unicorn/uc.c

/* Unicorn Emulator Engine */
/* By Nguyen Anh Quynh <aquynh@gmail.com>, 2015 */
/* Modified for Unicorn Engine by Chen Huitao<chenhuitao@hfmrit.com>, 2020 */

#if defined(UNICORN_HAS_OSXKERNEL)
#include <libkern/libkern.h>
#else
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#endif

#include <time.h>   // nanosleep
#include <string.h>

#include "uc_priv.h"

// target specific headers
#include "qemu/target/m68k/unicorn.h"
#include "qemu/target/i386/unicorn.h"
#include "qemu/target/arm/unicorn.h"
#include "qemu/target/mips/unicorn.h"
#include "qemu/target/sparc/unicorn.h"
#include "qemu/target/ppc/unicorn.h"
#include "qemu/target/riscv/unicorn.h"

#include "qemu/include/qemu/queue.h"

UNICORN_EXPORT
unsigned int uc_version(unsigned int *major, unsigned int *minor)
{
    if (major != NULL && minor != NULL) {
        *major = UC_API_MAJOR;
        *minor = UC_API_MINOR;
    }

    return (UC_API_MAJOR << 8) + UC_API_MINOR;
}


UNICORN_EXPORT
uc_err uc_errno(uc_engine *uc)
{
    return uc->errnum;
}


UNICORN_EXPORT
const char *uc_strerror(uc_err code)
{
    switch(code) {
        default:
            return "Unknown error code";
        case UC_ERR_OK:
            return "OK (UC_ERR_OK)";
        case UC_ERR_NOMEM:
            return "No memory available or memory not present (UC_ERR_NOMEM)";
        case UC_ERR_ARCH:
            return "Invalid/unsupported architecture (UC_ERR_ARCH)";
        case UC_ERR_HANDLE:
            return "Invalid handle (UC_ERR_HANDLE)";
        case UC_ERR_MODE:
            return "Invalid mode (UC_ERR_MODE)";
        case UC_ERR_VERSION:
            return "Different API version between core & binding (UC_ERR_VERSION)";
        case UC_ERR_READ_UNMAPPED:
            return "Invalid memory read (UC_ERR_READ_UNMAPPED)";
        case UC_ERR_WRITE_UNMAPPED:
            return "Invalid memory write (UC_ERR_WRITE_UNMAPPED)";
        case UC_ERR_FETCH_UNMAPPED:
            return "Invalid memory fetch (UC_ERR_FETCH_UNMAPPED)";
        case UC_ERR_HOOK:
            return "Invalid hook type (UC_ERR_HOOK)";
        case UC_ERR_INSN_INVALID:
            return "Invalid instruction (UC_ERR_INSN_INVALID)";
        case UC_ERR_MAP:
            return "Invalid memory mapping (UC_ERR_MAP)";
        case UC_ERR_WRITE_PROT:
            return "Write to write-protected memory (UC_ERR_WRITE_PROT)";
        case UC_ERR_READ_PROT:
            return "Read from non-readable memory (UC_ERR_READ_PROT)";
        case UC_ERR_FETCH_PROT:
            return "Fetch from non-executable memory (UC_ERR_FETCH_PROT)";
        case UC_ERR_ARG:
            return "Invalid argument (UC_ERR_ARG)";
        case UC_ERR_READ_UNALIGNED:
            return "Read from unaligned memory (UC_ERR_READ_UNALIGNED)";
        case UC_ERR_WRITE_UNALIGNED:
            return "Write to unaligned memory (UC_ERR_WRITE_UNALIGNED)";
        case UC_ERR_FETCH_UNALIGNED:
            return "Fetch from unaligned memory (UC_ERR_FETCH_UNALIGNED)";
        case UC_ERR_RESOURCE:
            return "Insufficient resource (UC_ERR_RESOURCE)";
        case UC_ERR_EXCEPTION:
            return "Unhandled CPU exception (UC_ERR_EXCEPTION)";
    }
}


UNICORN_EXPORT
bool uc_arch_supported(uc_arch arch)
{
    switch (arch) {
#ifdef UNICORN_HAS_ARM
        case UC_ARCH_ARM:   return true;
#endif
#ifdef UNICORN_HAS_ARM64
        case UC_ARCH_ARM64: return true;
#endif
#ifdef UNICORN_HAS_M68K
        case UC_ARCH_M68K:  return true;
#endif
#ifdef UNICORN_HAS_MIPS
        case UC_ARCH_MIPS:  return true;
#endif
#ifdef UNICORN_HAS_PPC
        case UC_ARCH_PPC:   return true;
#endif
#ifdef UNICORN_HAS_SPARC
        case UC_ARCH_SPARC: return true;
#endif
#ifdef UNICORN_HAS_X86
        case UC_ARCH_X86:   return true;
#endif
#ifdef UNICORN_HAS_RISCV
        case UC_ARCH_RISCV:   return true;
#endif
        /* Invalid or disabled arch */
        default:            return false;
    }
}


UNICORN_EXPORT
uc_err uc_open(uc_arch arch, uc_mode mode, uc_engine **result)
{
    struct uc_struct *uc;

    if (arch < UC_ARCH_MAX) {
        uc = calloc(1, sizeof(*uc));
        if (!uc) {
            // memory insufficient
            return UC_ERR_NOMEM;
        }

        /* qemu/exec.c: phys_map_node_reserve() */
        uc->alloc_hint = 16;
        uc->errnum = UC_ERR_OK;
        uc->arch = arch;
        uc->mode = mode;

        // uc->ram_list = { .blocks = QLIST_HEAD_INITIALIZER(ram_list.blocks) };
        QLIST_INIT(&uc->ram_list.blocks);

        QTAILQ_INIT(&uc->memory_listeners);

        QTAILQ_INIT(&uc->address_spaces);

        switch(arch) {
            default:
                break;
#ifdef UNICORN_HAS_M68K
            case UC_ARCH_M68K:
                if ((mode & ~UC_MODE_M68K_MASK) ||
                        !(mode & UC_MODE_BIG_ENDIAN)) {
                    free(uc);
                    return UC_ERR_MODE;
                }
                uc->init_arch = m68k_uc_init;
                break;
#endif
#ifdef UNICORN_HAS_X86
            case UC_ARCH_X86:
                if ((mode & ~UC_MODE_X86_MASK) ||
                        (mode & UC_MODE_BIG_ENDIAN) ||
                        !(mode & (UC_MODE_16|UC_MODE_32|UC_MODE_64))) {
                    free(uc);
                    return UC_ERR_MODE;
                }
                uc->init_arch = x86_uc_init;
                break;
#endif
#ifdef UNICORN_HAS_ARM
            case UC_ARCH_ARM:
                if ((mode & ~UC_MODE_ARM_MASK)) {
                    free(uc);
                    return UC_ERR_MODE;
                }
                if (mode & UC_MODE_BIG_ENDIAN) {
                    uc->init_arch = armeb_uc_init;
                } else {
                    uc->init_arch = arm_uc_init;
                }

                if (mode & UC_MODE_THUMB) {
                    uc->thumb = 1;
                }
                break;
#endif
#ifdef UNICORN_HAS_ARM64
            case UC_ARCH_ARM64:
                if (mode & ~UC_MODE_ARM_MASK) {
                    free(uc);
                    return UC_ERR_MODE;
                }
                if (mode & UC_MODE_BIG_ENDIAN) {
                    uc->init_arch = arm64eb_uc_init;
                } else {
                    uc->init_arch = arm64_uc_init;
                }
                break;
#endif

#if defined(UNICORN_HAS_MIPS) || defined(UNICORN_HAS_MIPSEL) || defined(UNICORN_HAS_MIPS64) || defined(UNICORN_HAS_MIPS64EL)
            case UC_ARCH_MIPS:
                if ((mode & ~UC_MODE_MIPS_MASK) ||
                        !(mode & (UC_MODE_MIPS32|UC_MODE_MIPS64))) {
                    free(uc);
                    return UC_ERR_MODE;
                }
                if (mode & UC_MODE_BIG_ENDIAN) {
#ifdef UNICORN_HAS_MIPS
                    if (mode & UC_MODE_MIPS32) {
                        uc->init_arch = mips_uc_init;
                    }
#endif
#ifdef UNICORN_HAS_MIPS64
                    if (mode & UC_MODE_MIPS64) {
                        uc->init_arch = mips64_uc_init;
                    }
#endif
                } else {    // little endian
#ifdef UNICORN_HAS_MIPSEL
                    if (mode & UC_MODE_MIPS32) {
                        uc->init_arch = mipsel_uc_init;
                    }
#endif
#ifdef UNICORN_HAS_MIPS64EL
                    if (mode & UC_MODE_MIPS64) {
                        uc->init_arch = mips64el_uc_init;
                    }
#endif
                }
                break;
#endif

#ifdef UNICORN_HAS_SPARC
            case UC_ARCH_SPARC:
                if ((mode & ~UC_MODE_SPARC_MASK) ||
                        !(mode & UC_MODE_BIG_ENDIAN) ||
                        !(mode & (UC_MODE_SPARC32|UC_MODE_SPARC64))) {
                    free(uc);
                    return UC_ERR_MODE;
                }
                if (mode & UC_MODE_SPARC64) {
                    uc->init_arch = sparc64_uc_init;
                } else {
                    uc->init_arch = sparc_uc_init;
                }
                break;
#endif
#ifdef UNICORN_HAS_PPC
            case UC_ARCH_PPC:
                if ((mode & ~UC_MODE_PPC_MASK) ||
                        !(mode & UC_MODE_BIG_ENDIAN) ||
                        !(mode & (UC_MODE_PPC32|UC_MODE_PPC64))) {
                    free(uc);
                    return UC_ERR_MODE;
                }
                if (mode & UC_MODE_PPC64) {
                    uc->init_arch = ppc64_uc_init;
                } else {
                    uc->init_arch = ppc_uc_init;
                }
                break;
#endif
#ifdef UNICORN_HAS_RISCV
            case UC_ARCH_RISCV:
                if ((mode & ~UC_MODE_RISCV_MASK) ||
                        !(mode & (UC_MODE_RISCV32|UC_MODE_RISCV64))) {
                    free(uc);
                    return UC_ERR_MODE;
                }
                if (mode & UC_MODE_RISCV32) {
                    uc->init_arch = riscv32_uc_init;
                } else if (mode & UC_MODE_RISCV64) {
                    uc->init_arch =riscv64_uc_init;
                } else {
                    free(uc);
                    return UC_ERR_MODE;
                }
                break;
#endif

        }

        if (uc->init_arch == NULL) {
            return UC_ERR_ARCH;
        }

        if (machine_initialize(uc)) {
            return UC_ERR_RESOURCE;
        }

        // init fpu softfloat
        uc->softfloat_initialize();

        *result = uc;

        if (uc->reg_reset) {
            uc->reg_reset(uc);
        }

        return UC_ERR_OK;
    } else {
        return UC_ERR_ARCH;
    }
}


UNICORN_EXPORT
uc_err uc_close(uc_engine *uc)
{
    int i;
    struct list_item *cur;
    struct hook *hook;
    MemoryRegion *mr;

    // Cleanup internally.
    if (uc->release) {
        uc->release(uc->tcg_ctx);
    }
    g_free(uc->tcg_ctx);

    // Cleanup CPU.
    g_free(uc->cpu->cpu_ases);
    g_free(uc->cpu->thread);

    /* cpu */
    free(uc->cpu);

    /* flatviews */
    g_hash_table_destroy(uc->flat_views);
    
    // During flatviews destruction, we may still access memory regions.
    // So we free them afterwards.
    /* memory */
    mr = &uc->io_mem_unassigned;
    mr->destructor(mr);
    mr = uc->system_io;
    mr->destructor(mr);
    mr = uc->system_memory;
    mr->destructor(mr);
    g_free(uc->system_memory);
    g_free(uc->system_io);

    // Thread relateds.
    if (uc->qemu_thread_data) {
        g_free(uc->qemu_thread_data);
    }

    /* free */
    g_free(uc->init_target_page);

    // Other auxilaries.
    g_free(uc->l1_map);

    if (uc->bounce.buffer) {
        free(uc->bounce.buffer);
    }

    // free hooks and hook lists
    for (i = 0; i < UC_HOOK_MAX; i++) {
        cur = uc->hook[i].head;
        // hook can be in more than one list
        // so we refcount to know when to free
        while (cur) {
            hook = (struct hook *)cur->data;
            if (--hook->refs == 0) {
                free(hook);
            }
            cur = cur->next;
        }
        list_clear(&uc->hook[i]);
    }

    free(uc->mapped_blocks);

    // free the saved contexts list and notify them that uc has been closed.
    cur = uc->saved_contexts.head;
    while (cur != NULL) {
        struct list_item *next = cur->next;
        struct uc_context *context = (struct uc_context*)cur->data;
        context->uc = NULL;
        cur = next;
    }
    list_clear(&uc->saved_contexts);

    // finally, free uc itself.
    memset(uc, 0, sizeof(*uc));
    free(uc);

    return UC_ERR_OK;
}


UNICORN_EXPORT
uc_err uc_reg_read_batch(uc_engine *uc, int *ids, void **vals, int count)
{
    int ret = UC_ERR_OK;
    if (uc->reg_read) {
        ret = uc->reg_read(uc, (unsigned int *)ids, vals, count);
    } else {
        return UC_ERR_HANDLE;
    }

    return ret;
}


UNICORN_EXPORT
uc_err uc_reg_write_batch(uc_engine *uc, int *ids, void *const *vals, int count)
{
    int ret = UC_ERR_OK;
    if (uc->reg_write) {
        ret = uc->reg_write(uc, (unsigned int *)ids, vals, count);
    } else {
        return UC_ERR_HANDLE;
    }

    return ret;
}


UNICORN_EXPORT
uc_err uc_reg_read(uc_engine *uc, int regid, void *value)
{
    return uc_reg_read_batch(uc, &regid, &value, 1);
}

UNICORN_EXPORT
uc_err uc_reg_write(uc_engine *uc, int regid, const void *value)
{
    return uc_reg_write_batch(uc, &regid, (void *const *)&value, 1);
}

// check if a memory area is mapped
// this is complicated because an area can overlap adjacent blocks
static bool check_mem_area(uc_engine *uc, uint64_t address, size_t size)
{
    size_t count = 0, len;

    while(count < size) {
        MemoryRegion *mr = memory_mapping(uc, address);
        if (mr) {
            len = (size_t)MIN(size - count, mr->end - address);
            count += len;
            address += len;
        } else {// this address is not mapped in yet
            break;
        }
    }

    return (count == size);
}


UNICORN_EXPORT
uc_err uc_mem_read(uc_engine *uc, uint64_t address, void *_bytes, size_t size)
{
    size_t count = 0, len;
    uint8_t *bytes = _bytes;

    // qemu cpu_physical_memory_rw() size is an int
    if (size > INT_MAX)
        return UC_ERR_ARG;

    if (uc->mem_redirect) {
        address = uc->mem_redirect(address);
    }

    if (!check_mem_area(uc, address, size)) {
        return UC_ERR_READ_UNMAPPED;
    }

    // memory area can overlap adjacent memory blocks
    while(count < size) {
        MemoryRegion *mr = memory_mapping(uc, address);
        if (mr) {
            len = (size_t)MIN(size - count, mr->end - address);
            if (uc->read_mem(&uc->address_space_memory, address, bytes, len) == false) {
                break;
            }
            count += len;
            address += len;
            bytes += len;
        } else { // this address is not mapped in yet
            break;
        }
    }

    if (count == size) {
        return UC_ERR_OK;
    } else {
        return UC_ERR_READ_UNMAPPED;
    }
}

UNICORN_EXPORT
uc_err uc_mem_write(uc_engine *uc, uint64_t address, const void *_bytes, size_t size)
{
    size_t count = 0, len;
    const uint8_t *bytes = _bytes;

    // qemu cpu_physical_memory_rw() size is an int
    if (size > INT_MAX)
        return UC_ERR_ARG;

    if (uc->mem_redirect) {
        address = uc->mem_redirect(address);
    }

    if (!check_mem_area(uc, address, size)) {
        return UC_ERR_WRITE_UNMAPPED;
    }

    // memory area can overlap adjacent memory blocks
    while(count < size) {
        MemoryRegion *mr = memory_mapping(uc, address);
        if (mr) {
            uint32_t operms = mr->perms;
            if (!(operms & UC_PROT_WRITE)) {// write protected
                // but this is not the program accessing memory, so temporarily mark writable
                uc->readonly_mem(mr, false);
            }

            len = (size_t)MIN(size - count, mr->end - address);
            if (uc->write_mem(&uc->address_space_memory, address, bytes, len) == false) {
                break;
            }

            if (!(operms & UC_PROT_WRITE)) {// write protected
                // now write protect it again
                uc->readonly_mem(mr, true);
            }

            count += len;
            address += len;
            bytes += len;
        } else {// this address is not mapped in yet
            break;
        }
    }

    if (count == size) {
        return UC_ERR_OK;
    } else {
        return UC_ERR_WRITE_UNMAPPED;
    }
}

#define TIMEOUT_STEP 2    // microseconds
static void *_timeout_fn(void *arg)
{
    struct uc_struct *uc = arg;
    int64_t current_time = get_clock();

    do {
        usleep(TIMEOUT_STEP);
        // perhaps emulation is even done before timeout?
        if (uc->emulation_done) {
            break;
        }
    } while((uint64_t)(get_clock() - current_time) < uc->timeout);

    // timeout before emulation is done?
    if (!uc->emulation_done) {
        uc->timed_out = true;
        // force emulation to stop
        uc_emu_stop(uc);
    }

    return NULL;
}

static void enable_emu_timer(uc_engine *uc, uint64_t timeout)
{
    uc->timeout = timeout;
    qemu_thread_create(uc, &uc->timer, "timeout", _timeout_fn,
            uc, QEMU_THREAD_JOINABLE);
}

static void hook_count_cb(struct uc_struct *uc, uint64_t address, uint32_t size, void *user_data)
{
    // count this instruction. ah ah ah.
    uc->emu_counter++;
    // printf(":: emu counter = %u, at %lx\n", uc->emu_counter, address);

    if (uc->emu_counter > uc->emu_count) {
        // printf(":: emu counter = %u, stop emulation\n", uc->emu_counter);
        uc_emu_stop(uc);
    }
}

static void clear_deleted_hooks(uc_engine *uc)
{
    struct list_item * cur;
    struct hook * hook;
    int i;
    
    for (cur = uc->hooks_to_del.head; cur != NULL && (hook = (struct hook *)cur->data); cur = cur->next) {
        assert(hook->to_delete);
        for (i = 0; i < UC_HOOK_MAX; i++) {
            if (list_remove(&uc->hook[i], (void *)hook)) {
                if (--hook->refs == 0) {
                    free(hook);
                }

                // a hook cannot be twice in the same list
                break;
            }
        }
    }

    list_clear(&uc->hooks_to_del);
}

UNICORN_EXPORT
uc_err uc_emu_start(uc_engine* uc, uint64_t begin, uint64_t until, uint64_t timeout, size_t count)
{
    // reset the counter
    uc->emu_counter = 0;
    uc->invalid_error = UC_ERR_OK;
    uc->emulation_done = false;
    uc->size_recur_mem = 0;
    uc->timed_out = false;
    uc->first_tb = true;

    switch(uc->arch) {
        default:
            break;
#ifdef UNICORN_HAS_M68K
        case UC_ARCH_M68K:
            uc_reg_write(uc, UC_M68K_REG_PC, &begin);
            break;
#endif
#ifdef UNICORN_HAS_X86
        case UC_ARCH_X86:
            switch(uc->mode) {
                default:
                    break;
                case UC_MODE_16: {
                    uint64_t ip;
                    uint16_t cs;

                    uc_reg_read(uc, UC_X86_REG_CS, &cs);
                    // compensate for later adding up IP & CS
                    ip = begin - cs*16;
                    uc_reg_write(uc, UC_X86_REG_IP, &ip);
                    break;
                }
                case UC_MODE_32:
                    uc_reg_write(uc, UC_X86_REG_EIP, &begin);
                    break;
                case UC_MODE_64:
                    uc_reg_write(uc, UC_X86_REG_RIP, &begin);
                    break;
            }
            break;
#endif
#ifdef UNICORN_HAS_ARM
        case UC_ARCH_ARM:
            uc_reg_write(uc, UC_ARM_REG_R15, &begin);
            break;
#endif
#ifdef UNICORN_HAS_ARM64
        case UC_ARCH_ARM64:
            uc_reg_write(uc, UC_ARM64_REG_PC, &begin);
            break;
#endif
#ifdef UNICORN_HAS_MIPS
        case UC_ARCH_MIPS:
            // TODO: MIPS32/MIPS64/BIGENDIAN etc
            uc_reg_write(uc, UC_MIPS_REG_PC, &begin);
            break;
#endif
#ifdef UNICORN_HAS_SPARC
        case UC_ARCH_SPARC:
            // TODO: Sparc/Sparc64
            uc_reg_write(uc, UC_SPARC_REG_PC, &begin);
            break;
#endif
#ifdef UNICORN_HAS_PPC
        case UC_ARCH_PPC:
            uc_reg_write(uc, UC_PPC_REG_PC, &begin);
            break;
#endif
#ifdef UNICORN_HAS_RISCV
        case UC_ARCH_RISCV:
            uc_reg_write(uc, UC_RISCV_REG_PC, &begin);
            break;
#endif
    }

    uc->stop_request = false;

    uc->emu_count = count;
    // remove count hook if counting isn't necessary
    if (count <= 0 && uc->count_hook != 0) {
        uc_hook_del(uc, uc->count_hook);
        uc->count_hook = 0;
    }
    // set up count hook to count instructions.
    if (count > 0 && uc->count_hook == 0) {
        uc_err err;
        // callback to count instructions must be run before everything else,
        // so instead of appending, we must insert the hook at the begin
        // of the hook list
        uc->hook_insert = 1;
        err = uc_hook_add(uc, &uc->count_hook, UC_HOOK_CODE, hook_count_cb, NULL, 1, 0);
        // restore to append mode for uc_hook_add()
        uc->hook_insert = 0;
        if (err != UC_ERR_OK) {
            return err;
        }
    }

    uc->addr_end = until;

    if (timeout) {
        enable_emu_timer(uc, timeout * 1000);   // microseconds -> nanoseconds
    }

    uc->vm_start(uc);

    // emulation is done
    uc->emulation_done = true;

    // remove hooks to delete
    clear_deleted_hooks(uc);

    if (timeout) {
        // wait for the timer to finish
        qemu_thread_join(&uc->timer);
    }

    return uc->invalid_error;
}


UNICORN_EXPORT
uc_err uc_emu_stop(uc_engine *uc)
{
    if (uc->emulation_done) {
        return UC_ERR_OK;
    }

    uc->stop_request = true;
    // TODO: make this atomic somehow?
    if (uc->cpu) {
        // exit the current TB
        cpu_exit(uc->cpu);
    }

    return UC_ERR_OK;
}

// find if a memory range overlaps with existing mapped regions
static bool memory_overlap(struct uc_struct *uc, uint64_t begin, size_t size)
{
    unsigned int i;
    uint64_t end = begin + size - 1;

    for(i = 0; i < uc->mapped_block_count; i++) {
        // begin address falls inside this region?
        if (begin >= uc->mapped_blocks[i]->addr && begin <= uc->mapped_blocks[i]->end - 1) {
            return true;
        }
        // end address falls inside this region?
        if (end >= uc->mapped_blocks[i]->addr && end <= uc->mapped_blocks[i]->end - 1) {
            return true;
        }
        // this region falls totally inside this range?
        if (begin < uc->mapped_blocks[i]->addr && end > uc->mapped_blocks[i]->end - 1) {
            return true;
        }
    }

    // not found
    return false;
}

// common setup/error checking shared between uc_mem_map and uc_mem_map_ptr
static uc_err mem_map(uc_engine *uc, uint64_t address, size_t size, uint32_t perms, MemoryRegion *block)
{
    MemoryRegion **regions;

    if (block == NULL) {
        return UC_ERR_NOMEM;
    }

    if ((uc->mapped_block_count & (MEM_BLOCK_INCR - 1)) == 0) {  //time to grow
        regions = (MemoryRegion**)g_realloc(uc->mapped_blocks,
                sizeof(MemoryRegion*) * (uc->mapped_block_count + MEM_BLOCK_INCR));
        if (regions == NULL) {
            return UC_ERR_NOMEM;
        }
        uc->mapped_blocks = regions;
    }

    uc->mapped_blocks[uc->mapped_block_count] = block;
    uc->mapped_block_count++;

    return UC_ERR_OK;
}

static uc_err mem_map_check(uc_engine *uc, uint64_t address, size_t size, uint32_t perms)
{
    if (size == 0) {
        // invalid memory mapping
        return UC_ERR_ARG;
    }

    // address cannot wrapp around
    if (address + size - 1 < address) {
        return UC_ERR_ARG;
    }

    // address must be aligned to uc->target_page_size
    if ((address & uc->target_page_align) != 0) {
        return UC_ERR_ARG;
    }

    // size must be multiple of uc->target_page_size
    if ((size & uc->target_page_align) != 0) {
        return UC_ERR_ARG;
    }

    // check for only valid permissions
    if ((perms & ~UC_PROT_ALL) != 0) {
        return UC_ERR_ARG;
    }

    // this area overlaps existing mapped regions?
    if (memory_overlap(uc, address, size)) {
        return UC_ERR_MAP;
    }

    return UC_ERR_OK;
}

UNICORN_EXPORT
uc_err uc_mem_map(uc_engine *uc, uint64_t address, size_t size, uint32_t perms)
{
    uc_err res;

    if (uc->mem_redirect) {
        address = uc->mem_redirect(address);
    }

    res = mem_map_check(uc, address, size, perms);
    if (res) {
        return res;
    }

    return mem_map(uc, address, size, perms, uc->memory_map(uc, address, size, perms));
}

UNICORN_EXPORT
uc_err uc_mem_map_ptr(uc_engine *uc, uint64_t address, size_t size, uint32_t perms, void *ptr)
{
    uc_err res;

    if (ptr == NULL) {
        return UC_ERR_ARG;
    }

    if (uc->mem_redirect) {
        address = uc->mem_redirect(address);
    }

    res = mem_map_check(uc, address, size, perms);
    if (res) {
        return res;
    }

    return mem_map(uc, address, size, UC_PROT_ALL, uc->memory_map_ptr(uc, address, size, perms, ptr));
}

UNICORN_EXPORT
uc_err uc_mmio_map(uc_engine *uc, uint64_t address, size_t size,
                   uc_cb_mmio_read_t read_cb, void *user_data_read,
                   uc_cb_mmio_write_t write_cb, void *user_data_write)
{
    uc_err res;

    if (uc->mem_redirect) {
        address = uc->mem_redirect(address);
    }

    res = mem_map_check(uc, address, size, UC_PROT_ALL);
    if (res)
        return res;

    // The callbacks do not need to be checked for NULL here, as their presence
    // (or lack thereof) will determine the permissions used.
    return mem_map(uc, address, size, UC_PROT_NONE,
                   uc->memory_map_io(uc, address, size, read_cb, write_cb, user_data_read, user_data_write));
}

// Create a backup copy of the indicated MemoryRegion.
// Generally used in prepartion for splitting a MemoryRegion.
static uint8_t *copy_region(struct uc_struct *uc, MemoryRegion *mr)
{
    uint8_t *block = (uint8_t *)g_malloc0((size_t)int128_get64(mr->size));
    if (block != NULL) {
        uc_err err = uc_mem_read(uc, mr->addr, block, (size_t)int128_get64(mr->size));
        if (err != UC_ERR_OK) {
            free(block);
            block = NULL;
        }
    }

    return block;
}

/*
   Split the given MemoryRegion at the indicated address for the indicated size
   this may result in the create of up to 3 spanning sections. If the delete
   parameter is true, the no new section will be created to replace the indicate
   range. This functions exists to support uc_mem_protect and uc_mem_unmap.

   This is a static function and callers have already done some preliminary
   parameter validation.

   The do_delete argument indicates that we are being called to support
   uc_mem_unmap. In this case we save some time by choosing NOT to remap
   the areas that are intended to get unmapped
 */
// TODO: investigate whether qemu region manipulation functions already offered
// this capability
static bool split_region(struct uc_struct *uc, MemoryRegion *mr, uint64_t address,
        size_t size, bool do_delete)
{
    uint8_t *backup;
    uint32_t perms;
    uint64_t begin, end, chunk_end;
    size_t l_size, m_size, r_size;
    RAMBlock *block = NULL;
    bool prealloc = false;

    chunk_end = address + size;

    // if this region belongs to area [address, address+size],
    // then there is no work to do.
    if (address <= mr->addr && chunk_end >= mr->end) {
        return true;
    }

    if (size == 0) {
        // trivial case
        return true;
    }

    if (address >= mr->end || chunk_end <= mr->addr) {
        // impossible case
        return false;
    }

    QLIST_FOREACH(block, &uc->ram_list.blocks, next) {
        if (block->offset <= mr->addr && block->used_length >= (mr->end - mr->addr)) {
            break;
        }
    }

    if (block == NULL) {
        return false;
    }

    // RAM_PREALLOC is not defined outside exec.c and I didn't feel like
    // moving it
    prealloc = !!(block->flags & 1);

    if (block->flags & 1) {
        backup = block->host;
    } else {
        backup = copy_region(uc, mr);
        if (backup == NULL) {
            return false;
        }
    }

    // save the essential information required for the split before mr gets deleted
    perms = mr->perms;
    begin = mr->addr;
    end = mr->end;

    // unmap this region first, then do split it later
    if (uc_mem_unmap(uc, mr->addr, (size_t)int128_get64(mr->size)) != UC_ERR_OK) {
        goto error;
    }

    /* overlapping cases
     *               |------mr------|
     * case 1    |---size--|
     * case 2           |--size--|
     * case 3                  |---size--|
     */

    // adjust some things
    if (address < begin) {
        address = begin;
    }
    if (chunk_end > end) {
        chunk_end = end;
    }

    // compute sub region sizes
    l_size = (size_t)(address - begin);
    r_size = (size_t)(end - chunk_end);
    m_size = (size_t)(chunk_end - address);

    // If there are error in any of the below operations, things are too far gone
    // at that point to recover. Could try to remap orignal region, but these smaller
    // allocation just failed so no guarantee that we can recover the original
    // allocation at this point
    if (l_size > 0) {
        if (!prealloc) {
            if (uc_mem_map(uc, begin, l_size, perms) != UC_ERR_OK) {
                goto error;
            }
            if (uc_mem_write(uc, begin, backup, l_size) != UC_ERR_OK) {
                goto error;
            }
        } else {
            if (uc_mem_map_ptr(uc, begin, l_size, perms, backup) != UC_ERR_OK) {
                goto error;
            }
        }
    }

    if (m_size > 0 && !do_delete) {
        if (!prealloc) {
            if (uc_mem_map(uc, address, m_size, perms) != UC_ERR_OK) {
                goto error;
            }
            if (uc_mem_write(uc, address, backup + l_size, m_size) != UC_ERR_OK) {
                goto error;
            }
        } else {
            if (uc_mem_map_ptr(uc, address, m_size, perms, backup + l_size) != UC_ERR_OK) {
                goto error;
            }
        }
    }

    if (r_size > 0) {
        if (!prealloc) {
            if (uc_mem_map(uc, chunk_end, r_size, perms) != UC_ERR_OK) {
                goto error;
            }
            if (uc_mem_write(uc, chunk_end, backup + l_size + m_size, r_size) != UC_ERR_OK) {
                goto error;
            }
        } else {
            if (uc_mem_map_ptr(uc, chunk_end, r_size, perms, backup + l_size + m_size) != UC_ERR_OK) {
                goto error;
            }
        }
    }

    if (!prealloc) {
        free(backup);
    }
    return true;

error:
    if (!prealloc) {
        free(backup);
    }
    return false;
}

UNICORN_EXPORT
uc_err uc_mem_protect(struct uc_struct *uc, uint64_t address, size_t size, uint32_t perms)
{
    MemoryRegion *mr;
    uint64_t addr = address;
    size_t count, len;
    bool remove_exec = false;

    if (size == 0) {
        // trivial case, no change
        return UC_ERR_OK;
    }

    // address must be aligned to uc->target_page_size
    if ((address & uc->target_page_align) != 0) {
        return UC_ERR_ARG;
    }

    // size must be multiple of uc->target_page_size
    if ((size & uc->target_page_align) != 0) {
        return UC_ERR_ARG;
    }

    // check for only valid permissions
    if ((perms & ~UC_PROT_ALL) != 0) {
        return UC_ERR_ARG;
    }

    if (uc->mem_redirect) {
        address = uc->mem_redirect(address);
    }

    // check that user's entire requested block is mapped
    if (!check_mem_area(uc, address, size)) {
        return UC_ERR_NOMEM;
    }

    // Now we know entire region is mapped, so change permissions
    // We may need to split regions if this area spans adjacent regions
    addr = address;
    count = 0;
    while(count < size) {
        mr = memory_mapping(uc, addr);
        len = (size_t)MIN(size - count, mr->end - addr);
        if (!split_region(uc, mr, addr, len, false)) {
            return UC_ERR_NOMEM;
        }

        mr = memory_mapping(uc, addr);
        // will this remove EXEC permission?
        if (((mr->perms & UC_PROT_EXEC) != 0) && ((perms & UC_PROT_EXEC) == 0)) {
            remove_exec = true;
        }
        mr->perms = perms;
        uc->readonly_mem(mr, (perms & UC_PROT_WRITE) == 0);

        count += len;
        addr += len;
    }

    // if EXEC permission is removed, then quit TB and continue at the same place
    if (remove_exec) {
        uc->quit_request = true;
        uc_emu_stop(uc);
    }

    return UC_ERR_OK;
}

UNICORN_EXPORT
uc_err uc_mem_unmap(struct uc_struct *uc, uint64_t address, size_t size)
{
    MemoryRegion *mr;
    uint64_t addr;
    size_t count, len;

    if (size == 0) {
        // nothing to unmap
        return UC_ERR_OK;
    }

    // address must be aligned to uc->target_page_size
    if ((address & uc->target_page_align) != 0) {
        return UC_ERR_ARG;
    }

    // size must be multiple of uc->target_page_size
    if ((size & uc->target_page_align) != 0) {
        return UC_ERR_ARG;
    }

    if (uc->mem_redirect) {
        address = uc->mem_redirect(address);
    }

    // check that user's entire requested block is mapped
    if (!check_mem_area(uc, address, size)) {
        return UC_ERR_NOMEM;
    }

    // Now we know entire region is mapped, so do the unmap
    // We may need to split regions if this area spans adjacent regions
    addr = address;
    count = 0;
    while(count < size) {
        mr = memory_mapping(uc, addr);
        len = (size_t)MIN(size - count, mr->end - addr);
        if (!split_region(uc, mr, addr, len, true)) {
            return UC_ERR_NOMEM;
        }

        // if we can retrieve the mapping, then no splitting took place
        // so unmap here
        mr = memory_mapping(uc, addr);
        if (mr != NULL) {
           uc->memory_unmap(uc, mr);
        }
        count += len;
        addr += len;
    }

    return UC_ERR_OK;
}

// find the memory region of this address
MemoryRegion *memory_mapping(struct uc_struct* uc, uint64_t address)
{
    unsigned int i;

    if (uc->mapped_block_count == 0) {
        return NULL;
    }

    if (uc->mem_redirect) {
        address = uc->mem_redirect(address);
    }

    // try with the cache index first
    i = uc->mapped_block_cache_index;

    if (i < uc->mapped_block_count && address >= uc->mapped_blocks[i]->addr && address < uc->mapped_blocks[i]->end) {
        return uc->mapped_blocks[i];
    }

    for(i = 0; i < uc->mapped_block_count; i++) {
        if (address >= uc->mapped_blocks[i]->addr && address <= uc->mapped_blocks[i]->end - 1) {
            // cache this index for the next query
            uc->mapped_block_cache_index = i;
            return uc->mapped_blocks[i];
        }
    }

    // not found
    return NULL;
}

UNICORN_EXPORT
uc_err uc_hook_add(uc_engine *uc, uc_hook *hh, int type, void *callback,
        void *user_data, uint64_t begin, uint64_t end, ...)
{
    int ret = UC_ERR_OK;
    int i = 0;

    struct hook *hook = calloc(1, sizeof(struct hook));
    if (hook == NULL) {
        return UC_ERR_NOMEM;
    }

    hook->begin = begin;
    hook->end = end;
    hook->type = type;
    hook->callback = callback;
    hook->user_data = user_data;
    hook->refs = 0;
    hook->to_delete = false;
    *hh = (uc_hook)hook;

    // UC_HOOK_INSN has an extra argument for instruction ID
    if (type & UC_HOOK_INSN) {
        va_list valist;

        va_start(valist, end);
        hook->insn = va_arg(valist, int);
        va_end(valist);

        if (uc->insn_hook_validate) {
            if (! uc->insn_hook_validate(hook->insn)) {
                free(hook);
                return UC_ERR_HOOK;
            }
        }

        if (uc->hook_insert) {
            if (list_insert(&uc->hook[UC_HOOK_INSN_IDX], hook) == NULL) {
                free(hook);
                return UC_ERR_NOMEM;
            }
        } else {
            if (list_append(&uc->hook[UC_HOOK_INSN_IDX], hook) == NULL) {
                free(hook);
                return UC_ERR_NOMEM;
            }
        }

        hook->refs++;
        return UC_ERR_OK;
    }

    while ((type >> i) > 0) {
        if ((type >> i) & 1) {
            // TODO: invalid hook error?
            if (i < UC_HOOK_MAX) {
                if (uc->hook_insert) {
                    if (list_insert(&uc->hook[i], hook) == NULL) {
                        if (hook->refs == 0) {
                            free(hook);
                        }
                        return UC_ERR_NOMEM;
                    }
                } else {
                    if (list_append(&uc->hook[i], hook) == NULL) {
                        if (hook->refs == 0) {
                            free(hook);
                        }
                        return UC_ERR_NOMEM;
                    }
                }
                hook->refs++;
            }
        }
        i++;
    }

    // we didn't use the hook
    // TODO: return an error?
    if (hook->refs == 0) {
        free(hook);
    }

    return ret;
}


UNICORN_EXPORT
uc_err uc_hook_del(uc_engine *uc, uc_hook hh)
{
    int i;
    struct hook *hook = (struct hook *)hh;

    // we can't dereference hook->type if hook is invalid
    // so for now we need to iterate over all possible types to remove the hook
    // which is less efficient
    // an optimization would be to align the hook pointer
    // and store the type mask in the hook pointer.
    for (i = 0; i < UC_HOOK_MAX; i++) {
        if (list_exists(&uc->hook[i], (void *) hook)) {
            hook->to_delete = true;
            list_append(&uc->hooks_to_del, hook);
        }
    }

    return UC_ERR_OK;
}

// TCG helper
void helper_uc_tracecode(int32_t size, uc_hook_idx index, void *handle, int64_t address);
void helper_uc_tracecode(int32_t size, uc_hook_idx index, void *handle, int64_t address)
{
    struct uc_struct *uc = handle;
    struct list_item *cur;
    struct hook *hook;
    int hook_flags = index & UC_HOOK_FLAG_MASK; // The index here may contain additional flags. See the comments of uc_hook_idx for details.

    index = index & UC_HOOK_IDX_MASK;

    // sync PC in CPUArchState with address
    if (uc->set_pc) {
        uc->set_pc(uc, address);
    }

    // the last callback may already asked to stop emulation
    if (uc->stop_request && !(hook_flags & UC_HOOK_FLAG_NO_STOP)) {
        return;
    }

    for (cur = uc->hook[index].head; cur != NULL && (hook = (struct hook *)cur->data); cur = cur->next) {
        if (hook->to_delete) {
            continue;
        }

        // on invalid block/instruction, call instruction counter (if enable), then quit
        if (size == 0) {
            if (index == UC_HOOK_CODE_IDX && uc->count_hook) {
                // this is the instruction counter (first hook in the list)
                ((uc_cb_hookcode_t)hook->callback)(uc, address, size, hook->user_data);
            }

            return;
        }

        if (HOOK_BOUND_CHECK(hook, (uint64_t)address)) {
            ((uc_cb_hookcode_t)hook->callback)(uc, address, size, hook->user_data);
        }

        // the last callback may already asked to stop emulation
        // Unicorn:
        //   In an ARM IT block, we behave like the emulation continues normally. No check_exit_request
        //   is generated and the hooks are triggered normally. In other words, the whole IT block is
        //   treated as a single instruction.
        if (uc->stop_request && !(hook_flags & UC_HOOK_FLAG_NO_STOP)) {
            break;
        }
    }
}

UNICORN_EXPORT
uc_err uc_mem_regions(uc_engine *uc, uc_mem_region **regions, uint32_t *count)
{
    uint32_t i;
    uc_mem_region *r = NULL;

    *count = uc->mapped_block_count;

    if (*count) {
        r = g_malloc0(*count * sizeof(uc_mem_region));
        if (r == NULL) {
            // out of memory
            return UC_ERR_NOMEM;
        }
    }

    for (i = 0; i < *count; i++) {
        r[i].begin = uc->mapped_blocks[i]->addr;
        r[i].end = uc->mapped_blocks[i]->end - 1;
        r[i].perms = uc->mapped_blocks[i]->perms;
    }

    *regions = r;

    return UC_ERR_OK;
}

UNICORN_EXPORT
uc_err uc_query(uc_engine *uc, uc_query_type type, size_t *result)
{
    switch(type) {
        default:
            return UC_ERR_ARG;

        case UC_QUERY_PAGE_SIZE:
            *result = uc->target_page_size;
            break;

        case UC_QUERY_ARCH:
            *result = uc->arch;
            break;

        case UC_QUERY_MODE:
#ifdef UNICORN_HAS_ARM
            if (uc->arch == UC_ARCH_ARM) {
                return uc->query(uc, type, result);
            }
#endif
            return UC_ERR_ARG;

        case UC_QUERY_TIMEOUT:
            *result = uc->timed_out;
            break;
    }

    return UC_ERR_OK;
}

UNICORN_EXPORT
uc_err uc_context_alloc(uc_engine *uc, uc_context **context)
{
    struct uc_context **_context = context;
    size_t size = uc_context_size(uc);

    *_context = g_malloc(size);
    if (*_context) {
        (*_context)->jmp_env_size = sizeof(*uc->cpu->jmp_env);
        (*_context)->context_size = uc->cpu_context_size;
        (*_context)->arch = uc->arch;
        (*_context)->mode = uc->mode;
        (*_context)->uc = uc;
        if (list_insert(&uc->saved_contexts, *_context)) {
            return UC_ERR_OK;
        } else {
            return UC_ERR_NOMEM;
        }
    } else {
        return UC_ERR_NOMEM;
    }
}

UNICORN_EXPORT
uc_err uc_free(void *mem)
{
    g_free(mem);
    return UC_ERR_OK;
}

UNICORN_EXPORT
size_t uc_context_size(uc_engine *uc)
{
    // return the total size of struct uc_context
    return sizeof(uc_context) + uc->cpu_context_size + sizeof(*uc->cpu->jmp_env);
}

UNICORN_EXPORT
uc_err uc_context_save(uc_engine *uc, uc_context *context)
{
    memcpy(context->data, uc->cpu->env_ptr, context->context_size);
    memcpy(context->data + context->context_size, uc->cpu->jmp_env, context->jmp_env_size);

    return UC_ERR_OK;
}



UNICORN_EXPORT
uc_err uc_context_reg_write(uc_context *ctx, int regid, const void *value)
{
    return uc_context_reg_write_batch(ctx, &regid, (void *const *)&value, 1);
}

UNICORN_EXPORT
uc_err uc_context_reg_read(uc_context *ctx, int regid, void *value)
{
    return uc_context_reg_read_batch(ctx, &regid, &value, 1);
}

// Keep in mind that we don't a uc_engine when r/w the registers of a context.
static void find_context_reg_rw_function(uc_arch arch, uc_mode mode, context_reg_rw_t *rw)
{
    // We believe that the arch/mode pair is correct.
    switch(arch) {
        default:
            rw->context_reg_read = NULL;
            rw->context_reg_write = NULL;
            break;
#ifdef UNICORN_HAS_M68K
        case UC_ARCH_M68K:
            rw->context_reg_read = m68k_context_reg_read;
            rw->context_reg_write = m68k_context_reg_write;
            break;
#endif
#ifdef UNICORN_HAS_X86
        case UC_ARCH_X86:
            rw->context_reg_read = x86_context_reg_read;
            rw->context_reg_write = x86_context_reg_write;
            break;
#endif
#ifdef UNICORN_HAS_ARM
        case UC_ARCH_ARM:
            if (mode & UC_MODE_BIG_ENDIAN) {
                rw->context_reg_read = armeb_context_reg_read;
                rw->context_reg_write = armeb_context_reg_write;
            } else {
                rw->context_reg_read = arm_context_reg_read;
                rw->context_reg_write = arm_context_reg_write;
            }
#endif
#ifdef UNICORN_HAS_ARM64
        case UC_ARCH_ARM64:
            if (mode & UC_MODE_BIG_ENDIAN) {
                rw->context_reg_read = arm64eb_context_reg_read;
                rw->context_reg_write = arm64eb_context_reg_write;
            } else {
                rw->context_reg_read = arm64_context_reg_read;
                rw->context_reg_write = arm64_context_reg_write;
            }
            break;
#endif

#if defined(UNICORN_HAS_MIPS) || defined(UNICORN_HAS_MIPSEL) || defined(UNICORN_HAS_MIPS64) || defined(UNICORN_HAS_MIPS64EL)
        case UC_ARCH_MIPS:
            if (mode & UC_MODE_BIG_ENDIAN) {
#ifdef UNICORN_HAS_MIPS
                if (mode & UC_MODE_MIPS32) {
                    rw->context_reg_read = mips_context_reg_read;
                    rw->context_reg_write = mips_context_reg_write;
                }
#endif
#ifdef UNICORN_HAS_MIPS64
                if (mode & UC_MODE_MIPS64) {
                    rw->context_reg_read = mips64_context_reg_read;
                    rw->context_reg_write = mips64_context_reg_write;
                }
#endif
            } else {    // little endian
#ifdef UNICORN_HAS_MIPSEL
                if (mode & UC_MODE_MIPS32) {
                    rw->context_reg_read = mipsel_context_reg_read;
                    rw->context_reg_write = mipsel_context_reg_write;
                }
#endif
#ifdef UNICORN_HAS_MIPS64EL
                if (mode & UC_MODE_MIPS64) {
                    rw->context_reg_read = mips64el_context_reg_read;
                    rw->context_reg_write = mips64el_context_reg_write;
                }
#endif
            }
            break;
#endif

#ifdef UNICORN_HAS_SPARC
        case UC_ARCH_SPARC:
            if (mode & UC_MODE_SPARC64) {
                rw->context_reg_read = sparc64_context_reg_read;
                rw->context_reg_write = sparc64_context_reg_write;
            } else {
                rw->context_reg_read = sparc_context_reg_read;
                rw->context_reg_write = sparc_context_reg_write;
            }
            break;
#endif
#ifdef UNICORN_HAS_PPC
        case UC_ARCH_PPC:
            if (mode & UC_MODE_PPC64) {
                rw->context_reg_read = ppc64_context_reg_read;
                rw->context_reg_write = ppc64_context_reg_write;
            } else {
                rw->context_reg_read = ppc_context_reg_read;
                rw->context_reg_write = ppc_context_reg_write;
            }
            break;
#endif
#ifdef UNICORN_HAS_RISCV
        case UC_ARCH_RISCV:
            if (mode & UC_MODE_RISCV32) {
                rw->context_reg_read = riscv32_context_reg_read;
                rw->context_reg_write = riscv32_context_reg_write;
            } else if (mode & UC_MODE_RISCV64) {
                rw->context_reg_read = riscv64_context_reg_read;
                rw->context_reg_write = riscv64_context_reg_write;
            }
            break;
#endif
    }
    
    return;
}

UNICORN_EXPORT
uc_err uc_context_reg_write_batch(uc_context *ctx, int *ids, void *const *vals, int count)
{
    int ret = UC_ERR_OK;
    context_reg_rw_t rw;

    find_context_reg_rw_function(ctx->arch, ctx->mode, &rw);
    if (rw.context_reg_write) {
        ret = rw.context_reg_write(ctx, (unsigned int *)ids, vals, count);
    } else {
        return UC_ERR_HANDLE;
    }

    return ret;
}

UNICORN_EXPORT
uc_err uc_context_reg_read_batch(uc_context *ctx, int *ids, void **vals, int count)
{
    int ret = UC_ERR_OK;
    context_reg_rw_t rw;

    find_context_reg_rw_function(ctx->arch, ctx->mode, &rw);
    if (rw.context_reg_read) {
        ret = rw.context_reg_read(ctx, (unsigned int *)ids, vals, count);
    } else {
        return UC_ERR_HANDLE;
    }

    return ret;
}

UNICORN_EXPORT
uc_err uc_context_restore(uc_engine *uc, uc_context *context)
{
    memcpy(uc->cpu->env_ptr, context->data, context->context_size);
    if (list_exists(&uc->saved_contexts, context)) {
        memcpy(uc->cpu->jmp_env, context->data + context->context_size, context->jmp_env_size);
    }

    return UC_ERR_OK;
}

UNICORN_EXPORT
uc_err uc_context_free(uc_context *context)
{
    uc_engine* uc = context->uc;
    // if uc is NULL, it means that uc_engine has been free-ed.
    if (uc) {
        list_remove(&uc->saved_contexts, context);
    }
    return uc_free(context);
}