linux-kernel - Re: x86 - clang / objtool status

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Date:   Thu, 18 Jul 2019 15:42:23 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: x86 - clang / objtool status

On Thu, Jul 18, 2019 at 1:40 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> after picking up Josh's objtool updates I gave clang a test ride again.

Thanks for testing and the reports; these are valuable and we
appreciate the help debugging them.

> 2) debian distro config

Is this checked into the tree, or where can I find it?

>
>  objtool warnings:
>
>   drivers/gpu/drm/amd/amdgpu/atom.o: warning: objtool: atom_op_move() falls through to next function atom_op_and()
>   drivers/infiniband/hw/hfi1/platform.o: warning: objtool: tune_serdes() falls through to next function apply_tx_lanes()
>   drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x86: redundant UACCESS disable
>   drivers/gpu/drm/radeon/evergreen_cs.o: warning: objtool: evergreen_cs_parse() falls through to next function evergreen_dma_cs_parse()

fall through warnings look new to me, but Linaro's KernelCI is
currently screaming with tons of reports of -Wfallthrough throughout
the kernel.  I assume they're related?

> 3) allmodconfig:
>
>  objtool warnings:
>
>   arch/x86/kernel/signal.o: warning: objtool: x32_setup_rt_frame()+0x255: call to memset() with UACCESS enabled
>   arch/x86/kernel/signal.o: warning: objtool: __setup_rt_frame()+0x254: call to memset() with UACCESS enabled
>   arch/x86/ia32/ia32_signal.o: warning: objtool: ia32_setup_rt_frame()+0x247: call to memset() with UACCESS enabled
>
>   mm/kasan/common.o: warning: objtool: kasan_report()+0x52: call to __stack_chk_fail() with UACCESS enabled
>   drivers/ata/sata_dwc_460ex.o: warning: objtool: sata_dwc_bmdma_start_by_tag()+0x3a0: can't find switch jump table
>
>   lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x88: call to memset() with UACCESS enabled
>   lib/ubsan.o: warning: objtool: ubsan_type_mismatch_common()+0x610: call to __stack_chk_fail() with UACCESS enabled
>   lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x88: call to memset() with UACCESS enabled
>   drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x56: redundant UACCESS disable

Do you still have these object files laying around? Josh asked for
them in a new thread (from the previous thread), not sure if it's ok
to attach object files to emails to LKML? (html email is not allowed,
are binary attachments?)
-- 
Thanks,
~Nick Desaulniers