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. 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.. > /* > * 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. > " ret;\n" \ > " .align 16\n" \ > "904: call 901b;\n", \ > - X86_FEATURE_RETPOLINE) > + X86_FEATURE_RETPOLINE, \ > + "lfence;\n" \ > + ANNOTATE_RETPOLINE_SAFE \ > + "call *%[thunk_target]\n", \ > + X86_FEATURE_RETPOLINE_AMD) And that's OK again.
