The loop is scanning until the original max_ip (size of the BO), but we want to not examine any code after the PROG_END's delay slots. There was a block trying to do that, except that we had some early continue statements if the signal wasn't a PROG_END or a BRANCH.
The failure mode would be that a valid shader is rejected because some undefined memory after the PROG_END slots is parsed as a branch and the rest of its setup is illegal. I haven't seen this in the wild, but valgrind was complaining when about this up in the userland simulator mode.
Signed-off-by: Eric Anholt eric@anholt.net --- drivers/gpu/drm/vc4/vc4_validate_shaders.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/vc4/vc4_validate_shaders.c b/drivers/gpu/drm/vc4/vc4_validate_shaders.c index 2543cf5b8b51..917321ce832f 100644 --- a/drivers/gpu/drm/vc4/vc4_validate_shaders.c +++ b/drivers/gpu/drm/vc4/vc4_validate_shaders.c @@ -608,9 +608,7 @@ 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++) { @@ -621,8 +619,13 @@ vc4_validate_branches(struct vc4_shader_validation_state *validation_state) uint32_t branch_target_ip;
if (sig == QPU_SIG_PROG_END) { - shader_end_ip = ip; - found_shader_end = true; + /* There are two delay slots after program end is + * signaled that are still executed, then we're + * finished. validation_state->max_ip is the + * instruction after the last valid instruction in the + * program. + */ + validation_state->max_ip = ip + 3; continue; }
@@ -676,15 +679,9 @@ vc4_validate_branches(struct vc4_shader_validation_state *validation_state) } 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) { + if (max_branch_target > validation_state->max_ip - 3) { DRM_ERROR("Branch landed after QPU_SIG_PROG_END"); return false; }