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SubjectRe: [PATCH 1/4] objtool: Implement base jump_assert support
Big props to you for braving the bowels of the objtool code.

On Mon, Jan 15, 2018 at 05:44:29PM +0100, Peter Zijlstra wrote:
> +static int read_jump_assertions(struct objtool_file *file)

This does more than just _read_ the assertions. Can you call it
something like assert_static_jumps() or do_static_jump_assertions() and
then call it from the main check() function?

> +{
> + struct section *sec, *relasec;
> + struct instruction *insn;
> + struct rela *rela;
> + int i;
> +
> + sec = find_section_by_name(file->elf, ".discard.jump_assert");
> + if (!sec)
> + return 0;
> +
> + relasec = sec->rela;
> + if (!relasec) {
> + WARN("missing .rela.discard.jump_assert section");
> + return -1;
> + }
> +
> + if (sec->len % sizeof(unsigned long)) {
> + WARN("jump_assert size mismatch: %d %ld", sec->len, sizeof(unsigned long));
> + return -1;
> + }
> +
> + for (i = 0; i < sec->len / sizeof(unsigned long); i++) {
> + rela = find_rela_by_dest(sec, i * sizeof(unsigned long));
> + if (!rela) {
> + WARN("can't find rela for jump_assert[%d]", i);
> + return -1;
> + }
> +
> + insn = find_insn(file, rela->sym->sec, rela->addend);
> + if (!insn) {
> + WARN("can't find insn for jump_assert[%d]", i);
> + return -1;
> + }
> +
> + if (!insn->br_static) {
> + WARN_FUNC("static assert FAIL", insn->sec, insn->offset);
> + return -1;
> + }
> + }
> +
> + return 0;
> +}
> +
> static int decode_sections(struct objtool_file *file)
> {
> int ret;
> @@ -1105,6 +1167,10 @@ static int decode_sections(struct objtoo
> if (ret)
> return ret;
>
> + ret = read_jump_assertions(file);
> + if (ret)
> + return ret;
> +
> return 0;
> }
>
> --- a/tools/objtool/check.h
> +++ b/tools/objtool/check.h
> @@ -45,6 +45,7 @@ struct instruction {
> unsigned char type;
> unsigned long immediate;
> bool alt_group, visited, dead_end, ignore, hint, save, restore, ignore_alts;
> + bool br_static;

s/br_static/static_jump_dest/?

Also, fellow objtool expert, you forgot the patch to the MAINTAINERS
file ;-)

--
Josh

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