Messages in this thread Patch in this message | | | From | Josh Poimboeuf <> | Subject | [PATCH v2 9/9] objtool: Ignore exc_double_fault() __noreturn warnings | Date | Wed, 12 Apr 2023 12:03:24 -0700 |
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This is a hack, but it works for now.
Problem is, exc_double_fault() may or may not return, depending on whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility to the kernel config.
"Fix" it by silencing the exc_double_fault() __noreturn warning.
This removes the following warning:
vmlinux.o: warning: objtool: xenpv_exc_double_fault+0xd: exc_double_fault() is missing a __noreturn annotation
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> --- tools/objtool/check.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 60f2d649f19f..7641e818db7d 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -4483,6 +4483,35 @@ static int validate_sls(struct objtool_file *file) return warnings; } +static bool ignore_noreturn_call(struct instruction *insn) +{ + struct symbol *call_dest = insn_call_dest(insn); + + /* + * This is a hack, but it works for now. + * + * Problem is, exc_double_fault() may or may not return, depending on + * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility + * to the kernel config. + * + * Other potential ways to fix it: + * + * - remove CONFIG_X86_ESPFIX64 + * - read the .config file + * - add a cmdline option + * - create a generic objtool annotation format (vs a bunch of custom + * formats) and annotate it + * - have compiler communicate __noreturn functions somehow + */ + if (!strcmp(call_dest->name, "exc_double_fault")) { + /* prevent further unreachable warnings for the caller */ + insn->sym->warned = 1; + return true; + } + + return false; +} + static int validate_reachable_instructions(struct objtool_file *file) { struct instruction *insn, *prev_insn; @@ -4499,7 +4528,7 @@ static int validate_reachable_instructions(struct objtool_file *file) prev_insn = prev_insn_same_sec(file, insn); if (prev_insn && prev_insn->dead_end) { call_dest = insn_call_dest(prev_insn); - if (call_dest) { + if (call_dest && !ignore_noreturn_call(prev_insn)) { WARN_INSN(insn, "%s() is missing a __noreturn annotation", call_dest->name); warnings++; -- 2.39.2
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