linux-kernel - Re: [PATCH v2 1/1] pgo: Fix allocate

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Message-ID: <202106031436.132E0ED9A@keescook>
Date:   Thu, 3 Jun 2021 14:36:39 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Jarmo Tiitto <jarmo.tiitto@...il.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Bill Wendling <wcw@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org,
        morbo@...gle.com
Subject: Re: [PATCH v2 1/1] pgo: Fix allocate_node() v2

On Thu, Jun 03, 2021 at 02:14:24PM -0700, Nathan Chancellor wrote:
> On 6/3/2021 6:38 AM, Jarmo Tiitto wrote:
> > Based on Kees and others feedback here is v2 patch
> > that clarifies why the current checks in allocate_node()
> > are flawed. I did fair amount of KGDB time on it.
> > 
> > When clang instrumentation eventually calls allocate_node()
> > the struct llvm_prf_data *p argument tells us from what section
> > we should reserve the vnode: It either points into vmlinux's
> > core __llvm_prf_data section or some loaded module's
> > __llvm_prf_data section.
> > 
> > But since we don't have access to corresponding
> > __llvm_prf_vnds section(s) for any module, the function
> > should return just NULL and ignore any profiling attempts
> > from modules for now.
> > 
> > Signed-off-by: Jarmo Tiitto <jarmo.tiitto@...il.com>
> 
> I agree with Nick on the comments about the commit message. A few more small
> nits below, not sure they necessitate a v3, up to you. Thank you for the
> patch!

It would make my life easier to get a v3. :) I agree with all of
Nathan's suggestions. :)

Thanks!

-Kees

-- 
Kees Cook