[PATCH v2] x86/sev: Mark snp_abort() noreturn

Borislav Petkov
2022-08-24T16:43:32Z

On Wed, Aug 24, 2022 at 06:16:34PM +0200, Peter Zijlstra wrote:
> If only there would be a trace of it left in the ELF file...

Ah, there's that.

---
From: Borislav Petkov <bp@suse.de>

Mark both the function prototype and definition as noreturn in order to
prevent the compiler from doing transformations which confuse objtool
like so:

vmlinux.o: warning: objtool: sme_enable+0x71: unreachable instruction

This triggers with gcc-12.

Add it and sev_es_terminate() to the objtool noreturn tracking array
too. Sort it while at it.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/sev.h | 2 +-
arch/x86/kernel/sev.c | 2 +-
tools/objtool/check.c | 34 ++++++++++++++++++----------------
3 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 4a23e52fe0ee..ebc271bb6d8e 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -195,7 +195,7 @@ void snp_set_memory_shared(unsigned long vaddr, unsigned int npages);
void snp_set_memory_private(unsigned long vaddr, unsigned int npages);
void snp_set_wakeup_secondary_cpu(void);
bool snp_init(struct boot_params *bp);
-void snp_abort(void);
+void __init __noreturn snp_abort(void);
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err);
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 4f84c3f11af5..a428c62330d3 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2112,7 +2112,7 @@ bool __init snp_init(struct boot_params *bp)
return true;
}

-void __init snp_abort(void)
+void __init __noreturn snp_abort(void)
{
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0cec74da7ffe..ad51689dfb41 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -162,32 +162,34 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,

/*
* Unfortunately these have to be hard coded because the noreturn
- * attribute isn't provided in ELF data.
+ * attribute isn't provided in ELF data. Keep 'em sorted.
*/
static const char * const global_noreturns[] = {
+ "__invalid_creds",
+ "__module_put_and_kthread_exit",
+ "__reiserfs_panic",
"__stack_chk_fail",
- "panic",
+ "__ubsan_handle_builtin_unreachable",
+ "cpu_bringup_and_idle",
+ "cpu_startup_entry",
"do_exit",
+ "do_group_exit",
"do_task_dead",
- "kthread_exit",
- "make_task_dead",
- "__module_put_and_kthread_exit",
+ "ex_handler_msr_mce",
+ "fortify_panic",
"kthread_complete_and_exit",
- "__reiserfs_panic",
+ "kthread_exit",
+ "kunit_try_catch_throw",
"lbug_with_loc",
- "fortify_panic",
- "usercopy_abort",
"machine_real_restart",
+ "make_task_dead",
+ "panic",
"rewind_stack_and_make_dead",
- "kunit_try_catch_throw",
- "xen_start_kernel",
- "cpu_bringup_and_idle",
- "do_group_exit",
+ "sev_es_terminate",
+ "snp_abort",
"stop_this_cpu",
- "__invalid_creds",
- "cpu_startup_entry",
- "__ubsan_handle_builtin_unreachable",
- "ex_handler_msr_mce",
+ "usercopy_abort",
+ "xen_start_kernel",
};

if (!func)
--
2.35.1

--
Regards/Gruss,
Boris.