php內核分析之opcode
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這里閱讀的php版本為PHP-7.1.0 RC3，閱讀代碼的平臺為linux
查看opcode
php是先把源碼解析成opcode，然后再把opcode傳遞給zend_vm進行執行的。
/pic/p>
struct _zend_op {
const void *handler; /pic/p>
znode_op op1; /pic/p>
znode_op op2; /pic/p>
znode_op result; /pic/p>
uint32_t extended_value; /pic/p>
uint32_t lineno; /pic/p>
zend_uchar opcode; /pic/pic/manual/zh/internals2.opcodes.php
zend_uchar op1_type; /pic/p>
zend_uchar op2_type; /pic/p>
zend_uchar result_type; /pic/p>
};
在php7中，我們能很方便用phpdbg來查看一個文件或者一個函數的opcode了。至于phpdbg的使用，現在網上介紹不多，不過好在有很詳細的help文檔。下面是一個最簡單的'opcode代碼：
$ bin/phpdbg -f /home/xiaoju/software/php7/demo/echo.php
prompt> list 100
00001:
00002:
00003: $a = 1;
00004: $b = $a;
00005: $b = $b + 1;
00006: echo $b;
00007:
prompt> print exec
[Context /home/xiaoju/software/php7/demo/echo.php (6 ops)]
L1-7 {main}() /home/xiaoju/software/php7/demo/echo.php - 0x7fe3fae63300 + 6 ops
L3 #0 ASSIGN $a 1
L4 #1 ASSIGN $b $a
L5 #2 ADD $b 1 ~2
L5 #3 ASSIGN $b ~2
L6 #4 ECHO $b
L7 #5 RETURN 1
這個php文件就做了一個最簡單的加法操作。生成了6個_zend_op。所展示的每一行代表一個_zend_op
_zendop.lineno op號 _zend_op.opcode _zend_op.op1 _zend_op.op2 _zend_op.result
L5 #2 ADD $b 1 ~2
這里_zend_op.opcode對應的操作在網有文檔和詳細的例子可以查看：/pic/manual/zh/internals2.opcodes.php
值得一說的是，phpdbg還有一個遠端UI版本，能讓我們在近端診斷服務端的php信息
gdb
但是我們的目標還是在于研究php源碼，phpdbg只能分析到opcode這層，還是不夠的，gdb可能是更好的選擇。
gdb的使用和平時使用差不多
比如我現在有個腳本echo.php:
1
2
3 $a = 1;
4 $b = $a;
5 $b = $b + 1;
6 echo $b;
我的php安裝路徑在：
/home/xiaoju/software/php7/bin/php
php源碼路徑在：
/home/xiaoju/webroot/php-src/php-src-master/
運行gdb
$ gdb /home/xiaoju/software/php7/bin/php
加載gdbinit:
(gdb) source /home/xiaoju/webroot/php-src/php-src-master/.gdbinit
設置斷點:
(gdb) b zend_execute_scripts
運行：
(gdb) run -f /home/xiaoju/software/php7/demo/echo.php
我想在1459這行設置個斷點：
1452 for (i = 0; i < file_count; i++) {
1453 file_handle = va_arg(files, zend_file_handle *);
1454 if (!file_handle) {
1455 continue;
1456 }
1457
1458 op_array = zend_compile_file(file_handle, type);
1459 if (file_handle->opened_path) {
1460 zend_hash_add_empty_element(&EG(included_files), file_handle->opened_path);
1461 }
(gdb) b 1459
繼續跑
(gdb) continue
(gdb) s
(gdb) s
打印出這個時候的op_array
(gdb) p *op_array
$4 = {type = 2 '02', arg_flags = "0000", fn_flags = 134217728, function_name = 0x0, scope = 0x0,
prototype = 0x0, num_args = 0, required_num_args = 0, arg_info = 0x0, refcount = 0x7ffff6002000, last = 6,
opcodes = 0x7ffff6076240, last_var = 2, T = 4, vars = 0x7ffff6079030, last_live_range = 0, last_try_catch = 0,
live_range = 0x0, try_catch_array = 0x0, static_variables = 0x0, filename = 0x7ffff605c2d0, line_start = 1,
line_end = 7, doc_comment = 0x0, early_binding = 4294967295, last_literal = 3, literals = 0x7ffff60030c0,
cache_size = 0, run_time_cache = 0x0, reserved = {0x0, 0x0, 0x0, 0x0}}
我可以優化輸出：
(gdb) set print pretty on
(gdb) p *op_array
$5 = {
type = 2 '02',
arg_flags = "0000",
fn_flags = 134217728,
function_name = 0x0,
scope = 0x0,
prototype = 0x0,
num_args = 0,
required_num_args = 0,
arg_info = 0x0,
refcount = 0x7ffff6002000,
last = 6,
opcodes = 0x7ffff6076240,
last_var = 2,
T = 4,
vars = 0x7ffff6079030,
last_live_range = 0,
last_try_catch = 0,
live_range = 0x0,
try_catch_array = 0x0,
static_variables = 0x0,
filename = 0x7ffff605c2d0,
line_start = 1,
line_end = 7,
doc_comment = 0x0,
early_binding = 4294967295,
last_literal = 3,
literals = 0x7ffff60030c0,
cache_size = 0,
run_time_cache = 0x0,
reserved = {0x0, 0x0, 0x0, 0x0}
}
我想打出op_array.filename.val的`具體值
(gdb) p (op_array.filename.len)
$12 = 40
(gdb) p *(op_array.filename.val)@40
$13 = "/home/xiaoju/software/php7/demo/echo.php"
好了，我們可以順便研究下_zend_op_array這個結構：
/pic/p>
struct _zend_op_array {
zend_uchar type; /pic/p>
zend_uchar arg_flags[3]; /* bitset of arg_info.pass_by_reference */
uint32_t fn_flags;
zend_string *function_name;
zend_class_entry *scope;
zend_function *prototype;
uint32_t num_args; /pic/p>
uint32_t required_num_args;
zend_arg_info *arg_info;
/* END of common elements */
uint32_t *refcount; /pic/p>
uint32_t last; /pic/p>
zend_op *opcodes; /pic/p>
int last_var; /pic/p>
uint32_t T;
zend_string **vars; /pic/p>
int last_live_range;
int last_try_catch; /pic/p>
zend_live_range *live_range;
zend_try_catch_element *try_catch_array; /pic/p>
/* static variables support */
HashTable *static_variables; /pic/p>
zend_string *filename; /pic/p>
uint32_t line_start; /pic/p>
uint32_t line_end; /pic/p>
zend_string *doc_comment; /pic/p>
uint32_t early_binding; /* the linked list of delayed declarations */
int last_literal;
zval *literals;
int cache_size;
void **run_time_cache;
void *reserved[ZEND_MAX_RESERVED_RESOURCES]; /pic/p>
};
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