Merge tag 'x86_bugs_pbrsb' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

[platform/kernel/linux-starfive.git] / arch / x86 / include / asm / nospec-branch.h

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index d3a3cc6..e64fd20 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -96,25 +96,37 @@
 .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().
+ */
+.macro __CS_PREFIX reg:req
+       .irp rs,r8,r9,r10,r11,r12,r13,r14,r15
+       .ifc \reg,\rs
+       .byte 0x2e
+       .endif
+       .endr
+.endm
+
+/*
  * JMP_NOSPEC and CALL_NOSPEC macros can be used instead of a simple
  * indirect jmp/call which may be susceptible to the Spectre variant 2
  * attack.
  */
 .macro JMP_NOSPEC reg:req
 #ifdef CONFIG_RETPOLINE
-       ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
-                     __stringify(jmp __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \
-                     __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE
+       __CS_PREFIX \reg
+       jmp     __x86_indirect_thunk_\reg
 #else
        jmp     *%\reg
+       int3
 #endif
 .endm
 
 .macro CALL_NOSPEC reg:req
 #ifdef CONFIG_RETPOLINE
-       ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; call *%\reg), \
-                     __stringify(call __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \
-                     __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *%\reg), X86_FEATURE_RETPOLINE_LFENCE
+       __CS_PREFIX \reg
+       call    __x86_indirect_thunk_\reg
 #else
        call    *%\reg
 #endif