Re: [PATCH v3 10/10] scripts/gdb: Decode compressed stack depot frames

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] scripts/gdb: stack_record_entry() reads _text contents instead
  of its address
--

commit 9494b015f36a201275730fea0979762f1a250f80
Author: Matt Fleming <mfleming@cloudflare.com>

scripts/gdb: Decode compressed stack depot frames

This commit exports STACK_RECORD_COMPRESSED to the GDB scripts and decodes
compressed stack depot frames on x86-64 and arm64 in stack_depot_fetch().

> diff --git a/scripts/gdb/linux/stackdepot.py b/scripts/gdb/linux/stackdepot.py
> index aaa18af25cd12..f689cacb3cb70 100644
> --- a/scripts/gdb/linux/stackdepot.py
> +++ b/scripts/gdb/linux/stackdepot.py
> @@ -20,6 +20,21 @@ def help():
>      gdb.write("Unrecognized command\n")
>      raise gdb.GdbError(t)
>  
> +def stack_record_entry(stack, i):
> +    if not int(stack['flags']) & constants.LX_STACK_RECORD_COMPRESSED:
> +        return int(stack['entries'][i])
> +
> +    # Mirror arch_stack_depot_frame_decompress().
> +    payload = int(stack['compressed_entries'][i])
> +    if utils.is_target_arch("x86-64"):
> +        return 0xffffffff00000000 | payload
> +    if utils.is_target_arch("aarch64"):
> +        text = int(gdb.parse_and_eval("(unsigned long)_text"))

[Severity: Low]
Does gdb.parse_and_eval("(unsigned long)_text") read the memory contents at
_text instead of taking its address?

Unlike in C where char _text[] decays to a pointer, _text is defined only in
the linker script as an untyped ELF symbol, so casting it without & in GDB
reads the first 8 bytes at .head.text and produces bogus decompressed frame
addresses on arm64.  Using (unsigned long)&_text, as in
scripts/gdb/linux/mm.py, evaluates to the symbol's address.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261113185702.1332171-1-matt@readmodwrite.com?part=10