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Message-ID: <CADnq5_M3dSMnKQMRv3SVaK6-w5ebJxX6w2-oy8v7+2muw3S3vg@mail.gmail.com>
Date: Fri, 5 Mar 2021 14:10:44 -0500
From: Alex Deucher <alexdeucher@...il.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: 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/radeon/si_dpm: Replace one-element array with
flexible-array in struct SISLANDS_SMC_SWSTATE
Applied. Thanks!
Alex
On Wed, Mar 3, 2021 at 2:05 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 by
> fixing the following warnings:
>
> drivers/gpu/drm/radeon/si_dpm.c: In function ‘si_convert_power_state_to_smc’:
> drivers/gpu/drm/radeon/si_dpm.c:2350:20: 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]
> 2350 | smc_state->levels[i].dpm2.MaxPS = (u8)((SISLANDS_DPM2_MAX_PULSE_SKIP * (max_sclk - min_sclk)) / max_sclk);
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/si_dpm.c:2351:20: 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]
> 2351 | smc_state->levels[i].dpm2.NearTDPDec = SISLANDS_DPM2_NEAR_TDP_DEC;
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/si_dpm.c:2352:20: 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]
> 2352 | smc_state->levels[i].dpm2.AboveSafeInc = SISLANDS_DPM2_ABOVE_SAFE_INC;
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/si_dpm.c:2353:20: 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]
> 2353 | smc_state->levels[i].dpm2.BelowSafeInc = SISLANDS_DPM2_BELOW_SAFE_INC;
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/si_dpm.c:2354:20: 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]
> 2354 | smc_state->levels[i].dpm2.PwrEfficiencyRatio = cpu_to_be16(pwr_efficiency_ratio);
> | ~~~~~~~~~~~~~~~~~^~~
> drivers/gpu/drm/radeon/si_dpm.c:5105:20: 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]
> 5105 | smc_state->levels[i + 1].aT = cpu_to_be32(a_t);
> | ~~~~~~~~~~~~~~~~~^~~~~~~
>
> [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/603f9a8f.aDLrpMFzzSApzVYQ%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
> drivers/gpu/drm/radeon/si_dpm.c | 5 ++---
> drivers/gpu/drm/radeon/sislands_smc.h | 10 +++++-----
> 2 files changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/si_dpm.c b/drivers/gpu/drm/radeon/si_dpm.c
> index 91bfc4762767..918609551804 100644
> --- a/drivers/gpu/drm/radeon/si_dpm.c
> +++ b/drivers/gpu/drm/radeon/si_dpm.c
> @@ -5250,10 +5250,9 @@ static int si_upload_sw_state(struct radeon_device *rdev,
> 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);
>
> diff --git a/drivers/gpu/drm/radeon/sislands_smc.h b/drivers/gpu/drm/radeon/sislands_smc.h
> index 966e3a556011..fbd6589bdab9 100644
> --- a/drivers/gpu/drm/radeon/sislands_smc.h
> +++ b/drivers/gpu/drm/radeon/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
>
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