深入PHP内核之opcode handler

1、opcode结构

在Zend/zend_compile.h文件下

struct _zend_op {
        opcode_handler_t handler;
        znode_op op1;
        znode_op op2;
        znode_op result;
        ulong extended_value;
        uint lineno;
        zend_uchar opcode;
        zend_uchar op1_type;
        zend_uchar op2_type;
        zend_uchar result_type;
};

opcode_handler_t是函数指针为opcode定义了执行方式，每一种opcode都对应一个的handler，也就是函数的入口地址，这些地址都保存在labels数组里面

比如赋值：$a = 1

通过vld可以看到

op = ASSIGN 那么对应到zend engine  操作为ZEND_ASSIGN ，对应的编号为38的  可以在Zend/zend_vm_opcodes.h中查到定义  

#define ZEND_ASSIGN                           38

可以推算出 op_type为const和cv，然后就能确定handler为函数ZEND_ASSIGN_SPEC_CV_CONST_HANDLER

然后就可以定位到具体的执行函数了

static int ZEND_FASTCALL  ZEND_ASSIGN_SPEC_CV_CONST_HANDLER(ZEND_OPCODE_HANDLER_ARGS)
{
        USE_OPLINE

        zval *value;
        zval **variable_ptr_ptr;

        SAVE_OPLINE();
        value = opline->op2.zv;
	……
｝

 zend engine在执行的是首先会调用 zend_startup() 位于（zend.c中），然后初始化zend_init_opcodes_handlers()

int zend_startup(zend_utility_functions *utility_functions, char **extensions TSRMLS_DC) /* {{{ */
{
#ifdef ZTS
        zend_compiler_globals *compiler_globals;
        zend_executor_globals *executor_globals;
        extern ZEND_API ts_rsrc_id ini_scanner_globals_id;
        extern ZEND_API ts_rsrc_id language_scanner_globals_id;
#else
        extern zend_ini_scanner_globals ini_scanner_globals;
        extern zend_php_scanner_globals language_scanner_globals;
#endif

        start_memory_manager(TSRMLS_C);

        virtual_cwd_startup(); /* Could use shutdown to free the main cwd but it would just slow it down for CGI */

#if defined(__FreeBSD__) || defined(__DragonFly__)
        /* FreeBSD and DragonFly floating point precision fix */
        fpsetmask(0);
#endif

        zend_startup_strtod();
        zend_startup_extensions_mechanism();

        /* Set up utility functions and values */
        zend_error_cb = utility_functions->error_function;
        zend_printf = utility_functions->printf_function;
        zend_write = (zend_write_func_t) utility_functions->write_function;
        zend_fopen = utility_functions->fopen_function;
        if (!zend_fopen) {
                zend_fopen = zend_fopen_wrapper;
        }
        zend_stream_open_function = utility_functions->stream_open_function;
        zend_message_dispatcher_p = utility_functions->message_handler;
#ifndef ZEND_SIGNALS
        zend_block_interruptions = utility_functions->block_interruptions;
        zend_unblock_interruptions = utility_functions->unblock_interruptions;
#endif
        zend_get_configuration_directive_p = utility_functions->get_configuration_directive;
        zend_ticks_function = utility_functions->ticks_function;
        zend_on_timeout = utility_functions->on_timeout;
        zend_unblock_interruptions = utility_functions->unblock_interruptions;
#endif
        zend_get_configuration_directive_p = utility_functions->get_configuration_directive;
        zend_ticks_function = utility_functions->ticks_function;
        zend_on_timeout = utility_functions->on_timeout;
        zend_vspprintf = utility_functions->vspprintf_function;
        zend_getenv = utility_functions->getenv_function;
        zend_resolve_path = utility_functions->resolve_path_function;

#if HAVE_DTRACE
/* build with dtrace support */
        zend_compile_file = dtrace_compile_file;
        zend_execute_ex = dtrace_execute_ex;
        zend_execute_internal = dtrace_execute_internal;
#else
        zend_compile_file = compile_file;
        zend_execute_ex = execute_ex;
        zend_execute_internal = NULL;
#endif /* HAVE_SYS_SDT_H */
        zend_compile_string = compile_string;
        zend_throw_exception_hook = NULL;

        zend_init_opcodes_handlers();
	……
｝
 

然后会初始化labels数组，这个数组的类型是opcode_handler_t （zend_compile.h）

void zend_init_opcodes_handlers(void)
{
  static const opcode_handler_t labels[] = {
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
        ZEND_NOP_SPEC_HANDLER,
    ……
    ｝
    zend_opcode_handlers = (opcode_handler_t*)labels;
｝
//Zend/zend_vm_execute.h

 opcode_handler_t

typedef int (*user_opcode_handler_t) (ZEND_OPCODE_HANDLER_ARGS);
typedef int (ZEND_FASTCALL *opcode_handler_t) (ZEND_OPCODE_HANDLER_ARGS);

extern ZEND_API opcode_handler_t *zend_opcode_handlers;

这个结构体包含了近4000个成员，这些成员都是函数名称，每次执行一个opcode的时候都要到这个labels里面找对应的handler处理函数

op_type函数

static opcode_handler_t zend_vm_get_opcode_handler(zend_uchar opcode, zend_op* op)
{               
                static const int zend_vm_decode[] = {
                        _UNUSED_CODE, /* 0              */
                        _CONST_CODE,  /* 1 = IS_CONST   */
                        _TMP_CODE,    /* 2 = IS_TMP_VAR */
                        _UNUSED_CODE, /* 3              */
                        _VAR_CODE,    /* 4 = IS_VAR     */
                        _UNUSED_CODE, /* 5              */
                        _UNUSED_CODE, /* 6              */
                        _UNUSED_CODE, /* 7              */
                        _UNUSED_CODE, /* 8 = IS_UNUSED  */
                        _UNUSED_CODE, /* 9              */
                        _UNUSED_CODE, /* 10             */
                        _UNUSED_CODE, /* 11             */
                        _UNUSED_CODE, /* 12             */
                        _UNUSED_CODE, /* 13             */
                        _UNUSED_CODE, /* 14             */
                        _UNUSED_CODE, /* 15             */
                        _CV_CODE      /* 16 = IS_CV     */
                };
                return zend_opcode_handlers[opcode * 25 + zend_vm_decode[op->op1_type] * 5 + zend_vm_decode[op->op2_type]];
}

ZEND_API void zend_vm_set_opcode_handler(zend_op* op)
{
        op->handler = zend_vm_get_opcode_handler(zend_user_opcodes[op->opcode], op);
}

返回对应的handler

zend_opcode_handlers[opcode * 25 + zend_vm_decode[op->op1.op_type] * 5 + zend_vm_decode[op->op2.op_type]];