Re: linux-next: build failure after merge of the tip tree

H. Peter Anvin
2021-05-13T11:12:32Z

Needed some head scratching, but then...

It makes sense for the cross-build: it's building for the host, and a non-x86 machine isn't doing to have a register named "%rsp".

So this needs to be protected from non-kernel use either via __KERNEL__ or by factoring the basic macros out into a separate file.

Incidentally, we seem to have three categories of include files now: kernel-only, uapi, and "tools api". Perhaps we need such a "tapi" directory instead of copying things around... the infrastructure for uapi with make headers_install etc ought to be generalizable.

On May 13, 2021 3:51:47 AM PDT, Ingo Molnar <mingo@kernel.org> wrote:
>
>* Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
>> Hi all,
>>
>> After merging the tip tree, today's linux-next build (x86_64
>allmodconfig)
>> failed like this:
>>
>> In file included from tools/arch/x86/include/asm/nops.h:5,
>> from arch/x86/decode.c:15:
>> tools/arch/x86/include/asm/asm.h:185:24: error: invalid register name
>for 'current_stack_pointer'
>> 185 | register unsigned long current_stack_pointer asm(_ASM_SP);
>> | ^~~~~~~~~~~~~~~~~~~~~
>>
>> Caused by commit
>>
>> eef23e72b78b ("x86/asm: Use _ASM_BYTES() in <asm/nops.h>")
>>
>> I have used the tip tree from next-20210512 for today.
>
>Hm, this must be some cross-build artifact or toolchain version
>dependency
>- as plain native build of x86-64 allmodconfig builds just fine:
>
> CC arch/x86/decode.o
> LD arch/x86/objtool-in.o
>
>I tried with gcc-8, but that didn't trigger it.
>
>I suppose the workaround below would make it build - but that's not a
>real
>solution.
>
>hpa, any ideas?
>
>Thanks,
>
> Ingo
>
>diff --git a/tools/arch/x86/include/asm/asm.h
>b/tools/arch/x86/include/asm/asm.h
>index 507a37a46027..ada5482c024a 100644
>--- a/tools/arch/x86/include/asm/asm.h
>+++ b/tools/arch/x86/include/asm/asm.h
>@@ -176,14 +176,6 @@
>
> /* For C file, we already have NOKPROBE_SYMBOL macro */
>
>-/*
>- * This output constraint should be used for any inline asm which has
>a "call"
>- * instruction. Otherwise the asm may be inserted before the frame
>pointer
>- * gets set up by the containing function. If you forget to do this,
>objtool
>- * may print a "call without frame pointer save/setup" warning.
>- */
>-register unsigned long current_stack_pointer asm(_ASM_SP);
>-#define ASM_CALL_CONSTRAINT "+r" (current_stack_pointer)
> #endif /* __ASSEMBLY__ */
>
> #endif /* _ASM_X86_ASM_H */

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