linux-kernel - Re: [PATCH] x86: Fix location of '-plugin-opt=' flags

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Message-ID: <202105211403.6E5ACDD@keescook>
Date:   Fri, 21 May 2021 14:04:05 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     x86@...nel.org, Sami Tolvanen <samitolvanen@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        clang-built-linux@...glegroups.com,
        Anthony Ruhier <aruhier@...lbox.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86: Fix location of '-plugin-opt=' flags

On Fri, May 21, 2021 at 11:31:54AM -0700, Nathan Chancellor wrote:
> On Fri, May 21, 2021 at 10:59:10AM -0700, Kees Cook wrote:
> > On Tue, 18 May 2021 12:01:06 -0700, Nathan Chancellor wrote:
> > > Commit b33fff07e3e3 ("x86, build: allow LTO to be selected") added a
> > > couple of '-plugin-opt=' flags to KBUILD_LDFLAGS because the code model
> > > and stack alignment are not stored in LLVM bitcode. However, these flags
> > > were added to KBUILD_LDFLAGS prior to the emulation flag assignment,
> > > which uses ':=', so they were overwritten and never added to $(LD)
> > > invocations. The absence of these flags caused misalignment issues in
> > > the AMDGPU driver when compiling with CONFIG_LTO_CLANG, resulting in
> > > general protection faults.
> > > 
> > > [...]
> > 
> > (I've slightly adjusted the title.)
> > 
> > Applied to for-next/clang/features, thanks!
> > 
> > [1/1] x86: lto: Fix location of '-plugin-opt=' flags
> >       https://git.kernel.org/kees/c/5d6c8592ee5f
> > 
> 
> Ingo picked this up in x86/urgent so you should not need to carry it.
> 
> https://git.kernel.org/tip/0024430e920f2900654ad83cd081cf52e02a3ef5

Ah-ha, thanks! I didn't see a reply on the thread.

-- 
Kees Cook