1. 根目录:
2. arch
3. x86
4. kernel
5. signal_compat.c

#include <linux/compat.h>
#include <linux/uaccess.h>

int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
{
	int err = 0;
	bool ia32 = test_thread_flag(TIF_IA32);

	if (!access_ok(VERIFY_WRITE, to, sizeof(compat_siginfo_t)))
		return -EFAULT;

	put_user_try {
		/* If you change siginfo_t structure, please make sure that
		   this code is fixed accordingly.
		   It should never copy any pad contained in the structure
		   to avoid security leaks, but must copy the generic
		   3 ints plus the relevant union member.  */
		put_user_ex(from->si_signo, &to->si_signo);
		put_user_ex(from->si_errno, &to->si_errno);
		put_user_ex((short)from->si_code, &to->si_code);

		if (from->si_code < 0) {
			put_user_ex(from->si_pid, &to->si_pid);
			put_user_ex(from->si_uid, &to->si_uid);
			put_user_ex(ptr_to_compat(from->si_ptr), &to->si_ptr);
		} else {
			/*
			 * First 32bits of unions are always present:
			 * si_pid === si_band === si_tid === si_addr(LS half)
			 */
			put_user_ex(from->_sifields._pad[0],
					  &to->_sifields._pad[0]);
			switch (from->si_code >> 16) {
			case __SI_FAULT >> 16:
				break;
			case __SI_SYS >> 16:
				put_user_ex(from->si_syscall, &to->si_syscall);
				put_user_ex(from->si_arch, &to->si_arch);
				break;
			case __SI_CHLD >> 16:
				if (ia32) {
					put_user_ex(from->si_utime, &to->si_utime);
					put_user_ex(from->si_stime, &to->si_stime);
				} else {
					put_user_ex(from->si_utime, &to->_sifields._sigchld_x32._utime);
					put_user_ex(from->si_stime, &to->_sifields._sigchld_x32._stime);
				}
				put_user_ex(from->si_status, &to->si_status);
				/* FALL THROUGH */
			default:
			case __SI_KILL >> 16:
				put_user_ex(from->si_uid, &to->si_uid);
				break;
			case __SI_POLL >> 16:
				put_user_ex(from->si_fd, &to->si_fd);
				break;
			case __SI_TIMER >> 16:
				put_user_ex(from->si_overrun, &to->si_overrun);
				put_user_ex(ptr_to_compat(from->si_ptr),
					    &to->si_ptr);
				break;
				 /* This is not generated by the kernel as of now.  */
			case __SI_RT >> 16:
			case __SI_MESGQ >> 16:
				put_user_ex(from->si_uid, &to->si_uid);
				put_user_ex(from->si_int, &to->si_int);
				break;
			}
		}
	} put_user_catch(err);

	return err;
}

int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
{
	int err = 0;
	u32 ptr32;

	if (!access_ok(VERIFY_READ, from, sizeof(compat_siginfo_t)))
		return -EFAULT;

	get_user_try {
		get_user_ex(to->si_signo, &from->si_signo);
		get_user_ex(to->si_errno, &from->si_errno);
		get_user_ex(to->si_code, &from->si_code);

		get_user_ex(to->si_pid, &from->si_pid);
		get_user_ex(to->si_uid, &from->si_uid);
		get_user_ex(ptr32, &from->si_ptr);
		to->si_ptr = compat_ptr(ptr32);
	} get_user_catch(err);

	return err;
}