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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Mon, 15 Feb 2021 13:56:58 -0500
Message-ID: <CADnq5_MSZJYLRJ-A8jAzUWAaK-7N46wj4BQk=FWxrBkDgbojbg@mail.gmail.com>
Subject: Re: [PATCH][next] drm/amd/pm: Replace one-element array with
 flexible-array in struct _ATOM_Vega10_GFXCLK_Dependency_Table
To:     "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc:     Evan Quan <evan.quan@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        linux-hardening@vger.kernel.org,
        Maling list - DRI developers 
        <dri-devel@lists.freedesktop.org>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Feb 10, 2021 at 6:36 PM Gustavo A. R. Silva
<gustavoars@kernel.org> wrote:
>
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use =E2=80=9Cflexible array members=E2=80=9D[1] for these c=
ases. The older
> style of one-element or zero-length arrays should no longer be used[2].
>
> Use flexible-array member in struct _ATOM_Vega10_GFXCLK_Dependency_Table,
> instead of one-element array.
>
> Also, this helps with the ongoing efforts to enable -Warray-bounds and
> fix the following warning:
>
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c: In funct=
ion =E2=80=98vega10_get_pp_table_entry_callback_func=E2=80=99:
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:3113:30: =
warning: array subscript 4 is above array bounds of =E2=80=98ATOM_Vega10_GF=
XCLK_Dependency_Record[1]=E2=80=99 {aka =E2=80=98struct _ATOM_Vega10_GFXCLK=
_Dependency_Record[1]=E2=80=99} [-Warray-bounds]
>  3113 |     gfxclk_dep_table->entries[4].ulClk;
>       |     ~~~~~~~~~~~~~~~~~~~~~~~~~^~~
>
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-len=
gth-and-one-element-arrays
>
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/109
> Build-tested-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/lkml/6023ff3d.WY3sSCkGRQPdPlVo%25lkp@intel.=
com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Applied.  Thanks!

Alex


> ---
>  drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_pptable.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_pptable.h b/dr=
ivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_pptable.h
> index c934e9612c1b..9c479bd9a786 100644
> --- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_pptable.h
> +++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_pptable.h
> @@ -161,9 +161,9 @@ typedef struct _ATOM_Vega10_MCLK_Dependency_Record {
>  } ATOM_Vega10_MCLK_Dependency_Record;
>
>  typedef struct _ATOM_Vega10_GFXCLK_Dependency_Table {
> -    UCHAR ucRevId;
> -    UCHAR ucNumEntries;                                         /* Numbe=
r of entries. */
> -    ATOM_Vega10_GFXCLK_Dependency_Record entries[1];            /* Dynam=
ically allocate entries. */
> +       UCHAR ucRevId;
> +       UCHAR ucNumEntries;                                     /* Number=
 of entries. */
> +       ATOM_Vega10_GFXCLK_Dependency_Record entries[];         /* Dynami=
cally allocate entries. */
>  } ATOM_Vega10_GFXCLK_Dependency_Table;
>
>  typedef struct _ATOM_Vega10_MCLK_Dependency_Table {
> --
> 2.27.0
>
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