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Message-ID: <CADnq5_M+dCHFDoOS3dSTMCTsk7mH=dFSss=u91VwwVuFA=9t6g@mail.gmail.com>
Date: Mon, 15 Feb 2021 13:56:10 -0500
From: Alex Deucher <alexdeucher@...il.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Evan Quan <evan.quan@....com>,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
linux-hardening@...r.kernel.org,
Maling list - DRI developers
<dri-devel@...ts.freedesktop.org>,
amd-gfx list <amd-gfx@...ts.freedesktop.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] drm/amd/pm: Replace one-element array with
flexible-array in struct SISLANDS_SMC_SWSTATE
On Wed, Feb 10, 2021 at 5:40 PM Gustavo A. R. Silva
<gustavoars@...nel.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 “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
>
> Refactor the code according to the use of a flexible-array member in
> struct SISLANDS_SMC_SWSTATE, instead of a one-element array, and use
> the struct_size() helper to calculate the size for the allocation.
>
> Also, this helps with the ongoing efforts to enable -Warray-bounds and
> fix the following warnings:
>
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/si_dpm.c:2448:20: warning: array
> subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’
> {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/si_dpm.c:2449:20: warning: array
> subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’
> {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/si_dpm.c:2450:20: warning: array
> subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’
> {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/si_dpm.c:2451:20: warning: array
> subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’
> {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/si_dpm.c:2452:20: warning: array
> subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’
> {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
> drivers/gpu/drm/amd/amdgpu/../pm/powerplay/si_dpm.c:5570:20: warning: array
> subscript 1 is above array bounds of ‘SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’
> {aka ‘struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL[1]’} [-Warray-bounds]
>
> [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 <lkp@...el.com>
> Link: https://lore.kernel.org/lkml/6023be58.sk66L%2FV4vuSJI5mI%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Applied. Thanks!
Alex
> ---
> drivers/gpu/drm/amd/pm/powerplay/si_dpm.c | 6 ++----
> drivers/gpu/drm/amd/pm/powerplay/sislands_smc.h | 10 +++++-----
> 2 files changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/pm/powerplay/si_dpm.c b/drivers/gpu/drm/amd/pm/powerplay/si_dpm.c
> index afa1711c9620..62291358fb1c 100644
> --- a/drivers/gpu/drm/amd/pm/powerplay/si_dpm.c
> +++ b/drivers/gpu/drm/amd/pm/powerplay/si_dpm.c
> @@ -5715,11 +5715,9 @@ static int si_upload_sw_state(struct amdgpu_device *adev,
> int ret;
> u32 address = si_pi->state_table_start +
> offsetof(SISLANDS_SMC_STATETABLE, driverState);
> - u32 state_size = sizeof(SISLANDS_SMC_SWSTATE) +
> - ((new_state->performance_level_count - 1) *
> - sizeof(SISLANDS_SMC_HW_PERFORMANCE_LEVEL));
> SISLANDS_SMC_SWSTATE *smc_state = &si_pi->smc_statetable.driverState;
> -
> + size_t state_size = struct_size(smc_state, levels,
> + new_state->performance_level_count);
> memset(smc_state, 0, state_size);
>
> ret = si_convert_power_state_to_smc(adev, amdgpu_new_state, smc_state);
> diff --git a/drivers/gpu/drm/amd/pm/powerplay/sislands_smc.h b/drivers/gpu/drm/amd/pm/powerplay/sislands_smc.h
> index d2930eceaf3c..0f7554052c90 100644
> --- a/drivers/gpu/drm/amd/pm/powerplay/sislands_smc.h
> +++ b/drivers/gpu/drm/amd/pm/powerplay/sislands_smc.h
> @@ -182,11 +182,11 @@ typedef struct SISLANDS_SMC_HW_PERFORMANCE_LEVEL SISLANDS_SMC_HW_PERFORMANCE_LEV
>
> struct SISLANDS_SMC_SWSTATE
> {
> - uint8_t flags;
> - uint8_t levelCount;
> - uint8_t padding2;
> - uint8_t padding3;
> - SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[1];
> + uint8_t flags;
> + uint8_t levelCount;
> + uint8_t padding2;
> + uint8_t padding3;
> + SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
> };
>
> typedef struct SISLANDS_SMC_SWSTATE SISLANDS_SMC_SWSTATE;
> --
> 2.27.0
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
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