Re: [PATCH v3 6/9] arm64: Recover kretprobe modified return address in stacktrace

[Will Deacon]

On Thu, Oct 21, 2021 at 09:55:09AM +0900, Masami Hiramatsu wrote:
> Since the kretprobe replaces the function return address with
> the kretprobe_trampoline on the stack, stack unwinder shows it
> instead of the correct return address.
> 
> This checks whether the next return address is the
> __kretprobe_trampoline(), and if so, try to find the correct
> return address from the kretprobe instance list. For this purpose
> this adds 'kr_cur' loop cursor to memorize the current kretprobe
> instance.
> 
> With this fix, now arm64 can enable
> CONFIG_ARCH_CORRECT_STACKTRACE_ON_KRETPROBE, and pass the
> kprobe self tests.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> ---
>  Changes in v2:
>   - Add comment for kr_cur.
>   - Make the kretprobe related code depends on CONFIG_KRETPROBES.
>   - Initialize "kr_cur" directly in start_backtrace() instead
>     of clearing "frame" data structure by memset().
> ---
>  arch/arm64/Kconfig                  |    1 +
>  arch/arm64/include/asm/stacktrace.h |    4 ++++
>  arch/arm64/kernel/stacktrace.c      |    7 +++++++
>  3 files changed, 12 insertions(+)

Acked-by: Will Deacon <will@xxxxxxxxxx>

I'm not sure how you're planning to merge this, so please let me know if
you want me to queue any of the arm64 bits.

Will