linux-kernel - Re: [PATCH v2] drm/amdgpu: Remove unnecessary variable shadow in gfx_v9_0_rlcg_wreg

Open Source and information security mailing list archives

Message-ID: <CADnq5_NjjorZhuAx+4gCW=LLGGvRhYqVKXUhAcXriehN3_y-UQ@mail.gmail.com>
Date:   Wed, 18 Mar 2020 23:15:40 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Nathan Chancellor <natechancellor@...il.com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        Joe Perches <joe@...ches.com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH v2] drm/amdgpu: Remove unnecessary variable shadow in gfx_v9_0_rlcg_wreg

On Wed, Mar 18, 2020 at 5:08 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Wed, Mar 18, 2020 at 2:05 PM Nathan Chancellor
> <natechancellor@...il.com> wrote:
> >
> > clang warns:
> >
> > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:6: warning: variable 'shadow'
> > is used uninitialized whenever 'if' condition is
> > false [-Wsometimes-uninitialized]
> >         if (offset == grbm_cntl || offset == grbm_idx)
> >             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:757:6: note: uninitialized use
> > occurs here
> >         if (shadow) {
> >             ^~~~~~
> > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:2: note: remove the 'if' if
> > its condition is always true
> >         if (offset == grbm_cntl || offset == grbm_idx)
> >         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:738:13: note: initialize the
> > variable 'shadow' to silence this warning
> >         bool shadow;
> >                    ^
> >                     = 0
> > 1 warning generated.
> >
> > shadow is only assigned in one condition and used as the condition for
> > another if statement; combine the two if statements and remove shadow
> > to make the code cleaner and resolve this warning.
> >
> > Fixes: 2e0cc4d48b91 ("drm/amdgpu: revise RLCG access path")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/936
> > Suggested-by: Joe Perches <joe@...ches.com>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

Applied.  thanks!

Alex

> > ---
> >
> > v1 -> v2:
> >
> > * Remove shadow altogether, as suggested by Joe Perches.
> > * Add Nick's Reviewed-by, as I assume it still stands.
>
> yep, thanks
>
> >
> >  drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 6 +-----
> >  1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> > index 7bc2486167e7..496b9edca3c3 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> > @@ -735,7 +735,6 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
> >         static void *spare_int;
> >         static uint32_t grbm_cntl;
> >         static uint32_t grbm_idx;
> > -       bool shadow;
> >
> >         scratch_reg0 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG0_BASE_IDX] + mmSCRATCH_REG0)*4;
> >         scratch_reg1 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG1_BASE_IDX] + mmSCRATCH_REG1)*4;
> > @@ -751,10 +750,7 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
> >                 return;
> >         }
> >
> > -       if (offset == grbm_cntl || offset == grbm_idx)
> > -               shadow = true;
> > -
> > -       if (shadow) {
> > +       if (offset == grbm_cntl || offset == grbm_idx) {
> >                 if (offset  == grbm_cntl)
> >                         writel(v, scratch_reg2);
> >                 else if (offset == grbm_idx)
> > --
> > 2.26.0.rc1
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives