Re: [PATCH] recordmcount: avoid using ABS symbol as reference

From: Mark-PK Tsai
Date: Mon Jun 07 2021 - 21:15:58 EST


> On Mon, Jun 07, 2021 at 01:44:21PM +0200, Peter Zijlstra wrote:
> > One should only use st_shndx when >SHN_UDEF and <SHN_LORESERVE. When
> > SHN_XINDEX, then use .symtab_shndx.
> >
> > Apparently you've found a case where neither is true? In that case
> > objtool seems to use shndx 0. A matching recordmcount patch would be
> > something like this.
> >
>
> Apparently I'm consistently bad at spelling SHM_UNDEF today..

I test the below patch and it work for me.
I only correct the UNDEF typo without any other modification.

Could I push this patch or you will push it?
I guess I have to add your signed-off-by.

>
> > diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
> > index f9b19524da11..d99cc0aed6fe 100644
> > --- a/scripts/recordmcount.h
> > +++ b/scripts/recordmcount.h
> > @@ -194,13 +194,18 @@ static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab,
> > unsigned long offset;
> > int index;
> >
> > - if (sym->st_shndx != SHN_XINDEX)
> > + if (sym->st_shndx > SHN_UDEF &&
> > + 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)