linux-kernel - [PATCH v2] x86/sev: Mark snp

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Date:   Wed, 24 Aug 2022 18:43:14 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     X86 ML <x86@...nel.org>, Michael Matz <matz@...e.de>,
        linux-toolchains@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH v2] x86/sev: Mark snp_abort() noreturn

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@...e.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@...e.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.

https://people.kernel.org/tglx/notes-about-netiquette