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

Boris Brezillon
2021-10-01T14:36:26Z

On Fri, 1 Oct 2021 16:34:25 +0200
Boris Brezillon <boris.brezillon@collabora.com> wrote:

> 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>

Oops, forgot:

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.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.