Where can i find __ioctl?

Question

In the android sdk path sdk/bionic/libc/bionic/ there are the C API resource code, such as fork.c, ioctl.c etc.. when open ioctl.c:

#include <stdarg.h>

extern int __ioctl(int, int, void *);

int ioctl(int fd, int request, ...)
{
    va_list ap;
    void * arg;
    enter code here
    va_start(ap, request);
    arg = va_arg(ap, void *);
    va_end(ap);

    return __ioctl(fd, request, arg);
}

extern int __ioctl(int, int, void *); this means __ioctl(int, int, void *) has been defined somewhere. So I want to know where is the original defined place. Thanks a lot!

Answer 1

As mentioned, the _ ioctl is just a wrapper to a syscall, implemented in asm. In the AOSP code, it can be found in bionic/libc/arch-XXX/syscalls/ _ioctl.S where arch-XXX is arch-arm, arch-x86 or arch-mips depending on your target architecture.

Answer 2

It may be elsewhere in the bionic tree (grep is your friend), or automatically generated as part of the build process, but either way, it's completely uninteresting. It's just a syscall wrapper. All of the interesting work is in the kernel.