Re: [PATCH] drm/i915: Seal busy-ioctl uABI and prevent leaking of internal ids

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 15/01/16 11:06, Chris Wilson wrote:
> Tvrtko was looking through the execbuffer-ioctl and noticed that the
> uABI was tightly coupled to our internal engine identifiers. Close
> inspection also revealed that we leak those internal engine identifiers
> through the busy-ioctl, and those internal identifiers already do not
> match the user identifiers. Fortuitiously, there is only one user of the
> set of busy rings from the busy-ioctl, and they only wish to choose
> between the RENDER and the BLT engines.
>
> Let's fix the userspace ABI while we still can.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>   drivers/gpu/drm/i915/i915_gem.c         | 18 ++++++++++++++----
>   drivers/gpu/drm/i915/intel_lrc.c        |  5 +++++
>   drivers/gpu/drm/i915/intel_ringbuffer.c |  5 +++++
>   drivers/gpu/drm/i915/intel_ringbuffer.h |  1 +
>   4 files changed, 25 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index bb44bad15403..85797813a3de 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -4328,10 +4328,20 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
>   	if (ret)
>   		goto unref;
>
> -	BUILD_BUG_ON(I915_NUM_RINGS > 16);
> -	args->busy = obj->active << 16;
> -	if (obj->last_write_req)
> -		args->busy |= obj->last_write_req->ring->id;
> +	args->busy = 0;
> +	if (obj->active) {
> +		int i;
> +
> +		for (i = 0; i < I915_NUM_RINGS; i++) {
> +			struct drm_i915_gem_request *req;
> +
> +			req = obj->last_read_req[i];
> +			if (req)
> +				args->busy |= 1 << (16 + req->ring->exec_id);

If I got it right bit 16 was RCS, now will always be clear. And blitter 
was bit 17 and now is 19.

Regards,

Tvrtko

> +		}
> +		if (obj->last_write_req)
> +			args->busy |= obj->last_write_req->ring->exec_id;
> +	}
>
>   unref:
>   	drm_gem_object_unreference(&obj->base);
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index f5d89c845ede..4aa209483237 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -2024,6 +2024,7 @@ static int logical_render_ring_init(struct drm_device *dev)
>
>   	ring->name = "render ring";
>   	ring->id = RCS;
> +	ring->exec_id = I915_EXEC_RENDER;
>   	ring->mmio_base = RENDER_RING_BASE;
>
>   	logical_ring_default_irqs(ring, GEN8_RCS_IRQ_SHIFT);
> @@ -2073,6 +2074,7 @@ static int logical_bsd_ring_init(struct drm_device *dev)
>
>   	ring->name = "bsd ring";
>   	ring->id = VCS;
> +	ring->exec_id = I915_EXEC_BSD;
>   	ring->mmio_base = GEN6_BSD_RING_BASE;
>
>   	logical_ring_default_irqs(ring, GEN8_VCS1_IRQ_SHIFT);
> @@ -2088,6 +2090,7 @@ static int logical_bsd2_ring_init(struct drm_device *dev)
>
>   	ring->name = "bsd2 ring";
>   	ring->id = VCS2;
> +	ring->exec_id = I915_EXEC_BSD;
>   	ring->mmio_base = GEN8_BSD2_RING_BASE;
>
>   	logical_ring_default_irqs(ring, GEN8_VCS2_IRQ_SHIFT);
> @@ -2103,6 +2106,7 @@ static int logical_blt_ring_init(struct drm_device *dev)
>
>   	ring->name = "blitter ring";
>   	ring->id = BCS;
> +	ring->exec_id = I915_EXEC_BLT;
>   	ring->mmio_base = BLT_RING_BASE;
>
>   	logical_ring_default_irqs(ring, GEN8_BCS_IRQ_SHIFT);
> @@ -2118,6 +2122,7 @@ static int logical_vebox_ring_init(struct drm_device *dev)
>
>   	ring->name = "video enhancement ring";
>   	ring->id = VECS;
> +	ring->exec_id = I915_EXEC_VEBOX;
>   	ring->mmio_base = VEBOX_RING_BASE;
>
>   	logical_ring_default_irqs(ring, GEN8_VECS_IRQ_SHIFT);
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 8cd8aabcc3ff..310d151c0db2 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -2680,6 +2680,7 @@ int intel_init_render_ring_buffer(struct drm_device *dev)
>
>   	ring->name = "render ring";
>   	ring->id = RCS;
> +	ring->exec_id = I915_EXEC_RENDER;
>   	ring->mmio_base = RENDER_RING_BASE;
>
>   	if (INTEL_INFO(dev)->gen >= 8) {
> @@ -2828,6 +2829,7 @@ int intel_init_bsd_ring_buffer(struct drm_device *dev)
>
>   	ring->name = "bsd ring";
>   	ring->id = VCS;
> +	ring->exec_id = I915_EXEC_BSD;
>
>   	ring->write_tail = ring_write_tail;
>   	if (INTEL_INFO(dev)->gen >= 6) {
> @@ -2904,6 +2906,7 @@ int intel_init_bsd2_ring_buffer(struct drm_device *dev)
>
>   	ring->name = "bsd2 ring";
>   	ring->id = VCS2;
> +	ring->exec_id = I915_EXEC_BSD;
>
>   	ring->write_tail = ring_write_tail;
>   	ring->mmio_base = GEN8_BSD2_RING_BASE;
> @@ -2934,6 +2937,7 @@ int intel_init_blt_ring_buffer(struct drm_device *dev)
>
>   	ring->name = "blitter ring";
>   	ring->id = BCS;
> +	ring->exec_id = I915_EXEC_BLT;
>
>   	ring->mmio_base = BLT_RING_BASE;
>   	ring->write_tail = ring_write_tail;
> @@ -2991,6 +2995,7 @@ int intel_init_vebox_ring_buffer(struct drm_device *dev)
>
>   	ring->name = "video enhancement ring";
>   	ring->id = VECS;
> +	ring->exec_id = I915_EXEC_VEBOX;
>
>   	ring->mmio_base = VEBOX_RING_BASE;
>   	ring->write_tail = ring_write_tail;
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 7349d9258191..2067f4700caa 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -156,6 +156,7 @@ struct  intel_engine_cs {
>   	} id;
>   #define I915_NUM_RINGS 5
>   #define LAST_USER_RING (VECS + 1)
> +	unsigned int exec_id;
>   	u32		mmio_base;
>   	struct		drm_device *dev;
>   	struct intel_ringbuffer *buffer;
>
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