ruby/ujit_iface.c

#include <assert.h>
#include "insns.inc"
#include "internal.h"
#include "vm_core.h"
#include "vm_sync.h"
#include "vm_callinfo.h"
#include "builtin.h"
#include "internal/compile.h"
#include "internal/class.h"
#include "insns_info.inc"
#include "ujit.h"
#include "ujit_iface.h"
#include "ujit_codegen.h"
#include "ujit_core.h"
#include "ujit_hooks.inc"
#include "ujit.rbinc"
#include <capstone/capstone.h>

VALUE cUjitBlock;
VALUE cUjitDisasm;
VALUE cUjitDisasmInsn;

extern st_table * version_tbl;
extern codeblock_t *cb;

static const rb_data_type_t ujit_block_type = {
    "UJIT/Block",
    {0, 0, 0, },
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

static const rb_data_type_t ujit_disasm_type = {
    "UJIT/Disasm",
    {0, (void(*)(void *))cs_close, 0, },
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

bool rb_ujit_enabled;

// Hash table of encoded instructions
extern st_table *rb_encoded_insn_data;

// Write the uJIT entry point pre-call bytes
void 
cb_write_pre_call_bytes(codeblock_t* cb)
{
    for (size_t i = 0; i < sizeof(ujit_with_ec_pre_call_bytes); ++i)
        cb_write_byte(cb, ujit_with_ec_pre_call_bytes[i]);
}

// Write the uJIT exit post-call bytes
void 
cb_write_post_call_bytes(codeblock_t* cb)
{
    for (size_t i = 0; i < sizeof(ujit_with_ec_post_call_bytes); ++i)
        cb_write_byte(cb, ujit_with_ec_post_call_bytes[i]);
}

// Keep track of mapping from instructions to generated code
// See comment for rb_encoded_insn_data in iseq.c
void
map_addr2insn(void *code_ptr, int insn)
{
    const void * const *table = rb_vm_get_insns_address_table();
    const void * const translated_address = table[insn];
    st_data_t encoded_insn_data;
    if (st_lookup(rb_encoded_insn_data, (st_data_t)translated_address, &encoded_insn_data)) {
        st_insert(rb_encoded_insn_data, (st_data_t)code_ptr, encoded_insn_data);
    }
    else {
        rb_bug("ujit: failed to find info for original instruction while dealing with addr2insn");
    }
}

int
opcode_at_pc(const rb_iseq_t *iseq, const VALUE *pc)
{
    const VALUE at_pc = *pc;
    if (FL_TEST_RAW((VALUE)iseq, ISEQ_TRANSLATED)) {
        return rb_vm_insn_addr2opcode((const void *)at_pc);
    }
    else {
        return (int)at_pc;
    }
}

// Verify that calling with cd on receiver goes to callee
void
check_cfunc_dispatch(VALUE receiver, struct rb_call_data *cd, void *callee, rb_callable_method_entry_t *compile_time_cme)
{
    if (METHOD_ENTRY_INVALIDATED(compile_time_cme)) {
        rb_bug("ujit: output code uses invalidated cme %p", (void *)compile_time_cme);
    }

    bool callee_correct = false;
    const rb_callable_method_entry_t *cme = rb_callable_method_entry(CLASS_OF(receiver), vm_ci_mid(cd->ci));
    if (cme->def->type == VM_METHOD_TYPE_CFUNC) {
        const rb_method_cfunc_t *cfunc = UNALIGNED_MEMBER_PTR(cme->def, body.cfunc);
        if ((void *)cfunc->func == callee) {
            callee_correct = true;
        }
    }
    if (!callee_correct) {
        rb_bug("ujit: output code calls wrong method cd->cc->klass: %p", (void *)cd->cc->klass);
    }
}

MJIT_FUNC_EXPORTED VALUE rb_hash_has_key(VALUE hash, VALUE key);

bool
cfunc_needs_frame(const rb_method_cfunc_t *cfunc)
{
    void* fptr = (void*)cfunc->func;

    // Leaf C functions do not need a stack frame
    // or a stack overflow check
    return !(
        // Hash#key?
        fptr == (void*)rb_hash_has_key
    );
}

// GC root for interacting with the GC
struct ujit_root_struct {};

// Map cme_or_cc => [[iseq, offset]]. An entry in the map means compiled code at iseq[offset]
// is only valid when cme_or_cc is valid
static st_table *method_lookup_dependency;

struct compiled_region_array {
    int32_t size;
    int32_t capa;
    block_t* data[];
};

// Add an element to a region array, or allocate a new region array.
static struct compiled_region_array *
add_compiled_region(struct compiled_region_array *array, block_t* block)
{
    if (!array) {
        // Allocate a brand new array with space for one
        array = malloc(sizeof(*array) + sizeof(block_t*));
        if (!array) {
            return NULL;
        }
        array->size = 0;
        array->capa = 1;
    }
    if (array->size == INT32_MAX) {
        return NULL;
    }
    // Check if the region is already present
    for (int32_t i = 0; i < array->size; i++) {
        if (array->data[i] == block) {
            return array;
        }
    }
    if (array->size + 1 > array->capa) {
        // Double the array's capacity.
        int64_t double_capa = ((int64_t)array->capa) * 2;
        int32_t new_capa = (int32_t)double_capa;
        if (new_capa != double_capa) {
            return NULL;
        }
        array = realloc(array, sizeof(*array) + new_capa * sizeof(block_t*));
        if (array == NULL) {
            return NULL;
        }
        array->capa = new_capa;
    }

    int32_t size = array->size;
    array->data[size] = block;
    array->size++;
    return array;
}

static int
add_lookup_dependency_i(st_data_t *key, st_data_t *value, st_data_t data, int existing)
{
    block_t *block = (block_t *)data;

    struct compiled_region_array *regions = NULL;
    if (existing) {
        regions = (struct compiled_region_array *)*value;
    }
    regions = add_compiled_region(regions, block);
    if (!regions) {
        rb_bug("ujit: failed to add method lookup dependency"); // TODO: we could bail out of compiling instead
    }
    *value = (st_data_t)regions;
    return ST_CONTINUE;
}

// Remember that the currently compiling region is only valid while cme and cc are valid
void
assume_method_lookup_stable(const struct rb_callcache *cc, const rb_callable_method_entry_t *cme, block_t* block)
{
    RUBY_ASSERT(block != NULL);
    st_update(method_lookup_dependency, (st_data_t)cme, add_lookup_dependency_i, (st_data_t)block);
    st_update(method_lookup_dependency, (st_data_t)cc, add_lookup_dependency_i, (st_data_t)block);
    // FIXME: This is a leak! When either the cme or the cc become invalid, the other also needs to go
}

static int
ujit_root_mark_i(st_data_t k, st_data_t v, st_data_t ignore)
{
    // FIXME: This leaks everything that end up in the dependency table!
    // One way to deal with this is with weak references...
    rb_gc_mark((VALUE)k);
    struct compiled_region_array *regions = (void *)v;
    for (int32_t i = 0; i < regions->size; i++) {
        rb_gc_mark((VALUE)regions->data[i]->blockid.iseq);
    }

    return ST_CONTINUE;
}

// GC callback during mark phase
static void
ujit_root_mark(void *ptr)
{
    if (method_lookup_dependency) {
        st_foreach(method_lookup_dependency, ujit_root_mark_i, 0);
    }
}

static void
ujit_root_free(void *ptr)
{
    // Do nothing. The root lives as long as the process.
}

static size_t
ujit_root_memsize(const void *ptr)
{
    // Count off-gc-heap allocation size of the dependency table
    return st_memsize(method_lookup_dependency); // TODO: more accurate accounting
}

// Custom type for interacting with the GC
// TODO: compaction support
// TODO: make this write barrier protected
static const rb_data_type_t ujit_root_type = {
    "ujit_root",
    {ujit_root_mark, ujit_root_free, ujit_root_memsize, },
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

// Callback when cme or cc become invalid
void
rb_ujit_method_lookup_change(VALUE cme_or_cc)
{
    if (!method_lookup_dependency)
        return;

    RUBY_ASSERT(IMEMO_TYPE_P(cme_or_cc, imemo_ment) || IMEMO_TYPE_P(cme_or_cc, imemo_callcache));

    st_data_t image;
    if (st_lookup(method_lookup_dependency, (st_data_t)cme_or_cc, &image)) {
        struct compiled_region_array *array = (void *)image;

        // Invalidate all regions that depend on the cme or cc
        for (int32_t i = 0; i < array->size; i++) {
            block_t* block = array->data[i];
            invalidate(block);
        }

        array->size = 0;
    }
}

void
rb_ujit_compile_iseq(const rb_iseq_t *iseq)
{
#if OPT_DIRECT_THREADED_CODE || OPT_CALL_THREADED_CODE
    RB_VM_LOCK_ENTER();
    VALUE *encoded = (VALUE *)iseq->body->iseq_encoded;

    // Compile a block version starting at the first instruction
    uint8_t* code_ptr = gen_entry_point(iseq, 0);

    if (code_ptr)
    {
        // Map the code address to the corresponding opcode
        int first_opcode = opcode_at_pc(iseq, &encoded[0]);
        map_addr2insn(code_ptr, first_opcode);
        encoded[0] = (VALUE)code_ptr;
    }

    RB_VM_LOCK_LEAVE();
#endif
}

struct ujit_block_itr {
    const rb_iseq_t *iseq;
    VALUE list;
};

static int
iseqw_ujit_collect_blocks(st_data_t key, st_data_t value, st_data_t argp)
{
    block_t * block = (block_t *)value;
    struct ujit_block_itr * itr = (struct ujit_block_itr *)argp;

    if (block->blockid.iseq == itr->iseq) {
        VALUE rb_block = TypedData_Wrap_Struct(cUjitBlock, &ujit_block_type, block);
        rb_ary_push(itr->list, rb_block);
    }
    return ST_CONTINUE;
}

/* Get a list of the UJIT blocks associated with `rb_iseq` */
static VALUE
ujit_blocks_for(VALUE mod, VALUE rb_iseq)
{
    const rb_iseq_t *iseq = rb_iseqw_to_iseq(rb_iseq);
    st_table * vt = (st_table *)version_tbl;
    struct ujit_block_itr itr;
    itr.iseq = iseq;
    itr.list = rb_ary_new();

    rb_st_foreach(vt, iseqw_ujit_collect_blocks, (st_data_t)&itr);

    return itr.list;
}

static VALUE
ujit_install_entry(VALUE mod, VALUE iseq)
{
    rb_ujit_compile_iseq(rb_iseqw_to_iseq(iseq));
    return iseq;
}

/* Get the address of the UJIT::Block */
static VALUE
block_address(VALUE self)
{
    block_t * block;
    TypedData_Get_Struct(self, block_t, &ujit_block_type, block);
    return LONG2NUM((intptr_t)block);
}

/* Get the machine code for UJIT::Block as a binary string */
static VALUE
block_code(VALUE self)
{
    block_t * block;
    TypedData_Get_Struct(self, block_t, &ujit_block_type, block);

    return (VALUE)rb_str_new(
        (const char*)cb->mem_block + block->start_pos,
        block->end_pos - block->start_pos
    );
}

/* Get the start index in the Instruction Sequence that corresponds to this
 * UJIT::Block */
static VALUE
iseq_start_index(VALUE self)
{
    block_t * block;
    TypedData_Get_Struct(self, block_t, &ujit_block_type, block);

    return INT2NUM(block->blockid.idx);
}

/* Get the end index in the Instruction Sequence that corresponds to this
 * UJIT::Block */
static VALUE
iseq_end_index(VALUE self)
{
    block_t * block;
    TypedData_Get_Struct(self, block_t, &ujit_block_type, block);

    return INT2NUM(block->end_idx);
}

static VALUE
ujit_disasm_open(VALUE mod, VALUE arch, VALUE mode)
{
    csh * handle;
    VALUE disasm = TypedData_Make_Struct(cUjitDisasm, csh, &ujit_disasm_type, handle);
    cs_open(NUM2INT(arch), NUM2INT(mode), handle);
    return disasm;
}

static VALUE
ujit_disasm(VALUE self, VALUE code, VALUE from)
{
    size_t count;
    csh * handle;
    cs_insn *insns;

    TypedData_Get_Struct(self, csh, &ujit_disasm_type, handle);
    count = cs_disasm(*handle, StringValuePtr(code), RSTRING_LEN(code), NUM2INT(from), 0, &insns);
    VALUE insn_list = rb_ary_new_capa(count);

    for (size_t i = 0; i < count; i++) {
        VALUE vals = rb_ary_new_from_args(3, LONG2NUM(insns[i].address),
                rb_str_new2(insns[i].mnemonic),
                rb_str_new2(insns[i].op_str));
        rb_ary_push(insn_list, rb_struct_alloc(cUjitDisasmInsn, vals));
    }
    cs_free(insns, count);
    return insn_list;
}

void
rb_ujit_init(void)
{
    if (!ujit_scrape_successful || !PLATFORM_SUPPORTED_P)
    {
        return;
    }

    rb_ujit_enabled = true;

    ujit_init_core();
    ujit_init_codegen();

    VALUE mUjit = rb_define_module("UJIT");
    rb_define_module_function(mUjit, "install_entry", ujit_install_entry, 1);
    rb_define_module_function(mUjit, "blocks_for", ujit_blocks_for, 1);

    cUjitBlock = rb_define_class_under(mUjit, "Block", rb_cObject);
    rb_define_method(cUjitBlock, "address", block_address, 0);
    rb_define_method(cUjitBlock, "code", block_code, 0);
    rb_define_method(cUjitBlock, "iseq_start_index", iseq_start_index, 0);
    rb_define_method(cUjitBlock, "iseq_end_index", iseq_end_index, 0);

    cUjitDisasm = rb_define_class_under(mUjit, "Disasm", rb_cObject);
    rb_define_const(cUjitDisasm, "ARCH_X86", INT2NUM(CS_ARCH_X86));
    rb_define_const(cUjitDisasm, "MODE_64", INT2NUM(CS_MODE_64));
    rb_define_module_function(cUjitDisasm, "open", ujit_disasm_open, 2);
    rb_define_method(cUjitDisasm, "disasm", ujit_disasm, 2);

    cUjitDisasmInsn = rb_struct_define_under(cUjitDisasm, "Insn", "address", "mnemonic", "op_str", NULL);

    // Initialize the GC hooks
    method_lookup_dependency = st_init_numtable();
    struct ujit_root_struct *root;
    VALUE ujit_root = TypedData_Make_Struct(0, struct ujit_root_struct, &ujit_root_type, root);
    rb_gc_register_mark_object(ujit_root);
}