linux-kernel - Re: [PATCH] lib/Kconfig.debug: Add check for non-constant .{s,u}leb128 support to DWARF5

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Message-ID: <CAKwvOdk87wRWoiVjswZPwoLbSm+sYsMW6FHZv+r6MHxLHn0Trw@mail.gmail.com>
Date:   Wed, 28 Sep 2022 14:53:38 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Tom Rix <trix@...hat.com>, Palmer Dabbelt <palmer@...belt.com>,
        linux-kbuild@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        llvm@...ts.linux.dev, Conor Dooley <conor.dooley@...rochip.com>
Subject: Re: [PATCH] lib/Kconfig.debug: Add check for non-constant
 .{s,u}leb128 support to DWARF5

On Wed, Sep 28, 2022 at 2:36 PM Nathan Chancellor <nathan@...nel.org> wrote:
>
> On Wed, Sep 28, 2022 at 02:13:47PM -0700, Nick Desaulniers wrote:
> > Reraising my concern from
> > https://github.com/ClangBuiltLinux/linux/issues/1719#issuecomment-1258678969
>
> Sorry, I thought I addressed your concern with my comment right below it
> but I probably should have worded it better.

No, I just missed your point about other architectures.

> > We've put a fair amount of work into getting CC=clang LLVM_IAS=0 to
> > work for DWARF v5 (both on the GNU binutils side, and Kbuild), I'd
> > hate to see that effectively knee-capped because of an issue in GNU
> > binutils that is only relevant for one architecture.
>
> Sure, that is a completely reasonable concern. However...
>
> > I'd concede support for ARCH=riscv, but not for all other
> > architectures, which this effectively does.
>
> No, it does not, CONFIG_AS_HAS_NON_CONST_LEB128 can still be enabled
> when GNU as supports this construct for a particular architecture; as
> far as I can tell, RISC-V is the only one that doesn't. See the tests
> with ARCH=arm64 and ARCH=x86_64 compared with ARCH=riscv below.

Ah, sorry for the noise then. Thanks for the patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

-- 
Thanks,
~Nick Desaulniers