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-rw-r--r--arch/x86/Makefile2
-rw-r--r--arch/x86/include/asm/nospec-branch.h2
-rw-r--r--arch/x86/lib/retpoline.S13
3 files changed, 17 insertions, 0 deletions
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index a74886aed349..6e16057737e5 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -15,11 +15,13 @@ endif
ifdef CONFIG_CC_IS_GCC
RETPOLINE_CFLAGS := $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register)
RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch-cs-prefix)
+RETPOLINE_CFLAGS += $(call cc-option,-mfunction-return=thunk-extern)
RETPOLINE_VDSO_CFLAGS := $(call cc-option,-mindirect-branch=thunk-inline -mindirect-branch-register)
endif
ifdef CONFIG_CC_IS_CLANG
RETPOLINE_CFLAGS := -mretpoline-external-thunk
RETPOLINE_VDSO_CFLAGS := -mretpoline
+RETPOLINE_CFLAGS += $(call cc-option,-mfunction-return=thunk-extern)
endif
export RETPOLINE_CFLAGS
export RETPOLINE_VDSO_CFLAGS
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 5728539a3e77..829c9f827a96 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -123,6 +123,8 @@
typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE];
extern retpoline_thunk_t __x86_indirect_thunk_array[];
+extern void __x86_return_thunk(void);
+
#ifdef CONFIG_RETPOLINE
#define GEN(reg) \
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 2cdd62499d54..4467c21215f4 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -67,3 +67,16 @@ SYM_CODE_END(__x86_indirect_thunk_array)
#define GEN(reg) EXPORT_THUNK(reg)
#include <asm/GEN-for-each-reg.h>
#undef GEN
+
+/*
+ * This function name is magical and is used by -mfunction-return=thunk-extern
+ * for the compiler to generate JMPs to it.
+ */
+SYM_CODE_START(__x86_return_thunk)
+ UNWIND_HINT_EMPTY
+ ANNOTATE_NOENDBR
+ ret
+ int3
+SYM_CODE_END(__x86_return_thunk)
+
+__EXPORT_THUNK(__x86_return_thunk)