[PATCH] drm/panfrost: Add PANFROST_BO_NO{READ,WRITE} flags

[Boris Brezillon]

So we can create GPU mappings without R/W permissions. Particularly
useful to debug corruptions caused by out-of-bound writes.

Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
---
 drivers/gpu/drm/panfrost/panfrost_drv.c | 14 ++++++++++++--
 drivers/gpu/drm/panfrost/panfrost_gem.c |  2 ++
 drivers/gpu/drm/panfrost/panfrost_gem.h |  2 ++
 drivers/gpu/drm/panfrost/panfrost_mmu.c |  8 +++++++-
 include/uapi/drm/panfrost_drm.h         |  2 ++
 5 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 82ad9a67f251..40e4a4db3ab1 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -75,6 +75,10 @@ static int panfrost_ioctl_get_param(struct drm_device *ddev, void *data, struct
 	return 0;
 }
 
+#define PANFROST_BO_FLAGS \
+	(PANFROST_BO_NOEXEC | PANFROST_BO_HEAP | \
+	 PANFROST_BO_NOREAD | PANFROST_BO_NOWRITE)
+
 static int panfrost_ioctl_create_bo(struct drm_device *dev, void *data,
 		struct drm_file *file)
 {
@@ -84,7 +88,7 @@ static int panfrost_ioctl_create_bo(struct drm_device *dev, void *data,
 	struct panfrost_gem_mapping *mapping;
 
 	if (!args->size || args->pad ||
-	    (args->flags & ~(PANFROST_BO_NOEXEC | PANFROST_BO_HEAP)))
+	    (args->flags & ~PANFROST_BO_FLAGS))
 		return -EINVAL;
 
 	/* Heaps should never be executable */
@@ -92,6 +96,11 @@ static int panfrost_ioctl_create_bo(struct drm_device *dev, void *data,
 	    !(args->flags & PANFROST_BO_NOEXEC))
 		return -EINVAL;
 
+	/* Executable implies readable */
+	if ((args->flags & PANFROST_BO_NOREAD) &&
+	    !(args->flags & PANFROST_BO_NOEXEC))
+		return -EINVAL;
+
 	bo = panfrost_gem_create_with_handle(file, dev, args->size, args->flags,
 					     &args->handle);
 	if (IS_ERR(bo))
@@ -520,6 +529,7 @@ DEFINE_DRM_GEM_FOPS(panfrost_drm_driver_fops);
  * - 1.0 - initial interface
  * - 1.1 - adds HEAP and NOEXEC flags for CREATE_BO
  * - 1.2 - adds AFBC_FEATURES query
+ * - 1.3 - adds PANFROST_BO_NO{READ,WRITE} flags
  */
 static const struct drm_driver panfrost_drm_driver = {
 	.driver_features	= DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ,
@@ -532,7 +542,7 @@ static const struct drm_driver panfrost_drm_driver = {
 	.desc			= "panfrost DRM",
 	.date			= "20180908",
 	.major			= 1,
-	.minor			= 2,
+	.minor			= 3,
 
 	.gem_create_object	= panfrost_gem_create_object,
 	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd,
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index 23377481f4e3..d6c1bb1445f2 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -251,6 +251,8 @@ panfrost_gem_create_with_handle(struct drm_file *file_priv,
 
 	bo = to_panfrost_bo(&shmem->base);
 	bo->noexec = !!(flags & PANFROST_BO_NOEXEC);
+	bo->noread = !!(flags & PANFROST_BO_NOREAD);
+	bo->nowrite = !!(flags & PANFROST_BO_NOWRITE);
 	bo->is_heap = !!(flags & PANFROST_BO_HEAP);
 
 	/*
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
index 8088d5fd8480..6246b5fef446 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.h
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
@@ -37,6 +37,8 @@ struct panfrost_gem_object {
 	atomic_t gpu_usecount;
 
 	bool noexec		:1;
+	bool noread		:1;
+	bool nowrite		:1;
 	bool is_heap		:1;
 };
 
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index f51d3f791a17..6a5c9d94d6f2 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -307,7 +307,7 @@ int panfrost_mmu_map(struct panfrost_gem_mapping *mapping)
 	struct drm_gem_object *obj = &bo->base.base;
 	struct panfrost_device *pfdev = to_panfrost_device(obj->dev);
 	struct sg_table *sgt;
-	int prot = IOMMU_READ | IOMMU_WRITE;
+	int prot = 0;
 
 	if (WARN_ON(mapping->active))
 		return 0;
@@ -315,6 +315,12 @@ int panfrost_mmu_map(struct panfrost_gem_mapping *mapping)
 	if (bo->noexec)
 		prot |= IOMMU_NOEXEC;
 
+	if (!bo->nowrite)
+		prot |= IOMMU_WRITE;
+
+	if (!bo->noread)
+		prot |= IOMMU_READ;
+
 	sgt = drm_gem_shmem_get_pages_sgt(obj);
 	if (WARN_ON(IS_ERR(sgt)))
 		return PTR_ERR(sgt);
diff --git a/include/uapi/drm/panfrost_drm.h b/include/uapi/drm/panfrost_drm.h
index 061e700dd06c..a2de81225125 100644
--- a/include/uapi/drm/panfrost_drm.h
+++ b/include/uapi/drm/panfrost_drm.h
@@ -86,6 +86,8 @@ struct drm_panfrost_wait_bo {
 
 #define PANFROST_BO_NOEXEC	1
 #define PANFROST_BO_HEAP	2
+#define PANFROST_BO_NOREAD	4
+#define PANFROST_BO_NOWRITE	8
 
 /**
  * struct drm_panfrost_create_bo - ioctl argument for creating Panfrost BOs.
-- 
2.31.1