On Sun, Mar 13, 2022 at 09:52:14AM +0100, Peter Zijlstra wrote:
> > and:
> > vmlinux.o: warning: objtool: ksys_unshare()+0x626: unreachable instruction
> > which stays even after make clean.
>
> Humm, I shall have to dig out gcc-8.5 then.
Ha!, I could reproduce using the bpf-selftest .config for x86_64. Fixing
that (the __noreturn on __invalid_creds) immediately yields another one
on that .config in asm_exc_double_fault. And a missing ENDBR if you
don't build 32bit compat.
I'll go clean up ...
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -551,6 +551,14 @@ SYM_CODE_START(\asmsym)
movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
call \cfunc
+ /*
+ * For some configurations exc_double_fault() is a noreturn
+ */
+1:
+ .pushsection .discard.reachable
+ .long 1b - .
+ .popsection
+
jmp paranoid_exit
_ASM_NOKPROBE(\asmsym)
@@ -1440,6 +1448,7 @@ SYM_CODE_END(asm_exc_nmi)
*/
SYM_CODE_START(ignore_sysret)
UNWIND_HINT_EMPTY
+ ENDBR
mov $-ENOSYS, %eax
sysretl
SYM_CODE_END(ignore_sysret)
diff --git a/include/linux/cred.h b/include/linux/cred.h
index fcbc6885cc09..9ed9232af934 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -176,7 +176,7 @@ extern int set_cred_ucounts(struct cred *);
* check for validity of credentials
*/
#ifdef CONFIG_DEBUG_CREDENTIALS
-extern void __invalid_creds(const struct cred *, const char *, unsigned);
+extern void __noreturn __invalid_creds(const struct cred *, const char *, unsigned);
extern void __validate_process_creds(struct task_struct *,
const char *, unsigned);
diff --git a/kernel/cred.c b/kernel/cred.c
index 933155c96922..e10c15f51c1f 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -870,7 +870,7 @@ static void dump_invalid_creds(const struct cred *cred, const char *label,
/*
* report use of invalid credentials
*/
-void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
+void __noreturn __invalid_creds(const struct cred *cred, const char *file, unsigned line)
{
printk(KERN_ERR "CRED: Invalid credentials\n");
printk(KERN_ERR "CRED: At %s:%u\n", file, line);
