[ltt-dev] [PATCH v2] add tracepoints of panic and kexec

[Zhaolei]

* From: "Mathieu Desnoyers" <compudj at krystal.dyndns.org>
>* Zhaolei (zhaolei at cn.fujitsu.com) wrote:
>> Instrumentation of following panic and kexec related events are added:
>> panic
>> kernel_kexec
>> crash_kexec
>> 
>> It is useful for build flight-recorder program based on lttng infrastructure.
>> 
> 
> Hrm, I'm wondering if these are events we are interested to trace or if
> you plan to use these tracepoints as hooks into the kernel to connect
> the tracer infrastructure to it ?
Hello, Mathieu

IMHO, both.

As a programmer who want to build  flight-recorder based on lttng infrastructure,
he can:
1: use lttng trace, and get lttng's trace datas from kernel-dump file.
or
2: use lttng's tracepoint, and record events himself.

But as a lttng's programmer, we can make both way possible.

What is your opinion?

B.R.
Zhaolei
> 
> If you plan to use those as hooks into the kernel, we should probably
> consider adding notifiers instead (notifier.h). This is the "blessed"
> way to be called upon such events.
> 
> Mathieu
> 
>> Signed-off-by: Zhao Lei <zhaolei at cn.fujitsu.com>
>> ---
>>  include/trace/kernel.h |   10 ++++++++++
>>  kernel/kexec.c         |    8 ++++++++
>>  kernel/panic.c         |    7 +++++++
>>  3 files changed, 25 insertions(+), 0 deletions(-)
>> 
>> diff --git a/include/trace/kernel.h b/include/trace/kernel.h
>> index d2c3320..06d585f 100644
>> --- a/include/trace/kernel.h
>> +++ b/include/trace/kernel.h
>> @@ -2,6 +2,7 @@
>>  #define _TRACE_KERNEL_H
>>  
>>  #include <linux/tracepoint.h>
>> +#include <linux/kexec.h>
>>  
>>  DECLARE_TRACE(kernel_printk,
>>  TPPROTO(unsigned long retaddr),
>> @@ -15,5 +16,14 @@ DECLARE_TRACE(kernel_module_free,
>>  DECLARE_TRACE(kernel_module_load,
>>  TPPROTO(struct module *mod),
>>  TPARGS(mod));
>> +DECLARE_TRACE(kernel_panic,
>> + TPPROTO(const char *fmt, va_list args),
>> + TPARGS(fmt, args));
>> +DECLARE_TRACE(kernel_kernel_kexec,
>> + TPPROTO(struct kimage *image),
>> + TPARGS(image));
>> +DECLARE_TRACE(kernel_crash_kexec,
>> + TPPROTO(struct kimage *image, struct pt_regs *regs),
>> + TPARGS(image, regs));
>>  
>>  #endif
>> diff --git a/kernel/kexec.c b/kernel/kexec.c
>> index aef2653..56cdaac 100644
>> --- a/kernel/kexec.c
>> +++ b/kernel/kexec.c
>> @@ -30,6 +30,7 @@
>>  #include <linux/pm.h>
>>  #include <linux/cpu.h>
>>  #include <linux/console.h>
>> +#include <trace/kernel.h>
>>  
>>  #include <asm/page.h>
>>  #include <asm/uaccess.h>
>> @@ -37,6 +38,9 @@
>>  #include <asm/system.h>
>>  #include <asm/sections.h>
>>  
>> +DEFINE_TRACE(kernel_kernel_kexec);
>> +DEFINE_TRACE(kernel_crash_kexec);
>> +
>>  /* Per cpu memory for storing cpu states in case of system crash. */
>>  note_buf_t* crash_notes;
>>  
>> @@ -1062,6 +1066,8 @@ asmlinkage long compat_sys_kexec_load(unsigned long entry,
>>  
>>  void crash_kexec(struct pt_regs *regs)
>>  {
>> + trace_kernel_crash_kexec(kexec_crash_image, regs);
>> +
>>  /* Take the kexec_mutex here to prevent sys_kexec_load
>>  * running on one cpu from replacing the crash kernel
>>  * we are using after a panic on a different cpu.
>> @@ -1428,6 +1434,8 @@ int kernel_kexec(void)
>>  {
>>  int error = 0;
>>  
>> + trace_kernel_kernel_kexec(kexec_image);
>> +
>>  if (!mutex_trylock(&kexec_mutex))
>>  return -EBUSY;
>>  if (!kexec_image) {
>> diff --git a/kernel/panic.c b/kernel/panic.c
>> index 12c5a0a..3fa642e 100644
>> --- a/kernel/panic.c
>> +++ b/kernel/panic.c
>> @@ -21,6 +21,9 @@
>>  #include <linux/debug_locks.h>
>>  #include <linux/random.h>
>>  #include <linux/kallsyms.h>
>> +#include <trace/kernel.h>
>> +
>> +DEFINE_TRACE(kernel_panic);
>>  
>>  int panic_on_oops;
>>  int tainted;
>> @@ -68,6 +71,10 @@ NORET_TYPE void panic(const char * fmt, ...)
>>  unsigned long caller = (unsigned long) __builtin_return_address(0);
>>  #endif
>>  
>> + va_start(args, fmt);
>> + trace_kernel_panic(fmt, args);
>> + va_end(args);
>> +
>>  /*
>>  * It's possible to come here directly from a panic-assertion and not
>>  * have preempt disabled. Some functions called from here want
>> -- 
>> 1.5.5.3
>> 
>> 
>> 
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>> 
> 
> -- 
> Mathieu Desnoyers
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
> 
>