On 2018/9/18 17:50, Peter Zijlstra wrote:
On Mon, Sep 17, 2018 at 10:17:30PM -0700, Zhenzhong Duan wrote:
Lfence is preferred than general retpoline on AMD, add this option
in C / inline asm just as the ASM code does.
For x86_64, it still help to have minimal retpoline for kernel even
if gcc doesn't support it, change the inline asm for x86 so that it
could also be used by x86_64.
Add ANNOTATE_NOSPEC_ALTERNATIVE for i386 to avoid below warning:
"warning: objtool: .altinstr_replacement+0x10: unsupported
intra-function call"
"warning: objtool: If this is a retpoline, please patch it
in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."
This Changelog is almost unreadable, please rewrite.
Sorry, I'll rewrite it.
Reverse engineering the patch you add RETPOLINE_AMD support to the
inline-asm CALL_NOSPEC so that they match the asm CALL_NOSPEC.
Signed-off-by: Zhenzhong Duan <zhenzhong.d...@oracle.com>
---
arch/x86/include/asm/nospec-branch.h | 23 ++++++++++++++++-------
1 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/nospec-branch.h
b/arch/x86/include/asm/nospec-branch.h
index fd2a8c1..2d49eab 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -170,21 +170,26 @@
*/
# define CALL_NOSPEC \
ANNOTATE_NOSPEC_ALTERNATIVE \
- ALTERNATIVE( \
+ ALTERNATIVE_2( \
ANNOTATE_RETPOLINE_SAFE \
"call *%[thunk_target]\n", \
"call __x86_indirect_thunk_%V[thunk_target]\n", \
- X86_FEATURE_RETPOLINE)
+ X86_FEATURE_RETPOLINE, \
+ "lfence;\n" \
+ ANNOTATE_RETPOLINE_SAFE \
+ "call *%[thunk_target]\n", \
+ X86_FEATURE_RETPOLINE_AMD)
# define THUNK_TARGET(addr) [thunk_target] "r" (addr)
That's OK.
-#elif defined(CONFIG_X86_32) && defined(CONFIG_RETPOLINE)
+#elif defined(CONFIG_RETPOLINE)
This doesn't make any sense..
This change is used for x86_64 to have minimal Retpoline support when
CONFIG_RETPOLINE is defined but RETPOLINE isn't defined, or I missed
something?
/*
* For i386 we use the original ret-equivalent retpoline, because
* otherwise we'll run out of registers. We don't care about CET
* here, anyway.
*/
# define CALL_NOSPEC \
- ALTERNATIVE( \
+ ANNOTATE_NOSPEC_ALTERNATIVE \
+ ALTERNATIVE_2( \
ANNOTATE_RETPOLINE_SAFE \
"call *%[thunk_target]\n", \
" jmp 904f;\n" \
@@ -194,12 +199,16 @@
" lfence;\n" \
" jmp 902b;\n" \
" .align 16\n" \
- "903: addl $4, %%esp;\n" \
- " pushl %[thunk_target];\n" \
+ "903: add $4, %%" _ASM_SP ";\n" \
+ " push %[thunk_target];\n" \
Yeah, don't do that.
This is the change for above reason.
Thanks
Zhenzhong
