[PATCH v2 3/3] drm/msm: Add a way to override processes comm/cmdline

From: Rob Clark
Date: Thu Mar 17 2022 - 12:51:28 EST


From: Rob Clark <robdclark@xxxxxxxxxxxx>

In the cause of using the GPU via virtgpu, the host side process is
really a sort of proxy, and not terribly interesting from the PoV of
crash/fault logging. Add a way to override these per process so that
we can see the guest process's name.

v2: Handle kmalloc failure, add comment to explain kstrdup returns
NULL if passed NULL [Dan Carpenter]

Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
---
drivers/gpu/drm/msm/adreno/adreno_gpu.c | 43 +++++++++++++++++++++++--
drivers/gpu/drm/msm/msm_gpu.c | 12 +++++--
drivers/gpu/drm/msm/msm_gpu.h | 6 ++++
drivers/gpu/drm/msm/msm_submitqueue.c | 2 ++
include/uapi/drm/msm_drm.h | 2 ++
5 files changed, 60 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index 3d307b34854d..45f2c6084aa7 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -290,11 +290,48 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_file_private *ctx,
int adreno_set_param(struct msm_gpu *gpu, struct msm_file_private *ctx,
uint32_t param, uint64_t value, uint32_t len)
{
- /* No pointer params yet */
- if (len != 0)
- return -EINVAL;
+ switch (param) {
+ case MSM_PARAM_COMM:
+ case MSM_PARAM_CMDLINE:
+ /* kstrdup_quotable_cmdline() limits to PAGE_SIZE, so
+ * that should be a reasonable upper bound
+ */
+ if (len > PAGE_SIZE)
+ return -EINVAL;
+ break;
+ default:
+ if (len != 0)
+ return -EINVAL;
+ }

switch (param) {
+ case MSM_PARAM_COMM:
+ case MSM_PARAM_CMDLINE: {
+ char *str, **paramp;
+
+ str = kmalloc(len + 1, GFP_KERNEL);
+ if (!str)
+ return -ENOMEM;
+
+ if (copy_from_user(str, u64_to_user_ptr(value), len)) {
+ kfree(str);
+ return -EFAULT;
+ }
+
+ /* Ensure string is null terminated: */
+ str[len] = '\0';
+
+ if (param == MSM_PARAM_COMM) {
+ paramp = &ctx->comm;
+ } else {
+ paramp = &ctx->cmdline;
+ }
+
+ kfree(*paramp);
+ *paramp = str;
+
+ return 0;
+ }
case MSM_PARAM_SYSPROF:
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index 4ec62b601adc..747b89aa9d13 100644
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -364,14 +364,22 @@ static void retire_submits(struct msm_gpu *gpu);

static void get_comm_cmdline(struct msm_gem_submit *submit, char **comm, char **cmd)
{
+ struct msm_file_private *ctx = submit->queue->ctx;
struct task_struct *task;

+ /* Note that kstrdup will return NULL if argument is NULL: */
+ *comm = kstrdup(ctx->comm, GFP_KERNEL);
+ *cmd = kstrdup(ctx->cmdline, GFP_KERNEL);
+
task = get_pid_task(submit->pid, PIDTYPE_PID);
if (!task)
return;

- *comm = kstrdup(task->comm, GFP_KERNEL);
- *cmd = kstrdup_quotable_cmdline(task, GFP_KERNEL);
+ if (!*comm)
+ *comm = kstrdup(task->comm, GFP_KERNEL);
+
+ if (!*cmd)
+ *cmd = kstrdup_quotable_cmdline(task, GFP_KERNEL);

put_task_struct(task);
}
diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index c28c2ad9f52e..2c0203fd6ce3 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -355,6 +355,12 @@ struct msm_file_private {
*/
int sysprof;

+ /** comm: Overridden task comm, see MSM_PARAM_COMM */
+ char *comm;
+
+ /** cmdline: Overridden task cmdline, see MSM_PARAM_CMDLINE */
+ char *cmdline;
+
/**
* elapsed:
*
diff --git a/drivers/gpu/drm/msm/msm_submitqueue.c b/drivers/gpu/drm/msm/msm_submitqueue.c
index 79b6ccd6ce64..f486a3cd4e55 100644
--- a/drivers/gpu/drm/msm/msm_submitqueue.c
+++ b/drivers/gpu/drm/msm/msm_submitqueue.c
@@ -61,6 +61,8 @@ void __msm_file_private_destroy(struct kref *kref)
}

msm_gem_address_space_put(ctx->aspace);
+ kfree(ctx->comm);
+ kfree(ctx->cmdline);
kfree(ctx);
}

diff --git a/include/uapi/drm/msm_drm.h b/include/uapi/drm/msm_drm.h
index 0aa1a8cb4e0d..794ad1948497 100644
--- a/include/uapi/drm/msm_drm.h
+++ b/include/uapi/drm/msm_drm.h
@@ -82,6 +82,8 @@ struct drm_msm_timespec {
#define MSM_PARAM_FAULTS 0x09 /* RO */
#define MSM_PARAM_SUSPENDS 0x0a /* RO */
#define MSM_PARAM_SYSPROF 0x0b /* WO: 1 preserves perfcntrs, 2 also disables suspend */
+#define MSM_PARAM_COMM 0x0c /* WO: override for task->comm */
+#define MSM_PARAM_CMDLINE 0x0d /* WO: override for task cmdline */

/* For backwards compat. The original support for preemption was based on
* a single ring per priority level so # of priority levels equals the #
--
2.35.1