[Intel-gfx] [RFC 07/22] drm/i915: Add support for rejecting commands during parsing

[bradley.d.volkin at intel.com]

From: Brad Volkin <bradley.d.volkin at intel.com>

Certain commands are always disallowed from userspace. This adds
the ability for the command parser to detect such commands and
reject batch buffers containing them.

OTC-Tracker: AXIA-4631
Change-Id: I000b0df4d441ec80b607a50d35e83418cdfd38b3
Signed-off-by: Brad Volkin <bradley.d.volkin at intel.com>
---
 drivers/gpu/drm/i915/i915_cmd_parser.c | 6 ++++++
 drivers/gpu/drm/i915/i915_drv.h        | 6 ++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index b01628e..c64f640 100644
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -368,6 +368,12 @@ int i915_parse_cmds(struct intel_ring_buffer *ring,
 			break;
 		}
 
+		if (desc->flags & CMD_DESC_REJECT) {
+			DRM_DEBUG_DRIVER("CMD: Rejected command: 0x%08X\n", *cmd);
+			ret = -EINVAL;
+			break;
+		}
+
 		cmd += length;
 	}
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 81ef047..6ace856 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1743,10 +1743,12 @@ struct drm_i915_cmd_descriptor {
 	 * CMD_DESC_SKIP: The command is allowed but does not follow the
 	 *                standard length encoding for the opcode range in
 	 *                which it falls
+	 * CMD_DESC_REJECT: The command is never allowed
 	 */
 	u32 flags;
-#define CMD_DESC_FIXED (1<<0)
-#define CMD_DESC_SKIP  (1<<1)
+#define CMD_DESC_FIXED  (1<<0)
+#define CMD_DESC_SKIP   (1<<1)
+#define CMD_DESC_REJECT (1<<2)
 
 	/**
 	 * The command's unique identification bits and the bitmask to get them.
-- 
1.8.4.4