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linux/kernel/trace
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Qiu Peiyang f36d1be293 tracing: Fix setting of start_index in find_next() 
When we do cat /sys/kernel/debug/tracing/printk_formats, we hit kernel
panic at t_show.

general protection fault: 0000 [#1] PREEMPT SMP
CPU: 0 PID: 2957 Comm: sh Tainted: G W  O 3.14.55-x86_64-01062-gd4acdc7 #2
RIP: 0010:[<ffffffff811375b2>]
 [<ffffffff811375b2>] t_show+0x22/0xe0
RSP: 0000:ffff88002b4ebe80  EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000004
RDX: 0000000000000004 RSI: ffffffff81fd26a6 RDI: ffff880032f9f7b1
RBP: ffff88002b4ebe98 R08: 0000000000001000 R09: 000000000000ffec
R10: 0000000000000000 R11: 000000000000000f R12: ffff880004d9b6c0
R13: 7365725f6d706400 R14: ffff880004d9b6c0 R15: ffffffff82020570
FS:  0000000000000000(0000) GS:ffff88003aa00000(0063) knlGS:00000000f776bc40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f6c02ff0 CR3: 000000002c2b3000 CR4: 00000000001007f0
Call Trace:
 [<ffffffff811dc076>] seq_read+0x2f6/0x3e0
 [<ffffffff811b749b>] vfs_read+0x9b/0x160
 [<ffffffff811b7f69>] SyS_read+0x49/0xb0
 [<ffffffff81a3a4b9>] ia32_do_call+0x13/0x13
 ---[ end trace 5bd9eb630614861e ]---
Kernel panic - not syncing: Fatal exception

When the first time find_next calls find_next_mod_format, it should
iterate the trace_bprintk_fmt_list to find the first print format of
the module. However in current code, start_index is smaller than *pos
at first, and code will not iterate the list. Latter container_of will
get the wrong address with former v, which will cause mod_fmt be a
meaningless object and so is the returned mod_fmt->fmt.

This patch will fix it by correcting the start_index. After fixed,
when the first time calls find_next_mod_format, start_index will be
equal to *pos, and code will iterate the trace_bprintk_fmt_list to
get the right module printk format, so is the returned mod_fmt->fmt.

Link: http://lkml.kernel.org/r/5684B900.9000309@intel.com

Cc: stable@vger.kernel.org # 3.12+
Fixes: 102c9323c3 "tracing: Add __tracepoint_string() to export string pointers"
Signed-off-by: Qiu Peiyang <peiyangx.qiu@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2016-01-04 15:22:47 -05:00
..
blktrace.c Most of the changes are clean ups and small fixes. Some of them have 2015-11-06 13:30:20 -08:00
bpf_trace.c bpf: make tracing helpers gpl only 2015-10-26 21:53:34 -07:00
ftrace.c Most of the changes are clean ups and small fixes. Some of them have 2015-11-06 13:30:20 -08:00
Kconfig Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2015-11-10 18:11:41 -08:00
Makefile bpf: Fix the build on BPF_SYSCALL=y && !CONFIG_TRACING kernels, make it more configurable 2015-04-02 16:28:06 +02:00
power-traces.c PM / sleep: export suspend_resume trace event 2015-01-30 02:10:41 +01:00
ring_buffer_benchmark.c ring_buffer: Remove unneeded smp_wmb() before wakeup of reader benchmark 2015-11-03 16:19:02 -05:00
ring_buffer.c ring-buffer: Put back the length if crossed page with add_timestamp 2015-11-24 09:27:25 -05:00
rpm-traces.c
trace_benchmark.c tracing: Only benchmark the time tracepoints take if tracing is on 2015-11-02 13:34:58 -05:00
trace_benchmark.h
trace_branch.c tracing: Remove {start,stop}_branch_trace 2015-10-21 10:10:09 -04:00
trace_clock.c tracing: Export tracing clock functions 2015-05-12 15:56:57 -04:00
trace_entries.h tracing: %pF is only for function pointers 2015-03-25 08:57:22 -04:00
trace_event_perf.c treewide: Remove old email address 2015-11-23 09:44:58 +01:00
trace_events_filter_test.h
trace_events_filter.c tracing: is_legal_op() can return boolean 2015-11-02 14:26:51 -05:00
trace_events_trigger.c tracing: Rename ftrace_raw_##call event structures to trace_event_raw_##call 2015-05-13 21:48:40 -04:00
trace_events.c tracing: Add sched_wakeup_new and sched_waking tracepoints for pid filter 2015-12-01 16:08:05 -05:00
trace_export.c tracing: ftrace_event_is_function() can return boolean 2015-11-02 14:28:05 -05:00
trace_functions_graph.c tracing: Remove unused ftrace_cpu_disabled per cpu variable 2015-11-07 13:25:14 -05:00
trace_functions.c
trace_irqsoff.c tracing: report_latency() in trace_irqsoff.c can return boolean 2015-11-02 14:20:19 -05:00
trace_kdb.c tracing: Move trace_flags from global to a trace_array field 2015-09-30 15:22:55 -04:00
trace_kprobe.c lib: introduce strncpy_from_unsafe() 2015-08-28 16:27:27 -07:00
trace_mmiotrace.c tracing: Pass trace_array into trace_buffer_unlock_commit() 2015-09-25 17:38:44 -04:00
trace_nop.c tracing: Remove unneeded includes of debugfs.h and fs.h 2015-01-22 11:19:48 -05:00
trace_output.c tracing: Move trace_flags from global to a trace_array field 2015-09-30 15:22:55 -04:00
trace_output.h tracing: Turn seq_print_user_ip() into a static function 2015-09-28 10:16:12 -04:00
trace_printk.c tracing: Fix setting of start_index in find_next() 2016-01-04 15:22:47 -05:00
trace_probe.c trace: Don't use __weak in header files 2015-03-25 08:57:23 -04:00
trace_probe.h kernel/trace_probe: is_good_name can be boolean 2015-09-22 13:11:30 -04:00
trace_sched_switch.c sched/core: Fix trace_sched_switch() 2015-10-06 17:08:15 +02:00
trace_sched_wakeup.c Most of the changes are clean ups and small fixes. Some of them have 2015-11-06 13:30:20 -08:00
trace_selftest_dynamic.c
trace_selftest.c
trace_seq.c tracing: use %*pb[l] to print bitmaps including cpumasks and nodemasks 2015-02-13 21:21:37 -08:00
trace_stack.c Most of the changes are clean ups and small fixes. Some of them have 2015-11-06 13:30:20 -08:00
trace_stat.c tracing: Convert the tracing facility over to use tracefs 2015-02-03 12:48:41 -05:00
trace_stat.h
trace_syscalls.c tracing: Move trace_flags from global to a trace_array field 2015-09-30 15:22:55 -04:00
trace_uprobe.c tracing/uprobes: Do not print '0x (null)' when offset is 0 2015-08-26 10:43:01 -03:00
trace.c tracing: #ifdef out uses of max trace when CONFIG_TRACER_MAX_TRACE is not set 2015-11-10 10:16:05 -05:00
trace.h tracing: Remove unused ftrace_cpu_disabled per cpu variable 2015-11-07 13:25:14 -05:00