[PATCH v3 1/6] drm: add DRM_SET_NAME ioctl
Pierre-Eric Pelloux-Prayer
pierre-eric at damsy.net
Mon Sep 23 16:29:14 UTC 2024
Hi Dmitry,
Le 23/09/2024 à 12:28, Dmitry Osipenko a écrit :
> On 9/20/24 12:06, Pierre-Eric Pelloux-Prayer wrote:
>> Giving the opportunity to userspace to associate a free-form
>> name with a drm_file struct is helpful for tracking and debugging.
>>
>> This is similar to the existing DMA_BUF_SET_NAME ioctl.
>>
>> Access to name is protected by a mutex, and the 'clients' debugfs
>> file has been updated to print it.
>>
>> Userspace MR to use this ioctl:
>> https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/1428
>>
>> The string passed by userspace is filtered a bit, to avoid messing
>> output when it's going to be printed (in dmesg, fdinfo, etc):
>> * all chars failing isgraph() are replaced by '-'
>> * if a 0-length string is passed the name is cleared
>>
>> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
>> ---
>> drivers/gpu/drm/drm_debugfs.c | 12 ++++++---
>> drivers/gpu/drm/drm_file.c | 5 ++++
>> drivers/gpu/drm/drm_ioctl.c | 48 +++++++++++++++++++++++++++++++++++
>> include/drm/drm_file.h | 9 +++++++
>> include/uapi/drm/drm.h | 17 +++++++++++++
>> 5 files changed, 87 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
>> index 6b239a24f1df..482e71160544 100644
>> --- a/drivers/gpu/drm/drm_debugfs.c
>> +++ b/drivers/gpu/drm/drm_debugfs.c
>> @@ -78,12 +78,13 @@ static int drm_clients_info(struct seq_file *m, void *data)
>> kuid_t uid;
>>
>> seq_printf(m,
>> - "%20s %5s %3s master a %5s %10s\n",
>> + "%20s %5s %3s master a %5s %10s %20s\n",
>> "command",
>> "tgid",
>> "dev",
>> "uid",
>> - "magic");
>> + "magic",
>> + "name");
>>
>> /* dev->filelist is sorted youngest first, but we want to present
>> * oldest first (i.e. kernel, servers, clients), so walk backwardss.
>> @@ -94,19 +95,22 @@ static int drm_clients_info(struct seq_file *m, void *data)
>> struct task_struct *task;
>> struct pid *pid;
>>
>> + mutex_lock(&priv->name_lock);
>> rcu_read_lock(); /* Locks priv->pid and pid_task()->comm! */
>> pid = rcu_dereference(priv->pid);
>> task = pid_task(pid, PIDTYPE_TGID);
>> uid = task ? __task_cred(task)->euid : GLOBAL_ROOT_UID;
>> - seq_printf(m, "%20s %5d %3d %c %c %5d %10u\n",
>> + seq_printf(m, "%20s %5d %3d %c %c %5d %10u %20s\n",
>> task ? task->comm : "<unknown>",
>> pid_vnr(pid),
>> priv->minor->index,
>> is_current_master ? 'y' : 'n',
>> priv->authenticated ? 'y' : 'n',
>> from_kuid_munged(seq_user_ns(m), uid),
>> - priv->magic);
>> + priv->magic,
>> + priv->name ?: "");
>
> There should be a default name similar to task->comm, like "<undefined>"
> when not set. Perhaps also set name to task->comm by default.
Honestly I don't see much value in printing "<undefined>" or any other default value (+ task->comm
is already printed above).
>
>> rcu_read_unlock();
>> + mutex_unlock(&priv->name_lock);
>> }
>> mutex_unlock(&dev->filelist_mutex);
>> return 0;
>> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
>> index 01fde94fe2a9..e9dd0e90a1f9 100644
>> --- a/drivers/gpu/drm/drm_file.c
>> +++ b/drivers/gpu/drm/drm_file.c
>> @@ -158,6 +158,7 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
>>
>> spin_lock_init(&file->master_lookup_lock);
>> mutex_init(&file->event_read_lock);
>> + mutex_init(&file->name_lock);
>>
>> if (drm_core_check_feature(dev, DRIVER_GEM))
>> drm_gem_open(dev, file);
>> @@ -259,6 +260,10 @@ void drm_file_free(struct drm_file *file)
>> WARN_ON(!list_empty(&file->event_list));
>>
>> put_pid(rcu_access_pointer(file->pid));
>> +
>> + mutex_destroy(&file->name_lock);
>> + kfree(file->name);
>> +
>> kfree(file);
>> }
>>
>> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
>> index 51f39912866f..46dadbd1bb35 100644
>> --- a/drivers/gpu/drm/drm_ioctl.c
>> +++ b/drivers/gpu/drm/drm_ioctl.c
>> @@ -540,6 +540,52 @@ int drm_version(struct drm_device *dev, void *data,
>> return err;
>> }
>>
>> +static int drm_set_name(struct drm_device *dev, void *data,
>> + struct drm_file *file_priv)
>> +{
>> + struct drm_set_name *name = data;
>> + void __user *user_ptr;
>> + char *new_name;
>> + size_t i, len;
>> +
>> + if (name->name_len > DRM_NAME_MAX_LEN)
>> + return -EINVAL;
>> +
>> + user_ptr = u64_to_user_ptr(name->name);
>> +
>> + new_name = memdup_user_nul(user_ptr, name->name_len);
>> + if (IS_ERR(new_name))
>> + return PTR_ERR(new_name);
>> +
>> + len = strlen(new_name);
>
> strnlen
memdup_user_nul returns a NUL-terminated string so I don't see much need for using strnlen.
>
>> + if (len != name->name_len) {
>> + kfree(new_name);
>> + return -EINVAL;
>> + }
>> +
>> + /*
>> + * Filter out control char / spaces / new lines etc in the name
>> + * since it's going to be used in dmesg or fdinfo's output.
>> + */
>> + for (i = 0; i < len; i++) {
>> + if (!isgraph(new_name[i]))
>> + new_name[i] = '-';
>> + }
>> +
>> + mutex_lock(&file_priv->name_lock);
>> + kfree(file_priv->name);
>> + if (len > 0) {
>> + file_priv->name = new_name;
>> + } else {
>> + kfree(new_name);
>> + file_priv->name = NULL;
>> + }
>> + mutex_unlock(&file_priv->name_lock);
>> +
>> + return 0;
>> +}
>> +
>> static int drm_ioctl_permit(u32 flags, struct drm_file *file_priv)
>> {
>> /* ROOT_ONLY is only for CAP_SYS_ADMIN */
>> @@ -610,6 +656,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
>> DRM_IOCTL_DEF(DRM_IOCTL_PRIME_HANDLE_TO_FD, drm_prime_handle_to_fd_ioctl, DRM_RENDER_ALLOW),
>> DRM_IOCTL_DEF(DRM_IOCTL_PRIME_FD_TO_HANDLE, drm_prime_fd_to_handle_ioctl, DRM_RENDER_ALLOW),
>>
>> + DRM_IOCTL_DEF(DRM_IOCTL_SET_NAME, drm_set_name, DRM_RENDER_ALLOW),
>> +
>> DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETPLANERESOURCES, drm_mode_getplane_res, 0),
>> DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETCRTC, drm_mode_getcrtc, 0),
>> DRM_IOCTL_DEF(DRM_IOCTL_MODE_SETCRTC, drm_mode_setcrtc, DRM_MASTER),
>> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
>> index 8c0030c77308..df26eee8f79c 100644
>> --- a/include/drm/drm_file.h
>> +++ b/include/drm/drm_file.h
>> @@ -388,6 +388,15 @@ struct drm_file {
>> * Per-file buffer caches used by the PRIME buffer sharing code.
>> */
>> struct drm_prime_file_private prime;
>> +
>> + /**
>> + * @name:
>> + *
>> + * Userspace-provided name; useful for accounting and debugging.
>> + */
>> + const char *name;
>
> I'd make the "name" string static, i.e. char name[DRM_NAME_MAX_LEN + 1].
> That will prevent pointer deref troubles and no additional MM code
> bloating will be needed.
>
Sure, I can do that if others prefer this way too.
>> + /** @name_lock: Protects @name. */
>> + struct mutex name_lock;
>
> And then this lock isn't strictly needed anymore and can be removed if
> "name" string is static.
The locking also prevents concurrent modification.
>
>> };
>>
>> /**
>> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
>> index 16122819edfe..f5e92e4f909b 100644
>> --- a/include/uapi/drm/drm.h
>> +++ b/include/uapi/drm/drm.h
>> @@ -1024,6 +1024,13 @@ struct drm_crtc_queue_sequence {
>> __u64 user_data; /* user data passed to event */
>> };
>>
>> +#define DRM_NAME_MAX_LEN 64
>
> What about 63, to align data size to 64 bytes including the NULL byte.
Same as "const char *name;" vs "char name[...]": I don't mind updating the code as long as there's a
consensus.
>
>> +struct drm_set_name {
>
> drm_set_name sounds very generic, IMO. Maybe drm_context_set_name?
drm_client_set_name?
(since other places use client, like drm_clients_info())
>
>> + __u64 name_len;
>> + __u64 name;
>> +};
>> +
>> +
>> #if defined(__cplusplus)
>> }
>> #endif
>> @@ -1288,6 +1295,16 @@ extern "C" {
>> */
>> #define DRM_IOCTL_MODE_CLOSEFB DRM_IOWR(0xD0, struct drm_mode_closefb)
>>
>> +/**
>> + * DRM_IOCTL_SET_NAME - Attach a name to a drm_file
>> + *
>> + * This ioctl is similar to DMA_BUF_SET_NAME - it allows for easier tracking
>> + * and debugging.
>
> Don't refer to DMA_BUF_SET_NAME, explain what DRM_IOCTL_SET_NAME
> actually do. Tell that it sets the DRM context name and that chars are
> filtered.
>
OK, I'll update based on your suggestion.
Thanks,
Pierre-Eric
More information about the dri-devel
mailing list