From: Peter Zijlstra <peterz@infradead.org>
Date: Sat, 4 Dec 2021 14:43:41 +0100
Subject: x86: Prepare inline-asm for straight-line-speculation
Git-commit: b17c2baa305cccbd16bafa289fd743cc2db77966
Patch-mainline: v5.17-rc1
References: bsc#1201050 CVE-2021-26341

Replace all ret/retq instructions with ASM_RET in preparation of
making it more than a single instruction.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211204134907.964635458@infradead.org
---
 arch/x86/include/asm/linkage.h            |    4 ++++
 arch/x86/include/asm/paravirt.h           |    2 +-
 arch/x86/include/asm/qspinlock_paravirt.h |    4 ++--
 arch/x86/kernel/alternative.c             |    2 +-
 arch/x86/kernel/kprobes/core.c            |    2 +-
 arch/x86/kernel/paravirt.c                |    2 +-
 arch/x86/kvm/emulate.c                    |    2 +-
 7 files changed, 11 insertions(+), 7 deletions(-)

--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -21,6 +21,10 @@
 #define __ALIGN_STR	__stringify(__ALIGN)
 #endif
 
+#else /* __ASSEMBLY__ */
+
+#define ASM_RET	"ret\n\t"
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_X86_LINKAGE_H */
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -793,7 +793,7 @@ static __always_inline bool pv_vcpu_is_p
 	    "call " #func ";"						\
 	    PV_RESTORE_ALL_CALLER_REGS					\
 	    FRAME_END							\
-	    "ret;"							\
+	    ASM_RET							\
 	    ".popsection")
 
 /* Get a reference to a callee-save function */
--- a/arch/x86/include/asm/qspinlock_paravirt.h
+++ b/arch/x86/include/asm/qspinlock_paravirt.h
@@ -47,7 +47,7 @@ asm    (".pushsection .text;"
 	"jne   .slowpath;"
 	"pop   %rdx;"
 	FRAME_END
-	"ret;"
+	ASM_RET
 	".slowpath: "
 	"push   %rsi;"
 	"movzbl %al,%esi;"
@@ -55,7 +55,7 @@ asm    (".pushsection .text;"
 	"pop    %rsi;"
 	"pop    %rdx;"
 	FRAME_END
-	"ret;"
+	ASM_RET
 	".size " PV_UNLOCK ", .-" PV_UNLOCK ";"
 	".popsection");
 
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -635,7 +635,7 @@ asm (
 "	.type		int3_magic, @function\n"
 "int3_magic:\n"
 "	movl	$1, (%" _ASM_ARG1 ")\n"
-"	ret\n"
+	ASM_RET
 "	.size		int3_magic, .-int3_magic\n"
 "	.popsection\n"
 );
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -736,7 +736,7 @@ asm(
 	RESTORE_REGS_STRING
 	"	popf\n"
 #endif
-	"	ret\n"
+	ASM_RET
 	".size kretprobe_trampoline, .-kretprobe_trampoline\n"
 );
 NOKPROBE_SYMBOL(kretprobe_trampoline);
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -50,7 +50,7 @@ extern void _paravirt_nop(void);
 asm (".pushsection .entry.text, \"ax\"\n"
      ".global _paravirt_nop\n"
      "_paravirt_nop:\n\t"
-     "ret\n\t"
+     ASM_RET
      ".size _paravirt_nop, . - _paravirt_nop\n\t"
      ".type _paravirt_nop, @function\n\t"
      ".popsection");
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -429,7 +429,7 @@ static int fastop(struct x86_emulate_ctx
 
 asm(".pushsection .fixup, \"ax\"\n"
     ".global kvm_fastop_exception \n"
-    "kvm_fastop_exception: xor %esi, %esi; ret\n"
+    "kvm_fastop_exception: xor %esi, %esi; " ASM_RET
     ".popsection");
 
 FOP_START(setcc)