Re: [RFC Patch 1/2][slimdump] Append CRASH_REASON to VMCOREINFO elf-note

[Dave Anderson]

----- Original Message -----
> Allow various crash paths to append the reason of crash into the
> VMCOREINFO elf-note through the field CRASH_REASON. We also make the
> fatal machine check exceptions append "PANIC_MCE" as the crash
> reason.  This string will be recognised by upstream tools like makedumpfile and
> crash to generate slimdump.

I don't understand -- how could "various paths" append a reason?
The patch below seems to return "PANIC_MCE" for every x86 crash.
What am I missing?

Dave
 
> With increased usage of the CRASH_REASON field, the crash strings can be
> encoded for better usage.
> 
> Signed-off-by: K.Prasad <prasad@xxxxxxxxxxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/mcheck/mce.c |    8 ++++++++
>  kernel/kexec.c                   |    6 ++++++
>  2 files changed, 14 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c
> b/arch/x86/kernel/cpu/mcheck/mce.c
> index 362056a..5b2cb6a 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -38,6 +38,7 @@
>  #include <linux/debugfs.h>
>  #include <linux/irq_work.h>
>  #include <linux/export.h>
> +#include <linux/kexec.h>
>  
>  #include <asm/processor.h>
>  #include <asm/mce.h>
> @@ -240,6 +241,13 @@ static atomic_t mce_paniced;
>  static int fake_panic;
>  static atomic_t mce_fake_paniced;
>  
> +char *arch_add_crash_reason(void)
> +{
> +	static char crash_reason[] = "PANIC_MCE";
> +
> +	return crash_reason;
> +}
> +
>  /* Panic in progress. Enable interrupts and wait for final IPI */
>  static void wait_for_panic(void)
>  {
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index dc7bc08..a731693 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -1080,6 +1080,11 @@ asmlinkage long compat_sys_kexec_load(unsigned
> long entry,
>  }
>  #endif
>  
> +__weak char *arch_add_crash_reason(void)
> +{
> +	return (char *)NULL;
> +}
> +
>  void crash_kexec(struct pt_regs *regs)
>  {
>  	/* Take the kexec_mutex here to prevent sys_kexec_load
> @@ -1411,6 +1416,7 @@ static void update_vmcoreinfo_note(void)
>  void crash_save_vmcoreinfo(void)
>  {
>  	vmcoreinfo_append_str("CRASHTIME=%ld", get_seconds());
> +	vmcoreinfo_append_str("\nCRASH_REASON=%s\n", arch_add_crash_reason());
>  	update_vmcoreinfo_note();
>  }
>  
> 
> 
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