vc4: Rewrite the kernel ABI to support texture uniform relocation.

This required building a shader parser that would walk the program to find
where the texturing-related uniforms are in the uniforms stream.

Note that as of this commit, a new kernel is required for rendering on
actual VC4 hardware (currently that commit is named "drm/vc4: Introduce
shader validation and better command stream validation.", but is likely to
be squashed as part of an eventual merge of the kernel driver).

1 files changed, 334 insertions, 0 deletions

diff --git a/src/gallium/drivers/vc4/vc4_simulator_validate_shaders.c b/src/gallium/drivers/vc4/vc4_simulator_validate_shaders.c
new file mode 100644
index 00000000000..c02deb406c7
--- /dev/null
+++ b/src/gallium/drivers/vc4/vc4_simulator_validate_shaders.c
@@ -0,0 +1,334 @@
+/*
+ * Copyright © 2014 Broadcom
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+/**
+ * DOC: Shader validator for VC4.
+ *
+ * The VC4 has no IOMMU between it and system memory.  So, a user with access
+ * to execute shaders could escalate privilege by overwriting system memory
+ * (using the VPM write address register in the general-purpose DMA mode) or
+ * reading system memory it shouldn't (reading it as a texture, or uniform
+ * data, or vertex data).
+ *
+ * This walks over a shader starting from some offset within a BO, ensuring
+ * that its accesses are appropriately bounded, and recording how many texture
+ * accesses are made and where so that we can do relocations for them in the
+ * uniform stream.
+ *
+ * The kernel API has shaders stored in user-mapped BOs.  The BOs will be
+ * forcibly unmapped from the process before validation, and any cache of
+ * validated state will be flushed if the mapping is faulted back in.
+ *
+ * Storing the shaders in BOs means that the validation process will be slow
+ * due to uncached reads, but since shaders are long-lived and shader BOs are
+ * never actually modified, this shouldn't be a problem.
+ */
+
+#include "vc4_simulator_validate.h"
+#include "vc4_qpu.h"
+#include "vc4_qpu_defines.h"
+
+struct vc4_shader_validation_state {
+	struct vc4_texture_sample_info tmu_setup[2];
+	int tmu_write_count[2];
+};
+
+static bool
+is_tmu_write(uint32_t waddr)
+{
+	return (waddr >= QPU_W_TMU0_S &&
+		waddr <= QPU_W_TMU1_B);
+}
+
+static bool
+check_register_write(uint32_t waddr, bool is_b)
+{
+	switch (waddr) {
+	case QPU_W_UNIFORMS_ADDRESS:
+		/* XXX: We'll probably need to support this for reladdr, but
+		 * it's definitely a security-related one.
+		 */
+		DRM_ERROR("uniforms address load unsupported\n");
+		return false;
+
+	case QPU_W_TLB_COLOR_MS:
+	case QPU_W_TLB_COLOR_ALL:
+	case QPU_W_TLB_Z:
+		/* XXX: We need to track which buffers get written by the
+		 * shader, to make sure that we have those buffers set up by
+		 * the config packets.  But we need to pass them for now to
+		 * get things up and running.
+		 */
+		return true;
+
+	case QPU_W_TMU0_S:
+	case QPU_W_TMU0_T:
+	case QPU_W_TMU0_R:
+	case QPU_W_TMU0_B:
+	case QPU_W_TMU1_S:
+	case QPU_W_TMU1_T:
+	case QPU_W_TMU1_R:
+	case QPU_W_TMU1_B:
+		/* XXX: We need to track where the uniforms get loaded for
+		 * texturing so that we can do relocations, and to validate
+		 * those uniform contents.
+		 */
+		return true;
+
+	case QPU_W_HOST_INT:
+	case QPU_W_TMU_NOSWAP:
+	case QPU_W_TLB_STENCIL_SETUP:
+	case QPU_W_TLB_ALPHA_MASK:
+	case QPU_W_MUTEX_RELEASE:
+		/* XXX: I haven't thought about these, so don't support them
+		 * for now.
+		 */
+		DRM_ERROR("Unsupported waddr %d\n", waddr);
+		return false;
+
+	case QPU_W_VPM_ADDR:
+		DRM_ERROR("General VPM DMA unsupported\n");
+		return false;
+
+	case QPU_W_VPM:
+	case QPU_W_VPMVCD_SETUP:
+		/* We allow VPM setup in general, even including VPM DMA
+		 * configuration setup, because the (unsafe) DMA can only be
+		 * triggered by QPU_W_VPM_ADDR writes.
+		 */
+		return true;
+	}
+
+	return true;
+}
+
+static bool
+record_validated_texture_sample(struct vc4_validated_shader_info *validated_shader,
+				struct vc4_shader_validation_state *validation_state,
+				int tmu)
+{
+	uint32_t s = validated_shader->num_texture_samples;
+	int i;
+	struct vc4_texture_sample_info *temp_samples;
+
+	temp_samples = krealloc(validated_shader->texture_samples,
+				(s + 1) * sizeof(*temp_samples),
+				GFP_KERNEL);
+	if (!temp_samples)
+		return false;
+
+	memcpy(temp_samples[s].p_offset,
+	       validation_state->tmu_setup[tmu].p_offset,
+	       validation_state->tmu_write_count[tmu] * sizeof(uint32_t));
+	for (i = validation_state->tmu_write_count[tmu]; i < 4; i++)
+		temp_samples[s].p_offset[i] = ~0;
+
+	validated_shader->num_texture_samples = s + 1;
+	validated_shader->texture_samples = temp_samples;
+
+	return true;
+}
+
+static bool
+check_tmu_writes(uint64_t inst,
+		 struct vc4_validated_shader_info *validated_shader,
+		 struct vc4_shader_validation_state *validation_state,
+		 uint32_t waddr)
+{
+	int tmu = waddr > QPU_W_TMU0_B;
+
+	if (!is_tmu_write(waddr))
+		return true;
+
+	if (validation_state->tmu_write_count[tmu] >= 4) {
+		DRM_ERROR("TMU%d got too many parameters before dispatch\n",
+			  tmu);
+		return false;
+	}
+	validation_state->tmu_setup[tmu].p_offset[validation_state->tmu_write_count[tmu]] =
+		validated_shader->uniforms_size;
+	validation_state->tmu_write_count[tmu]++;
+	validated_shader->uniforms_size += 4;
+
+	if (waddr == QPU_W_TMU0_S || waddr == QPU_W_TMU1_S) {
+		if (!record_validated_texture_sample(validated_shader,
+						     validation_state, tmu)) {
+			return false;
+		}
+
+		validation_state->tmu_write_count[tmu] = 0;
+	}
+
+	return true;
+}
+
+static bool
+check_instruction_writes(uint64_t inst,
+			 struct vc4_validated_shader_info *validated_shader,
+			 struct vc4_shader_validation_state *validation_state)
+{
+	uint32_t waddr_add = QPU_GET_FIELD(inst, QPU_WADDR_ADD);
+	uint32_t waddr_mul = QPU_GET_FIELD(inst, QPU_WADDR_MUL);
+	bool ws = inst & QPU_WS;
+
+	if (is_tmu_write(waddr_add) && is_tmu_write(waddr_mul)) {
+		DRM_ERROR("ADD and MUL both set up textures\n");
+		return false;
+	}
+
+	if (!check_tmu_writes(inst, validated_shader, validation_state,
+			      waddr_add)) {
+		return false;
+	}
+
+	if (!check_tmu_writes(inst, validated_shader, validation_state,
+			      waddr_mul)) {
+		return false;
+	}
+
+	return (check_register_write(waddr_add, ws) &&
+		check_register_write(waddr_mul, !ws));
+}
+
+static bool
+check_instruction_reads(uint64_t inst,
+			struct vc4_validated_shader_info *validated_shader)
+{
+	uint32_t waddr_add = QPU_GET_FIELD(inst, QPU_WADDR_ADD);
+	uint32_t waddr_mul = QPU_GET_FIELD(inst, QPU_WADDR_MUL);
+	uint32_t raddr_a = QPU_GET_FIELD(inst, QPU_RADDR_A);
+	uint32_t raddr_b = QPU_GET_FIELD(inst, QPU_RADDR_B);
+
+	if (raddr_a == QPU_R_UNIF ||
+	    raddr_b == QPU_R_UNIF) {
+		if (is_tmu_write(waddr_add) || is_tmu_write(waddr_mul)) {
+			DRM_ERROR("uniform read in the same instruction as "
+				  "texture setup");
+			return false;
+		}
+
+		/* This can't overflow the uint32_t, because we're reading 8
+		 * bytes of instruction to increment by 4 here, so we'd
+		 * already be OOM.
+		 */
+		validated_shader->uniforms_size += 4;
+	}
+
+	return true;
+}
+
+struct vc4_validated_shader_info *
+vc4_validate_shader(struct drm_gem_cma_object *shader_obj,
+		    uint32_t start_offset)
+{
+	bool found_shader_end = false;
+	int shader_end_ip = 0;
+	uint32_t ip, max_ip;
+	uint64_t *shader;
+	struct vc4_validated_shader_info *validated_shader;
+	struct vc4_shader_validation_state validation_state;
+
+	memset(&validation_state, 0, sizeof(validation_state));
+
+	if (start_offset + sizeof(uint64_t) > shader_obj->base.size) {
+		DRM_ERROR("shader starting at %d outside of BO sized %d\n",
+			  start_offset,
+			  shader_obj->base.size);
+		return NULL;
+	}
+	shader = shader_obj->vaddr + start_offset;
+	max_ip = (shader_obj->base.size - start_offset) / sizeof(uint64_t);
+
+	validated_shader = kcalloc(sizeof(*validated_shader), 1, GFP_KERNEL);
+	if (!validated_shader)
+		return NULL;
+
+	for (ip = 0; ip < max_ip; ip++) {
+		uint64_t inst = shader[ip];
+		uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);
+
+		switch (sig) {
+		case QPU_SIG_NONE:
+		case QPU_SIG_WAIT_FOR_SCOREBOARD:
+		case QPU_SIG_SCOREBOARD_UNLOCK:
+		case QPU_SIG_LOAD_TMU0:
+		case QPU_SIG_LOAD_TMU1:
+			if (!check_instruction_writes(inst, validated_shader,
+						      &validation_state)) {
+				DRM_ERROR("Bad write at ip %d\n", ip);
+				goto fail;
+			}
+
+			if (!check_instruction_reads(inst, validated_shader))
+				goto fail;
+
+			break;
+
+		case QPU_SIG_LOAD_IMM:
+			if (!check_instruction_writes(inst, validated_shader,
+						      &validation_state)) {
+				DRM_ERROR("Bad LOAD_IMM write at ip %d\n", ip);
+				goto fail;
+			}
+			break;
+
+		case QPU_SIG_PROG_END:
+			found_shader_end = true;
+			shader_end_ip = ip;
+			break;
+
+		default:
+			DRM_ERROR("Unsupported QPU signal %d at "
+				  "instruction %d\n", sig, ip);
+			goto fail;
+		}
+
+		/* There are two delay slots after program end is signaled
+		 * that are still executed, then we're finished.
+		 */
+		if (found_shader_end && ip == shader_end_ip + 2)
+			break;
+	}
+
+	if (ip == max_ip) {
+		DRM_ERROR("shader starting at %d failed to terminate before "
+			  "shader BO end at %d\n",
+			  start_offset,
+			  shader_obj->base.size);
+		goto fail;
+	}
+
+	/* Again, no chance of integer overflow here because the worst case
+	 * scenario is 8 bytes of uniforms plus handles per 8-byte
+	 * instruction.
+	 */
+	validated_shader->uniforms_src_size =
+		(validated_shader->uniforms_size +
+		 4 * validated_shader->num_texture_samples);
+
+	return validated_shader;
+
+fail:
+	kfree(validated_shader);
+	return NULL;
+}