2023-12-26 17:34:40

by Markus Elfring

[permalink] [raw]
Subject: [PATCH] drm/vc4: Improve exception handling in vc4_validate_shader()

From: Markus Elfring <[email protected]>
Date: Tue, 26 Dec 2023 18:22:54 +0100

Memory releases were triggered during error handling only over
the label “fail”.

1. Return directly after a call of the function “kcalloc” failed
at the beginning.

2. Reduce the data processing at the end to a required kfree() call order
also by adjusting jump targets.

3. Delete an initialisation for the variable “validated_shader”
which became unnecessary with this refactoring.

Signed-off-by: Markus Elfring <[email protected]>
---
drivers/gpu/drm/vc4/vc4_validate_shaders.c | 42 +++++++++++-----------
1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_validate_shaders.c b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
index 9745f8810eca..d76787bb7d51 100644
--- a/drivers/gpu/drm/vc4/vc4_validate_shaders.c
+++ b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
@@ -783,7 +783,7 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
int shader_end_ip = 0;
uint32_t last_thread_switch_ip = -3;
uint32_t ip;
- struct vc4_validated_shader_info *validated_shader = NULL;
+ struct vc4_validated_shader_info *validated_shader;
struct vc4_shader_validation_state validation_state;

if (WARN_ON_ONCE(vc4->is_vc5))
@@ -799,14 +799,14 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
kcalloc(BITS_TO_LONGS(validation_state.max_ip),
sizeof(unsigned long), GFP_KERNEL);
if (!validation_state.branch_targets)
- goto fail;
+ return NULL;

validated_shader = kcalloc(1, sizeof(*validated_shader), GFP_KERNEL);
if (!validated_shader)
- goto fail;
+ goto free_targets;

if (!vc4_validate_branches(&validation_state))
- goto fail;
+ goto free_shader;

for (ip = 0; ip < validation_state.max_ip; ip++) {
uint64_t inst = validation_state.shader[ip];
@@ -815,7 +815,7 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
validation_state.ip = ip;

if (!vc4_handle_branch_target(&validation_state))
- goto fail;
+ goto free_offsets;

if (ip == last_thread_switch_ip + 3) {
/* Reset r0-r3 live clamp data */
@@ -842,12 +842,12 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
if (!check_instruction_writes(validated_shader,
&validation_state)) {
DRM_DEBUG("Bad write at ip %d\n", ip);
- goto fail;
+ goto free_offsets;
}

if (!check_instruction_reads(validated_shader,
&validation_state))
- goto fail;
+ goto free_offsets;

if (sig == QPU_SIG_PROG_END) {
found_shader_end = true;
@@ -861,7 +861,7 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
if (ip < last_thread_switch_ip + 3) {
DRM_DEBUG("Thread switch too soon after "
"last switch at ip %d\n", ip);
- goto fail;
+ goto free_offsets;
}
last_thread_switch_ip = ip;
}
@@ -872,26 +872,26 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
if (!check_instruction_writes(validated_shader,
&validation_state)) {
DRM_DEBUG("Bad LOAD_IMM write at ip %d\n", ip);
- goto fail;
+ goto free_offsets;
}
break;

case QPU_SIG_BRANCH:
if (!check_branch(inst, validated_shader,
&validation_state, ip))
- goto fail;
+ goto free_offsets;

if (ip < last_thread_switch_ip + 3) {
DRM_DEBUG("Branch in thread switch at ip %d",
ip);
- goto fail;
+ goto free_offsets;
}

break;
default:
DRM_DEBUG("Unsupported QPU signal %d at "
"instruction %d\n", sig, ip);
- goto fail;
+ goto free_offsets;
}

/* There are two delay slots after program end is signaled
@@ -905,7 +905,7 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
DRM_DEBUG("shader failed to terminate before "
"shader BO end at %zd\n",
shader_obj->base.size);
- goto fail;
+ goto free_offsets;
}

/* Might corrupt other thread */
@@ -913,7 +913,7 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
validation_state.all_registers_used) {
DRM_DEBUG("Shader uses threading, but uses the upper "
"half of the registers, too\n");
- goto fail;
+ goto free_offsets;
}

/* If we did a backwards branch and we haven't emitted a uniforms
@@ -927,7 +927,7 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)
*/
if (validation_state.needs_uniform_address_for_loop) {
if (!require_uniform_address_uniform(validated_shader))
- goto fail;
+ goto free_offsets;
validated_shader->uniforms_size += 4;
}

@@ -943,12 +943,12 @@ vc4_validate_shader(struct drm_gem_dma_object *shader_obj)

return validated_shader;

-fail:
+free_offsets:
+ kfree(validated_shader->uniform_addr_offsets);
+ kfree(validated_shader->texture_samples);
+free_shader:
+ kfree(validated_shader);
+free_targets:
kfree(validation_state.branch_targets);
- if (validated_shader) {
- kfree(validated_shader->uniform_addr_offsets);
- kfree(validated_shader->texture_samples);
- kfree(validated_shader);
- }
return NULL;
}
--
2.43.0