Re: [PATCH 03/11] objtool: Convert ANNOTATE_RETPOLINE_SAFE to ANNOTATE

James Houghton
2024-10-30T20:09:05Z

On Fri, Sep 13, 2024 at 1:47 PM James Houghton <jthoughton@google.com> wrote:
>
> On Wed, 6 Dec 2023, Sean Christopherson wrote:
> > On Mon, Dec 04, 2023, Peter Zijlstra wrote:
> > >
> > > --- a/arch/x86/include/asm/nospec-branch.h
> > > +++ b/arch/x86/include/asm/nospec-branch.h
> > > @@ -193,12 +193,7 @@
> > > * objtool the subsequent indirect jump/call is vouched safe for retpoline
> > > * builds.
> > > */
> > > -.macro ANNOTATE_RETPOLINE_SAFE
> > > -.Lhere_\@:
> > > - .pushsection .discard.retpoline_safe
> > > - .long .Lhere_\@
> > > - .popsection
> > > -.endm
> > > +#define ANNOTATE_RETPOLINE_SAFE ANNOTATE type=ANNOTYPE_RETPOLINE_SAFE
> > >
> > > /*
> > > * (ab)use RETPOLINE_SAFE on RET to annotate away 'bare' RET instructions
> > > @@ -317,11 +312,7 @@
> > >
> > > #else /* __ASSEMBLY__ */
> > >
> > > -#define ANNOTATE_RETPOLINE_SAFE \
> > > - "999:\n\t" \
> > > - ".pushsection .discard.retpoline_safe\n\t" \
> > > - ".long 999b\n\t" \
> > > - ".popsection\n\t"
> > > +#define ANNOTATE_RETPOLINE_SAFE ASM_ANNOTATE(ANNOTYPE_RETPOLINE_SAFE)
> >
> > This fails for some of my builds that end up with CONFIG_OBJTOOl=n. Adding a
> > stub for ASM_ANNOTATE() gets me past that:
> >
> > @@ -156,6 +171,7 @@
> > #define STACK_FRAME_NON_STANDARD(func)
> > #define STACK_FRAME_NON_STANDARD_FP(func)
> > #define ANNOTATE_NOENDBR
> > +#define ASM_ANNOTATE(x)
> > #define ASM_REACHABLE
> > #else
> > #define ANNOTATE_INTRA_FUNCTION_CALL
> >
> > but then I run into other issues:
> >
> > arch/x86/kernel/relocate_kernel_32.S: Assembler messages:
> > arch/x86/kernel/relocate_kernel_32.S:96: Error: Parameter named `type' does not exist for macro `annotate'
> > arch/x86/kernel/relocate_kernel_32.S:166: Error: Parameter named `type' does not exist for macro `annotate'
> > arch/x86/kernel/relocate_kernel_32.S:174: Error: Parameter named `type' does not exist for macro `annotate'
> > arch/x86/kernel/relocate_kernel_32.S:200: Error: Parameter named `type' does not exist for macro `annotate'
> > arch/x86/kernel/relocate_kernel_32.S:220: Error: Parameter named `type' does not exist for macro `annotate'
> > arch/x86/kernel/relocate_kernel_32.S:285: Error: Parameter named `type' does not exist for macro `annotate'
>
> Sean pointed me at this series recently. It seems like these compile errors
> (and some others) go away with the following diff:
>
> diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
> index 0bebdcad7ba1..036ab199859a 100644
> --- a/arch/x86/include/asm/nospec-branch.h
> +++ b/arch/x86/include/asm/nospec-branch.h
> @@ -489,7 +489,7 @@ static inline void call_depth_return_thunk(void) {}
> " .align 16\n" \
> "903: lea 4(%%esp), %%esp;\n" \
> " pushl %[thunk_target];\n" \
> - " ret;\n" \
> + " ret;\n", \
> X86_FEATURE_RETPOLINE, \
> "lfence;\n" \
> ANNOTATE_RETPOLINE_SAFE \
> diff --git a/include/linux/objtool.h b/include/linux/objtool.h
> index f6f80bfefe3b..e811b2ff3a9c 100644
> --- a/include/linux/objtool.h
> +++ b/include/linux/objtool.h
> @@ -159,6 +159,7 @@
> #define STACK_FRAME_NON_STANDARD_FP(func)
> #define ANNOTATE_NOENDBR
> #define ASM_REACHABLE
> +#define ASM_ANNOTATE(x)
> #else
> #define ANNOTATE_INTRA_FUNCTION_CALL
> .macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
> @@ -169,7 +170,7 @@
> .endm
> .macro REACHABLE
> .endm
> -.macro ANNOTATE
> +.macro ANNOTATE type:req
> .endm
> #endif
>
> This series applies on top of the latest kvm-x86/next with only a few trivial
> conflicts, so I hope you are able to send a new version.
>
> I could send one for you, but I have no idea how to properly test it.

Hi Peter,

I'll go ahead and repost this series soon unless you tell me otherwise. :)