drm/msm: Add a way to override processes comm/cmdline

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@chromium.org>
Link: https://lore.kernel.org/r/20220317165144.222101-4-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>

1 files changed, 40 insertions, 3 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;