| Message ID | 20220830233129.30610-17-samitolvanen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KCFI support | expand |
On Tue, Aug 30, 2022 at 04:31:24PM -0700, Sami Tolvanen wrote: > The __cfi_ preambles contain a mov instruction that embeds the KCFI > type identifier in the following format: > > ; type preamble > __cfi_function: > mov <id>, %eax > function: > ... > > While the preamble symbols are STT_FUNC and contain valid > instructions, they are never executed and always fall through. Skip > the warning for them. > > .kcfi_traps sections point to CFI traps in text sections. Also skip > the warning about them referencing !ENDBR instructions. > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org>
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index e55fdf952a3a..48e18737a2d1 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -3316,6 +3316,10 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, next_insn = next_insn_to_validate(file, insn); if (func && insn->func && func != insn->func->pfunc) { + /* Ignore KCFI type preambles, which always fall through */ + if (!strncmp(func->name, "__cfi_", 6)) + return 0; + WARN("%s() falls through to next function %s()", func->name, insn->func->name); return 1; @@ -4113,7 +4117,8 @@ static int validate_ibt(struct objtool_file *file) !strcmp(sec->name, "__bug_table") || !strcmp(sec->name, "__ex_table") || !strcmp(sec->name, "__jump_table") || - !strcmp(sec->name, "__mcount_loc")) + !strcmp(sec->name, "__mcount_loc") || + !strcmp(sec->name, ".kcfi_traps")) continue; list_for_each_entry(reloc, &sec->reloc->reloc_list, list)
The __cfi_ preambles contain a mov instruction that embeds the KCFI type identifier in the following format: ; type preamble __cfi_function: mov <id>, %eax function: ... While the preamble symbols are STT_FUNC and contain valid instructions, they are never executed and always fall through. Skip the warning for them. .kcfi_traps sections point to CFI traps in text sections. Also skip the warning about them referencing !ENDBR instructions. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> --- tools/objtool/check.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)