gdb 调试PHP

2023-12-22 16:49:45

PHP的代码包中提供了一个 .gdbinit 的gdb脚本文件，里面提供了20多个 gdb 的自定义命令，用于方便PHP的调试，下面举几个例子：
测试脚本a.php：

<?php
$a = "AAA";
$b = "BBB";
test("phpor");
function test($name) {
        $m = "MMM";
        $n = "NNN";
        sleep(1);
        echo$name;
}

<?php

$a = "AAA";

$b = "BBB";

test("phpor");

function test($name) {

$m = "MMM";

$n = "NNN";

sleep(1);

echo$name;

}

gdb 调试命令：
———————–
gdb php
set args a.php
break sleep
r
…
———————–

1. print_cvs 打印当前执行环境中已编译的PHP变量，如：

(gdb) print_cvs
Compiled variables count: 3
0 = name
[0x9543f7c] (refcount=2) string(5): "phpor"
1 = m
[0x9543f98] (refcount=1) string(3): "MMM"
2 = n
[0x9543fb4] (refcount=1) string(3): "NNN"
(gdb)

(gdb) print_cvs

Compiled variables count: 3

0 = name

[0x9543f7c] (refcount=2) string(5): "phpor"

1 = m

[0x9543f98] (refcount=1) string(3): "MMM"

2 = n

[0x9543fb4] (refcount=1) string(3): "NNN"

(gdb)

2. printzv 打印指定的PHP变量，需要指定地址，如：
(gdb) printzv 0x9543f98
[0x9543f98] (refcount=1) string(3): “MMM”
(gdb)

3. 打印PHP的函数调用栈，如：
(gdb) zbacktrace
[0x95770a4] sleep(1) /usr/home/junjie2/a.php:11
[0x9576fe0] test(“phpor”) /usr/home/junjie2/a.php:7
(gdb)

4. print_ft 打印函数表（ HashTable ）
(gdb) set $eg = executor_globals
(gdb) print $eg.function_table
$6 = (HashTable *) 0xa5bd450
(gdb) print_ft $eg.function_table
[0xa5bd450] {
“zend_version\0″ => “zend_version”
“func_num_args\0″ => “func_num_args”
“func_get_arg\0″ => “func_get_arg”
“func_get_args\0″ => “func_get_args”
“strlen\0″ => “strlen”
“strcmp\0″ => “strcmp”
“strncmp\0″ => “strncmp”
“strcasecmp\0″ => “strcasecmp”
“strncasecmp\0″ => “strncasecmp”
“each\0″ => “each”
…

学习：
1. 通过阅读 print_cvs 命令的实现，可以知道可以通过prev_execute_data来打印上一执行空间的PHP变量，如：
(gdb) printzv *executor_globals.current_execute_data->prev_execute_data->CVs[1]
[0x9543408] (refcount=1) string(3): “AAA”
(gdb) printzv *executor_globals.current_execute_data->prev_execute_data->CVs[2]
[0x95433ec] (refcount=1) string(3): “BBB”
(gdb)

2. 通过 op_array->vars 来找到对应的变量的名字
(gdb) printf “%s\n” ,executor_globals.current_execute_data->prev_execute_data->op_array->vars[1].name
a
(gdb) printf “%s\n” ,executor_globals.current_execute_data->prev_execute_data->op_array->vars[2].name
b

3. 修改了一下 print_cvs 命令，通过参数来获取每个执行空间的PHP的已编译变量

define print_cvs
        ____executor_globals
        set $f = $eg.current_execute_data
        if $argc == 1
                set $j = 1
                while $j < $arg0 && $f.prev_execute_data != 0
                        set $f = $f.prev_execute_data
                        set $j = $j + 1
                end
        end
        set $p = $f.CVs
        set $c = $f.op_array.last_var
        set $v = $f.op_array.vars
        set $i = 0
        printf "Compiled variables count: %d\n", $c
        while $i < $c
                printf "%d = %s\n", $i, $v[$i].name
                if $p[$i] != 0
                        printzv *$p[$i]
                else
                        printf "*uninitialized*\n"
                end
                set $i = $i + 1
        end
end


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define print_cvs
        ____executor_globals
        set $f = $eg.current_execute_data
        if $argc == 1
                set $j = 1
                while $j < $arg0 && $f.prev_execute_data != 0
                        set $f = $f.prev_execute_data
                        set $j = $j + 1
                end
        end
        set $p = $f.CVs
        set $c = $f.op_array.last_var
        set $v = $f.op_array.vars
        set $i = 0
        printf "Compiled variables count: %d\n", $c
        while $i < $c
                printf "%d = %s\n", $i, $v[$i].name
                if $p[$i] != 0
                        printzv *$p[$i]
                else
                        printf "*uninitialized*\n"
                end
                set $i = $i + 1
        end
end

使用方法：
———————
(gdb) zbacktrace #查看PHP的调用栈
[0x8ce2078] sleep(1) /usr/home/junjie2/a.php:9
[0x8ce1fe0] test(“phpor”) /usr/home/junjie2/a.php:5
(gdb) print_cvs #查看当前执行空间中的PHP变量
Compiled variables count: 3
0 = name
[0x8cae3d0] (refcount=2) string(5): “phpor”
1 = m
[0x8cae93c] (refcount=1) string(3): “MMM”
2 = n
[0x8cae958] (refcount=1) string(3): “NNN”
(gdb) print_cvs 2 # 查看指定执行空间中的PHP变量，这个参数给大了也没关系，最多打印最外层的PHP变量
Compiled variables count: 2
0 = a
[0x8cae408] (refcount=1) string(3): “AAA”
1 = b
[0x8cae3ec] (refcount=1) string(3): “BBB”
(gdb)
———————

4. 有时候需要借助环境变量，如：
(gdb) print_ft (HashTable *)0xa5bd450
A syntax error in expression, near `’.
(gdb) set $phpor=(HashTable *)0xa5bd450
(gdb) print_ft $phpor
[0xa5bd450] {
“zend_version\0″ => “zend_version”
“func_num_args\0″ => “func_num_args”
“func_get_arg\0″ => “func_get_arg”
“func_get_args\0″ => “func_get_args”
“strlen\0″ => “strlen”
“strcmp\0″ => “strcmp”
“strncmp\0″ => “strncmp”

5. 打印指定的PHP变量

define print_pval
    ____executor_globals
    set $p = $eg.current_execute_data.CVs
    set $c = $eg.current_execute_data.op_array.last_var
    set $v = $eg.current_execute_data.op_array.vars
    set $i = 0
    set $name = $arg0 

    #printf "search php var: %s c:%d\n", $name, $c
    while $i < $c 
        #printf "name: %s\n", $name
        set $n = $v[$i].name
        # use strcmp but ==
        if strcmp($n, $name) == 0
            if $p[$i] != 0
                printzv *$p[$i] 
                # use loop_break but break
                loop_break
            end     
        end     
        #printf "i %d, %s\n", $i, $v[$i].name
        set $i = $i + 1
    end
    if $i == $c
        printf "no found var named: %s\n", $name
    end
end

define print_pval

____executor_globals

set $p = $eg.current_execute_data.CVs

set $c = $eg.current_execute_data.op_array.last_var

set $v = $eg.current_execute_data.op_array.vars

set $i = 0

set $name = $arg0

#printf "search php var: %s c:%d\n", $name, $c

while $i < $c

#printf "name: %s\n", $name

set $n = $v[$i].name

# use strcmp but ==

if strcmp($n, $name) == 0

if $p[$i] != 0

printzv *$p[$i]

# use loop_break but break

loop_break

end

#printf "i %d, %s\n", $i, $v[$i].name

set $i = $i + 1

end

if $i == $c

printf "no found var named: %s\n", $name

end

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