On Thu, Jan 21, 2021 at 03:32:40PM -0800, Andrii Nakryiko wrote:
SNIP
> > @@ -598,9 +599,36 @@ static void collect_symbol(GElf_Sym *sym, struct funcs_layout *fl)
> > fl->mcount_stop = sym->st_value;
> > }
> >
> > +static bool elf_sym__get(Elf_Data *syms, Elf_Data *syms_sec_idx_table,
> > + int id, GElf_Sym *sym, Elf32_Word *sym_sec_idx)
> > +{
> > + if (!gelf_getsym(syms, id, sym))
> > + return false;
> > +
> > + *sym_sec_idx = sym->st_shndx;
> > +
> > + if (sym->st_shndx == SHN_XINDEX) {
> > + if (!syms_sec_idx_table)
> > + return false;
> > + if (!gelf_getsymshndx(syms, syms_sec_idx_table,
> > + id, sym, sym_sec_idx))
>
>
> gelf_getsymshndx() is supposed to work even for cases that don't use
> extended numbering, so this should work, right?
>
> if (!gelf_getsymshndx(syms, syms_sec_idx_table, id, sym, sym_sec_idx))
> return false;
>
it seems you're right, gelf_getsymshndx seem to work for
both cases, I'll check
> if (sym->st_shndx == SHN_XINDEX)
> *sym_sec_idx = sym->st_shndx;
I don't understand this.. gelf_getsymshndx will return both
symbol and proper index, no? also sym_sec_idx is already
assigned from previou call
>
> return true;
>
> ?
>
> > + return false;
> > + }
> > +
> > + return true;
> > +}
> > +
> > +#define elf_symtab__for_each_symbol_index(symtab, id, sym, sym_sec_idx) \
> > + for (id = 0, elf_sym__get(symtab->syms, symtab->syms_sec_idx_table, \
> > + id, &sym, &sym_sec_idx); \
> > + id < symtab->nr_syms; \
> > + id++, elf_sym__get(symtab->syms, symtab->syms_sec_idx_table, \
> > + id, &sym, &sym_sec_idx))
>
> what do we want to do if elf_sym__get() returns error (false)? We can
> either stop or ignore that symbol, right? But currently you are
> returning invalid symbol data.
>
> so either
>
> for (id = 0; id < symtab->nr_syms && elf_sym__get(symtab->syms,
> symtab->syms_sec_idx_table, d, &sym, &sym_sec_idx); id++)
>
> or
>
> for (id = 0; id < symtab->nr_syms; id++)
> if (elf_sym__get(symtab->syms, symtab->syms_sec_idx_table, d, &sym,
> &sym_sec_idx))
if we go ahead with skipping symbols, this one seems good
>
>
> But the current variant looks broken. Oh, and
> elf_symtab__for_each_symbol() is similarly broken, can you please fix
> that as well?
>
> And this new macro should probably be in elf_symtab.h, along the
> elf_symtab__for_each_symbol.
thanks,
jirka
