signal.c

讲述linux的初始化过程

		if (err)
			goto sigsegv;

		regs->u_regs[UREG_I0] = signr;
		regs->u_regs[UREG_I1] = (uint) si;
		regs->u_regs[UREG_I2] = (uint) uc;
	}
	return;

sigill_and_return:
	do_exit(SIGILL);
sigsegv:
	do_exit(SIGSEGV);
}

asmlinkage int svr4_getcontext (svr4_ucontext_t *uc, struct pt_regs *regs)
{
	svr4_gregset_t  *gr;
	svr4_mcontext_t *mc;
	svr4_sigset_t	setv;
	int err = 0;

	synchronize_user_stack();

	if (current->thread.w_saved)
		goto sigsegv_and_return;

	err = clear_user(uc, sizeof (*uc));
	if (err)
		return -EFAULT;

	/* Setup convenience variables */
	mc = &uc->mcontext;
	gr = &mc->greg;

	setv.sigbits[0] = current->blocked.sig[0];
	setv.sigbits[1] = current->blocked.sig[1];
	if (_NSIG_WORDS >= 4) {
		setv.sigbits[2] = current->blocked.sig[2];
		setv.sigbits[3] = current->blocked.sig[3];
		err |= __copy_to_user(&uc->sigmask, &setv, sizeof(svr4_sigset_t));
	} else
		err |= __copy_to_user(&uc->sigmask, &setv, 2 * sizeof(unsigned int));

	/* Store registers */
	err |= __put_user(regs->pc, &uc->mcontext.greg [SVR4_PC]);
	err |= __put_user(regs->npc, &uc->mcontext.greg [SVR4_NPC]);
	err |= __put_user(regs->psr, &uc->mcontext.greg [SVR4_PSR]);
	err |= __put_user(regs->y, &uc->mcontext.greg [SVR4_Y]);
	
	/* Copy g [1..7] and o [0..7] registers */
	err |= __copy_to_user(&(*gr)[SVR4_G1], &regs->u_regs [UREG_G1], sizeof (uint) * 7);
	err |= __copy_to_user(&(*gr)[SVR4_O0], &regs->u_regs [UREG_I0], sizeof (uint) * 8);

	/* Setup sigaltstack */
	err |= __put_user(current->sas_ss_sp, &uc->stack.sp);
	err |= __put_user(sas_ss_flags(regs->u_regs[UREG_FP]), &uc->stack.flags);
	err |= __put_user(current->sas_ss_size, &uc->stack.size);

	/* The register file is not saved
	 * we have already stuffed all of it with sync_user_stack
	 */
	return (err ? -EFAULT : 0);

sigsegv_and_return:
	do_exit(SIGSEGV);
}

/* Set the context for a svr4 application, this is Solaris way to sigreturn */
asmlinkage int svr4_setcontext (svr4_ucontext_t *c, struct pt_regs *regs)
{
	struct thread_struct *tp = &current->thread;
	svr4_gregset_t  *gr;
	unsigned long pc, npc, psr;
	sigset_t set;
	svr4_sigset_t setv;
	int err;
	stack_t st;
	
	/* Fixme: restore windows, or is this already taken care of in
	 * svr4_setup_frame when sync_user_windows is done?
	 */
	flush_user_windows();
	
	if (tp->w_saved)
		goto sigsegv_and_return;

	if (((uint) c) & 3)
		goto sigsegv_and_return;

	if(!__access_ok((unsigned long)c, sizeof(*c)))
		goto sigsegv_and_return;

	/* Check for valid PC and nPC */
	gr = &c->mcontext.greg;
	err = __get_user(pc, &((*gr)[SVR4_PC]));
	err |= __get_user(npc, &((*gr)[SVR4_NPC]));

	if((pc | npc) & 3)
		goto sigsegv_and_return;

	/* Retrieve information from passed ucontext */
	/* note that nPC is ored a 1, this is used to inform entry.S */
	/* that we don't want it to mess with our PC and nPC */

	/* This is pretty much atomic, no amount locking would prevent
	 * the races which exist anyways.
	 */
	err |= __copy_from_user(&setv, &c->sigmask, sizeof(svr4_sigset_t));
	
	err |= __get_user(st.ss_sp, &c->stack.sp);
	err |= __get_user(st.ss_flags, &c->stack.flags);
	err |= __get_user(st.ss_size, &c->stack.size);
	
	if (err)
		goto sigsegv_and_return;
		
	/* It is more difficult to avoid calling this function than to
	   call it and ignore errors.  */
	do_sigaltstack(&st, NULL, regs->u_regs[UREG_I6]);
	
	set.sig[0] = setv.sigbits[0];
	set.sig[1] = setv.sigbits[1];
	if (_NSIG_WORDS >= 4) {
		set.sig[2] = setv.sigbits[2];
		set.sig[3] = setv.sigbits[3];
	}
	sigdelsetmask(&set, ~_BLOCKABLE);
	spin_lock_irq(&current->sigmask_lock);
	current->blocked = set;
	recalc_sigpending(current);
	spin_unlock_irq(&current->sigmask_lock);
	regs->pc = pc;
	regs->npc = npc | 1;
	err |= __get_user(regs->y, &((*gr) [SVR4_Y]));
	err |= __get_user(psr, &((*gr) [SVR4_PSR]));
	regs->psr &= ~(PSR_ICC);
	regs->psr |= (psr & PSR_ICC);

	/* Restore g[1..7] and o[0..7] registers */
	err |= __copy_from_user(&regs->u_regs [UREG_G1], &(*gr)[SVR4_G1],
			      sizeof (long) * 7);
	err |= __copy_from_user(&regs->u_regs [UREG_I0], &(*gr)[SVR4_O0],
			      sizeof (long) * 8);
	return (err ? -EFAULT : 0);

sigsegv_and_return:
	do_exit(SIGSEGV);
}

static inline void
handle_signal(unsigned long signr, struct k_sigaction *ka,
	      siginfo_t *info, sigset_t *oldset, struct pt_regs *regs,
	      int svr4_signal)
{
	if (svr4_signal)
		setup_svr4_frame(&ka->sa, regs->pc, regs->npc, regs, signr, oldset);
	else {
		if (ka->sa.sa_flags & SA_SIGINFO)
			new_setup_rt_frame(ka, regs, signr, oldset, info);
		else if (current->thread.new_signal)
			new_setup_frame (ka, regs, signr, oldset);
		else
			setup_frame(&ka->sa, regs, signr, oldset, info);
	}
	if(ka->sa.sa_flags & SA_ONESHOT)
		ka->sa.sa_handler = SIG_DFL;
	if(!(ka->sa.sa_flags & SA_NOMASK)) {
		spin_lock_irq(&current->sigmask_lock);
		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
		sigaddset(&current->blocked, signr);
		recalc_sigpending(current);
		spin_unlock_irq(&current->sigmask_lock);
	}
}

static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
				   struct sigaction *sa)
{
	switch(regs->u_regs[UREG_I0]) {
		case ERESTARTNOHAND:
		no_system_call_restart:
			regs->u_regs[UREG_I0] = EINTR;
			regs->psr |= PSR_C;
			break;
		case ERESTARTSYS:
			if(!(sa->sa_flags & SA_RESTART))
				goto no_system_call_restart;
		/* fallthrough */
		case ERESTARTNOINTR:
			regs->u_regs[UREG_I0] = orig_i0;
			regs->pc -= 4;
			regs->npc -= 4;
	}
}

#ifdef DEBUG_SIGNALS_MAPS

#define MAPS_LINE_FORMAT	  "%08lx-%08lx %s %08lx %s %lu "

static inline void read_maps (void)
{
	struct vm_area_struct * map, * next;
	char * buffer;
	ssize_t i;

	buffer = (char*)__get_free_page(GFP_KERNEL);
	if (!buffer)
		return;

	for (map = current->mm->mmap ; map ; map = next ) {
		/* produce the next line */
		char *line;
		char str[5], *cp = str;
		int flags;
		kdev_t dev;
		unsigned long ino;

		/*
		 * Get the next vma now (but it won't be used if we sleep).
		 */
		next = map->vm_next;
		flags = map->vm_flags;

		*cp++ = flags & VM_READ ? 'r' : '-';
		*cp++ = flags & VM_WRITE ? 'w' : '-';
		*cp++ = flags & VM_EXEC ? 'x' : '-';
		*cp++ = flags & VM_MAYSHARE ? 's' : 'p';
		*cp++ = 0;

		dev = 0;
		ino = 0;
		if (map->vm_file != NULL) {
			dev = map->vm_file->f_dentry->d_inode->i_dev;
			ino = map->vm_file->f_dentry->d_inode->i_ino;
			line = d_path(map->vm_file->f_dentry,
				      map->vm_file->f_vfsmnt,
				      buffer, PAGE_SIZE);
		}
		printk(MAPS_LINE_FORMAT, map->vm_start, map->vm_end, str, map->vm_pgoff << PAGE_SHIFT,
			      kdevname(dev), ino);
		if (map->vm_file != NULL)
			printk("%s\n", line);
		else
			printk("\n");
	}
	free_page((unsigned long)buffer);
	return;
}
#endif

/* 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.
 */
asmlinkage int do_signal(sigset_t *oldset, struct pt_regs * regs,
			 unsigned long orig_i0, int restart_syscall)
{
	unsigned long signr;
	struct k_sigaction *ka;
	siginfo_t info;

	/*
	 * XXX Disable svr4 signal handling until solaris emulation works.
	 * It is buggy - Anton
	 */
#define SVR4_SIGNAL_BROKEN 1
#ifdef SVR4_SIGNAL_BROKEN
	int svr4_signal = 0;
#else
	int svr4_signal = current->personality == PER_SVR4;
#endif

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

	for (;;) {
		spin_lock_irq(&current->sigmask_lock);
		signr = dequeue_signal(&current->blocked, &info);
		spin_unlock_irq(&current->sigmask_lock);

		if (!signr) break;

		if ((current->ptrace & PT_PTRACED) && signr != SIGKILL) {
			current->exit_code = signr;
			current->state = TASK_STOPPED;

			/* This happens to be SMP safe so no need to
			 * grab master kernel lock even in this case.
			 */
			notify_parent(current, SIGCHLD);
			schedule();
			if (!(signr = current->exit_code))
				continue;
			current->exit_code = 0;
			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];

		if(ka->sa.sa_handler == SIG_IGN) {
			if(signr != SIGCHLD)
				continue;

			/* sys_wait4() grabs the master kernel lock, so
			 * we need not do so, that sucker should be
			 * threaded and would not be that difficult to
			 * do anyways.
			 */
			while(sys_wait4(-1, NULL, WNOHANG, NULL) > 0)
				;
			continue;
		}
		if(ka->sa.sa_handler == SIG_DFL) {
			unsigned long exit_code = signr;

			if(current->pid == 1)
				continue;
			switch(signr) {
			case SIGCONT: case SIGCHLD: case SIGWINCH:
				continue;

			case SIGTSTP: case SIGTTIN: case SIGTTOU:
				/* The operations performed by
				 * is_orphaned_pgrp() are protected by
				 * the tasklist_lock.
				 */
				if (is_orphaned_pgrp(current->pgrp))
					continue;

			case SIGSTOP:
				if (current->ptrace & PT_PTRACED)
					continue;
				current->state = TASK_STOPPED;
				current->exit_code = signr;

				/* notify_parent() is SMP safe */
				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 (do_coredump(signr, regs))
					exit_code |= 0x80;
#ifdef DEBUG_SIGNALS
				/* Very useful to debug dynamic linker problems */
				printk ("Sig %ld going for %s[%d]...\n", signr, current->comm, current->pid);
				show_regs (regs);
#ifdef DEBUG_SIGNALS_TRACE
				{
					struct reg_window *rw = (struct reg_window *)regs->u_regs[UREG_FP];
					unsigned int ins[8];

					while(rw &&
					      !(((unsigned long) rw) & 0x3)) {
						copy_from_user(ins, &rw->ins[0], sizeof(ins));
						printk("Caller[%08x](%08x,%08x,%08x,%08x,%08x,%08x)\n", ins[7], ins[0], ins[1], ins[2], ins[3], ins[4], ins[5]);
						rw = (struct reg_window *)(unsigned long)ins[6];
					}
				}
#endif
#ifdef DEBUG_SIGNALS_MAPS
				printk("Maps:\n");
				read_maps();
#endif
#endif
				/* fall through */
			default:
				sigaddset(&current->pending.signal, signr);
				recalc_sigpending(current);
				current->flags |= PF_SIGNALED;
				do_exit(exit_code);
				/* NOT REACHED */
			}
		}
		if(restart_syscall)
			syscall_restart(orig_i0, regs, &ka->sa);
		handle_signal(signr, ka, &info, oldset, regs, svr4_signal);
		return 1;
	}
	if(restart_syscall &&
	   (regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
	    regs->u_regs[UREG_I0] == ERESTARTSYS ||
	    regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
		/* replay the system call when we are done */
		regs->u_regs[UREG_I0] = orig_i0;
		regs->pc -= 4;
		regs->npc -= 4;
	}
	return 0;
}

asmlinkage int
do_sys_sigstack(struct sigstack *ssptr, struct sigstack *ossptr, unsigned long sp)
{
	int ret = -EFAULT;

	/* First see if old state is wanted. */
	if (ossptr) {
		if (put_user(current->sas_ss_sp + current->sas_ss_size, &ossptr->the_stack) ||
		    __put_user(on_sig_stack(sp), &ossptr->cur_status))
			goto out;
	}

	/* Now see if we want to update the new state. */
	if (ssptr) {
		void *ss_sp;

		if (get_user((long)ss_sp, &ssptr->the_stack))
			goto out;
		/* If the current stack was set with sigaltstack, don't
		   swap stacks while we are on it.  */
		ret = -EPERM;
		if (current->sas_ss_sp && on_sig_stack(sp))
			goto out;

		/* Since we don't know the extent of the stack, and we don't
		   track onstack-ness, but rather calculate it, we must
		   presume a size.  Ho hum this interface is lossy.  */
		current->sas_ss_sp = (unsigned long)ss_sp - SIGSTKSZ;
		current->sas_ss_size = SIGSTKSZ;
	}
	ret = 0;
out:
	return ret;
}