Re: [PATCH v2] panic: Add options to print system info when panic happens

[Kees Cook]

On Mon, Nov 26, 2018 at 11:15 PM, Feng Tang <feng.tang@xxxxxxxxx> wrote:
> Kernel panic issues are always painful to debug, partially
> because it's not easy to get enough information of the
> context when panic happens.
>
> And we have ramoops and kdump for that, while this commit
> tries to provide a easier way to show the system info by adding
> a cmdline parameter, referring some idea from sysrq handler.
>
> Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: John Stultz <john.stultz@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees


> ---
> Changelog:
>  v2:
>     - change text "dump/DUMP" to "print/PRINT" which
>       is more accurate, suggested by Andrew Morton
>     - add code to print ftrace buffer
>
>  Documentation/admin-guide/kernel-parameters.txt |  8 +++++++
>  kernel/panic.c                                  | 28 +++++++++++++++++++++++++
>  2 files changed, 36 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 19f4423..80c819a 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3081,6 +3081,14 @@
>                         timeout < 0: reboot immediately
>                         Format: <timeout>
>
> +       panic_print=    Bitmask for printing system info when panic happens.
> +                       User can chose combination of the following bits:
> +                       bit 0: print all tasks info
> +                       bit 1: print system memory info
> +                       bit 2: print timer info
> +                       bit 3: print locks info if CONFIG_LOCKDEP is on
> +                       bit 4: print ftrace buffer
> +
>         panic_on_warn   panic() instead of WARN().  Useful to cause kdump
>                         on a WARN().
>
> diff --git a/kernel/panic.c b/kernel/panic.c
> index f6d549a..fb6ccd1 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -45,6 +45,13 @@ int panic_on_warn __read_mostly;
>  int panic_timeout = CONFIG_PANIC_TIMEOUT;
>  EXPORT_SYMBOL_GPL(panic_timeout);
>
> +#define PANIC_PRINT_TASK_INFO          0x00000001
> +#define PANIC_PRINT_MEM_INFO           0x00000002
> +#define PANIC_PRINT_TIMER_INFO         0x00000004
> +#define PANIC_PRINT_LOCK_INFO          0x00000008
> +#define PANIC_PRINT_FTRACE_INFO                0x00000010
> +static unsigned long panic_print;
> +
>  ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
>
>  EXPORT_SYMBOL(panic_notifier_list);
> @@ -124,6 +131,24 @@ void nmi_panic(struct pt_regs *regs, const char *msg)
>  }
>  EXPORT_SYMBOL(nmi_panic);
>
> +static void panic_print_sys_info(void)
> +{
> +       if (panic_print & PANIC_PRINT_TASK_INFO)
> +               show_state();
> +
> +       if (panic_print & PANIC_PRINT_MEM_INFO)
> +               show_mem(0, NULL);
> +
> +       if (panic_print & PANIC_PRINT_TIMER_INFO)
> +               sysrq_timer_list_show();
> +
> +       if (panic_print & PANIC_PRINT_LOCK_INFO)
> +               debug_show_all_locks();
> +
> +       if (panic_print & PANIC_PRINT_FTRACE_INFO)
> +               ftrace_dump(DUMP_ALL);
> +}
> +
>  /**
>   *     panic - halt the system
>   *     @fmt: The text string to print
> @@ -250,6 +275,8 @@ void panic(const char *fmt, ...)
>         debug_locks_off();
>         console_flush_on_panic();
>
> +       panic_print_sys_info();
> +
>         if (!panic_blink)
>                 panic_blink = no_blink;
>
> @@ -654,6 +681,7 @@ void refcount_error_report(struct pt_regs *regs, const char *err)
>  #endif
>
>  core_param(panic, panic_timeout, int, 0644);
> +core_param(panic_print, panic_print, ulong, 0644);
>  core_param(pause_on_oops, pause_on_oops, int, 0644);
>  core_param(panic_on_warn, panic_on_warn, int, 0644);
>  core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
> --
> 2.7.4
>



-- 
Kees Cook