drm/[radeon|amdgpu]: Replace one-element array and use struct_size() helper (4541ea81) · Commits · 戴 / test

The current codebase makes use of one-element arrays in the following form: struct something { int length; u8 data[1]; }; struct something *instance; instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL); instance->length = size; memcpy(instance->data, source, size); but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. So, replace the one-element array with a flexible-array member. Also, make use of the new struct_size() helper to properly calculate the size of struct SISLANDS_SMC_SWSTATE. This issue was found with the help of Coccinelle and, audited and fixed _manually_. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by:

Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by:

Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/si_dpm.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -5715,10 +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);

drivers/gpu/drm/amd/amdgpu/sislands_smc.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -186,7 +186,7 @@ struct SISLANDS_SMC_SWSTATE
		uint8_t levelCount;
		uint8_t padding2;
		uint8_t padding3;
		SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[1];
		SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
		};

		typedef struct SISLANDS_SMC_SWSTATE SISLANDS_SMC_SWSTATE;

drivers/gpu/drm/radeon/si_dpm.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -5253,10 +5253,9 @@ 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);

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