2021-02-10 23:29:51

by Gustavo A. R. Silva

Subject: [PATCH][next] drm/amd/pm: Replace one-element array with flexible-array in struct _ATOM_Vega10_GFXCLK_Dependency_Table

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 “flexible array members”[1] for these cases. 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 function ‘vega10_get_pp_table_entry_callback_func’:
drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:3113:30: warning: array subscript 4 is above array bounds of ‘ATOM_Vega10_GFXCLK_Dependency_Record[1]’ {aka ‘struct _ATOM_Vega10_GFXCLK_Dependency_Record[1]’} [-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-length-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 <[email protected]>
Link: https://lore.kernel.org/lkml/6023ff3d.WY3sSCkGRQPdPlVo%[email protected]/
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
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/drivers/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; /* Number of entries. */
- ATOM_Vega10_GFXCLK_Dependency_Record entries[1]; /* Dynamically allocate entries. */
+ UCHAR ucRevId;
+ UCHAR ucNumEntries; /* Number of entries. */
+ ATOM_Vega10_GFXCLK_Dependency_Record entries[]; /* Dynamically allocate entries. */
} ATOM_Vega10_GFXCLK_Dependency_Table;

typedef struct _ATOM_Vega10_MCLK_Dependency_Table {
--
2.27.0

2021-02-15 19:00:12

by Alex Deucher

Subject: Re: [PATCH][next] drm/amd/pm: Replace one-element array with flexible-array in struct _ATOM_Vega10_GFXCLK_Dependency_Table

On Wed, Feb 10, 2021 at 6:36 PM Gustavo A. R. Silva
<[email protected]> 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 “flexible array members”[1] for these cases. 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 function ‘vega10_get_pp_table_entry_callback_func’:
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/vega10_hwmgr.c:3113:30: warning: array subscript 4 is above array bounds of ‘ATOM_Vega10_GFXCLK_Dependency_Record[1]’ {aka ‘struct _ATOM_Vega10_GFXCLK_Dependency_Record[1]’} [-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-length-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 <[email protected]>
> Link: https://lore.kernel.org/lkml/6023ff3d.WY3sSCkGRQPdPlVo%[email protected]/
> Signed-off-by: Gustavo A. R. Silva <[email protected]>

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/drivers/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; /* Number of entries. */
> - ATOM_Vega10_GFXCLK_Dependency_Record entries[1]; /* Dynamically allocate entries. */
> + UCHAR ucRevId;
> + UCHAR ucNumEntries; /* Number of entries. */
> + ATOM_Vega10_GFXCLK_Dependency_Record entries[]; /* Dynamically allocate entries. */
> } ATOM_Vega10_GFXCLK_Dependency_Table;
>
> typedef struct _ATOM_Vega10_MCLK_Dependency_Table {
> --
> 2.27.0
>
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