drm/vc4: Add an API for creating GPU shaders in GEM BOs.

Since we have no MMU, the kernel needs to validate that the submitted
shader code won't make any accesses to memory that the user doesn't
control, which involves banning some operations (general purpose DMA
writes), and tracking where we need to write out pointers for other
operations (texture sampling).  Once it's validated, we return a GEM
BO containing the shader, which doesn't allow mapping for write or
exporting to other subsystems.

v2: Use __u32-style types.

Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 513 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_validate_shaders.c b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
new file mode 100644
index 000000000000..f67124b4c534
--- /dev/null
+++ b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
@@ -0,0 +1,513 @@
+/*
+ * 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 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.
+ */
+
+#include "vc4_drv.h"
+#include "vc4_qpu_defines.h"
+
+struct vc4_shader_validation_state {
+	struct vc4_texture_sample_info tmu_setup[2];
+	int tmu_write_count[2];
+
+	/* For registers that were last written to by a MIN instruction with
+	 * one argument being a uniform, the address of the uniform.
+	 * Otherwise, ~0.
+	 *
+	 * This is used for the validation of direct address memory reads.
+	 */
+	uint32_t live_min_clamp_offsets[32 + 32 + 4];
+	bool live_max_clamp_regs[32 + 32 + 4];
+};
+
+static uint32_t
+waddr_to_live_reg_index(uint32_t waddr, bool is_b)
+{
+	if (waddr < 32) {
+		if (is_b)
+			return 32 + waddr;
+		else
+			return waddr;
+	} else if (waddr <= QPU_W_ACC3) {
+		return 64 + waddr - QPU_W_ACC0;
+	} else {
+		return ~0;
+	}
+}
+
+static uint32_t
+raddr_add_a_to_live_reg_index(uint64_t inst)
+{
+	uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);
+	uint32_t add_a = QPU_GET_FIELD(inst, QPU_ADD_A);
+	uint32_t raddr_a = QPU_GET_FIELD(inst, QPU_RADDR_A);
+	uint32_t raddr_b = QPU_GET_FIELD(inst, QPU_RADDR_B);
+
+	if (add_a == QPU_MUX_A)
+		return raddr_a;
+	else if (add_a == QPU_MUX_B && sig != QPU_SIG_SMALL_IMM)
+		return 32 + raddr_b;
+	else if (add_a <= QPU_MUX_R3)
+		return 64 + add_a;
+	else
+		return ~0;
+}
+
+static bool
+is_tmu_submit(uint32_t waddr)
+{
+	return (waddr == QPU_W_TMU0_S ||
+		waddr == QPU_W_TMU1_S);
+}
+
+static bool
+is_tmu_write(uint32_t waddr)
+{
+	return (waddr >= QPU_W_TMU0_S &&
+		waddr <= QPU_W_TMU1_B);
+}
+
+static bool
+record_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],
+	       &validation_state->tmu_setup[tmu],
+	       sizeof(*temp_samples));
+
+	validated_shader->num_texture_samples = s + 1;
+	validated_shader->texture_samples = temp_samples;
+
+	for (i = 0; i < 4; i++)
+		validation_state->tmu_setup[tmu].p_offset[i] = ~0;
+
+	return true;
+}
+
+static bool
+check_tmu_write(uint64_t inst,
+		struct vc4_validated_shader_info *validated_shader,
+		struct vc4_shader_validation_state *validation_state,
+		bool is_mul)
+{
+	uint32_t waddr = (is_mul ?
+			  QPU_GET_FIELD(inst, QPU_WADDR_MUL) :
+			  QPU_GET_FIELD(inst, QPU_WADDR_ADD));
+	uint32_t raddr_a = QPU_GET_FIELD(inst, QPU_RADDR_A);
+	uint32_t raddr_b = QPU_GET_FIELD(inst, QPU_RADDR_B);
+	int tmu = waddr > QPU_W_TMU0_B;
+	bool submit = is_tmu_submit(waddr);
+	bool is_direct = submit && validation_state->tmu_write_count[tmu] == 0;
+	uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);
+
+	if (is_direct) {
+		uint32_t add_b = QPU_GET_FIELD(inst, QPU_ADD_B);
+		uint32_t clamp_reg, clamp_offset;
+
+		if (sig == QPU_SIG_SMALL_IMM) {
+			DRM_ERROR("direct TMU read used small immediate\n");
+			return false;
+		}
+
+		/* Make sure that this texture load is an add of the base
+		 * address of the UBO to a clamped offset within the UBO.
+		 */
+		if (is_mul ||
+		    QPU_GET_FIELD(inst, QPU_OP_ADD) != QPU_A_ADD) {
+			DRM_ERROR("direct TMU load wasn't an add\n");
+			return false;
+		}
+
+		/* We assert that the the clamped address is the first
+		 * argument, and the UBO base address is the second argument.
+		 * This is arbitrary, but simpler than supporting flipping the
+		 * two either way.
+		 */
+		clamp_reg = raddr_add_a_to_live_reg_index(inst);
+		if (clamp_reg == ~0) {
+			DRM_ERROR("direct TMU load wasn't clamped\n");
+			return false;
+		}
+
+		clamp_offset = validation_state->live_min_clamp_offsets[clamp_reg];
+		if (clamp_offset == ~0) {
+			DRM_ERROR("direct TMU load wasn't clamped\n");
+			return false;
+		}
+
+		/* Store the clamp value's offset in p1 (see reloc_tex() in
+		 * vc4_validate.c).
+		 */
+		validation_state->tmu_setup[tmu].p_offset[1] =
+			clamp_offset;
+
+		if (!(add_b == QPU_MUX_A && raddr_a == QPU_R_UNIF) &&
+		    !(add_b == QPU_MUX_B && raddr_b == QPU_R_UNIF)) {
+			DRM_ERROR("direct TMU load didn't add to a uniform\n");
+			return false;
+		}
+
+		validation_state->tmu_setup[tmu].is_direct = true;
+	} else {
+		if (raddr_a == QPU_R_UNIF || (sig != QPU_SIG_SMALL_IMM &&
+					      raddr_b == QPU_R_UNIF)) {
+			DRM_ERROR("uniform read in the same instruction as "
+				  "texture setup.\n");
+			return false;
+		}
+	}
+
+	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]++;
+	/* Since direct uses a RADDR uniform reference, it will get counted in
+	 * check_instruction_reads()
+	 */
+	if (!is_direct)
+		validated_shader->uniforms_size += 4;
+
+	if (submit) {
+		if (!record_texture_sample(validated_shader,
+					   validation_state, tmu)) {
+			return false;
+		}
+
+		validation_state->tmu_write_count[tmu] = 0;
+	}
+
+	return true;
+}
+
+static bool
+check_reg_write(uint64_t inst,
+		struct vc4_validated_shader_info *validated_shader,
+		struct vc4_shader_validation_state *validation_state,
+		bool is_mul)
+{
+	uint32_t waddr = (is_mul ?
+			  QPU_GET_FIELD(inst, QPU_WADDR_MUL) :
+			  QPU_GET_FIELD(inst, QPU_WADDR_ADD));
+
+	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:
+		/* These only interact with the tile buffer, not main memory,
+		 * so they're safe.
+		 */
+		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:
+		return check_tmu_write(inst, validated_shader, validation_state,
+				       is_mul);
+
+	case QPU_W_HOST_INT:
+	case QPU_W_TMU_NOSWAP:
+	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;
+
+	case QPU_W_TLB_STENCIL_SETUP:
+		return true;
+	}
+
+	return true;
+}
+
+static void
+track_live_clamps(uint64_t inst,
+		  struct vc4_validated_shader_info *validated_shader,
+		  struct vc4_shader_validation_state *validation_state)
+{
+	uint32_t op_add = QPU_GET_FIELD(inst, QPU_OP_ADD);
+	uint32_t waddr_add = QPU_GET_FIELD(inst, QPU_WADDR_ADD);
+	uint32_t waddr_mul = QPU_GET_FIELD(inst, QPU_WADDR_MUL);
+	uint32_t cond_add = QPU_GET_FIELD(inst, QPU_COND_ADD);
+	uint32_t add_a = QPU_GET_FIELD(inst, QPU_ADD_A);
+	uint32_t add_b = QPU_GET_FIELD(inst, QPU_ADD_B);
+	uint32_t raddr_a = QPU_GET_FIELD(inst, QPU_RADDR_A);
+	uint32_t raddr_b = QPU_GET_FIELD(inst, QPU_RADDR_B);
+	uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);
+	bool ws = inst & QPU_WS;
+	uint32_t lri_add_a, lri_add, lri_mul;
+	bool add_a_is_min_0;
+
+	/* Check whether OP_ADD's A argumennt comes from a live MAX(x, 0),
+	 * before we clear previous live state.
+	 */
+	lri_add_a = raddr_add_a_to_live_reg_index(inst);
+	add_a_is_min_0 = (lri_add_a != ~0 &&
+			  validation_state->live_max_clamp_regs[lri_add_a]);
+
+	/* Clear live state for registers written by our instruction. */
+	lri_add = waddr_to_live_reg_index(waddr_add, ws);
+	lri_mul = waddr_to_live_reg_index(waddr_mul, !ws);
+	if (lri_mul != ~0) {
+		validation_state->live_max_clamp_regs[lri_mul] = false;
+		validation_state->live_min_clamp_offsets[lri_mul] = ~0;
+	}
+	if (lri_add != ~0) {
+		validation_state->live_max_clamp_regs[lri_add] = false;
+		validation_state->live_min_clamp_offsets[lri_add] = ~0;
+	} else {
+		/* Nothing further to do for live tracking, since only ADDs
+		 * generate new live clamp registers.
+		 */
+		return;
+	}
+
+	/* Now, handle remaining live clamp tracking for the ADD operation. */
+
+	if (cond_add != QPU_COND_ALWAYS)
+		return;
+
+	if (op_add == QPU_A_MAX) {
+		/* Track live clamps of a value to a minimum of 0 (in either
+		 * arg).
+		 */
+		if (sig != QPU_SIG_SMALL_IMM || raddr_b != 0 ||
+		    (add_a != QPU_MUX_B && add_b != QPU_MUX_B)) {
+			return;
+		}
+
+		validation_state->live_max_clamp_regs[lri_add] = true;
+	} else if (op_add == QPU_A_MIN) {
+		/* Track live clamps of a value clamped to a minimum of 0 and
+		 * a maximum of some uniform's offset.
+		 */
+		if (!add_a_is_min_0)
+			return;
+
+		if (!(add_b == QPU_MUX_A && raddr_a == QPU_R_UNIF) &&
+		    !(add_b == QPU_MUX_B && raddr_b == QPU_R_UNIF &&
+		      sig != QPU_SIG_SMALL_IMM)) {
+			return;
+		}
+
+		validation_state->live_min_clamp_offsets[lri_add] =
+			validated_shader->uniforms_size;
+	}
+}
+
+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 ok;
+
+	if (is_tmu_write(waddr_add) && is_tmu_write(waddr_mul)) {
+		DRM_ERROR("ADD and MUL both set up textures\n");
+		return false;
+	}
+
+	ok = (check_reg_write(inst, validated_shader, validation_state,
+			      false) &&
+	      check_reg_write(inst, validated_shader, validation_state,
+			      true));
+
+	track_live_clamps(inst, validated_shader, validation_state);
+
+	return ok;
+}
+
+static bool
+check_instruction_reads(uint64_t inst,
+			struct vc4_validated_shader_info *validated_shader)
+{
+	uint32_t raddr_a = QPU_GET_FIELD(inst, QPU_RADDR_A);
+	uint32_t raddr_b = QPU_GET_FIELD(inst, QPU_RADDR_B);
+	uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);
+
+	if (raddr_a == QPU_R_UNIF ||
+	    (raddr_b == QPU_R_UNIF && sig != QPU_SIG_SMALL_IMM)) {
+		/* 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)
+{
+	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;
+	int i;
+
+	memset(&validation_state, 0, sizeof(validation_state));
+
+	for (i = 0; i < 8; i++)
+		validation_state.tmu_setup[i / 4].p_offset[i % 4] = ~0;
+	for (i = 0; i < ARRAY_SIZE(validation_state.live_min_clamp_offsets); i++)
+		validation_state.live_min_clamp_offsets[i] = ~0;
+
+	shader = shader_obj->vaddr;
+	max_ip = shader_obj->base.size / sizeof(uint64_t);
+
+	validated_shader = kcalloc(1, sizeof(*validated_shader), 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_COLOR_LOAD:
+		case QPU_SIG_LOAD_TMU0:
+		case QPU_SIG_LOAD_TMU1:
+		case QPU_SIG_PROG_END:
+		case QPU_SIG_SMALL_IMM:
+			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;
+
+			if (sig == QPU_SIG_PROG_END) {
+				found_shader_end = true;
+				shader_end_ip = ip;
+			}
+
+			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;
+
+		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 failed to terminate before "
+			  "shader BO end at %zd\n",
+			  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:
+	if (validated_shader) {
+		kfree(validated_shader->texture_samples);
+		kfree(validated_shader);
+	}
+	return NULL;
+}