[Intel-gfx] [RFC 09/22] drm/i915: Add support for rejecting commands via bitmasks

[bradley.d.volkin at intel.com]

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

A variety of checks we want to do amount to verifying that a given
bit or bits are set/clear in a given dword of a command. For now,
allow a small but arbitrary number of bitmasks for each command.

OTC-Tracker: AXIA-4631
Change-Id: Icc77316c243b6e218774c15e2c090cc470d59317
Signed-off-by: Brad Volkin <bradley.d.volkin at intel.com>
---
 drivers/gpu/drm/i915/i915_cmd_parser.c | 22 ++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_drv.h        | 16 ++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index 2dbca01..99d15f3 100644
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -400,6 +400,28 @@ int i915_parse_cmds(struct intel_ring_buffer *ring,
 			}
 		}
 
+		if (desc->flags & CMD_DESC_BITMASK) {
+			int i;
+
+			for (i = 0; i < desc->bits_count; i++) {
+				u32 dword = cmd[desc->bits[i].offset] &
+					desc->bits[i].mask;
+
+				if (dword != desc->bits[i].expected) {
+					DRM_DEBUG_DRIVER("CMD: Rejected command 0x%08X for bitmask 0x%08X (exp=0x%08X act=0x%08X) (ring=%d)\n",
+							 *cmd,
+							 desc->bits[i].mask,
+							 desc->bits[i].expected,
+							 dword, ring->id);
+					ret = -EINVAL;
+					break;
+				}
+			}
+
+			if (ret)
+				break;
+		}
+
 		cmd += length;
 	}
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 83b6031..f31fc68 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1752,6 +1752,7 @@ struct drm_i915_cmd_descriptor {
 #define CMD_DESC_SKIP     (1<<1)
 #define CMD_DESC_REJECT   (1<<2)
 #define CMD_DESC_REGISTER (1<<3)
+#define CMD_DESC_BITMASK  (1<<4)
 
 	/**
 	 * The command's unique identification bits and the bitmask to get them.
@@ -1784,6 +1785,21 @@ struct drm_i915_cmd_descriptor {
 		u32 offset;
 		u32 mask;
 	} reg;
+
+#define MAX_CMD_DESC_BITMASKS 3
+	/**
+	 * Describes command checks where a particular dword is masked and
+	 * compared against an expected value. If the command does not match
+	 * the expected value, the parser rejects it. Only valid if flags has
+	 * the CMD_DESC_BITMASK bit set.
+	 */
+	struct {
+		u32 offset;
+		u32 mask;
+		u32 expected;
+	} bits[MAX_CMD_DESC_BITMASKS];
+	/** Number of valid entries in the bits array */
+	int bits_count;
 };
 
 /**
-- 
1.8.4.4