, in this particular case, the code comment is modified
in accordance with what GCC is expecting to find.
This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
defcmd_in_progress is the state trace for command group processing
- within a command group or not - usable is an indicator if a command
set is valid (allocated/non-empty) - so use a bool for those binary
indication here.
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
If you have a CPU that fails to round up and then run 'btc' you'll end
up crashing in kdb becaue we dereferenced NULL. Let's add a check.
It's wise to also set the task to NULL when leaving the debugger so
that if we fail to round up on a later entry into the debugger we
won't backtrace a stale task.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
If we're using the default implementation of kgdb_roundup_cpus() that
uses smp_call_function_single_async() we can end up hanging
kgdb_roundup_cpus() if we try to round up a CPU that failed to round
up before.
Specifically smp_call_function_single_async() will try to wait on the
csd lock for the CPU that we're trying to round up. If the previous
round up never finished then that lock could still be held and we'll
just sit there hanging.
There's not a lot of use trying to round up a CPU that failed to round
up before. Let's keep a flag that indicates whether the CPU started
but didn't finish to round up before. If we see that flag set then
we'll skip the next round up.
In general we have a few goals here:
- We never want to end up calling smp_call_function_single_async()
when the csd is still locked. This is accomplished because
flush_smp_call_function_queue() unlocks the csd _before_ invoking
the callback. That means that when kgdb_nmicallback() runs we know
for sure the the csd is no longer locked. Thus when we set
"rounding_up = false" we know for sure that the csd is unlocked.
- If there are no timeouts rounding up we should never skip a round
up.
NOTE #1: In general trying to continue running after failing to round
up CPUs doesn't appear to be supported in the debugger. When I
simulate this I find that kdb reports "Catastrophic error detected"
when I try to continue. I can overrule and continue anyway, but it
should be noted that we may be entering the land of dragons here.
Possibly the "Catastrophic error detected" was added _because_ of the
future failure to round up, but even so this is an area of the code
that hasn't been strongly tested.
NOTE #2: I did a bit of testing before and after this change. I
introduced a 10 second hang in the kernel while holding a spinlock
that I could invoke on a certain CPU with 'taskset -c 3 cat /sys/...".
Before this change if I did:
- Invoke hang
- Enter debugger
- g (which warns about Catastrophic error, g again to go anyway)
- g
- Enter debugger
...I'd hang the rest of the 10 seconds without getting a debugger
prompt. After this change I end up in the debugger the 2nd time after
only 1 second with the standard warning about 'Timed out waiting for
secondary CPUs.'
I'll also note that once the CPU finished waiting I could actually
debug it (aka "btc" worked)
I won't promise that everything works perfectly if the errant CPU
comes back at just the wrong time (like as we're entering or exiting
the debugger) but it certainly seems like an improvement.
NOTE #3: setting 'kgdb_info[cpu].rounding_up = false' is in
kgdb_nmicallback() instead of kgdb_call_nmi_hook() because some
implementations override kgdb_call_nmi_hook(). It shouldn't hurt to
have it in kgdb_nmicallback() in any case.
NOTE #4: this logic is really only needed because there is no API call
like "smp_try_call_function_single_async()" or "smp_csd_is_locked()".
If such an API existed then we'd use it instead, but it seemed a bit
much to add an API like this just for kgdb.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
When I had lockdep turned on and dropped into kgdb I got a nice splat
on my system. Specifically it hit:
DEBUG_LOCKS_WARN_ON(current->hardirq_context)
Specifically it looked like this:
sysrq: SysRq : DEBUG
------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(current->hardirq_context)
WARNING: CPU: 0 PID: 0 at .../kernel/locking/lockdep.c:2875 lockdep_hardirqs_on+0xf0/0x160
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.0 #27
pstate: 604003c9 (nZCv DAIF +PAN -UAO)
pc : lockdep_hardirqs_on+0xf0/0x160
...
Call trace:
lockdep_hardirqs_on+0xf0/0x160
trace_hardirqs_on+0x188/0x1ac
kgdb_roundup_cpus+0x14/0x3c
kgdb_cpu_enter+0x53c/0x5cc
kgdb_handle_exception+0x180/0x1d4
kgdb_compiled_brk_fn+0x30/0x3c
brk_handler+0x134/0x178
do_debug_exception+0xfc/0x178
el1_dbg+0x18/0x78
kgdb_breakpoint+0x34/0x58
sysrq_handle_dbg+0x54/0x5c
__handle_sysrq+0x114/0x21c
handle_sysrq+0x30/0x3c
qcom_geni_serial_isr+0x2dc/0x30c
...
...
irq event stamp: ...45
hardirqs last enabled at (...44): [...] __do_softirq+0xd8/0x4e4
hardirqs last disabled at (...45): [...] el1_irq+0x74/0x130
softirqs last enabled at (...42): [...] _local_bh_enable+0x2c/0x34
softirqs last disabled at (...43): [...] irq_exit+0xa8/0x100
---[ end trace adf21f830c46e638 ]---
Looking closely at it, it seems like a really bad idea to be calling
local_irq_enable() in kgdb_roundup_cpus(). If nothing else that seems
like it could violate spinlock semantics and cause a deadlock.
Instead, let's use a private csd alongside
smp_call_function_single_async() to round up the other CPUs. Using
smp_call_function_single_async() doesn't require interrupts to be
enabled so we can remove the offending bit of code.
In order to avoid duplicating this across all the architectures that
use the default kgdb_roundup_cpus(), we'll add a "weak" implementation
to debug_core.c.
Looking at all the people who previously had copies of this code,
there were a few variants. I've attempted to keep the variants
working like they used to. Specifically:
* For arch/arc we passed NULL to kgdb_nmicallback() instead of
get_irq_regs().
* For arch/mips there was a bit of extra code around
kgdb_nmicallback()
NOTE: In this patch we will still get into trouble if we try to round
up a CPU that failed to round up before. We'll try to round it up
again and potentially hang when we try to grab the csd lock. That's
not new behavior but we'll still try to do better in a future patch.
Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
The function kgdb_roundup_cpus() was passed a parameter that was
documented as:
> the flags that will be used when restoring the interrupts. There is
> local_irq_save() call before kgdb_roundup_cpus().
Nobody used those flags. Anyone who wanted to temporarily turn on
interrupts just did local_irq_enable() and local_irq_disable() without
looking at them. So we can definitely remove the flags.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.
Notice that in this particular case, I replaced the code comments with
a proper "fall through" annotation, which is what GCC is expecting
to find.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.
Notice that in this particular case, I replaced the code comments with
a proper "fall through" annotation, which is what GCC is expecting
to find.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Replace the whole switch statement with a for loop. This makes the
code clearer and easy to read.
This also addresses the following Coverity warnings:
Addresses-Coverity-ID: 115090 ("Missing break in switch")
Addresses-Coverity-ID: 115091 ("Missing break in switch")
Addresses-Coverity-ID: 114700 ("Missing break in switch")
Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
[daniel.thompson@linaro.org: Tiny grammar change in description]
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
gcc 8.1.0 warns with:
kernel/debug/kdb/kdb_support.c: In function ‘kallsyms_symbol_next’:
kernel/debug/kdb/kdb_support.c:239:4: warning: ‘strncpy’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
strncpy(prefix_name, name, strlen(name)+1);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/debug/kdb/kdb_support.c:239:31: note: length computed here
Use strscpy() with the destination buffer size, and use ellipses when
displaying truncated symbols.
v2: Use strscpy()
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Jonathan Toppins <jtoppins@redhat.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: kgdb-bugreport@lists.sourceforge.net
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Since commit ad67b74d24 ("printk: hash addresses printed with %p"),
all pointers printed with %p are printed with hashed addresses
instead of real addresses in order to avoid leaking addresses in
dmesg and syslog. But this applies to kdb too, with is unfortunate:
Entering kdb (current=0x(ptrval), pid 329) due to Keyboard Entry
kdb> ps
15 sleeping system daemon (state M) processes suppressed,
use 'ps A' to see all.
Task Addr Pid Parent [*] cpu State Thread Command
0x(ptrval) 329 328 1 0 R 0x(ptrval) *sh
0x(ptrval) 1 0 0 0 S 0x(ptrval) init
0x(ptrval) 3 2 0 0 D 0x(ptrval) rcu_gp
0x(ptrval) 4 2 0 0 D 0x(ptrval) rcu_par_gp
0x(ptrval) 5 2 0 0 D 0x(ptrval) kworker/0:0
0x(ptrval) 6 2 0 0 D 0x(ptrval) kworker/0:0H
0x(ptrval) 7 2 0 0 D 0x(ptrval) kworker/u2:0
0x(ptrval) 8 2 0 0 D 0x(ptrval) mm_percpu_wq
0x(ptrval) 10 2 0 0 D 0x(ptrval) rcu_preempt
The whole purpose of kdb is to debug, and for debugging real addresses
need to be known. In addition, data displayed by kdb doesn't go into
dmesg.
This patch replaces all %p by %px in kdb in order to display real
addresses.
Fixes: ad67b74d24 ("printk: hash addresses printed with %p")
Cc: <stable@vger.kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
On a powerpc 8xx, 'btc' fails as follows:
Entering kdb (current=0x(ptrval), pid 282) due to Keyboard Entry
kdb> btc
btc: cpu status: Currently on cpu 0
Available cpus: 0
kdb_getarea: Bad address 0x0
when booting the kernel with 'debug_boot_weak_hash', it fails as well
Entering kdb (current=0xba99ad80, pid 284) due to Keyboard Entry
kdb> btc
btc: cpu status: Currently on cpu 0
Available cpus: 0
kdb_getarea: Bad address 0xba99ad80
On other platforms, Oopses have been observed too, see
https://github.com/linuxppc/linux/issues/139
This is due to btc calling 'btt' with %p pointer as an argument.
This patch replaces %p by %px to get the real pointer value as
expected by 'btt'
Fixes: ad67b74d24 ("printk: hash addresses printed with %p")
Cc: <stable@vger.kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
There are several definitions of those functions/macros in places that
mess with fixed-point load averages. Provide an official version.
[akpm@linux-foundation.org: fix missed conversion in block/blk-iolatency.c]
Link: http://lkml.kernel.org/r/20180828172258.3185-5-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Tested-by: Daniel Drake <drake@endlessm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* minor regression test cleanup
* formatting fixes for end user use of kdb
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Merge tag 'for_linus-4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb
Pull kdb updates from Jason Wessel:
- fix 2032 time access issues and new compiler warnings
- minor regression test cleanup
- formatting fixes for end user use of kdb
* tag 'for_linus-4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb:
kdb: use memmove instead of overlapping memcpy
kdb: use ktime_get_mono_fast_ns() instead of ktime_get_ts()
kdb: bl: don't use tab character in output
kdb: drop newline in unknown command output
kdb: make "mdr" command repeat
kdb: use __ktime_get_real_seconds instead of __current_kernel_time
misc: kgdbts: Display progress of asynchronous tests
gcc discovered that the memcpy() arguments in kdbnearsym() overlap, so
we should really use memmove(), which is defined to handle that correctly:
In function 'memcpy',
inlined from 'kdbnearsym' at /git/arm-soc/kernel/debug/kdb/kdb_support.c:132:4:
/git/arm-soc/include/linux/string.h:353:9: error: '__builtin_memcpy' accessing 792 bytes at offsets 0 and 8 overlaps 784 bytes at offset 8 [-Werror=restrict]
return __builtin_memcpy(p, q, size);
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The kdb code will print the monotonic time by ktime_get_ts(), but
the ktime_get_ts() will be protected by a sequence lock, that will
introduce one deadlock risk if the lock was already held in the
context from which we entered the debugger.
Thus we can use the ktime_get_mono_fast_ns() to get the monotonic
time, which is NMI safe access to clock monotonic. Moreover we can
remove the 'struct timespec', which is not y2038 safe.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The "bl" (list breakpoints) command prints a '\t' (tab) character
in its output, but on a console (video device), that just prints
some odd graphics character. Instead of printing a tab character,
just align the output with spaces.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: kgdb-bugreport@lists.sourceforge.net
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
When an unknown command is entered, kdb prints "Unknown kdb command:"
and then the unknown text, including the newline character. This
causes the ending single-quote mark to be printed on the next line
by itself, so just change the ending newline character to a null
character (end of string) so that it won't be "printed."
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: kgdb-bugreport@lists.sourceforge.net
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The "mdr" command should repeat (continue) when only Enter/Return
is pressed, so make it do so.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: kgdb-bugreport@lists.sourceforge.net
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
kdb is the only user of the __current_kernel_time() interface, which is
not y2038 safe and should be removed at some point.
The kdb code also goes to great lengths to print the time in a
human-readable format from 'struct timespec', again using a non-y2038-safe
re-implementation of the generic time_to_tm() code.
Using __current_kernel_time() here is necessary since the regular
accessors that require a sequence lock might hang when called during the
xtime update. However, this is safe in the particular case since kdb is
only interested in the tv_sec field that is updated atomically.
In order to make this y2038-safe, I'm converting the code to the generic
time64_to_tm helper, but that introduces the problem that we have no
interface like __current_kernel_time() that provides a 64-bit timestamp
in a lockless, safe and architecture-independent way. I have multiple
ideas for how to solve that:
- __ktime_get_real_seconds() is lockless, but can return
incorrect results on 32-bit architectures in the special case that
we are in the process of changing the time across the epoch, either
during the timer tick that overflows the seconds in 2038, or while
calling settimeofday.
- ktime_get_real_fast_ns() would work in this context, but does
require a call into the clocksource driver to return a high-resolution
timestamp. This may have undesired side-effects in the debugger,
since we want to limit the interactions with the rest of the kernel.
- Adding a ktime_get_real_fast_seconds() based on tk_fast_mono
plus tkr->base_real without the tk_clock_read() delta. Not sure about
the value of adding yet another interface here.
- Changing the existing ktime_get_real_seconds() to use
tk_fast_mono on 32-bit architectures rather than xtime_sec. I think
this could work, but am not entirely sure if this is an improvement.
I picked the first of those for simplicity here. It's technically
not correct but probably good enough as the time is only used for the
debugging output and the race will likely never be hit in practice.
Another downside is having to move the declaration into a public header
file.
Let me know if anyone has a different preference.
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patchwork.kernel.org/patch/9775309/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
- Rename from kdb_send_sig_info to kdb_send_sig
As there is no meaningful siginfo sent
- Use SEND_SIG_PRIV instead of generating a siginfo for a kdb
signal. The generated siginfo had a bogus rationale and was
not correct in the face of pid namespaces. SEND_SIG_PRIV
is simpler and actually correct.
- As the code grabs siglock just send the signal with siglock
held instead of dropping siglock and attempting to grab it again.
- Move the sig_valid test into kdb_kill where it can generate
a good error message.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
kallsyms_symbol_next() returns a boolean (true on success). Currently
kdb_read() tests the return value with an inequality that
unconditionally evaluates to true.
This is fixed in the obvious way and, since the conditional branch is
supposed to be unreachable, we also add a WARN_ON().
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/debug.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We are going to split <linux/sched/stat.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/stat.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We are going to move softlockup APIs out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
<linux/nmi.h> already includes <linux/sched.h>.
Include the <linux/nmi.h> header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We are going to split <linux/sched/signal.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/signal.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We are going to split <linux/sched/loadavg.h> out of <linux/sched.h>, which
will have to be picked up from a couple of .c files.
Create a trivial placeholder <linux/sched/topology.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The <linux/sched.h> header includes various vmacache related defines,
which are arguably misplaced.
Move them to mm_types.h and minimize the sched.h impact by putting
all task vmacache state into a new 'struct vmacache' structure.
No change in functionality.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kdb_trap_printk allows to pass normal printk() messages to kdb via
vkdb_printk(). For example, it is used to get backtrace using the
classic show_stack(), see kdb_show_stack().
vkdb_printf() tries to avoid a potential infinite loop by disabling the
trap. But this approach is racy, for example:
CPU1 CPU2
vkdb_printf()
// assume that kdb_trap_printk == 0
saved_trap_printk = kdb_trap_printk;
kdb_trap_printk = 0;
kdb_show_stack()
kdb_trap_printk++;
Problem1: Now, a nested printk() on CPU0 calls vkdb_printf()
even when it should have been disabled. It will not
cause a deadlock but...
// using the outdated saved value: 0
kdb_trap_printk = saved_trap_printk;
kdb_trap_printk--;
Problem2: Now, kdb_trap_printk == -1 and will stay like this.
It means that all messages will get passed to kdb from
now on.
This patch removes the racy saved_trap_printk handling. Instead, the
recursion is prevented by a check for the locked CPU.
The solution is still kind of racy. A non-related printk(), from
another process, might get trapped by vkdb_printf(). And the wanted
printk() might not get trapped because kdb_printf_cpu is assigned. But
this problem existed even with the original code.
A proper solution would be to get_cpu() before setting kdb_trap_printk
and trap messages only from this CPU. I am not sure if it is worth the
effort, though.
In fact, the race is very theoretical. When kdb is running any of the
commands that use kdb_trap_printk there is a single active CPU and the
other CPUs should be in a holding pen inside kgdb_cpu_enter().
The only time this is violated is when there is a timeout waiting for
the other CPUs to report to the holding pen.
Finally, note that the situation is a bit schizophrenic. vkdb_printf()
explicitly allows recursion but only from KDB code that calls
kdb_printf() directly. On the other hand, the generic printk()
recursion is not allowed because it might cause an infinite loop. This
is why we could not hide the decision inside vkdb_printf() easily.
Link: http://lkml.kernel.org/r/1480412276-16690-4-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kdb_printf_lock does not prevent other CPUs from entering the critical
section because it is ignored when KDB_STATE_PRINTF_LOCK is set.
The problematic situation might look like:
CPU0 CPU1
vkdb_printf()
if (!KDB_STATE(PRINTF_LOCK))
KDB_STATE_SET(PRINTF_LOCK);
spin_lock_irqsave(&kdb_printf_lock, flags);
vkdb_printf()
if (!KDB_STATE(PRINTF_LOCK))
BANG: The PRINTF_LOCK state is set and CPU1 is entering the critical
section without spinning on the lock.
The problem is that the code tries to implement locking using two state
variables that are not handled atomically. Well, we need a custom
locking because we want to allow reentering the critical section on the
very same CPU.
Let's use solution from Petr Zijlstra that was proposed for a similar
scenario, see
https://lkml.kernel.org/r/20161018171513.734367391@infradead.org
This patch uses the same trick with cmpxchg(). The only difference is
that we want to handle only recursion from the same context and
therefore we disable interrupts.
In addition, KDB_STATE_PRINTF_LOCK is removed. In fact, we are not able
to set it a non-racy way.
Link: http://lkml.kernel.org/r/1480412276-16690-3-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kdb_event state variable is only set but never checked in the kernel
code.
http://www.spinics.net/lists/kdb/msg01733.html suggests that this
variable affected WARN_CONSOLE_UNLOCKED() in the original
implementation. But this check never went upstream.
The semantic is unclear and racy. The value is updated after the
kdb_printf_lock is acquired and after it is released. It should be
symmetric at minimum. The value should be manipulated either inside or
outside the locked area.
Fortunately, it seems that the original function is gone and we could
simply remove the state variable.
Link: http://lkml.kernel.org/r/1480412276-16690-2-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We've got a delay loop waiting for secondary CPUs. That loop uses
loops_per_jiffy. However, loops_per_jiffy doesn't actually mean how
many tight loops make up a jiffy on all architectures. It is quite
common to see things like this in the boot log:
Calibrating delay loop (skipped), value calculated using timer
frequency.. 48.00 BogoMIPS (lpj=24000)
In my case I was seeing lots of cases where other CPUs timed out
entering the debugger only to print their stack crawls shortly after the
kdb> prompt was written.
Elsewhere in kgdb we already use udelay(), so that should be safe enough
to use to implement our timeout. We'll delay 1 ms for 1000 times, which
should give us a full second of delay (just like the old code wanted)
but allow us to notice that we're done every 1 ms.
[akpm@linux-foundation.org: simplifications, per Daniel]
Link: http://lkml.kernel.org/r/1477091361-2039-1-git-send-email-dianders@chromium.org
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Brian Norris <briannorris@chromium.org>
Cc: <stable@vger.kernel.org> [4.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 4bcc595ccd ("printk: reinstate KERN_CONT for printing
continuation lines") allows to define more message headers for a single
message. The motivation is that continuous lines might get mixed.
Therefore it make sense to define the right log level for every piece of
a cont line.
This patch introduces printk_skip_headers() that will skip all headers
and uses it in the kdb code instead of printk_skip_level().
This approach helps to fix other printk_skip_level() users
independently.
Link: http://lkml.kernel.org/r/1478695291-12169-3-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Cc: Joe Perches <joe@perches.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: David Sterba <dsterba@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It may be useful to debug writes to the readonly sections of memory,
so provide a cmdline "rodata=off" to allow for this. This can be
expanded in the future to support "log" and "write" modes, but that
will need to be architecture-specific.
This also makes KDB software breakpoints more usable, as read-only
mappings can now be disabled on any kernel.
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Brown <david.brown@linaro.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Krause <minipli@googlemail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-hardening@lists.openwall.com
Cc: linux-arch <linux-arch@vger.kernel.org>
Link: http://lkml.kernel.org/r/1455748879-21872-3-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Makes it easier to handle init vs core cleanly, though the change is
fairly invasive across random architectures.
It simplifies the rbtree code immediately, however, while keeping the
core data together in the same cachline (now iff the rbtree code is
enabled).
Acked-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
On non-developer devices, kgdb prevents the device from rebooting
after a panic.
Incase of panics and exceptions, to allow the device to reboot, prevent
entering debug mode to avoid getting stuck waiting for the user to
interact with debugger.
To avoid entering the debugger on panic/exception without any extra
configuration, panic_timeout is being used which can be set via
/proc/sys/kernel/panic at run time and CONFIG_PANIC_TIMEOUT sets the
default value.
Setting panic_timeout indicates that the user requested machine to
perform unattended reboot after panic. We dont want to get stuck waiting
for the user input incase of panic.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org
Cc: Android Kernel Team <kernel-team@android.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Colin Cross <ccross@android.com>
[Kiran: Added context to commit message.
panic_timeout is used instead of break_on_panic and
break_on_exception to honor CONFIG_PANIC_TIMEOUT
Modified the commit as per community feedback]
Signed-off-by: Kiran Raparthy <kiran.kumar@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
All current callers of kdb_getstr() can pass constant pointers via the
prompt argument. This patch adds a const qualification to make explicit
the fact that this is safe.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently kdb allows the output of comamnds to be filtered using the
| grep feature. This is useful but does not permit the output emitted
shortly after a string match to be examined without wading through the
entire unfiltered output of the command. Such a feature is particularly
useful to navigate function traces because these traces often have a
useful trigger string *before* the point of interest.
This patch reuses the existing filtering logic to introduce a simple
forward search to kdb that can be triggered from the more prompt.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently when the "| grep" feature is used to filter the output of a
command then the prompt is not displayed for the subsequent command.
Likewise any characters typed by the user are also not echoed to the
display. This rather disconcerting problem eventually corrects itself
when the user presses Enter and the kdb_grepping_flag is cleared as
kdb_parse() tries to make sense of whatever they typed.
This patch resolves the problem by moving the clearing of this flag
from the middle of command processing to the beginning.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Issuing a stack dump feels ergonomically wrong when entering due to NMI.
Entering due to NMI is normally a reaction to a user request, either the
NMI button on a server or a "magic knock" on a UART. Therefore the
backtrace behaviour on entry due to NMI should be like SysRq-g (no stack
dump) rather than like oops.
Note also that the stack dump does not offer any information that
cannot be trivial retrieved using the 'bt' command.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently when kdb traps printk messages then the raw log level prefix
(consisting of '\001' followed by a numeral) does not get stripped off
before the message is issued to the various I/O handlers supported by
kdb. This causes annoying visual noise as well as causing problems
grepping for ^. It is also a change of behaviour compared to normal usage
of printk() usage. For example <SysRq>-h ends up with different output to
that of kdb's "sr h".
This patch addresses the problem by stripping log levels from messages
before they are issued to the I/O handlers. printk() which can also
act as an i/o handler in some cases is special cased; if the caller
provided a log level then the prefix will be preserved when sent to
printk().
The addition of non-printable characters to the output of kdb commands is a
regression, albeit and extremely elderly one, introduced by commit
04d2c8c83d ("printk: convert the format for KERN_<LEVEL> to a 2 byte
pattern"). Note also that this patch does *not* restore the original
behaviour from v3.5. Instead it makes printk() from within a kdb command
display the message without any prefix (i.e. like printk() normally does).
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Joe Perches <joe@perches.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
There was a follow on replacement patch against the prior
"kgdb: Timeout if secondary CPUs ignore the roundup".
See: https://lkml.org/lkml/2015/1/7/442
This patch is the delta vs the patch that was committed upstream:
* Fix an off-by-one error in kdb_cpu().
* Replace NR_CPUS with CONFIG_NR_CPUS to tell checkpatch that we
really want a static limit.
* Removed the "KGDB: " prefix from the pr_crit() in debug_core.c
(kgdb-next contains a patch which introduced pr_fmt() to this file
to the tag will now be applied automatically).
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The output of KDB 'summary' command should report MemTotal, MemFree
and Buffers output in kB. Current codes report in unit of pages.
A define of K(x) as
is defined in the code, but not used.
This patch would apply the define to convert the values to kB.
Please include me on Cc on replies. I do not subscribe to linux-kernel.
Signed-off-by: Jay Lan <jlan@sgi.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
First two are minor fallout from the param rework which went in this merge
window.
Next three are a series which fixes a longstanding (but never previously
reported and unlikely , so no CC stable) race between kallsyms and freeing
the init section.
Finally, a minor cleanup as our module refcount will now be -1 during
unload.
Thanks,
Rusty.
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Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux
Pull module and param fixes from Rusty Russell:
"Surprising number of fixes this merge window :(
The first two are minor fallout from the param rework which went in
this merge window.
The next three are a series which fixes a longstanding (but never
previously reported and unlikely , so no CC stable) race between
kallsyms and freeing the init section.
Finally, a minor cleanup as our module refcount will now be -1 during
unload"
* tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux:
module: make module_refcount() a signed integer.
module: fix race in kallsyms resolution during module load success.
module: remove mod arg from module_free, rename module_memfree().
module_arch_freeing_init(): new hook for archs before module->module_init freed.
param: fix uninitialized read with CONFIG_DEBUG_LOCK_ALLOC
param: initialize store function to NULL if not available.
James Bottomley points out that it will be -1 during unload. It's
only used for diagnostics, so let's not hide that as it could be a
clue as to what's gone wrong.
Cc: Jason Wessel <jason.wessel@windriver.com>
Acked-and-documention-added-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Masami Hiramatsu <maasami.hiramatsu.pt@hitachi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-Convert printk( to pr_foo()
-Add pr_fmt
-Coalesce formats
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently if an active CPU fails to respond to a roundup request the CPU
that requested the roundup will become stuck. This needlessly reduces the
robustness of the debugger.
This patch introduces a timeout allowing the system state to be examined
even when the system contains unresponsive processors. It also modifies
kdb's cpu command to make it censor attempts to switch to unresponsive
processors and to report their state as (D)ead.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently kiosk mode must be explicitly requested by the bootloader or
userspace. It is convenient to be able to change the default value in a
similar manner to CONFIG_MAGIC_SYSRQ_DEFAULT_MASK.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Currently all kdb commands are enabled whenever kdb is deployed. This
makes it difficult to deploy kdb to help debug certain types of
systems.
Android phones provide one example; the FIQ debugger found on some
Android devices has a deliberately weak set of commands to allow the
debugger to enabled very late in the production cycle.
Certain kiosk environments offer another interesting case where an
engineer might wish to probe the system state using passive inspection
commands without providing sufficient power for a passer by to root it.
Without any restrictions, obtaining the root rights via KDB is a matter of
a few commands, and works everywhere. For example, log in as a normal
user:
cbou:~$ id
uid=1001(cbou) gid=1001(cbou) groups=1001(cbou)
Now enter KDB (for example via sysrq):
Entering kdb (current=0xffff8800065bc740, pid 920) due to Keyboard Entry
kdb> ps
23 sleeping system daemon (state M) processes suppressed,
use 'ps A' to see all.
Task Addr Pid Parent [*] cpu State Thread Command
0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash
0xffff880007078000 1 0 0 0 S 0xffff8800070782e0 init
[...snip...]
0xffff8800065be3c0 918 1 0 0 S 0xffff8800065be6a0 getty
0xffff8800065b9c80 919 1 0 0 S 0xffff8800065b9f60 login
0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash
All we need is the offset of cred pointers. We can look up the offset in
the distro's kernel source, but it is unnecessary. We can just start
dumping init's task_struct, until we see the process name:
kdb> md 0xffff880007078000
0xffff880007078000 0000000000000001 ffff88000703c000 ................
0xffff880007078010 0040210000000002 0000000000000000 .....!@.........
[...snip...]
0xffff8800070782b0 ffff8800073e0580 ffff8800073e0580 ..>.......>.....
0xffff8800070782c0 0000000074696e69 0000000000000000 init............
^ Here, 'init'. Creds are just above it, so the offset is 0x02b0.
Now we set up init's creds for our non-privileged shell:
kdb> mm 0xffff8800065bc740+0x02b0 0xffff8800073e0580
0xffff8800065bc9f0 = 0xffff8800073e0580
kdb> mm 0xffff8800065bc740+0x02b8 0xffff8800073e0580
0xffff8800065bc9f8 = 0xffff8800073e0580
And thus gaining the root:
kdb> go
cbou:~$ id
uid=0(root) gid=0(root) groups=0(root)
cbou:~$ bash
root:~#
p.s. No distro enables kdb by default (although, with a nice KDB-over-KMS
feature availability, I would expect at least some would enable it), so
it's not actually some kind of a major issue.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
This patch introduces several new flags to collect kdb commands into
groups (later allowing them to be optionally disabled).
This follows similar prior art to enable/disable magic sysrq
commands.
The commands have been categorized as follows:
Always on: go (w/o args), env, set, help, ?, cpu (w/o args), sr,
dmesg, disable_nmi, defcmd, summary, grephelp
Mem read: md, mdr, mdp, mds, ef, bt (with args), per_cpu
Mem write: mm
Reg read: rd
Reg write: go (with args), rm
Inspect: bt (w/o args), btp, bta, btc, btt, ps, pid, lsmod
Flow ctrl: bp, bl, bph, bc, be, bd, ss
Signal: kill
Reboot: reboot
All: cpu, kgdb, (and all of the above), nmi_console
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Since we now treat KDB_REPEAT_* as flags, there is no need to
pass KDB_REPEAT_NONE. It's just the default behaviour when no
flags are specified.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The actual values of KDB_REPEAT_* enum values and overall logic stayed
the same, but we now treat the values as flags.
This makes it possible to add other flags and combine them, plus makes
the code a lot simpler and shorter. But functionality-wise, there should
be no changes.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
We're about to add more options for commands behaviour, so let's give
a more generic name to the low-level kdb command registration function.
There are just various renames, no functional changes.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
We're about to add more options for command behaviour, so let's expand
the meaning of kdb_repeat_t.
So far we just do various renames, there should be no functional changes.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The struct member is never used in the code, so we can remove it.
We will introduce real flags soon by renaming cmd_repeat to cmd_flags.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The kernel used to contain two functions for length-delimited,
case-insensitive string comparison, strnicmp with correct semantics and
a slightly buggy strncasecmp. The latter is the POSIX name, so strnicmp
was renamed to strncasecmp, and strnicmp made into a wrapper for the new
strncasecmp to avoid breaking existing users.
To allow the compat wrapper strnicmp to be removed at some point in the
future, and to avoid the extra indirection cost, do
s/strnicmp/strncasecmp/g.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
do_posix_clock_monotonic_gettime() is a leftover from the initial
posix timer implementation which maps to ktime_get_ts().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Link: http://lkml.kernel.org/r/20140611234607.261629142@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
... instead of naked numbers.
Stuff in sysrq.c used to set it to 8 which is supposed to mean above
default level so set it to DEBUG instead as we're terminating/killing all
tasks and we want to be verbose there.
Also, correct the check in x86_64_start_kernel which should be >= as
we're clearly issuing the string there for all debug levels, not only
the magical 10.
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Joe Perches <joe@perches.com>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch is a continuation of efforts trying to optimize find_vma(),
avoiding potentially expensive rbtree walks to locate a vma upon faults.
The original approach (https://lkml.org/lkml/2013/11/1/410), where the
largest vma was also cached, ended up being too specific and random,
thus further comparison with other approaches were needed. There are
two things to consider when dealing with this, the cache hit rate and
the latency of find_vma(). Improving the hit-rate does not necessarily
translate in finding the vma any faster, as the overhead of any fancy
caching schemes can be too high to consider.
We currently cache the last used vma for the whole address space, which
provides a nice optimization, reducing the total cycles in find_vma() by
up to 250%, for workloads with good locality. On the other hand, this
simple scheme is pretty much useless for workloads with poor locality.
Analyzing ebizzy runs shows that, no matter how many threads are
running, the mmap_cache hit rate is less than 2%, and in many situations
below 1%.
The proposed approach is to replace this scheme with a small per-thread
cache, maximizing hit rates at a very low maintenance cost.
Invalidations are performed by simply bumping up a 32-bit sequence
number. The only expensive operation is in the rare case of a seq
number overflow, where all caches that share the same address space are
flushed. Upon a miss, the proposed replacement policy is based on the
page number that contains the virtual address in question. Concretely,
the following results are seen on an 80 core, 8 socket x86-64 box:
1) System bootup: Most programs are single threaded, so the per-thread
scheme does improve ~50% hit rate by just adding a few more slots to
the cache.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 50.61% | 19.90 |
| patched | 73.45% | 13.58 |
+----------------+----------+------------------+
2) Kernel build: This one is already pretty good with the current
approach as we're dealing with good locality.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 75.28% | 11.03 |
| patched | 88.09% | 9.31 |
+----------------+----------+------------------+
3) Oracle 11g Data Mining (4k pages): Similar to the kernel build workload.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 70.66% | 17.14 |
| patched | 91.15% | 12.57 |
+----------------+----------+------------------+
4) Ebizzy: There's a fair amount of variation from run to run, but this
approach always shows nearly perfect hit rates, while baseline is just
about non-existent. The amounts of cycles can fluctuate between
anywhere from ~60 to ~116 for the baseline scheme, but this approach
reduces it considerably. For instance, with 80 threads:
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 1.06% | 91.54 |
| patched | 99.97% | 14.18 |
+----------------+----------+------------------+
[akpm@linux-foundation.org: fix nommu build, per Davidlohr]
[akpm@linux-foundation.org: document vmacache_valid() logic]
[akpm@linux-foundation.org: attempt to untangle header files]
[akpm@linux-foundation.org: add vmacache_find() BUG_ON]
[hughd@google.com: add vmacache_valid_mm() (from Oleg)]
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: adjust and enhance comments]
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The function kgdb_breakpoint() sets up break point at
compile time by calling arch_kgdb_breakpoint();
Though this call is surrounded by wmb() barrier,
the compile can still re-order the break point,
because this scheduling barrier is not a code motion
barrier in gcc.
Making kgdb_breakpoint() as noinline solves this problem
of code reording around break point instruction and also
avoids problem of being called as inline function from
other places
More details about discussion on this can be found here
http://comments.gmane.org/gmane.linux.ports.arm.kernel/269732
Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Some code added to the debug_core module had KDB dependencies
that it shouldn't have. Move the KDB dependent REASON back to
the caller to remove the dependency in the debug core code.
Update the call from the UV NMI handler to conform to the new
interface.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Russ Anderson <rja@sgi.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Link: http://lkml.kernel.org/r/20140114162551.318251993@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch adds a kgdb_nmicallin() interface that can be used by
external NMI handlers to call the KGDB/KDB handler. The primary
need for this is for those types of NMI interrupts where all the
CPUs have already received the NMI signal. Therefore no
send_IPI(NMI) is required, and in fact it will cause a 2nd
unhandled NMI to occur. This generates the "Dazed and Confuzed"
messages.
Since all the CPUs are getting the NMI at roughly the same time,
it's not guaranteed that the first CPU that hits the NMI handler
will manage to enter KGDB and set the dbg_master_lock before the
slaves start entering. The new argument "send_ready" was added
for KGDB to signal the NMI handler to release the slave CPUs for
entry into KGDB.
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Link: http://lkml.kernel.org/r/20131002151417.928886849@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
