From: Andi Kleen <[email protected]>
[This fixes a boot failure in the earlier patches
so may want to be moved earlier to keep git bisect
happy]
With the latest tip x86/pti I get oopses when booting
a 64bit VM in qemu with RETPOLINE/gcc7 and PTI enabled.
Something is wrong with the ALTERNATIVE_2 sequence
used in NOSPEC_JMP
Linus suggested a better sequence that is shorter
and simpler and avoids the problem.
It requires excluding X86_FEATURE_RETPOLINE and
X86_FEATURE_RETPOLINE_AMD, but that has been done
in the previous patch.
Use the new sequence for NOSPEC_CALL and NOSPEC_JMP.
v2: Use new sequence for CALL/RET. Add extra patch
for _COMMON.
v3: Use RETPOLINE_GENERIC for Intel
Fixes: ce004e1cb ("x86/retpoline: Add initial retpoline")
Fixes: f3433c101 ("x86/retpoline/entry: Convert entry")
Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Andi Kleen <[email protected]>
---
arch/x86/include/asm/nospec-branch.h | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/nospec-branch.h
b/arch/x86/include/asm/nospec-branch.h
index 8ddf8513550e..dc13325a9890 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -46,9 +46,8 @@
*/
.macro JMP_NOSPEC reg:req
#ifdef CONFIG_RETPOLINE
- ALTERNATIVE_2 __stringify(jmp *\reg), \
- __stringify(RETPOLINE_JMP \reg), X86_FEATURE_RETPOLINE, \
- __stringify(lfence; jmp *\reg), X86_FEATURE_RETPOLINE_AMD
+ ALTERNATIVE "", "lfence", X86_FEATURE_RETPOLINE_AMD
+ ALTERNATIVE __stringify(jmp *\reg), __stringify(RETPOLINE_JMP \reg),
X86_FEATURE_RETPOLINE_GENERIC
#else
jmp *\reg
#endif
@@ -56,9 +55,8 @@
.macro CALL_NOSPEC reg:req
#ifdef CONFIG_RETPOLINE
- ALTERNATIVE_2 __stringify(call *\reg), \
- __stringify(RETPOLINE_CALL \reg), X86_FEATURE_RETPOLINE,\
- __stringify(lfence; call *\reg), X86_FEATURE_RETPOLINE_AMD
+ ALTERNATIVE "", "lfence", X86_FEATURE_RETPOLINE_AMD
+ ALTERNATIVE __stringify(call *\reg), __stringify(RETPOLINE_CALL \reg),
X86_FEATURE_RETPOLINE_GENERIC
#else
call *\reg
#endif
--
2.14.3
