Merge tag 'block-5.11-2021-01-10' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / drivers / gpu / drm / vc4 / vc4_validate_shaders.c

/*
 * 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.
 *
 * Since the VC4 has no IOMMU between it and system memory, 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, uniform data, or direct-addressed TMU
 * lookup).
 *
 * The shader validator walks over a shader's BO, ensuring that its
 * accesses are appropriately bounded, and recording where texture
 * accesses are made so that we can do relocations for them in the
 * uniform stream.
 *
 * Shader BO are immutable for their lifetimes (enforced by not
 * allowing mmaps, GEM prime export, or rendering to from a CL), so
 * this validation is only performed at BO creation time.
 */

#include "vc4_drv.h"
#include "vc4_qpu_defines.h"

#define LIVE_REG_COUNT (32 + 32 + 4)

struct vc4_shader_validation_state {
        /* Current IP being validated. */
        uint32_t ip;

        /* IP at the end of the BO, do not read shader[max_ip] */
        uint32_t max_ip;

        uint64_t *shader;

        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[LIVE_REG_COUNT];
        bool live_max_clamp_regs[LIVE_REG_COUNT];
        uint32_t live_immediates[LIVE_REG_COUNT];

        /* Bitfield of which IPs are used as branch targets.
         *
         * Used for validation that the uniform stream is updated at the right
         * points and clearing the texturing/clamping state.
         */
        unsigned long *branch_targets;

        /* Set when entering a basic block, and cleared when the uniform
         * address update is found.  This is used to make sure that we don't
         * read uniforms when the address is undefined.
         */
        bool needs_uniform_address_update;

        /* Set when we find a backwards branch.  If the branch is backwards,
         * the taraget is probably doing an address reset to read uniforms,
         * and so we need to be sure that a uniforms address is present in the
         * stream, even if the shader didn't need to read uniforms in later
         * basic blocks.
         */
        bool needs_uniform_address_for_loop;

        /* Set when we find an instruction writing the top half of the
         * register files.  If we allowed writing the unusable regs in
         * a threaded shader, then the other shader running on our
         * QPU's clamp validation would be invalid.
         */
        bool all_registers_used;
};

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
live_reg_is_upper_half(uint32_t lri)
{
        return  (lri >= 16 && lri < 32) ||
                (lri >= 32 + 16 && lri < 32 + 32);
}

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(struct vc4_validated_shader_info *validated_shader,
                struct vc4_shader_validation_state *validation_state,
                bool is_mul)
{
        uint64_t inst = validation_state->shader[validation_state->ip];
        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_DEBUG("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_DEBUG("direct TMU load wasn't an add\n");
                        return false;
                }

                /* We assert that 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_DEBUG("direct TMU load wasn't clamped\n");
                        return false;
                }

                clamp_offset = validation_state->live_min_clamp_offsets[clamp_reg];
                if (clamp_offset == ~0) {
                        DRM_DEBUG("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_DEBUG("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_DEBUG("uniform read in the same instruction as "
                                  "texture setup.\n");
                        return false;
                }
        }

        if (validation_state->tmu_write_count[tmu] >= 4) {
                DRM_DEBUG("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) {
                if (validation_state->needs_uniform_address_update) {
                        DRM_DEBUG("Texturing with undefined uniform address\n");
                        return false;
                }

                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 require_uniform_address_uniform(struct vc4_validated_shader_info *validated_shader)
{
        uint32_t o = validated_shader->num_uniform_addr_offsets;
        uint32_t num_uniforms = validated_shader->uniforms_size / 4;

        validated_shader->uniform_addr_offsets =
                krealloc(validated_shader->uniform_addr_offsets,
                         (o + 1) *
                         sizeof(*validated_shader->uniform_addr_offsets),
                         GFP_KERNEL);
        if (!validated_shader->uniform_addr_offsets)
                return false;

        validated_shader->uniform_addr_offsets[o] = num_uniforms;
        validated_shader->num_uniform_addr_offsets++;

        return true;
}

static bool
validate_uniform_address_write(struct vc4_validated_shader_info *validated_shader,
                               struct vc4_shader_validation_state *validation_state,
                               bool is_mul)
{
        uint64_t inst = validation_state->shader[validation_state->ip];
        u32 add_b = QPU_GET_FIELD(inst, QPU_ADD_B);
        u32 raddr_a = QPU_GET_FIELD(inst, QPU_RADDR_A);
        u32 raddr_b = QPU_GET_FIELD(inst, QPU_RADDR_B);
        u32 add_lri = raddr_add_a_to_live_reg_index(inst);
        /* We want our reset to be pointing at whatever uniform follows the
         * uniforms base address.
         */
        u32 expected_offset = validated_shader->uniforms_size + 4;

        /* We only support absolute uniform address changes, and we
         * require that they be in the current basic block before any
         * of its uniform reads.
         *
         * One could potentially emit more efficient QPU code, by
         * noticing that (say) an if statement does uniform control
         * flow for all threads and that the if reads the same number
         * of uniforms on each side.  However, this scheme is easy to
         * validate so it's all we allow for now.
         */
        switch (QPU_GET_FIELD(inst, QPU_SIG)) {
        case QPU_SIG_NONE:
        case QPU_SIG_SCOREBOARD_UNLOCK:
        case QPU_SIG_COLOR_LOAD:
        case QPU_SIG_LOAD_TMU0:
        case QPU_SIG_LOAD_TMU1:
                break;
        default:
                DRM_DEBUG("uniforms address change must be "
                          "normal math\n");
                return false;
        }

        if (is_mul || QPU_GET_FIELD(inst, QPU_OP_ADD) != QPU_A_ADD) {
                DRM_DEBUG("Uniform address reset must be an ADD.\n");
                return false;
        }

        if (QPU_GET_FIELD(inst, QPU_COND_ADD) != QPU_COND_ALWAYS) {
                DRM_DEBUG("Uniform address reset must be unconditional.\n");
                return false;
        }

        if (QPU_GET_FIELD(inst, QPU_PACK) != QPU_PACK_A_NOP &&
            !(inst & QPU_PM)) {
                DRM_DEBUG("No packing allowed on uniforms reset\n");
                return false;
        }

        if (add_lri == -1) {
                DRM_DEBUG("First argument of uniform address write must be "
                          "an immediate value.\n");
                return false;
        }

        if (validation_state->live_immediates[add_lri] != expected_offset) {
                DRM_DEBUG("Resetting uniforms with offset %db instead of %db\n",
                          validation_state->live_immediates[add_lri],
                          expected_offset);
                return false;
        }

        if (!(add_b == QPU_MUX_A && raddr_a == QPU_R_UNIF) &&
            !(add_b == QPU_MUX_B && raddr_b == QPU_R_UNIF)) {
                DRM_DEBUG("Second argument of uniform address write must be "
                          "a uniform.\n");
                return false;
        }

        validation_state->needs_uniform_address_update = false;
        validation_state->needs_uniform_address_for_loop = false;
        return require_uniform_address_uniform(validated_shader);
}

static bool
check_reg_write(struct vc4_validated_shader_info *validated_shader,
                struct vc4_shader_validation_state *validation_state,
                bool is_mul)
{
        uint64_t inst = validation_state->shader[validation_state->ip];
        uint32_t waddr = (is_mul ?
                          QPU_GET_FIELD(inst, QPU_WADDR_MUL) :
                          QPU_GET_FIELD(inst, QPU_WADDR_ADD));
        uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);
        bool ws = inst & QPU_WS;
        bool is_b = is_mul ^ ws;
        u32 lri = waddr_to_live_reg_index(waddr, is_b);

        if (lri != -1) {
                uint32_t cond_add = QPU_GET_FIELD(inst, QPU_COND_ADD);
                uint32_t cond_mul = QPU_GET_FIELD(inst, QPU_COND_MUL);

                if (sig == QPU_SIG_LOAD_IMM &&
                    QPU_GET_FIELD(inst, QPU_PACK) == QPU_PACK_A_NOP &&
                    ((is_mul && cond_mul == QPU_COND_ALWAYS) ||
                     (!is_mul && cond_add == QPU_COND_ALWAYS))) {
                        validation_state->live_immediates[lri] =
                                QPU_GET_FIELD(inst, QPU_LOAD_IMM);
                } else {
                        validation_state->live_immediates[lri] = ~0;
                }

                if (live_reg_is_upper_half(lri))
                        validation_state->all_registers_used = true;
        }

        switch (waddr) {
        case QPU_W_UNIFORMS_ADDRESS:
                if (is_b) {
                        DRM_DEBUG("relative uniforms address change "
                                  "unsupported\n");
                        return false;
                }

                return validate_uniform_address_write(validated_shader,
                                                      validation_state,
                                                      is_mul);

        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(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_DEBUG("Unsupported waddr %d\n", waddr);
                return false;

        case QPU_W_VPM_ADDR:
                DRM_DEBUG("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(struct vc4_validated_shader_info *validated_shader,
                  struct vc4_shader_validation_state *validation_state)
{
        uint64_t inst = validation_state->shader[validation_state->ip];
        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(struct vc4_validated_shader_info *validated_shader,
                         struct vc4_shader_validation_state *validation_state)
{
        uint64_t inst = validation_state->shader[validation_state->ip];
        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_DEBUG("ADD and MUL both set up textures\n");
                return false;
        }

        ok = (check_reg_write(validated_shader, validation_state, false) &&
              check_reg_write(validated_shader, validation_state, true));

        track_live_clamps(validated_shader, validation_state);

        return ok;
}

static bool
check_branch(uint64_t inst,
             struct vc4_validated_shader_info *validated_shader,
             struct vc4_shader_validation_state *validation_state,
             int ip)
{
        int32_t branch_imm = QPU_GET_FIELD(inst, QPU_BRANCH_TARGET);
        uint32_t waddr_add = QPU_GET_FIELD(inst, QPU_WADDR_ADD);
        uint32_t waddr_mul = QPU_GET_FIELD(inst, QPU_WADDR_MUL);

        if ((int)branch_imm < 0)
                validation_state->needs_uniform_address_for_loop = true;

        /* We don't want to have to worry about validation of this, and
         * there's no need for it.
         */
        if (waddr_add != QPU_W_NOP || waddr_mul != QPU_W_NOP) {
                DRM_DEBUG("branch instruction at %d wrote a register.\n",
                          validation_state->ip);
                return false;
        }

        return true;
}

static bool
check_instruction_reads(struct vc4_validated_shader_info *validated_shader,
                        struct vc4_shader_validation_state *validation_state)
{
        uint64_t inst = validation_state->shader[validation_state->ip];
        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;

                if (validation_state->needs_uniform_address_update) {
                        DRM_DEBUG("Uniform read with undefined uniform "
                                  "address\n");
                        return false;
                }
        }

        if ((raddr_a >= 16 && raddr_a < 32) ||
            (raddr_b >= 16 && raddr_b < 32 && sig != QPU_SIG_SMALL_IMM)) {
                validation_state->all_registers_used = true;
        }

        return true;
}

/* Make sure that all branches are absolute and point within the shader, and
 * note their targets for later.
 */
static bool
vc4_validate_branches(struct vc4_shader_validation_state *validation_state)
{
        uint32_t max_branch_target = 0;
        int ip;
        int last_branch = -2;

        for (ip = 0; ip < validation_state->max_ip; ip++) {
                uint64_t inst = validation_state->shader[ip];
                int32_t branch_imm = QPU_GET_FIELD(inst, QPU_BRANCH_TARGET);
                uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);
                uint32_t after_delay_ip = ip + 4;
                uint32_t branch_target_ip;

                if (sig == QPU_SIG_PROG_END) {
                        /* There are two delay slots after program end is
                         * signaled that are still executed, then we're
                         * finished.  validation_state->max_ip is the
                         * instruction after the last valid instruction in the
                         * program.
                         */
                        validation_state->max_ip = ip + 3;
                        continue;
                }

                if (sig != QPU_SIG_BRANCH)
                        continue;

                if (ip - last_branch < 4) {
                        DRM_DEBUG("Branch at %d during delay slots\n", ip);
                        return false;
                }
                last_branch = ip;

                if (inst & QPU_BRANCH_REG) {
                        DRM_DEBUG("branching from register relative "
                                  "not supported\n");
                        return false;
                }

                if (!(inst & QPU_BRANCH_REL)) {
                        DRM_DEBUG("relative branching required\n");
                        return false;
                }

                /* The actual branch target is the instruction after the delay
                 * slots, plus whatever byte offset is in the low 32 bits of
                 * the instruction.  Make sure we're not branching beyond the
                 * end of the shader object.
                 */
                if (branch_imm % sizeof(inst) != 0) {
                        DRM_DEBUG("branch target not aligned\n");
                        return false;
                }

                branch_target_ip = after_delay_ip + (branch_imm >> 3);
                if (branch_target_ip >= validation_state->max_ip) {
                        DRM_DEBUG("Branch at %d outside of shader (ip %d/%d)\n",
                                  ip, branch_target_ip,
                                  validation_state->max_ip);
                        return false;
                }
                set_bit(branch_target_ip, validation_state->branch_targets);

                /* Make sure that the non-branching path is also not outside
                 * the shader.
                 */
                if (after_delay_ip >= validation_state->max_ip) {
                        DRM_DEBUG("Branch at %d continues past shader end "
                                  "(%d/%d)\n",
                                  ip, after_delay_ip, validation_state->max_ip);
                        return false;
                }
                set_bit(after_delay_ip, validation_state->branch_targets);
                max_branch_target = max(max_branch_target, after_delay_ip);
        }

        if (max_branch_target > validation_state->max_ip - 3) {
                DRM_DEBUG("Branch landed after QPU_SIG_PROG_END");
                return false;
        }

        return true;
}

/* Resets any known state for the shader, used when we may be branched to from
 * multiple locations in the program (or at shader start).
 */
static void
reset_validation_state(struct vc4_shader_validation_state *validation_state)
{
        int i;

        for (i = 0; i < 8; i++)
                validation_state->tmu_setup[i / 4].p_offset[i % 4] = ~0;

        for (i = 0; i < LIVE_REG_COUNT; i++) {
                validation_state->live_min_clamp_offsets[i] = ~0;
                validation_state->live_max_clamp_regs[i] = false;
                validation_state->live_immediates[i] = ~0;
        }
}

static bool
texturing_in_progress(struct vc4_shader_validation_state *validation_state)
{
        return (validation_state->tmu_write_count[0] != 0 ||
                validation_state->tmu_write_count[1] != 0);
}

static bool
vc4_handle_branch_target(struct vc4_shader_validation_state *validation_state)
{
        uint32_t ip = validation_state->ip;

        if (!test_bit(ip, validation_state->branch_targets))
                return true;

        if (texturing_in_progress(validation_state)) {
                DRM_DEBUG("Branch target landed during TMU setup\n");
                return false;
        }

        /* Reset our live values tracking, since this instruction may have
         * multiple predecessors.
         *
         * One could potentially do analysis to determine that, for
         * example, all predecessors have a live max clamp in the same
         * register, but we don't bother with that.
         */
        reset_validation_state(validation_state);

        /* Since we've entered a basic block from potentially multiple
         * predecessors, we need the uniforms address to be updated before any
         * unforms are read.  We require that after any branch point, the next
         * uniform to be loaded is a uniform address offset.  That uniform's
         * offset will be marked by the uniform address register write
         * validation, or a one-off the end-of-program check.
         */
        validation_state->needs_uniform_address_update = true;

        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 last_thread_switch_ip = -3;
        uint32_t ip;
        struct vc4_validated_shader_info *validated_shader = NULL;
        struct vc4_shader_validation_state validation_state;

        memset(&validation_state, 0, sizeof(validation_state));
        validation_state.shader = shader_obj->vaddr;
        validation_state.max_ip = shader_obj->base.size / sizeof(uint64_t);

        reset_validation_state(&validation_state);

        validation_state.branch_targets =
                kcalloc(BITS_TO_LONGS(validation_state.max_ip),
                        sizeof(unsigned long), GFP_KERNEL);
        if (!validation_state.branch_targets)
                goto fail;

        validated_shader = kcalloc(1, sizeof(*validated_shader), GFP_KERNEL);
        if (!validated_shader)
                goto fail;

        if (!vc4_validate_branches(&validation_state))
                goto fail;

        for (ip = 0; ip < validation_state.max_ip; ip++) {
                uint64_t inst = validation_state.shader[ip];
                uint32_t sig = QPU_GET_FIELD(inst, QPU_SIG);

                validation_state.ip = ip;

                if (!vc4_handle_branch_target(&validation_state))
                        goto fail;

                if (ip == last_thread_switch_ip + 3) {
                        /* Reset r0-r3 live clamp data */
                        int i;

                        for (i = 64; i < LIVE_REG_COUNT; i++) {
                                validation_state.live_min_clamp_offsets[i] = ~0;
                                validation_state.live_max_clamp_regs[i] = false;
                                validation_state.live_immediates[i] = ~0;
                        }
                }

                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:
                case QPU_SIG_THREAD_SWITCH:
                case QPU_SIG_LAST_THREAD_SWITCH:
                        if (!check_instruction_writes(validated_shader,
                                                      &validation_state)) {
                                DRM_DEBUG("Bad write at ip %d\n", ip);
                                goto fail;
                        }

                        if (!check_instruction_reads(validated_shader,
                                                     &validation_state))
                                goto fail;

                        if (sig == QPU_SIG_PROG_END) {
                                found_shader_end = true;
                                shader_end_ip = ip;
                        }

                        if (sig == QPU_SIG_THREAD_SWITCH ||
                            sig == QPU_SIG_LAST_THREAD_SWITCH) {
                                validated_shader->is_threaded = true;

                                if (ip < last_thread_switch_ip + 3) {
                                        DRM_DEBUG("Thread switch too soon after "
                                                  "last switch at ip %d\n", ip);
                                        goto fail;
                                }
                                last_thread_switch_ip = ip;
                        }

                        break;

                case QPU_SIG_LOAD_IMM:
                        if (!check_instruction_writes(validated_shader,
                                                      &validation_state)) {
                                DRM_DEBUG("Bad LOAD_IMM write at ip %d\n", ip);
                                goto fail;
                        }
                        break;

                case QPU_SIG_BRANCH:
                        if (!check_branch(inst, validated_shader,
                                          &validation_state, ip))
                                goto fail;

                        if (ip < last_thread_switch_ip + 3) {
                                DRM_DEBUG("Branch in thread switch at ip %d",
                                          ip);
                                goto fail;
                        }

                        break;
                default:
                        DRM_DEBUG("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 == validation_state.max_ip) {
                DRM_DEBUG("shader failed to terminate before "
                          "shader BO end at %zd\n",
                          shader_obj->base.size);
                goto fail;
        }

        /* Might corrupt other thread */
        if (validated_shader->is_threaded &&
            validation_state.all_registers_used) {
                DRM_DEBUG("Shader uses threading, but uses the upper "
                          "half of the registers, too\n");
                goto fail;
        }

        /* If we did a backwards branch and we haven't emitted a uniforms
         * reset since then, we still need the uniforms stream to have the
         * uniforms address available so that the backwards branch can do its
         * uniforms reset.
         *
         * We could potentially prove that the backwards branch doesn't
         * contain any uses of uniforms until program exit, but that doesn't
         * seem to be worth the trouble.
         */
        if (validation_state.needs_uniform_address_for_loop) {
                if (!require_uniform_address_uniform(validated_shader))
                        goto fail;
                validated_shader->uniforms_size += 4;
        }

        /* 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);

        kfree(validation_state.branch_targets);

        return validated_shader;

fail:
        kfree(validation_state.branch_targets);
        if (validated_shader) {
                kfree(validated_shader->uniform_addr_offsets);
                kfree(validated_shader->texture_samples);
                kfree(validated_shader);
        }
        return NULL;
}