signal.c

MIZI Research, Inc.发布的嵌入式Linux内核源码

/*
 * BK Id: SCCS/s.signal.c 1.10 11/23/01 16:38:30 paulus
 */
/*
 *  linux/arch/ppc/kernel/signal.c
 *
 *  PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas ([e-mail])
 *
 *  Derived from "arch/i386/kernel/signal.c"
 *    Copyright (C) 1991, 1992 Linus Torvalds
 *    1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/elf.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>

#define DEBUG_SIG 0

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

#ifndef MIN
#define MIN(a,b) (((a) < (b)) ? (a) : (b))
#endif

#define GP_REGS_SIZE	MIN(sizeof(elf_gregset_t), sizeof(struct pt_regs))

/* 
 * These are the flags in the MSR that the user is allowed to change
 * by modifying the saved value of the MSR on the stack.  SE and BE
 * should not be in this list since gdb may want to change these.  I.e,
 * you should be able to step out of a signal handler to see what
 * instruction executes next after the signal handler completes.
 * Alternately, if you stepped into a signal handler, you should be
 * able to continue 'til the next breakpoint from within the signal
 * handler, even if the handler returns.
 */
#define MSR_USERCHANGE	(MSR_FE0 | MSR_FE1)

int do_signal(sigset_t *oldset, struct pt_regs *regs);

int copy_siginfo_to_user(siginfo_t *to, siginfo_t *from)
{
	if (!access_ok (VERIFY_WRITE, to, sizeof(siginfo_t)))
		return -EFAULT;
	if (from->si_code < 0)
		return __copy_to_user(to, from, sizeof(siginfo_t));
	else {
		int err;

		/* If you change siginfo_t structure, please be sure
		   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.  */
		err = __put_user(from->si_signo, &to->si_signo);
		err |= __put_user(from->si_errno, &to->si_errno);
		err |= __put_user((short)from->si_code, &to->si_code);
		/* First 32bits of unions are always present.  */
		err |= __put_user(from->si_pid, &to->si_pid);
		switch (from->si_code >> 16) {
		case __SI_FAULT >> 16:
			break;
		case __SI_CHLD >> 16:
			err |= __put_user(from->si_utime, &to->si_utime);
			err |= __put_user(from->si_stime, &to->si_stime);
			err |= __put_user(from->si_status, &to->si_status);
		default:
			err |= __put_user(from->si_uid, &to->si_uid);
			break;
		/* case __SI_RT: This is not generated by the kernel as of now.  */
		}
		return err;
	}
}

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
int
sys_sigsuspend(old_sigset_t mask, int p2, int p3, int p4, int p6, int p7,
	       struct pt_regs *regs)
{
	sigset_t saveset;

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

	regs->gpr[3] = -EINTR;
	while (1) {
		current->state = TASK_INTERRUPTIBLE;
		schedule();
		if (do_signal(&saveset, regs))
			/*
			 * If a signal handler needs to be called,
			 * do_signal() has set R3 to the signal number (the
			 * first argument of the signal handler), so don't
			 * overwrite that with EINTR !
			 * In the other cases, do_signal() doesn't touch 
			 * R3, so it's still set to -EINTR (see above).
			 */
			return regs->gpr[3];
	}
}

int
sys_rt_sigsuspend(sigset_t *unewset, size_t sigsetsize, int p3, int p4, int p6,
		  int p7, struct pt_regs *regs)
{
	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->sigmask_lock);
	saveset = current->blocked;
	current->blocked = newset;
	recalc_sigpending(current);
	spin_unlock_irq(&current->sigmask_lock);

	regs->gpr[3] = -EINTR;
	while (1) {
		current->state = TASK_INTERRUPTIBLE;
		schedule();
		if (do_signal(&saveset, regs))
			return regs->gpr[3];
	}
}


int
sys_sigaltstack(const stack_t *uss, stack_t *uoss)
{
	struct pt_regs *regs = (struct pt_regs *) &uss;
	return do_sigaltstack(uss, uoss, regs->gpr[1]);
}

int 
sys_sigaction(int sig, const struct old_sigaction *act,
	      struct old_sigaction *oact)
{
	struct k_sigaction new_ka, old_ka;
	int ret;

	if (act) {
		old_sigset_t mask;
		if (verify_area(VERIFY_READ, act, sizeof(*act)) ||
		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
		    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
			return -EFAULT;
		__get_user(new_ka.sa.sa_flags, &act->sa_flags);
		__get_user(mask, &act->sa_mask);
		siginitset(&new_ka.sa.sa_mask, mask);
	}

	ret = do_sigaction(sig, (act? &new_ka: NULL), (oact? &old_ka: NULL));

	if (!ret && oact) {
		if (verify_area(VERIFY_WRITE, oact, sizeof(*oact)) ||
		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
		    __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer))
			return -EFAULT;
		__put_user(old_ka.sa.sa_flags, &oact->sa_flags);
		__put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
	}

	return ret;
}

/*
 * When we have signals to deliver, we set up on the
 * user stack, going down from the original stack pointer:
 *	a sigregs struct
 *	one or more sigcontext structs with
 *	a gap of __SIGNAL_FRAMESIZE bytes
 *
 * Each of these things must be a multiple of 16 bytes in size.
 *
 */
struct sigregs {
	elf_gregset_t	gp_regs;
	double		fp_regs[ELF_NFPREG];
	unsigned long	tramp[2];
	/* Programs using the rs6000/xcoff abi can save up to 19 gp regs
	   and 18 fp regs below sp before decrementing it. */
	int		abigap[56];
};

struct rt_sigframe
{
	unsigned long	_unused[2];
	struct siginfo *pinfo;
	void *puc;
	struct siginfo info;
	struct ucontext uc;
};


/*
 *  When we have rt signals to deliver, we set up on the
 *  user stack, going down from the original stack pointer:
 *	   a sigregs struct
 *	   one rt_sigframe struct (siginfo + ucontext)
 *	   a gap of __SIGNAL_FRAMESIZE bytes
 *
 *  Each of these things must be a multiple of 16 bytes in size.
 *
 */
int sys_rt_sigreturn(struct pt_regs *regs)
{
	struct rt_sigframe *rt_sf;
	struct sigcontext_struct sigctx;
	struct sigregs *sr;
	int ret;
	elf_gregset_t saved_regs;  /* an array of ELF_NGREG unsigned longs */
	sigset_t set;
	stack_t st;
	unsigned long prevsp;

	rt_sf = (struct rt_sigframe *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
	if (copy_from_user(&sigctx, &rt_sf->uc.uc_mcontext, sizeof(sigctx))
	    || copy_from_user(&set, &rt_sf->uc.uc_sigmask, sizeof(set))
	    || copy_from_user(&st, &rt_sf->uc.uc_stack, sizeof(st)))
		goto badframe;
	sigdelsetmask(&set, ~_BLOCKABLE);
	spin_lock_irq(&current->sigmask_lock);
	current->blocked = set;
	recalc_sigpending(current);
	spin_unlock_irq(&current->sigmask_lock);
	if (regs->msr & MSR_FP)
		giveup_fpu(current);

	rt_sf++;			/* Look at next rt_sigframe */
	if (rt_sf == (struct rt_sigframe *)(sigctx.regs)) {
		/* Last stacked signal - restore registers -
		 * sigctx is initialized to point to the 
		 * preamble frame (where registers are stored) 
		 * see handle_signal()
		 */
		sr = (struct sigregs *) sigctx.regs;
		if (copy_from_user(saved_regs, &sr->gp_regs,
				   sizeof(sr->gp_regs)))
			goto badframe;
		saved_regs[PT_MSR] = (regs->msr & ~MSR_USERCHANGE)
			| (saved_regs[PT_MSR] & MSR_USERCHANGE);
		memcpy(regs, saved_regs, GP_REGS_SIZE);
		if (copy_from_user(current->thread.fpr, &sr->fp_regs,
				   sizeof(sr->fp_regs)))
			goto badframe;
		/* This function sets back the stack flags into
		   the current task structure.  */
		sys_sigaltstack(&st, NULL);

		ret = regs->result;
	} else {
		/* More signals to go */
		/* Set up registers for next signal handler */
		regs->gpr[1] = (unsigned long)rt_sf - __SIGNAL_FRAMESIZE;
		if (copy_from_user(&sigctx, &rt_sf->uc.uc_mcontext, sizeof(sigctx)))
			goto badframe;
		sr = (struct sigregs *) sigctx.regs;
		regs->gpr[3] = ret = sigctx.signal;
		/* Get the siginfo   */
		get_user(regs->gpr[4], (unsigned long *)&rt_sf->pinfo);
		/* Get the ucontext */
		get_user(regs->gpr[5], (unsigned long *)&rt_sf->puc);
		regs->gpr[6] = (unsigned long) rt_sf;

		regs->link = (unsigned long) &sr->tramp;
		regs->nip = sigctx.handler;
		if (get_user(prevsp, &sr->gp_regs[PT_R1])
		    || put_user(prevsp, (unsigned long *) regs->gpr[1]))
			goto badframe;
		current->thread.fpscr = 0;
	}
	return ret;

badframe:
	do_exit(SIGSEGV);
}

static void
setup_rt_frame(struct pt_regs *regs, struct sigregs *frame,
	       signed long newsp)
{
	struct rt_sigframe *rt_sf = (struct rt_sigframe *) newsp;

	/* Set up preamble frame */
	if (verify_area(VERIFY_WRITE, frame, sizeof(*frame)))
		goto badframe;
	if (regs->msr & MSR_FP)
		giveup_fpu(current);
	if (__copy_to_user(&frame->gp_regs, regs, GP_REGS_SIZE)
	    || __copy_to_user(&frame->fp_regs, current->thread.fpr,
			      ELF_NFPREG * sizeof(double))
	/* Set up to return from user space.
	   It calls the sc exception at offset 0x9999 
	   for sys_rt_sigreturn().
	*/
	    || __put_user(0x38006666UL, &frame->tramp[0])	/* li r0,0x6666 */
	    || __put_user(0x44000002UL, &frame->tramp[1]))	/* sc */
		goto badframe;
	flush_icache_range((unsigned long) &frame->tramp[0],
			   (unsigned long) &frame->tramp[2]);
	current->thread.fpscr = 0;	/* turn off all fp exceptions */

	/* Retrieve rt_sigframe from stack and
	   set up registers for signal handler
	*/
	newsp -= __SIGNAL_FRAMESIZE;
	if (put_user(regs->gpr[1], (unsigned long *)newsp)
	    || get_user(regs->nip, &rt_sf->uc.uc_mcontext.handler)
	    || get_user(regs->gpr[3], &rt_sf->uc.uc_mcontext.signal)
	    || get_user(regs->gpr[4], (unsigned long *)&rt_sf->pinfo)
	    || get_user(regs->gpr[5], (unsigned long *)&rt_sf->puc))
		goto badframe;