linux-kernel - [PATCH 17/21] x86/acpi: Convert indirect jump to retpoline

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Message-Id: <a1e4f5620deb81fc644b436eca5f51ec3a694459.1610652862.git.jpoimboe@redhat.com>
Date:   Thu, 14 Jan 2021 13:40:13 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com,
        Miroslav Benes <mbenes@...e.cz>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>
Subject: [PATCH 17/21] x86/acpi: Convert indirect jump to retpoline

It's kernel policy to not have (unannotated) indirect jumps because of
Spectre v2.  This one's probably harmless, but better safe than sorry.
Convert it to a retpoline.

Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Len Brown <len.brown@...el.com>
Cc: Pavel Machek <pavel@....cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/kernel/acpi/wakeup_64.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
index 5d3a0b8fd379..0b371580e620 100644
--- a/arch/x86/kernel/acpi/wakeup_64.S
+++ b/arch/x86/kernel/acpi/wakeup_64.S
@@ -7,6 +7,7 @@
 #include <asm/msr.h>
 #include <asm/asm-offsets.h>
 #include <asm/frame.h>
+#include <asm/nospec-branch.h>
 
 # Copyright 2003 Pavel Machek <pavel@...e.cz
 
@@ -39,7 +40,7 @@ SYM_FUNC_START(wakeup_long64)
 	movq	saved_rbp, %rbp
 
 	movq	saved_rip, %rax
-	jmp	*%rax
+	JMP_NOSPEC rax
 SYM_FUNC_END(wakeup_long64)
 
 SYM_FUNC_START(do_suspend_lowlevel)
-- 
2.29.2