diff options
| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2025-04-08 01:21:14 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-04-08 22:03:51 +0200 |
| commit | 2d12c6fb78753925f494ca9079e2383529e8ae0e (patch) | |
| tree | b3143293b0ba006ca7315ae406c8200715f121a0 /tools | |
| parent | 2dbbca9be4e5ed68d0972a2bcf4561d9cb85b7b7 (diff) | |
objtool: Remove ANNOTATE_IGNORE_ALTERNATIVE from CLAC/STAC
ANNOTATE_IGNORE_ALTERNATIVE adds additional noise to the code generated
by CLAC/STAC alternatives, hurting readability for those whose read
uaccess-related code generation on a regular basis.
Remove the annotation specifically for the "NOP patched with CLAC/STAC"
case in favor of a manual check.
Leave the other uses of that annotation in place as they're less common
and more difficult to detect.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/fc972ba4995d826fcfb8d02733a14be8d670900b.1744098446.git.jpoimboe@kernel.org
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/objtool/check.c | 30 |
1 files changed, 29 insertions, 1 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 69f94bc47499..b649049b6a11 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -3505,6 +3505,34 @@ next_orig: return next_insn_same_sec(file, alt_group->orig_group->last_insn); } +static bool skip_alt_group(struct instruction *insn) +{ + struct instruction *alt_insn = insn->alts ? insn->alts->insn : NULL; + + /* ANNOTATE_IGNORE_ALTERNATIVE */ + if (insn->alt_group && insn->alt_group->ignore) + return true; + + /* + * For NOP patched with CLAC/STAC, only follow the latter to avoid + * impossible code paths combining patched CLAC with unpatched STAC + * or vice versa. + * + * ANNOTATE_IGNORE_ALTERNATIVE could have been used here, but Linus + * requested not to do that to avoid hurting .s file readability + * around CLAC/STAC alternative sites. + */ + + if (!alt_insn) + return false; + + /* Don't override ASM_{CLAC,STAC}_UNSAFE */ + if (alt_insn->alt_group && alt_insn->alt_group->ignore) + return false; + + return alt_insn->type == INSN_CLAC || alt_insn->type == INSN_STAC; +} + /* * Follow the branch starting at the given instruction, and recursively follow * any other branches (jumps). Meanwhile, track the frame pointer state at @@ -3625,7 +3653,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, } } - if (insn->alt_group && insn->alt_group->ignore) + if (skip_alt_group(insn)) return 0; if (handle_insn_ops(insn, next_insn, &state)) |