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

[Mathieu Desnoyers]

* 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 ?

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
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