signal_kern.c

来自「优龙2410linux2.6.8内核源代码」· C语言 代码 · 共 285 行

/* 
 * Copyright (C) 2000, 2001, 2002 Jeff Dike ([e-mail])
 * Licensed under the GPL
 */

#include "linux/config.h"
#include "linux/stddef.h"
#include "linux/sys.h"
#include "linux/sched.h"
#include "linux/wait.h"
#include "linux/kernel.h"
#include "linux/smp_lock.h"
#include "linux/module.h"
#include "linux/slab.h"
#include "linux/tty.h"
#include "linux/binfmts.h"
#include "linux/ptrace.h"
#include "asm/signal.h"
#include "asm/uaccess.h"
#include "asm/unistd.h"
#include "user_util.h"
#include "asm/ucontext.h"
#include "kern_util.h"
#include "signal_kern.h"
#include "signal_user.h"
#include "kern.h"
#include "frame_kern.h"
#include "sigcontext.h"
#include "mode.h"

EXPORT_SYMBOL(block_signals);
EXPORT_SYMBOL(unblock_signals);

static void force_segv(int sig)
{
	if(sig == SIGSEGV){
		struct k_sigaction *ka;

		ka = &current->sig->action[SIGSEGV - 1];
		ka->sa.sa_handler = SIG_DFL;
	}
	force_sig(SIGSEGV, current);
}

#define _S(nr) (1<<((nr)-1))

#define _BLOCKABLE (~(_S(SIGKILL) | _S(SIGSTOP)))

/*
 * OK, we're invoking a handler
 */	
static int handle_signal(struct pt_regs *regs, unsigned long signr, 
			 struct k_sigaction *ka, siginfo_t *info, 
			 sigset_t *oldset, int error)
{
        __sighandler_t handler;
	void (*restorer)(void);
	unsigned long sp;
	sigset_t save;
	int err, ret;

	ret = 0;
	switch(error){
	case -ERESTART_RESTARTBLOCK:
		current_thread_info()->restart_block.fn = 
			do_no_restart_syscall;
	case -ERESTARTNOHAND:
		ret = -EINTR;
		break;

	case -ERESTARTSYS:
		if (!(ka->sa.sa_flags & SA_RESTART)) {
			ret = -EINTR;
			break;
		}
		/* fallthrough */
	case -ERESTARTNOINTR:
		PT_REGS_RESTART_SYSCALL(regs);
		PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);

		/* This is because of the UM_SET_SYSCALL_RETURN and the fact
		 * that on i386 the system call number and return value are
		 * in the same register.  When the system call restarts, %eax
		 * had better have the system call number in it.  Since the
		 * return value doesn't matter (except that it shouldn't be
		 * -ERESTART*), we'll stick the system call number there.
		 */
		ret = PT_REGS_SYSCALL_NR(regs);
		break;
	}

	handler = ka->sa.sa_handler;
	save = *oldset;

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

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

	sp = PT_REGS_SP(regs);

	if((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
		sp = current->sas_ss_sp + current->sas_ss_size;
	
	if(error != 0) PT_REGS_SET_SYSCALL_RETURN(regs, ret);

	if (ka->sa.sa_flags & SA_RESTORER) restorer = ka->sa.sa_restorer;
	else restorer = NULL;

	if(ka->sa.sa_flags & SA_SIGINFO)
		err = setup_signal_stack_si(sp, signr, (unsigned long) handler,
					    restorer, regs, info, &save);
	else
		err = setup_signal_stack_sc(sp, signr, (unsigned long) handler,
					    restorer, regs, &save);
	if(err) goto segv;

	return(0);
 segv:
	force_segv(signr);
	return(1);
}

static int kern_do_signal(struct pt_regs *regs, sigset_t *oldset, int error)
{
	siginfo_t info;
	struct k_sigaction *ka;
	int err, sig;

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

	sig = get_signal_to_deliver(&info, regs, NULL);
	if(sig == 0)
		return(0);

	/* Whee!  Actually deliver the signal.  */
	ka = &current->sig->action[sig -1 ];
	err = handle_signal(regs, sig, ka, &info, oldset, error);
	if(!err) return(1);

	/* Did we come from a system call? */
	if(PT_REGS_SYSCALL_NR(regs) >= 0){
		/* Restart the system call - no handlers present */
		if(PT_REGS_SYSCALL_RET(regs) == -ERESTARTNOHAND ||
		   PT_REGS_SYSCALL_RET(regs) == -ERESTARTSYS ||
		   PT_REGS_SYSCALL_RET(regs) == -ERESTARTNOINTR){
			PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);
			PT_REGS_RESTART_SYSCALL(regs);
		}
		else if(PT_REGS_SYSCALL_RET(regs) == -ERESTART_RESTARTBLOCK){
			PT_REGS_SYSCALL_RET(regs) = __NR_restart_syscall;
			PT_REGS_RESTART_SYSCALL(regs);
 		}
	}

	/* This closes a way to execute a system call on the host.  If
	 * you set a breakpoint on a system call instruction and singlestep
	 * from it, the tracing thread used to PTRACE_SINGLESTEP the process
	 * rather than PTRACE_SYSCALL it, allowing the system call to execute
	 * on the host.  The tracing thread will check this flag and 
	 * PTRACE_SYSCALL if necessary.
	 */
	if((current->ptrace & PT_DTRACE) && 
	   is_syscall(PT_REGS_IP(&current->thread.regs)))
 		(void) CHOOSE_MODE(current->thread.mode.tt.singlestep_syscall = 1, 0);
	return(0);
}

int do_signal(int error)
{
	return(kern_do_signal(&current->thread.regs, NULL, error));
}

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
int sys_sigsuspend(int history0, int history1, old_sigset_t mask)
{
	sigset_t saveset;

	mask &= _BLOCKABLE;
	spin_lock_irq(&current->sighand->siglock);
	saveset = current->blocked;
	siginitset(&current->blocked, mask);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	while (1) {
		current->state = TASK_INTERRUPTIBLE;
		schedule();
		if(kern_do_signal(&current->thread.regs, &saveset, -EINTR))
			return(-EINTR);
	}
}

int sys_rt_sigsuspend(sigset_t *unewset, size_t sigsetsize)
{
	sigset_t saveset, newset;

	/* XXX: Don't preclude handling different sized sigset_t's.  */
	if (sigsetsize != sizeof(sigset_t))
		return -EINVAL;

	if (copy_from_user(&newset, unewset, sizeof(newset)))
		return -EFAULT;
	sigdelsetmask(&newset, ~_BLOCKABLE);

	spin_lock_irq(&current->sighand->siglock);
	saveset = current->blocked;
	current->blocked = newset;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	while (1) {
		current->state = TASK_INTERRUPTIBLE;
		schedule();
		if (kern_do_signal(&current->thread.regs, &saveset, -EINTR))
			return(-EINTR);
	}
}

static int copy_sc_from_user(struct pt_regs *to, void *from, 
			     struct arch_frame_data *arch)
{
	int ret;

	ret = CHOOSE_MODE(copy_sc_from_user_tt(UPT_SC(&to->regs), from, arch),
			  copy_sc_from_user_skas(&to->regs, from));
	return(ret);
}

int sys_sigreturn(struct pt_regs regs)
{
	void *sc = sp_to_sc(PT_REGS_SP(&current->thread.regs));
	void *mask = sp_to_mask(PT_REGS_SP(&current->thread.regs));
	int sig_size = (_NSIG_WORDS - 1) * sizeof(unsigned long);

	spin_lock_irq(&current->sighand->siglock);
	copy_from_user(&current->blocked.sig[0], sc_sigmask(sc), 
		       sizeof(current->blocked.sig[0]));
	copy_from_user(&current->blocked.sig[1], mask, sig_size);
	sigdelsetmask(&current->blocked, ~_BLOCKABLE);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);
	copy_sc_from_user(&current->thread.regs, sc, 
			  &signal_frame_sc.common.arch);
	return(PT_REGS_SYSCALL_RET(&current->thread.regs));
}

int sys_rt_sigreturn(struct pt_regs regs)
{
	struct ucontext *uc = sp_to_uc(PT_REGS_SP(&current->thread.regs));
	void *fp;
	int sig_size = _NSIG_WORDS * sizeof(unsigned long);

	spin_lock_irq(&current->sighand->siglock);
	copy_from_user(&current->blocked, &uc->uc_sigmask, sig_size);
	sigdelsetmask(&current->blocked, ~_BLOCKABLE);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);
	fp = (void *) (((unsigned long) uc) + sizeof(struct ucontext));
	copy_sc_from_user(&current->thread.regs, &uc->uc_mcontext,
			  &signal_frame_si.common.arch);
	return(PT_REGS_SYSCALL_RET(&current->thread.regs));
}

/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-file-style: "linux"
 * End:
 */