diff mbox series

[v3,7/7] x86: make guarding against straight-line speculation optional

Message ID 06067023-0f61-3e37-a0a4-4254df1f5c16@suse.com (mailing list archive)
State Superseded
Headers show
Series x86: some assembler macro rework | expand

Commit Message

Jan Beulich Oct. 23, 2020, 8:39 a.m. UTC 
Put insertion of INT3 behind CONFIG_SPECULATIVE_HARDEN_BRANCH
conditionals.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v3: New.
diff mbox series

Patch

--- a/xen/arch/x86/indirect-thunk.S
+++ b/xen/arch/x86/indirect-thunk.S
@@ -11,8 +11,10 @@ 
 
 #include <asm/asm_defns.h>
 
+#ifdef CONFIG_SPECULATIVE_HARDEN_BRANCH
 /* Don't transform the "ret" further down. */
 .purgem ret
+#endif
 
 .macro IND_THUNK_RETPOLINE reg:req
         call 2f
@@ -45,7 +47,9 @@  ENTRY(__x86_indirect_thunk_\reg)
         __stringify(IND_THUNK_LFENCE \reg), X86_FEATURE_IND_THUNK_LFENCE, \
         __stringify(IND_THUNK_JMP \reg),    X86_FEATURE_IND_THUNK_JMP
 
+#ifdef CONFIG_SPECULATIVE_HARDEN_BRANCH
         int3 /* Halt straight-line speculation */
+#endif
 
         .size __x86_indirect_thunk_\reg, . - __x86_indirect_thunk_\reg
         .type __x86_indirect_thunk_\reg, @function
--- a/xen/include/asm-x86/asm-defns.h
+++ b/xen/include/asm-x86/asm-defns.h
@@ -51,6 +51,8 @@ 
     INDIRECT_BRANCH jmp \arg
 .endm
 
+#ifdef CONFIG_SPECULATIVE_HARDEN_BRANCH
+
 /*
  * To guard against speculation past RET, insert a breakpoint insn
  * immediately after them.
@@ -66,3 +68,5 @@ 
     .word \operand
     .endif
 .endm
+
+#endif