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

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@kernel.org>
---
 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@kernel.org>

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

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