Re: [PATCH] gpu: drm: use struct_size() in kmalloc()

From: Alex Deucher <alexdeucher@gmail.com>
To: xiaolinkui <xiaolinkui@kylinos.cn>
Cc: "Deucher, Alexander" <alexander.deucher@amd.com>,
	Christian Koenig <christian.koenig@amd.com>,
	Chunming Zhou <David1.Zhou@amd.com>,
	Dave Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	xinhui pan <xinhui.pan@amd.com>, "Quan, Evan" <evan.quan@amd.com>,
	Maling list - DRI developers  <dri-devel@lists.freedesktop.org>,
	amd-gfx list <amd-gfx@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] gpu: drm: use struct_size() in kmalloc()
Date: Mon, 20 May 2019 13:41:00 -0400	[thread overview]
Message-ID: <CADnq5_PE-mvW2zwNeHn6prvTQvh-en9E9F7VE-hCS=a8jJWhAQ@mail.gmail.com> (raw)
In-Reply-To: <1558082760-4915-1-git-send-email-xiaolinkui@kylinos.cn>

On Fri, May 17, 2019 at 8:43 AM xiaolinkui <xiaolinkui@kylinos.cn> wrote:
>
> Use struct_size() helper to keep code simple.
>
> Signed-off-by: xiaolinkui <xiaolinkui@kylinos.cn>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)

This patch results in the following build error:
  DESCEND  objtool
  CALL    scripts/checksyscalls.sh
  CHK     include/generated/compile.h
  CC [M]  drivers/gpu/drm/amd/amdgpu/amdgpu_ras.o
In file included from ./include/linux/kernel.h:15,
                 from ./include/linux/list.h:9,
                 from ./include/linux/wait.h:7,
                 from ./include/linux/wait_bit.h:8,
                 from ./include/linux/fs.h:6,
                 from ./include/linux/debugfs.h:15,
                 from drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c:24:
drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c: In function ‘amdgpu_ras_init’:
./include/linux/build_bug.h:16:45: error: negative width in bit-field
‘<anonymous>’
 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); }))
                                             ^
./include/linux/compiler.h:349:28: note: in expansion of macro
‘BUILD_BUG_ON_ZERO’
 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
                            ^~~~~~~~~~~~~~~~~
./include/linux/overflow.h:306:30: note: in expansion of macro ‘__must_be_array’
       sizeof(*(p)->member) + __must_be_array((p)->member),\
                              ^~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c:1556:16: note: in expansion of
macro ‘struct_size’
  con = kmalloc(struct_size(con, objs, AMDGPU_RAS_BLOCK_COUNT),
                ^~~~~~~~~~~
make[4]: *** [scripts/Makefile.build:276:
drivers/gpu/drm/amd/amdgpu/amdgpu_ras.o] Error 1
make[4]: *** Waiting for unfinished jobs....
make[3]: *** [scripts/Makefile.build:492: drivers/gpu/drm/amd/amdgpu] Error 2
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [scripts/Makefile.build:492: drivers/gpu/drm] Error 2
make[1]: *** [scripts/Makefile.build:492: drivers/gpu] Error 2
make: *** [Makefile:1042: drivers] Error 2

Alex


>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> index 22bd21e..4717a64 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> @@ -1375,8 +1375,7 @@ int amdgpu_ras_init(struct amdgpu_device *adev)
>         if (con)
>                 return 0;
>
> -       con = kmalloc(sizeof(struct amdgpu_ras) +
> -                       sizeof(struct ras_manager) * AMDGPU_RAS_BLOCK_COUNT,
> +       con = kmalloc(struct_size(con, objs, AMDGPU_RAS_BLOCK_COUNT),
>                         GFP_KERNEL|__GFP_ZERO);
>         if (!con)
>                 return -ENOMEM;
> --
> 2.7.4
>
>
>
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