[PATCH v2 3/5] drm/panfrost: Add PANFROST_BO_NO{READ,WRITE} flags

Boris Brezillon
2021-10-01T14:34:43Z

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@collabora.com>
---
drivers/gpu/drm/panfrost/panfrost_drv.c | 11 ++++++++++-
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, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 82ad9a67f251..b29ac942ae2d 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))
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