On 10/6/2021 12:05 PM, Christian König wrote:
Am 06.10.21 um 08:32 schrieb Lazar, Lijo:
On 10/6/2021 11:49 AM, Christian König wrote:
Am 06.10.21 um 06:51 schrieb Lazar, Lijo:
On 10/5/2021 10:15 PM, Christian König wrote:
Am 05.10.21 um 15:49 schrieb Das, Nirmoy:
On 10/5/2021 3:22 PM, Christian König wrote:
Am 05.10.21 um 15:11 schrieb Nirmoy Das:
Debugfs core APIs will throw -EPERM when user disables debugfs
using CONFIG_DEBUG_FS_ALLOW_NONE or with kernel param. We shouldn't
see that as an error. Also validate drm root dentry before creating
amdgpu debugfs files.
Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
index 6611b3c7c149..d786072e918b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
@@ -1617,6 +1617,16 @@ int amdgpu_debugfs_init(struct
amdgpu_device *adev)
struct dentry *ent;
int r, i;
+ if (IS_ERR(root)) {
+ /* When debugfs is disabled we get -EPERM which is not an
+ * error as this is user controllable.
+ */
Well setting primary->debugfs_root to an error code is probably
not a good idea to begin with.
When debugfs is disabled that should most likely be NULL.
If we set primary->debugfs_root to NULL then we need to add bunch
of NULL checks everywhere before creating any debugfs files
because debugfs_create_{file|dir}() with NULL root is still valid.
I am assuming a hypothetical case when debugfs_root dir creation
fails even with debugfs enabled
but further calls are successful. This wont be a problem if we
propagate the error code.
Yeah, but an error code in members is ugly like hell and
potentially causes crashes instead.
I strongly suggest to fix this so that root is NULL when debugfs
isn't available and we add proper checks for that instead.
This shouldn't be done. A NULL is a valid parent for debugfs API. An
invalid parent is always checked like this
if (IS_ERR(parent))
return parent;
Instead of adding redundant work like NULL checks, let the API do
its work and don't break the API contract. For ex: usage of sample
client, you may look at the drm usage; it does the same.
Yeah, but that is horrible API design and should be avoided.
ERR_PTR(), PTR_ERR(), IS_ERR() and similar are supposed to be used as
alternative to signaling errors as return values from functions and
should *never* ever be used to signal errors in pointer members.
One escape route may be - add another export from debugfs like
debugfs_is_valid_node() which adheres to the current logic in debugfs
API and use that in client code. Whenever debugfs changes to a
different logic from IS_ERR, let that be changed.
Well that would then rather be drm_is_debugfs_enabled(), because that we
separate debugfs handling into a drm core and individual drivers is drm
specific.
Had one more look and looks like this will do the job. In other cases,
API usage is allowed.
if (!debugfs_initialized())
return;
Thanks,
Lijo
Christian.
Thanks,
Lijo
Regards,
Christian.
Thanks,
Lijo
Regards,
Christian.
Regards,
Nirmoy
Regards,
Christian.
+ if (PTR_ERR(root) == -EPERM)
+ return 0;
+
+ return PTR_ERR(ent);
+ }
+
ent = debugfs_create_file("amdgpu_preempt_ib", 0600, root,
adev,
&fops_ib_preempt);
if (IS_ERR(ent)) {
