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

		fp = get_stack(ka, regs, sizeof(struct _fpstate)); 
		frame = (void *)round_down((unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;

		if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate))) { 
			goto give_sigsegv;
		}
		if (save_i387(fp) < 0) 
			err |= -1; 
	} else {
		frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;
		fp = NULL;
	}

	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
		goto give_sigsegv;
	}


	if (ka->sa.sa_flags & SA_SIGINFO) { 
		err |= copy_siginfo_to_user(&frame->info, info);
		if (err)
			goto give_sigsegv;
	}
		
	/* Create the ucontext.  */
	err |= __put_user(0, &frame->uc.uc_flags);
	err |= __put_user(0, &frame->uc.uc_link);
	err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
	err |= __put_user(sas_ss_flags(regs->rsp),
			  &frame->uc.uc_stack.ss_flags);
	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
	err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

	/* Set up to return from userspace.  If provided, use a stub
	   already in userspace.  */
	/* x86-64 should always use SA_RESTORER. */
	if (ka->sa.sa_flags & SA_RESTORER) {
		err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
	} else {
		printk("%s forgot to set SA_RESTORER for signal %d.\n", current->comm, sig); 
		goto give_sigsegv; 
	}

	if (err)
		goto give_sigsegv;

#if DEBUG_SIG
	printk("%d old rip %lx old rsp %lx old rax %lx\n", current->pid,regs->rip,regs->rsp,regs->rax);
#endif

	/* Set up registers for signal handler */
	{ 
		struct exec_domain *ed = current->exec_domain;
		if (unlikely(ed && ed->signal_invmap && sig < 32))
			sig = ed->signal_invmap[sig];
	} 
	regs->rdi = sig;

	/* could reload DS/ES to __USER_DS here, but assume for now
	   that 64bit does not care */

	/* In case the signal handler was declared without prototypes */ 
	regs->rax = 0;

	/* This also works for non SA_SIGINFO handlers because they expect the
	   next argument after the signal number on the stack. */
	regs->rsi = (unsigned long)&frame->info; 
	regs->rdx = (unsigned long)&frame->uc; 
	regs->rsp = (unsigned long) frame;
	regs->rip = (unsigned long) ka->sa.sa_handler;
	regs->cs = __USER_CS;
	regs->ss = __USER_DS; 

	set_fs(USER_DS);
	regs->eflags &= ~TF_MASK;

#if DEBUG_SIG
	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
		current->comm, current->pid, frame, regs->rip, frame->pretcode);
#endif

	return;

give_sigsegv:
	if (sig == SIGSEGV)
		ka->sa.sa_handler = SIG_DFL;
	signal_fault(regs, frame, "signal deliver"); 
}

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

static void
handle_signal(unsigned long sig, struct k_sigaction *ka,
	      siginfo_t *info, sigset_t *oldset, struct pt_regs * regs)
{
#if DEBUG_SIG
	printk("handle_signal pid:%d sig:%lu rip:%lx rsp:%lx regs=%p\n", current->pid, sig, 
		regs->rip, regs->rsp, regs);
#endif

	/* Are we from a system call? */
	if ((long)regs->orig_rax >= 0) {
		/* If so, check system call restarting.. */
		switch (regs->rax) {
			case -ERESTARTNOHAND:
				regs->rax = -EINTR;
				break;

			case -ERESTARTSYS:
				if (!(ka->sa.sa_flags & SA_RESTART)) {
					regs->rax = -EINTR;
					break;
				}
			/* fallthrough */
			case -ERESTARTNOINTR:
				regs->rax = regs->orig_rax;
				regs->rip -= 2;
				break; 
		}
	}

#ifdef CONFIG_IA32_EMULATION
	if (current->thread.flags & THREAD_IA32) { 
		if (ka->sa.sa_flags & SA_SIGINFO)
			ia32_setup_rt_frame(sig, ka, info, oldset, regs);
		else
			ia32_setup_frame(sig, ka, oldset, regs);
	} else 
#endif
	setup_rt_frame(sig, ka, info, oldset, regs);

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

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

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

	/*
	 * We want the common case to go fast, which
	 * is why we may in certain cases get here from
	 * kernel mode. Just return without doing anything
	 * if so.
	 */
	if ((regs->cs & 3) != 3) {
		return 1;
	} 	

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

	for (;;) {
		unsigned long signr;

		spin_lock_irq(&current->sig->siglock);
		signr = dequeue_signal(&current->blocked, &info);
		spin_unlock_irq(&current->sig->siglock);

		if (!signr) { 
			break;
		}

		if ((current->ptrace & PT_PTRACED) && signr != SIGKILL) {
			/* Let the debugger run.  */
			current->exit_code = signr;
			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->parent->pid;
				info.si_uid = current->parent->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];
		if (ka->sa.sa_handler == SIG_IGN) {
			if (signr != SIGCHLD)
				continue;
			/* Check for SIGCHLD: it's special.  */
			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: case SIGURG:
				continue;

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

			case SIGSTOP: {
				struct signal_struct *sig;
				current->state = TASK_STOPPED;
				current->exit_code = signr;
				sig = current->parent->sig;
				if (sig && !(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 (do_coredump(signr, regs))
					exit_code |= 0x80;
				/* FALLTHRU */

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

		/* Reenable any watchpoints before delivering the
		 * signal to user space. The processor register will
		 * have been cleared if the watchpoint triggered
		 * inside the kernel.
		 */
		asm volatile("movq %0,%%db7"::"r"(current->thread.debugreg[7]));
		/* Whee!  Actually deliver the signal.  */
		handle_signal(signr, ka, &info, oldset, regs);
		return 1;
	}

	/* Did we come from a system call? */
	if (regs->orig_rax >= 0) {
		/* Restart the system call - no handlers present */
		if (regs->rax == -ERESTARTNOHAND ||
		    regs->rax == -ERESTARTSYS ||
		    regs->rax == -ERESTARTNOINTR) {
			regs->rax = regs->orig_rax;
			regs->rip -= 2;
		}
	}
	return 0;
}


void signal_fault(struct pt_regs *regs, void *frame, char *where)
{ 
	struct task_struct *me = current; 
	if (exception_trace)
		printk("%s[%d] bad frame in %s frame:%p rip:%lx rsp:%lx orax:%lx\n",
	       me->comm,me->pid,where,frame,regs->rip,regs->rsp,regs->orig_rax); 

	force_sig(SIGSEGV, me); 
}