在GLIBC里查找系统调用

来源：互联网发布：cf自动领枪软件编辑：程序博客网时间：2024/04/28 22:41

有些系统调用在GLIBC里是找不到相应的函数的. 这一类函数会按照 sysdeps/unix/syscall-template.S 里的参数要求在 sysdeps/unix/syscall.S里定义每一个系统调用. 编译的时候,sysdev/unix/make-syscalls.sh 会根据上面的文件生成每个函数的汇编代码到 glibc库里面.

比如, 如果查看 mmap 的反汇编)(MIPS),你会看到:

(gdb) disass mmapDump of assembler code for function mmap:   0x77f3107c <+0>:luigp,0xa   0x77f31080 <+4>:addiugp,gp,-29292   0x77f31084 <+8>:addugp,gp,t9   0x77f31088 <+12>:liv0,4090   0x77f3108c <+16>:syscall   0x77f31090 <+20>:bneza3,0x77f31070   0x77f31094 <+24>:nop   0x77f31098 <+28>:jrra   0x77f3109c <+32>:nop   0x77f310a0 <+36>:nop

查看 mmap的源码:

(gdb) list mmap76#else7778/* This is a "normal" system call stub: if there is an error,79   it returns -1 and sets errno.  */8081T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)82ret83T_PSEUDO_END (SYSCALL_SYMBOL)8485#endif

../sysdeps/unix/syscall-template.S:82

其中, T_PSEUDO定义为:

# define PSEUDO(name, syscall_name, args)                     \  .align 2;                                   \  99: la t9,__syscall_error;                              \  jr t9;                                      \  ENTRY (name)                                    \    .set noreorder;                               \    .cpload t9;                                   \    .set reorder;                                 \    SINGLE_THREAD_P(t0);                              \    bne zero, t0, L(pseudo_cancel);                       \    .set noreorder;                               \    li v0, SYS_ify(syscall_name);                         \    syscall;                                      \    .set reorder;                                 \    bne a3, zero, SYSCALL_ERROR_LABEL;                            \    ret;                                      \

基本上和前面的反汇编代码是一致的.

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