diff options
| -rw-r--r-- | arch/x86/include/asm/nospec-branch.h | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 1e6b915ce956..aee26bb8230f 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -198,9 +198,8 @@ .endm /* - * Equivalent to -mindirect-branch-cs-prefix; emit the 5 byte jmp/call - * to the retpoline thunk with a CS prefix when the register requires - * a RAX prefix byte to encode. Also see apply_retpolines(). + * Emits a conditional CS prefix that is compatible with + * -mindirect-branch-cs-prefix. */ .macro __CS_PREFIX reg:req .irp rs,r8,r9,r10,r11,r12,r13,r14,r15 @@ -421,11 +420,23 @@ static inline void call_depth_return_thunk(void) {} #ifdef CONFIG_X86_64 /* + * Emits a conditional CS prefix that is compatible with + * -mindirect-branch-cs-prefix. + */ +#define __CS_PREFIX(reg) \ + ".irp rs,r8,r9,r10,r11,r12,r13,r14,r15\n" \ + ".ifc \\rs," reg "\n" \ + ".byte 0x2e\n" \ + ".endif\n" \ + ".endr\n" + +/* * Inline asm uses the %V modifier which is only in newer GCC * which is ensured when CONFIG_MITIGATION_RETPOLINE is defined. */ #ifdef CONFIG_MITIGATION_RETPOLINE -#define CALL_NOSPEC "call __x86_indirect_thunk_%V[thunk_target]\n" +#define CALL_NOSPEC __CS_PREFIX("%V[thunk_target]") \ + "call __x86_indirect_thunk_%V[thunk_target]\n" #else #define CALL_NOSPEC "call *%[thunk_target]\n" #endif |