Re: [PATCH v2] drm/ioctl: Add a ioctl to label GEM objects

On Thu, Sep 19, 2019 at 02:53:21PM +0200, Rohan Garg wrote:

DRM_IOCTL_BO_SET_LABEL lets you label GEM objects, making it easier to debug issues in userspace applications.

Changes in v2:

• Hoist the IOCTL up into the drm_driver framework

Signed-off-by: Rohan Garg rohan.garg@collabora.com

drivers/gpu/drm/drm_gem.c | 64 ++++++++++++++++++++++++++++++++++ drivers/gpu/drm/drm_internal.h | 4 +++ drivers/gpu/drm/drm_ioctl.c | 1 + include/drm/drm_drv.h | 18 ++++++++++ include/drm/drm_gem.h | 7 ++++ include/uapi/drm/drm.h | 20 +++++++++++ 6 files changed, 114 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 6854f5867d51..785ac561619a 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -941,6 +941,65 @@ drm_gem_release(struct drm_device *dev, struct drm_file *file_private) idr_destroy(&file_private->object_idr); }

+int drm_bo_set_label_ioctl(struct drm_device *dev, void *data,

•        struct drm_file *file_priv)
  

Perhaps call this drm_gem_set_label_ioctl() so that it's consistent with the other GEM related IOCTLs?

+{

• struct drm_label_object *args = data;

Similarly, perhaps make this struct drm_gem_set_label for consistency.

• if (!args->len || !args->name)

• return -EINVAL;
  

• if (dev->driver->label)

• return dev->driver->label(dev, args, file_priv);
  

• return -EOPNOTSUPP;

+}

+/**

• • drm_gem_label - label a given GEM object
• • @dev: drm_device for the associated GEM object
• • @data: drm_label_bo struct with a label, label length and any relevant flags
• • @file_private: drm file-private structure to clean up
• */

+int drm_gem_set_label(struct drm_device *dev, struct drm_label_object *args, struct drm_file *file_priv)

Function name doesn't match the kerneldoc.

+{

• struct drm_gem_object *gem_obj;
• int err = 0;
• char *label;
• if (args->len > 0)

• label = strndup_user(u64_to_user_ptr(args->name), args->len);
  

• gem_obj = drm_gem_object_lookup(file_priv, args->handle);
• if (!gem_obj) {

• DRM_ERROR("Failed to look up GEM BO %d\n", args->handle);
  

People could abuse this to spam the system logs with these error messages. Better make this DRM_DEBUG() or leave it out completely.

• err = -ENOENT;
  

• goto err;
  

I think you're leaking the label string here.

• }
• if ((args->len == 0 && args->name == NULL) || gem_obj->label) {

• kfree(gem_obj->label);
  

• gem_obj->label = NULL;
  

• }
• gem_obj->label = label;
• drm_gem_object_put_unlocked(gem_obj);
• if (IS_ERR(gem_obj->label)) {

• err = PTR_ERR(gem_obj->label);
  

• goto err;
  

• }

Why don't you check for this earlier? That seems suboptimal because now you've got some error value in gem_obj->label that you're going to have to special case at every step of the way.

+err:

• if (err != 0)

• args->flags = err;
  

Why the flags? We typically just return the error...

• return err;

... like here.

+}

Do we want to export this so that drivers can use it?

/**

• drm_gem_object_release - release GEM buffer object resources
• @obj: GEM buffer object

@@ -958,6 +1017,11 @@ drm_gem_object_release(struct drm_gem_object *obj)

dma_resv_fini(&obj->_resv); drm_gem_free_mmap_offset(obj);

• if (obj->label) {

• kfree(obj->label);
  

• obj->label = NULL;
  

• }

} EXPORT_SYMBOL(drm_gem_object_release);

diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h index 51a2055c8f18..8259622f9ab6 100644 --- a/drivers/gpu/drm/drm_internal.h +++ b/drivers/gpu/drm/drm_internal.h @@ -137,6 +137,10 @@ int drm_gem_pin(struct drm_gem_object *obj); void drm_gem_unpin(struct drm_gem_object *obj); void *drm_gem_vmap(struct drm_gem_object *obj); void drm_gem_vunmap(struct drm_gem_object *obj, void *vaddr); +int drm_bo_set_label_ioctl(struct drm_device *dev, void *data,

• 	struct drm_file *file_priv);
  

+int drm_gem_set_label(struct drm_device *dev, struct drm_label_object *args,

• 	struct drm_file *file_priv);
  

This one seems to be unused now.

/* drm_debugfs.c drm_debugfs_crc.c */ #if defined(CONFIG_DEBUG_FS) diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index f675a3bb2c88..079d1422f9c5 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -709,6 +709,7 @@ static const struct drm_ioctl_desc drm_ioctls[] = { DRM_IOCTL_DEF(DRM_IOCTL_MODE_LIST_LESSEES, drm_mode_list_lessees_ioctl, DRM_MASTER), DRM_IOCTL_DEF(DRM_IOCTL_MODE_GET_LEASE, drm_mode_get_lease_ioctl, DRM_MASTER), DRM_IOCTL_DEF(DRM_IOCTL_MODE_REVOKE_LEASE, drm_mode_revoke_lease_ioctl, DRM_MASTER),

• DRM_IOCTL_DEF(DRM_IOCTL_BO_SET_LABEL, drm_bo_set_label_ioctl, DRM_RENDER_ALLOW),

};

#define DRM_CORE_IOCTL_COUNT ARRAY_SIZE( drm_ioctls ) diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index 8976afe48c1c..f736ba1f42a6 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -715,6 +715,24 @@ struct drm_driver { struct drm_device *dev, uint32_t handle);

• /**

• * @label:
  

• *
  

• * This label's a buffer object.
  

• *
  

• * Called by the user via ioctl.
  

• *
  

• * The default implementation is drm_gem_label(). GEM based drivers
  

• * must not overwrite this.
  

Spurious blank line.

• * Returns:
  

• *
  

• * Zero on success, negative errno on failure.
  

• */
  

• int (*label)(struct drm_device *dev, struct drm_label_object *args,

• 		struct drm_file *file_priv);
  

If I understand correctly, you use this so that non-GEM drivers can use this IOCTL to label their non-GEM objects. Do you think that's really useful? I mean they've already got quite a bit of special code to deal with their objects, so singling out this IOCTL seems a bit odd.

Then again, I guess it doesn't really hurt since GEM-based drivers will always use the standard implementation.

• /**
  • @gem_vm_ops: Driver private ops for this object

diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h index 6aaba14f5972..f801c054e972 100644 --- a/include/drm/drm_gem.h +++ b/include/drm/drm_gem.h @@ -237,6 +237,13 @@ struct drm_gem_object { */ int name;

• /**

• * @label:
  

• *
  

• * Label for this object, should be a human readable string.
  

• */
  

• char *label;
• /**
  • @dma_buf:

diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h index 8a5b2f8f8eb9..23b507f5c571 100644 --- a/include/uapi/drm/drm.h +++ b/include/uapi/drm/drm.h @@ -626,6 +626,25 @@ struct drm_gem_open { __u64 size; };

+/** struct drm_label_object - ioctl argument for labelling BOs.

• • This label's a BO with a userspace label
• */

+struct drm_label_object {

• /** Handle for the object being labelled. */
• __u32 handle;
• /** Label and label length.

• *  length includes the trailing NULL.
  

Nit: I think you mean "trailing NUL". Also, the parameter is called len below, so the comment here should match.

Thierry

• */
  

• __u32 len;
• __u64 name;
• /** Flags */
• int flags;

+};

#define DRM_CAP_DUMB_BUFFER 0x1 #define DRM_CAP_VBLANK_HIGH_CRTC 0x2 #define DRM_CAP_DUMB_PREFERRED_DEPTH 0x3 @@ -946,6 +965,7 @@ extern "C" { #define DRM_IOCTL_SYNCOBJ_QUERY DRM_IOWR(0xCB, struct drm_syncobj_timeline_array) #define DRM_IOCTL_SYNCOBJ_TRANSFER DRM_IOWR(0xCC, struct drm_syncobj_transfer) #define DRM_IOCTL_SYNCOBJ_TIMELINE_SIGNAL DRM_IOWR(0xCD, struct drm_syncobj_timeline_array) +#define DRM_IOCTL_BO_SET_LABEL DRM_IOWR(0xCE, struct drm_label_object)

/**

• Device specific ioctls should only be in their respective headers

-- 2.17.1

---

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