Re: [PATCH] recordmcount: Correct st_shndx handling

[Ard Biesheuvel]

On Tue, 8 Jun 2021 at 12:34, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
>
> One should only use st_shndx when >SHN_UNDEF and <SHN_LORESERVE. When
> SHN_XINDEX, then use .symtab_shndx. Otherwise use 0.
>
> This handles the case: st_shndx >= SHN_LORESERVE && st_shndx != SHN_XINDEX.
>
> Reported-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Tested-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>

Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>

> ---
>  scripts/recordmcount.h |   13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> --- a/scripts/recordmcount.h
> +++ b/scripts/recordmcount.h
> @@ -194,13 +194,18 @@ static unsigned int get_symindex(Elf_Sym
>         unsigned long offset;
>         int index;
>
> -       if (sym->st_shndx != SHN_XINDEX)
> +       if (sym->st_shndx > SHN_UNDEF &&
> +           sym->st_shndx < SHN_LORESERVE)
>                 return w2(sym->st_shndx);
>
> -       offset = (unsigned long)sym - (unsigned long)symtab;
> -       index = offset / sizeof(*sym);
> +       if (sym->st_shndx == SHN_XINDEX) {
> +               offset = (unsigned long)sym - (unsigned long)symtab;
> +               index = offset / sizeof(*sym);
>
> -       return w(symtab_shndx[index]);
> +               return w(symtab_shndx[index]);
> +       }
> +
> +       return 0;
>  }
>
>  static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)