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drm/vc4: Fix termination of the initial scan for branch targets. 

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>
This commit is contained in:
Eric Anholt 2016-10-20 16:48:12 -07:00
parent b2cdeb19f1
commit 457e67a728
1 changed files with 8 additions and 11 deletions
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19
drivers/gpu/drm/vc4/vc4_validate_shaders.c
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@ -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;
}