Messages in this thread Patch in this message | | | Date | Tue, 28 Nov 2017 14:55:53 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: perf test LLVM & clang 6 failing |
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Em Mon, Nov 27, 2017 at 01:45:21PM -0800, Matthias Kaehlcke escreveu: > El Mon, Nov 27, 2017 at 01:57:56PM -0600 Josh Poimboeuf ha dit: > > > On Mon, Nov 27, 2017 at 04:34:25PM -0300, Arnaldo Carvalho de Melo wrote: > > > Em Mon, Nov 27, 2017 at 11:11:56AM -0800, Yonghong Song escreveu: > > > > On 11/27/17 9:04 AM, Arnaldo Carvalho de Melo wrote: > > > > > Em Fri, Nov 24, 2017 at 04:16:52PM +0100, Daniel Borkmann escreveu: > > > > > > [ +Yonghong ] > > > > > > > > > > + Josh > > > > > > On 11/24/2017 03:47 PM, Arnaldo Carvalho de Melo wrote: > > > > > > > FYI, just noticed, recently updated clang to version 6, from its > > > > > > > upstream git repo. > > > > > > > > > > > > Do you recall what was your LLVM version prior to this where it was > > > > > > working fine? (Wild guess from below would be the BPF inline asm > > > > > > support that was added recently to LLVM (2865ab6996) vs asm() used > > > > > > in headers included in the stdin header causing trouble due to arch > > > > > > mixup?) > > > > > > > > > > So, if I go to the cset just before: > > > > > > > > > > commit f5caf621ee357279e759c0911daf6d55c7d36f03 > > > > > Author: Josh Poimboeuf <jpoimboe@redhat.com> > > > > > Date: Wed Sep 20 16:24:33 2017 -0500 > > > > > > > > > > x86/asm: Fix inline asm call constraints for Clang > > > > > --- > > > > > > > > > > 'perf test LLVM' works again: > > > > > > > > > > [root@jouet ~]# perf test LLVM > > > > > 37: LLVM search and compile : > > > > > 37.1: Basic BPF llvm compile : Ok > > > > > 37.2: kbuild searching : Ok > > > > > 37.3: Compile source for BPF prologue generation : Ok > > > > > 37.4: Compile source for BPF relocation : Ok > > > > > [root@jouet ~]# > > > > > > > > > > I.e. 'perf test LLVM' built from what is in my acme/perf/urgent branch, > > > > > targetted to v4.15, uses kernel headers and if I go to just before > > > > > f5caf621ee, it works again, both with clang from fedora26 (4.0.1) and > > > > > with 6.0, built from sources. > > > > > > > > This patch introduced a module level inline assembly. > > > > > > > > ... > > > > --- a/arch/x86/include/asm/asm.h > > > > +++ b/arch/x86/include/asm/asm.h > > > > @@ -132,4 +132,15 @@ > > > > /* For C file, we already have NOKPROBE_SYMBOL macro */ > > > > #endif > > > > > > > > +#ifndef __ASSEMBLY__ > > > > +/* > > > > + * 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 int __asm_call_sp asm("esp"); > > > > +#define ASM_CALL_CONSTRAINT "+r" (__asm_call_sp) > > > > +#endif > > > > ... > > > > > > > > This will cause "clang ... -target bpf ..." failure since 4.0 does not have > > > > bpf inline asm support and 6.0 does not recognize the register 'esp'. > > > > > > Ok, explains the problem then, Josh, ideas on how to proceed here? > > > > The original change to add the global inline asm: > > > > 5caf621ee35 ("x86/asm: Fix inline asm call constraints for Clang") > > > > was done to support clang in the first place. Before that change, a > > clang-built kernel didn't even boot. So I'm a bit perplexed by the fact > > that this change would be causing clang problems, since it was done to > > fix clang in the first place. > > > > Adding Andrey and Matthias, maybe they can help clarify things. > > Indeed the change was needed to boot on x86. > > I know next to nothing about BPF, if I understand correctly the error > is generated when compiling for the BPF "architecture" not for x86. In > this process x86 assembly headers are included, one of which contains > the declaration of the register variable, in an register that exists > on x86, but not BPS. > > I guess the first questions is whether the x86 asm headers should/need > to be included when compiling for BPF. If this needed/can not be > easily avoided one option could be to put the declaration within an > ifdef __x86_64__ block.
Right, unsure if this is the way to go, but fixes the problem here:
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h index 219faaec51df..d180d573fd38 100644 --- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -136,6 +136,8 @@ #endif #ifndef __ASSEMBLY__ +#if defined(__i386__) || defined(__x86_64__) +/* bpf target builds also include these headers */ /* * 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 @@ -145,5 +147,6 @@ register unsigned long current_stack_pointer asm(_ASM_SP); #define ASM_CALL_CONSTRAINT "+r" (current_stack_pointer) #endif +#endif #endif /* _ASM_X86_ASM_H */ [root@jouet ~]# perf test LLVM 37: LLVM search and compile : 37.1: Basic BPF llvm compile : Ok 37.2: kbuild searching : Ok 37.3: Compile source for BPF prologue generation : Ok 37.4: Compile source for BPF relocation : Ok [root@jouet ~]#
Is there any define clang generates for the bpf target?
- Arnaldo
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