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Subject[PATCH 3/7] drm/vc4: Add a bitmap of branch targets during shader validation.
Date
This isn't used yet, it's just a first step toward loop validation.
During the main parsing of instructions, we need to know when we hit a
new basic block so that we can reset validated state.

Signed-off-by: Eric Anholt <eric@anholt.net>
---
drivers/gpu/drm/vc4/vc4_qpu_defines.h | 12 +++
drivers/gpu/drm/vc4/vc4_validate_shaders.c | 114 ++++++++++++++++++++++++++++-
2 files changed, 124 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_qpu_defines.h b/drivers/gpu/drm/vc4/vc4_qpu_defines.h
index d5c2f3c85ebb..82ef0e525d55 100644
--- a/drivers/gpu/drm/vc4/vc4_qpu_defines.h
+++ b/drivers/gpu/drm/vc4/vc4_qpu_defines.h
@@ -230,6 +230,15 @@ enum qpu_unpack_r4 {
#define QPU_COND_MUL_SHIFT 46
#define QPU_COND_MUL_MASK QPU_MASK(48, 46)

+#define QPU_BRANCH_COND_SHIFT 52
+#define QPU_BRANCH_COND_MASK QPU_MASK(55, 52)
+
+#define QPU_BRANCH_REL ((uint64_t)1 << 51)
+#define QPU_BRANCH_REG ((uint64_t)1 << 50)
+
+#define QPU_BRANCH_RADDR_A_SHIFT 45
+#define QPU_BRANCH_RADDR_A_MASK QPU_MASK(49, 45)
+
#define QPU_SF ((uint64_t)1 << 45)

#define QPU_WADDR_ADD_SHIFT 38
@@ -261,4 +270,7 @@ enum qpu_unpack_r4 {
#define QPU_OP_ADD_SHIFT 24
#define QPU_OP_ADD_MASK QPU_MASK(28, 24)

+#define QPU_BRANCH_TARGET_SHIFT 0
+#define QPU_BRANCH_TARGET_MASK QPU_MASK(31, 0)
+
#endif /* VC4_QPU_DEFINES_H */
diff --git a/drivers/gpu/drm/vc4/vc4_validate_shaders.c b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
index 771d904653f2..bcf3c31b2765 100644
--- a/drivers/gpu/drm/vc4/vc4_validate_shaders.c
+++ b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
@@ -59,6 +59,13 @@ struct vc4_shader_validation_state {
*/
uint32_t live_min_clamp_offsets[32 + 32 + 4];
bool live_max_clamp_regs[32 + 32 + 4];
+
+ /* Bitfield of which IPs are used as branch targets.
+ *
+ * Used for validation that the uniform stream is updated at the right
+ * points and clearing the texturing/clamping state.
+ */
+ unsigned long *branch_targets;
};

static uint32_t
@@ -418,13 +425,104 @@ check_instruction_reads(uint64_t inst,
return true;
}

+/* Make sure that all branches are absolute and point within the shader, and
+ * note their targets for later.
+ */
+static bool
+vc4_validate_branches(struct vc4_shader_validation_state *validation_state)
+{
+ uint32_t max_branch_target = 0;
+ bool found_shader_end = false;
+ int ip;
+ int shader_end_ip = 0;
+ int last_branch = -2;
+
+ for (ip = 0; ip < validation_state->max_ip; ip++) {
+ uint64_t inst = validation_state->shader[ip];
+ int32_t branch_imm = QPU_GET_FIELD(inst, QPU_BRANCH_TARGET);
+ uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);
+ uint32_t after_delay_ip = ip + 4;
+ uint32_t branch_target_ip;
+
+ if (sig == QPU_SIG_PROG_END) {
+ shader_end_ip = ip;
+ found_shader_end = true;
+ continue;
+ }
+
+ if (sig != QPU_SIG_BRANCH)
+ continue;
+
+ if (ip - last_branch < 4) {
+ DRM_ERROR("Branch at %d during delay slots\n", ip);
+ return false;
+ }
+ last_branch = ip;
+
+ if (inst & QPU_BRANCH_REG) {
+ DRM_ERROR("branching from register relative "
+ "not supported\n");
+ return false;
+ }
+
+ if (!(inst & QPU_BRANCH_REL)) {
+ DRM_ERROR("relative branching required\n");
+ return false;
+ }
+
+ /* The actual branch target is the instruction after the delay
+ * slots, plus whatever byte offset is in the low 32 bits of
+ * the instruction. Make sure we're not branching beyond the
+ * end of the shader object.
+ */
+ if (branch_imm % sizeof(inst) != 0) {
+ DRM_ERROR("branch target not aligned\n");
+ return false;
+ };
+
+ branch_target_ip = after_delay_ip + (branch_imm >> 3);
+ if (branch_target_ip >= validation_state->max_ip) {
+ DRM_ERROR("Branch at %d outside of shader (ip %d/%d)\n",
+ ip, branch_target_ip,
+ validation_state->max_ip);
+ return false;
+ }
+ set_bit(branch_target_ip, validation_state->branch_targets);
+
+ /* Make sure that the non-branching path is also not outside
+ * the shader.
+ */
+ if (after_delay_ip >= validation_state->max_ip) {
+ DRM_ERROR("Branch at %d continues past shader end "
+ "(%d/%d)\n",
+ ip, after_delay_ip, validation_state->max_ip);
+ return false;
+ }
+ set_bit(after_delay_ip, validation_state->branch_targets);
+ max_branch_target = max(max_branch_target, after_delay_ip);
+
+ /* There are two delay slots after program end is signaled
+ * that are still executed, then we're finished.
+ */
+ if (found_shader_end && ip == shader_end_ip + 2)
+ break;
+ }
+
+ if (max_branch_target > shader_end_ip) {
+ DRM_ERROR("Branch landed after QPU_SIG_PROG_END");
+ return false;
+ }
+
+ return true;
+}
+
struct vc4_validated_shader_info *
vc4_validate_shader(struct drm_gem_cma_object *shader_obj)
{
bool found_shader_end = false;
int shader_end_ip = 0;
uint32_t ip;
- struct vc4_validated_shader_info *validated_shader;
+ struct vc4_validated_shader_info *validated_shader = NULL;
struct vc4_shader_validation_state validation_state;
int i;

@@ -437,9 +535,18 @@ vc4_validate_shader(struct drm_gem_cma_object *shader_obj)
for (i = 0; i < ARRAY_SIZE(validation_state.live_min_clamp_offsets); i++)
validation_state.live_min_clamp_offsets[i] = ~0;

+ validation_state.branch_targets =
+ kcalloc(BITS_TO_LONGS(validation_state.max_ip),
+ sizeof(unsigned long), GFP_KERNEL);
+ if (!validation_state.branch_targets)
+ goto fail;
+
validated_shader = kcalloc(1, sizeof(*validated_shader), GFP_KERNEL);
if (!validated_shader)
- return NULL;
+ goto fail;
+
+ if (!vc4_validate_branches(&validation_state))
+ goto fail;

for (ip = 0; ip < validation_state.max_ip; ip++) {
uint64_t inst = validation_state.shader[ip];
@@ -508,9 +615,12 @@ vc4_validate_shader(struct drm_gem_cma_object *shader_obj)
(validated_shader->uniforms_size +
4 * validated_shader->num_texture_samples);

+ kfree(validation_state.branch_targets);
+
return validated_shader;

fail:
+ kfree(validation_state.branch_targets);
if (validated_shader) {
kfree(validated_shader->texture_samples);
kfree(validated_shader);
--
2.8.1
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