IF YOU WOULD LIKE TO GET AN ACCOUNT, please write an
email to Administrator. User accounts are meant only to access repo
and report issues and/or generate pull requests.
This is a purpose-specific Git hosting for
BaseALT
projects. Thank you for your understanding!
Только зарегистрированные пользователи имеют доступ к сервису!
Для получения аккаунта, обратитесь к администратору.
This prototype is obtained indirectly, by luck, from some other header
in probe-event.c in most systems, but recently exploded on alpine:edge:
8 13.39 alpine:edge : FAIL gcc version 13.2.1 20240309 (Alpine 13.2.1_git20240309)
util/probe-event.c: In function 'convert_exec_to_group':
util/probe-event.c:225:16: error: implicit declaration of function 'basename' [-Werror=implicit-function-declaration]
225 | ptr1 = basename(exec_copy);
| ^~~~~~~~
util/probe-event.c:225:14: error: assignment to 'char *' from 'int' makes pointer from integer without a cast [-Werror=int-conversion]
225 | ptr1 = basename(exec_copy);
| ^
cc1: all warnings being treated as errors
make[3]: *** [/git/perf-6.8.0/tools/build/Makefile.build:158: util] Error 2
Fix it by adding the libgen.h header where basename() is prototyped.
Fixes: fb7345bbf7 ("perf probe: Support basic dwarf-based operations on uprobe events")
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
It was using the first variation on producing a string representation
for a binary flag, one that used the system's stat.h and preprocessor
tricks that had to be updated everytime a new flag was introduced.
Use the more recent scrape script + strarray +
strarray__scnprintf_flags() combo.
$ tools/perf/trace/beauty/statx_mask.sh
static const char *statx_mask[] = {
[ilog2(0x00000001) + 1] = "TYPE",
[ilog2(0x00000002) + 1] = "MODE",
[ilog2(0x00000004) + 1] = "NLINK",
[ilog2(0x00000008) + 1] = "UID",
[ilog2(0x00000010) + 1] = "GID",
[ilog2(0x00000020) + 1] = "ATIME",
[ilog2(0x00000040) + 1] = "MTIME",
[ilog2(0x00000080) + 1] = "CTIME",
[ilog2(0x00000100) + 1] = "INO",
[ilog2(0x00000200) + 1] = "SIZE",
[ilog2(0x00000400) + 1] = "BLOCKS",
[ilog2(0x00000800) + 1] = "BTIME",
[ilog2(0x00001000) + 1] = "MNT_ID",
[ilog2(0x00002000) + 1] = "DIOALIGN",
[ilog2(0x00004000) + 1] = "MNT_ID_UNIQUE",
};
$
Now we need a copy of uapi/linux/stat.h from tools/include/ in the
scrape only directory tools/perf/trace/beauty/include.
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/20240320193115.811899-3-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
It was using the first variation on producing a string representation
for a binary flag, one that used the system's fcntl.h and preprocessor
tricks that had to be updated everytime a new flag was introduced.
Use the more recent scrape script + strarray + strarray__scnprintf_flags() combo.
$ tools/perf/trace/beauty/fs_at_flags.sh
static const char *fs_at_flags[] = {
[ilog2(0x100) + 1] = "SYMLINK_NOFOLLOW",
[ilog2(0x200) + 1] = "REMOVEDIR",
[ilog2(0x400) + 1] = "SYMLINK_FOLLOW",
[ilog2(0x800) + 1] = "NO_AUTOMOUNT",
[ilog2(0x1000) + 1] = "EMPTY_PATH",
[ilog2(0x0000) + 1] = "STATX_SYNC_AS_STAT",
[ilog2(0x2000) + 1] = "STATX_FORCE_SYNC",
[ilog2(0x4000) + 1] = "STATX_DONT_SYNC",
[ilog2(0x8000) + 1] = "RECURSIVE",
[ilog2(0x80000000) + 1] = "GETATTR_NOSEC",
};
$
Now we need a copy of uapi/linux/fcntl.h from tools/include/ in the
scrape only directory tools/perf/trace/beauty/include and will use that
fs_at_flags array for other fs syscalls.
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/20240320193115.811899-2-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The session has a header in it which contains a perf env with
bpf_progs. The bpf_progs are accessed by the sideband thread and so
the sideband thread must be stopped before the session is deleted, to
avoid a use after free. This error was detected by AddressSanitizer
in the following:
==2054673==ERROR: AddressSanitizer: heap-use-after-free on address 0x61d000161e00 at pc 0x55769289de54 bp 0x7f9df36d4ab0 sp 0x7f9df36d4aa8
READ of size 8 at 0x61d000161e00 thread T1
#0 0x55769289de53 in __perf_env__insert_bpf_prog_info util/env.c:42
#1 0x55769289dbb1 in perf_env__insert_bpf_prog_info util/env.c:29
#2 0x557692bbae29 in perf_env__add_bpf_info util/bpf-event.c:483
#3 0x557692bbb01a in bpf_event__sb_cb util/bpf-event.c:512
#4 0x5576928b75f4 in perf_evlist__poll_thread util/sideband_evlist.c:68
#5 0x7f9df96a63eb in start_thread nptl/pthread_create.c:444
#6 0x7f9df9726a4b in clone3 ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
0x61d000161e00 is located 384 bytes inside of 2136-byte region [0x61d000161c80,0x61d0001624d8)
freed by thread T0 here:
#0 0x7f9dfa6d7288 in __interceptor_free libsanitizer/asan/asan_malloc_linux.cpp:52
#1 0x557692978d50 in perf_session__delete util/session.c:319
#2 0x557692673959 in __cmd_record tools/perf/builtin-record.c:2884
#3 0x55769267a9f0 in cmd_record tools/perf/builtin-record.c:4259
#4 0x55769286710c in run_builtin tools/perf/perf.c:349
#5 0x557692867678 in handle_internal_command tools/perf/perf.c:402
#6 0x557692867a40 in run_argv tools/perf/perf.c:446
#7 0x557692867fae in main tools/perf/perf.c:562
#8 0x7f9df96456c9 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
Fixes: 657ee55319 ("perf evlist: Introduce side band thread")
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Disha Goel <disgoel@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20240301074639.2260708-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Add perf_pmu__name_from_config that does a reverse lookup from a
config number to an alias name. The lookup is expensive as the config
is computed for every alias by filling in a perf_event_attr, but this
is only done when verbose output is enabled. The lookup also only
considers config, and not config1, config2 or config3.
An example of the output:
$ perf stat -vv -e data_read true
...
perf_event_attr:
type 24 (uncore_imc_free_running_0)
size 136
config 0x20ff (data_read)
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
exclude_guest 1
...
Committer notes:
Fix the python binding build by adding dummies for not strictly
needed perf_pmu__name_from_config() and perf_pmus__find_by_type().
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Link: https://lore.kernel.org/r/20240308001915.4060155-7-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
When dumping a perf_event_attr, use pmus to find the PMU and its name
by the type number. This allows dynamically added PMUs to be described.
Before:
$ perf stat -vv -e data_read true
...
perf_event_attr:
type 24
size 136
config 0x20ff
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
exclude_guest 1
...
After:
$ perf stat -vv -e data_read true
...
perf_event_attr:
type 24 (uncore_imc_free_running_0)
size 136
config 0x20ff
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
exclude_guest 1
...
However, it also means that when we have a PMU name we prefer it to a
hard coded name:
Before:
$ perf stat -vv -e faults true
...
perf_event_attr:
type 1 (PERF_TYPE_SOFTWARE)
size 136
config 0x2 (PERF_COUNT_SW_PAGE_FAULTS)
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
enable_on_exec 1
exclude_guest 1
...
After:
$ perf stat -vv -e faults true
...
perf_event_attr:
type 1 (software)
size 136
config 0x2 (PERF_COUNT_SW_PAGE_FAULTS)
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
inherit 1
enable_on_exec 1
exclude_guest 1
...
It feels more consistent to do this, rather than only prefer a PMU
name when a hard coded name isn't available.
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Link: https://lore.kernel.org/r/20240308001915.4060155-6-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
It was using the first variation on producing a string representation
for a binary flag, one that used the copy of uapi/linux/sched.h with
preprocessor tricks that had to be updated everytime a new flag was
introduced.
Use the more recent scrape script + strarray + strarray__scnprintf_flags() combo.
$ tools/perf/trace/beauty/clone.sh | head -5
static const char *clone_flags[] = {
[ilog2(0x00000100) + 1] = "VM",
[ilog2(0x00000200) + 1] = "FS",
[ilog2(0x00000400) + 1] = "FILES",
[ilog2(0x00000800) + 1] = "SIGHAND",
$
Now we can move uapi/linux/sched.h from tools/include/, that is used for
building perf to the scrape only directory tools/perf/trace/beauty/include.
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/ZfnULIn3XKDq0bpc@x1
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
There are different patterns for percpu variable access using a constant
value added to the base.
2aeb: mov -0x7da0f7e0(,%rax,8),%r14 # r14 = __per_cpu_offset[cpu]
2af3: mov $0x34740,%rax # rax = address of runqueues
* 2afa: add %rax,%r14 # r14 = &per_cpu(runqueues, cpu)
2bfd: cmpl $0x0,0x10(%r14) # cpu_rq(cpu)->has_blocked_load
2b03: je 0x2b36
At the first instruction, r14 has the __per_cpu_offset. And then rax
has an immediate value and then added to r14 to calculate the address of
a per-cpu variable. So it needs to track the immediate values and ADD
instructions.
Similar but a little different case is to use "this_cpu_off" instead of
"__per_cpu_offset" for the current CPU. This time the variable address
comes with PC-rel addressing.
89: mov $0x34740,%rax # rax = address of runqueues
* 90: add %gs:0x7f015f60(%rip),%rax # 19a78 <this_cpu_off>
98: incl 0xd8c(%rax) # cpu_rq(cpu)->sched_count
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240319055115.4063940-21-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This is to support per-cpu variable access often without a matching
DWARF entry. For some reason, I cannot find debug info of per-cpu
variables sometimes. They have more complex pattern to calculate the
address of per-cpu variables like below.
2b7d: mov -0x1e0(%rbp),%rax ; rax = cpu
2b84: mov -0x7da0f7e0(,%rax,8),%rcx ; rcx = __per_cpu_offset[cpu]
* 2b8c: mov 0x34870(%rcx),%rax ; *(__per_cpu_offset[cpu] + 0x34870)
Let's assume the rax register has a number for a CPU at 2b7d. The next
instruction is to get the per-cpu offset' for that cpu. The offset
-0x7da0f7e0 is 0xffffffff825f0820 in u64 which is the address of the
'__per_cpu_offset' array in my system. So it'd get the actual offset
of that CPU's per-cpu region and save it to the rcx register.
Then, at 2b8c, accesses using rcx can be handled same as the global
variable access. To handle this case, it should check if the offset
of the instruction matches to the address of '__per_cpu_offset'.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240319055115.4063940-20-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
On x86, the kernel gets the current task using the current macro like
below:
#define current get_current()
static __always_inline struct task_struct *get_current(void)
{
return this_cpu_read_stable(pcpu_hot.current_task);
}
So it returns the current_task field of struct pcpu_hot which is the
first member. On my build, it's located at 0x32940.
$ nm vmlinux | grep pcpu_hot
0000000000032940 D pcpu_hot
And the current macro generates the instructions like below:
mov %gs:0x32940, %rcx
So the %gs segment register points to the beginning of the per-cpu
region of this cpu and it points the variable with a constant.
Let's update the instruction location info to have a segment register
and handle %gs in kernel to look up a global variable. Pretend it as
a global variable by changing the register number to DWARF_REG_PC.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240319055115.4063940-18-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
If it failed to find a variable for the location directly, it might be
due to a missing variable in the source code. For example, accessing
pointer variables in a chain can result in the case like below:
struct foo *foo = ...;
int i = foo->bar->baz;
The DWARF debug information is created for each variable so it'd have
one for 'foo'. But there's no variable for 'foo->bar' and then it
cannot know the type of 'bar' and 'baz'.
The above source code can be compiled to the follow x86 instructions:
mov 0x8(%rax), %rcx
mov 0x4(%rcx), %rdx <=== PMU sample
mov %rdx, -4(%rbp)
Let's say 'foo' is located in the %rax and it has a pointer to struct
foo. But perf sample is captured in the second instruction and there
is no variable or type info for the %rcx.
It'd be great if compiler could generate debug info for %rcx, but we
should handle it on our side. So this patch implements the logic to
iterate instructions and update the type table for each location.
As it already collected a list of scopes including the target
instruction, we can use it to construct the type table smartly.
+---------------- scope[0] subprogram
|
| +-------------- scope[1] lexical_block
| |
| | +------------ scope[2] inlined_subroutine
| | |
| | | +---------- scope[3] inlined_subroutine
| | | |
| | | | +-------- scope[4] lexical_block
| | | | |
| | | | | *** target instruction
...
Image the target instruction has 5 scopes, each scope will have its own
variables and parameters. Then it can start with the innermost scope
(4). So it'd search the shortest path from the start of scope[4] to
the target address and build a list of basic blocks. Then it iterates
the basic blocks with the variables in the scope and update the table.
If it finds a type at the target instruction, then returns it.
Otherwise, it moves to the upper scope[3]. Now it'd search the shortest
path from the start of scope[3] to the start of scope[4]. Then connect
it to the existing basic block list. Then it'd iterate the blocks with
variables for both scopes. It can repeat this until it finds a type at
the target instruction or reaches to the top scope[0].
As the basic blocks contain the shortest path, it won't worry about
branches and can update the table simply.
The final check will be done by find_matching_type() in the next patch.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240319055115.4063940-15-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Add a new debug option "type-profile" to enable the detailed info during
the type analysis especially for instruction tracking. You can use this
before the command name like 'report' or 'annotate'.
$ perf --debug type-profile annotate --data-type
Committer testing:
First get some memory events:
$ perf mem record ls
Then, without data-type profiling debug:
$ perf annotate --data-type | head
Annotate type: 'struct rtld_global' in /usr/lib64/ld-linux-x86-64.so.2 (1 samples):
============================================================================
samples offset size field
1 0 4336 struct rtld_global {
0 0 0 struct link_namespaces* _dl_ns;
0 2560 8 size_t _dl_nns;
0 2568 40 __rtld_lock_recursive_t _dl_load_lock {
0 2568 40 pthread_mutex_t mutex {
0 2568 40 struct __pthread_mutex_s __data {
0 2568 4 int __lock;
$
And with only data-type profiling:
$ perf --debug type-profile annotate --data-type | head
-----------------------------------------------------------
find_data_type_die [1e67] for reg13873052 (PC) offset=0x150e2 in dl_main
CU die offset: 0x29cd3
found PC-rel by addr=0x34020 offset=0x20
-----------------------------------------------------------
find_data_type_die [2e] for reg12 offset=0 in __GI___readdir64
CU die offset: 0x137a45
frame base: cfa=1 fbreg=-1
found "__futex" in scope=2/2 (die: 0x137ad5) 0(reg12) type=int (die:2a)
-----------------------------------------------------------
find_data_type_die [52] for reg5 offset=0 in __memmove_avx_unaligned_erms
CU die offset: 0x1124ed
no variable found
Annotate type: 'struct rtld_global' in /usr/lib64/ld-linux-x86-64.so.2 (1 samples):
============================================================================
samples offset size field
1 0 4336 struct rtld_global {
0 0 0 struct link_namespaces* _dl_ns;
0 2560 8 size_t _dl_nns;
0 2568 40 __rtld_lock_recursive_t _dl_load_lock {
0 2568 40 pthread_mutex_t mutex {
0 2568 40 struct __pthread_mutex_s __data {
0 2568 4 int __lock;
$
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240319055115.4063940-9-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
We want to track type states as instructions are executed. Each
instruction can access compound types like struct or union and load/
store its members to a different location.
The die_deref_ptr_type() is to find a type of memory access with a
pointer variable. If it points to a compound type like struct, the
target memory is a member in the struct. The access will happen with an
offset indicating which member it refers. Let's follow the DWARF info
to figure out the type of the pointer target.
For example, say we have the following code.
struct foo {
int a;
int b;
};
struct foo *p = malloc(sizeof(*p));
p->b = 0;
The last pointer access should produce x86 asm like below:
mov 0x0, 4(%rbx)
And we know %rbx register has a pointer to struct foo. Then offset 4
should return the debug info of member 'b'.
Also variables of compound types can be accessed directly without a
pointer. The die_get_member_type() is to handle a such case.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240319055115.4063940-4-namhyung@kernel.org
[ Check if die_get_real_type() returned NULL ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
