The following commit has been merged into the objtool/core branch of tip:
Commit-ID: 55eeab2a8a11b71586ef0ad3adf532ca5f97d4be
Gitweb: https://git.kernel.org/tip/55eeab2a8a11b71586ef0ad3adf532ca5f97d4be
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Tue, 18 Apr 2023 14:27:51 -07:00
Committer: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
CommitterDate: Tue, 16 May 2023 06:31:53 -07:00
objtool: Ignore exc_double_fault() __noreturn warnings
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
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Link: https://lore.kernel.org/r/a45b085071d3a7d049a20f9e78754452336ecbe8.1681853186.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
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 8d1b422..8dac1e3 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4505,6 +4505,35 @@ 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);
+
+ /*
+ * FIXME: hack, we need a real noreturn solution
+ *
+ * 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:
+ *
+ * - have compiler communicate __noreturn functions somehow
+ * - 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
+ */
+ 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;
@@ -4521,7 +4550,7 @@ 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++;
|