Re: [PATCH 3/5] objtool: Support Clang non-section symbols in ORC generation

Peter Zijlstra
2020-04-01T18:50:05Z

On Wed, Apr 01, 2020 at 01:23:27PM -0500, Josh Poimboeuf wrote:

> @@ -105,8 +100,32 @@ static int create_orc_entry(struct elf *elf, struct section *u_sec, struct secti
> }
> memset(rela, 0, sizeof(*rela));
>
> - rela->sym = insn_sec->sym;
> - rela->addend = insn_off;
> + if (insn_sec->sym) {
> + rela->sym = insn_sec->sym;
> + rela->addend = insn_off;
> + } else {
> + /*
> + * The Clang assembler doesn't produce section symbols, so we
> + * have to reference the function symbol instead:
> + */
> + rela->sym = find_symbol_containing(insn_sec, insn_off);

It's a good thing I made that a lot faster I suppose ;-)

> + if (!rela->sym) {
> + /*
> + * Hack alert. This happens when we need to reference
> + * the NOP pad insn immediately after the function.
> + */
> + rela->sym = find_symbol_containing(insn_sec,
> + insn_off - 1);

Urgh, when does that happen?

> + }
> + if (!rela->sym) {
> + WARN("missing symbol for insn at offset 0x%lx\n",
> + insn_off);
> + return -1;
> + }
> +
> + rela->addend = insn_off - rela->sym->offset;
> + }
> +
> rela->type = R_X86_64_PC32;
> rela->offset = idx * sizeof(int);
> rela->sec = ip_relasec;
> --
> 2.21.1
>