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

[Boris Brezillon <boris.brezillon@collabora.com>]

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.

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