signal.c

这个linux源代码是很全面的~基本完整了~使用c编译的~由于时间问题我没有亲自测试~但就算用来做参考资料也是非常好的

		asm ("mfsp %%sr3,%0" : "=r" (sid));
		DBG(("flushing 64 bytes at space %#x offset %p\n",
		       sid, frame->tramp));
	}
#endif

#if CACHE_FLUSHING_IS_NOT_BROKEN
	flush_icache_range((unsigned long) &frame->tramp[0],
			   (unsigned long) &frame->tramp[4]);
#else
	/* It should *always* be cache line-aligned, but the compiler
           sometimes screws up. */
	asm volatile("fdc 0(%%sr3,%0)\n\t"
		     "fdc %1(%%sr3,%0)\n\t"
		     "sync\n\t"
		     "fic 0(%%sr3,%0)\n\t"
		     "fic %1(%%sr3,%0)\n\t"
		     "sync\n\t"
		     : : "r" (frame->tramp), "r" (L1_CACHE_BYTES));
#endif
	rp = (unsigned long) frame->tramp;

	if (err)
		goto give_sigsegv;

#ifdef __LP64__
/* Much more has to happen with signals than this -- but it'll at least */
/* provide a pointer to some places which definitely need a look. */
#define HACK unsigned int
#else
#define HACK unsigned long
#endif
	haddr = (HACK) ka->sa.sa_handler;
	/* ARGH!  Fucking brain damage.  You don't want to know. */
	if (haddr & 2) {
		HACK *plabel;
		HACK ltp;

		plabel = (HACK *) (haddr & ~3);
		err |= __get_user(haddr, plabel);
		err |= __get_user(ltp, plabel + 1);
		if (err)
			goto give_sigsegv;
		regs->gr[19] = ltp;
	}

	/* The syscall return path will create IAOQ values from r31.
	 */
	if (in_syscall)
		regs->gr[31] = (HACK) haddr;
	else {
		regs->gr[0] = USER_PSW;
		regs->iaoq[0] = (HACK) haddr | 3;
		regs->iaoq[1] = regs->iaoq[0] + 4;
	}

	regs->gr[2]  = rp;                /* userland return pointer */
	regs->gr[26] = sig;               /* signal number */
	regs->gr[25] = (HACK) &frame->info; /* siginfo pointer */
	regs->gr[24] = (HACK) &frame->uc;   /* ucontext pointer */
	DBG(("making sigreturn frame: %#lx + %#x = %#lx\n",
	       regs->gr[30], PARISC_RT_SIGFRAME_SIZE,
	       regs->gr[30] + PARISC_RT_SIGFRAME_SIZE));
	/* Raise the user stack pointer to make a proper call frame. */
	regs->gr[30] = ((HACK) frame + PARISC_RT_SIGFRAME_SIZE);

	DBG(("SIG deliver (%s:%d): frame=0x%p sp=%#lx iaoq=%#lx/%#lx rp=%#lx\n",
	       current->comm, current->pid, frame, regs->gr[30],
	       regs->iaoq[0], regs->iaoq[1], rp));

	return 1;

give_sigsegv:
	DBG(("setup_rt_frame sending SIGSEGV\n"));
	if (sig == SIGSEGV)
		ka->sa.sa_handler = SIG_DFL;
	si.si_signo = SIGSEGV;
	si.si_errno = 0;
	si.si_code = SI_KERNEL;
	si.si_pid = current->pid;
	si.si_uid = current->uid;
	si.si_addr = frame;
	force_sig_info(SIGSEGV, &si, current);
	return 0;
}

/*
 * OK, we're invoking a handler.
 */	

static long
handle_signal(unsigned long sig, struct k_sigaction *ka,
	      siginfo_t *info, sigset_t *oldset,
	      struct pt_regs *regs, int in_syscall)
{
	DBG(("handle_signal(sig=%ld, ka=%p, info=%p, oldset=%p, regs=%p)\n",
	       sig, ka, info, oldset, regs));
	
	/* Set up the stack frame */
	if (!setup_rt_frame(sig, ka, info, oldset, regs, in_syscall))
		return 0;

	if (ka->sa.sa_flags & SA_ONESHOT)
		ka->sa.sa_handler = SIG_DFL;

	if (!(ka->sa.sa_flags & SA_NODEFER)) {
		spin_lock_irq(&current->sigmask_lock);
		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
		sigaddset(&current->blocked,sig);
		recalc_sigpending(current);
		spin_unlock_irq(&current->sigmask_lock);
	}
	return 1;
}

/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 *
 * We need to be able to restore the syscall arguments (r21-r26) to
 * restart syscalls.  Thus, the syscall path should save them in the
 * pt_regs structure (it's okay to do so since they are caller-save
 * registers).  As noted below, the syscall number gets restored for
 * us due to the magic of delayed branching.
 */

asmlinkage int
do_signal(sigset_t *oldset, struct pt_regs *regs, int in_syscall)
{
	siginfo_t info;
	struct k_sigaction *ka;

	DBG(("do_signal(oldset=0x%p, regs=0x%p, sr7 %#lx, pending %d, in_syscall=%d\n",
	       oldset, regs, regs->sr[7], current->sigpending, in_syscall));

	/* Everyone else checks to see if they are in kernel mode at
	   this point and exits if that's the case.  I'm not sure why
	   we would be called in that case, but for some reason we
	   are. */

	if (!oldset)
		oldset = &current->blocked;

	DBG(("do_signal: oldset %08lx:%08lx\n", 
		oldset->sig[0], oldset->sig[1]));

	for (;;) {
		unsigned long signr;

		spin_lock_irq(&current->sigmask_lock);
		signr = dequeue_signal(&current->blocked, &info);
		spin_unlock_irq(&current->sigmask_lock);
		DBG(("do_signal: signr=%ld, pid=%d\n", signr, current->pid));
		if (!signr)
			break;

		if ((current->ptrace & PT_PTRACED) && signr != SIGKILL) {
			/* Let the debugger run.  */
			current->exit_code = signr;
			set_current_state(TASK_STOPPED);
			notify_parent(current, SIGCHLD);
			schedule();

			/* We're back.  Did the debugger cancel the sig?  */
			if (!(signr = current->exit_code))
				continue;
			current->exit_code = 0;

			/* The debugger continued.  Ignore SIGSTOP.  */
			if (signr == SIGSTOP)
				continue;

			/* Update the siginfo structure.  Is this good?  */
			if (signr != info.si_signo) {
				info.si_signo = signr;
				info.si_errno = 0;
				info.si_code = SI_USER;
				info.si_pid = current->p_pptr->pid;
				info.si_uid = current->p_pptr->uid;
			}

			/* If the (new) signal is now blocked, requeue it.  */
			if (sigismember(&current->blocked, signr)) {
				send_sig_info(signr, &info, current);
				continue;
			}
		}

		ka = &current->sig->action[signr-1];
		DBG(("sa_handler is %x\n", 
			(unsigned int) ka->sa.sa_handler));
		if (ka->sa.sa_handler == SIG_IGN) {
			if (signr != SIGCHLD)
				continue;
			while (sys_wait4(-1, NULL, WNOHANG, NULL) > 0)
				/* nothing */;
			continue;
		}

		if (ka->sa.sa_handler == SIG_DFL) {
			int exit_code = signr;

			/* Init gets no signals it doesn't want.  */
			if (current->pid == 1)
				continue;

			switch (signr) {
			case SIGCONT: case SIGCHLD: case SIGWINCH:
				continue;

			case SIGTSTP: case SIGTTIN: case SIGTTOU:
				if (is_orphaned_pgrp(current->pgrp))
					continue;
				/* FALLTHRU */

			case SIGSTOP:
				set_current_state(TASK_STOPPED);
				current->exit_code = signr;
				if (!(current->p_pptr->sig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
					notify_parent(current, SIGCHLD);
				schedule();
				continue;

			case SIGQUIT: case SIGILL: case SIGTRAP:
			case SIGABRT: case SIGFPE: case SIGSEGV:
			case SIGBUS: case SIGSYS: case SIGXCPU: case SIGXFSZ:
				if (signr == SIGQUIT) /* Userspace debugging */
					show_regs(regs);
				if (do_coredump(signr, regs))
					exit_code |= 0x80;
				/* FALLTHRU */

			default:
				sig_exit(signr, exit_code, &info);
				/* NOTREACHED */
			}
		}

		/* Restart a system call if necessary. */
		if (in_syscall) {
			/* Check the return code */
			switch (regs->gr[28]) {
			case -ERESTARTNOHAND:
				DBG(("ERESTARTNOHAND: returning -EINTR\n"));
				regs->gr[28] = -EINTR;
				break;

			case -ERESTARTSYS:
				if (!(ka->sa.sa_flags & SA_RESTART)) {
					DBG(("ERESTARTSYS: putting -EINTR\n"));
					regs->gr[28] = -EINTR;
					break;
				}
			/* fallthrough */
			case -ERESTARTNOINTR:
				/* A syscall is just a branch, so all
                                   we have to do is fiddle the return
                                   pointer. */
				regs->gr[31] -= 8; /* delayed branching */
				/* Preserve original r28. */
				regs->gr[28] = regs->orig_r28;
				break;
			}
		}
		/* Whee!  Actually deliver the signal.  If the
		   delivery failed, we need to continue to iterate in
		   this loop so we can deliver the SIGSEGV... */
		if (handle_signal(signr, ka, &info, oldset, regs, in_syscall)) {
			DBG((KERN_DEBUG
				"Exiting do_signal (success), regs->gr[28] = %ld\n",
				regs->gr[28]));
			return 1;
		}
	}

	/* Did we come from a system call? */
	if (in_syscall) {
		/* Restart the system call - no handlers present */
		if (regs->gr[28] == -ERESTARTNOHAND ||
		    regs->gr[28] == -ERESTARTSYS ||
		    regs->gr[28] == -ERESTARTNOINTR) {
			/* Hooray for delayed branching.  We don't
                           have to restore %r20 (the system call
                           number) because it gets loaded in the delay
                           slot of the branch external instruction. */
			regs->gr[31] -= 8;
			/* Preserve original r28. */
			regs->gr[28] = regs->orig_r28;
		}
	}
	
	DBG(("Exiting do_signal (not delivered), regs->gr[28] = %ld\n", 
		regs->gr[28]));

	return 0;
}