signal.c

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/*
 *  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))

extern void syscall_direct_return(struct pt_regs *regs);

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->result = -EINTR;
	regs->gpr[3] = EINTR;
	regs->ccr |= 0x10000000;
	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->result = -EINTR;
	regs->gpr[3] = EINTR;
	regs->ccr |= 0x10000000;
	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, int r5, int r6,
		int r7, int r8, struct pt_regs *regs)
{
	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
 *	a sigcontext struct
 *	a gap of __SIGNAL_FRAMESIZE bytes
 *
 * Each of these things must be a multiple of 16 bytes in size.
 *
 */
struct sigregs {
	struct mcontext	mctx;		/* all the register values */
	/* 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];
};

/* We use the mc_pad field for the signal return trampoline. */
#define tramp	mc_pad

/*
 *  When we have rt signals to deliver, we set up on the
 *  user stack, going down from the original stack pointer:
 *	one rt_sigframe struct (siginfo + ucontext + ABI gap)
 *	a gap of __SIGNAL_FRAMESIZE+16 bytes
 *  (the +16 is to get the siginfo and ucontext in the same
 *  positions as in older kernels).
 *
 *  Each of these things must be a multiple of 16 bytes in size.
 *
 */
struct rt_sigframe
{
	struct siginfo info;
	struct ucontext uc;
	/* 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];
};

/*
 * Save the current user registers on the user stack.
 * We only save the altivec registers if the process has used
 * altivec instructions at some point.
 */
static int
save_user_regs(struct pt_regs *regs, struct mcontext *frame, int sigret)
{
	/* save general and floating-point registers */
	if (regs->msr & MSR_FP)
		giveup_fpu(current);
	if (__copy_to_user(&frame->mc_gregs, regs, GP_REGS_SIZE)
	    || __copy_to_user(&frame->mc_fregs, current->thread.fpr,
			      ELF_NFPREG * sizeof(double)))
		return 1;

	current->thread.fpscr = 0;	/* turn off all fp exceptions */

#ifdef CONFIG_ALTIVEC
	/* save altivec registers */
	if (current->thread.used_vr) {
		if (regs->msr & MSR_VEC)
			giveup_altivec(current);
		if (__copy_to_user(&frame->mc_vregs, current->thread.vr,
				   ELF_NVRREG * sizeof(vector128)))
			return 1;
		/* set MSR_VEC in the saved MSR value to indicate that
		   frame->mc_vregs contains valid data */
		if (__put_user(regs->msr | MSR_VEC, &frame->mc_gregs[PT_MSR]))
			return 1;
	}
	/* else assert((regs->msr & MSR_VEC) == 0) */

	/* We always copy to/from vrsave, it's 0 if we don't have or don't
	 * use altivec. Since VSCR only contains 32 bits saved in the least
	 * significant bits of a vector, we "cheat" and stuff VRSAVE in the
	 * most significant bits of that same vector. --BenH
	 */
	if (__put_user(current->thread.vrsave, (u32 *)&frame->mc_vregs[32]))
		return 1;
#endif /* CONFIG_ALTIVEC */

	if (sigret) {
		/* Set up the sigreturn trampoline: li r0,sigret; sc */
		if (__put_user(0x38000000UL + sigret, &frame->tramp[0])
		    || __put_user(0x44000002UL, &frame->tramp[1]))
			return 1;
		flush_icache_range((unsigned long) &frame->tramp[0],
				   (unsigned long) &frame->tramp[2]);
	}

	return 0;
}

/*
 * Restore the current user register values from the user stack,
 * (except for MSR).
 */
static int
restore_user_regs(struct pt_regs *regs, struct mcontext *sr)
{
#ifdef CONFIG_ALTIVEC
	unsigned long msr;
#endif

	/* copy up to but not including MSR */
	if (__copy_from_user(regs, &sr->mc_gregs, PT_MSR * sizeof(elf_greg_t)))
		return 1;
	/* copy from orig_r3 (the word after the MSR) up to the end */
	if (__copy_from_user(&regs->orig_gpr3, &sr->mc_gregs[PT_ORIG_R3],
			     GP_REGS_SIZE - PT_ORIG_R3 * sizeof(elf_greg_t)))
		return 1;

	/* force the process to reload the FP registers from
	   current->thread when it next does FP instructions */
	regs->msr &= ~MSR_FP;
	if (__copy_from_user(current->thread.fpr, &sr->mc_fregs,
			     sizeof(sr->mc_fregs)))
		return 1;

#ifdef CONFIG_ALTIVEC
	/* force the process to reload the altivec registers from
	   current->thread when it next does altivec instructions */
	regs->msr &= ~MSR_VEC;
	if (!__get_user(msr, &sr->mc_gregs[PT_MSR]) && (msr & MSR_VEC) != 0) {
		/* restore altivec registers from the stack */
		if (__copy_from_user(current->thread.vr, &sr->mc_vregs,
				     sizeof(sr->mc_vregs)))
			return 1;
	} else if (current->thread.used_vr)
		memset(&current->thread.vr, 0, ELF_NVRREG * sizeof(vector128));

	/* Always get VRSAVE back */
	if (__get_user(current->thread.vrsave, (u32 *)&sr->mc_vregs[32]))
		return 1;
#endif /* CONFIG_ALTIVEC */

	return 0;
}

/*
 * Restore the user process's signal mask
 */
static void
restore_sigmask(sigset_t *set)
{
	sigdelsetmask(set, ~_BLOCKABLE);
	spin_lock_irq(&current->sigmask_lock);
	current->blocked = *set;
	recalc_sigpending(current);
	spin_unlock_irq(&current->sigmask_lock);
}

/*
 * Set up a signal frame for a "real-time" signal handler
 * (one which gets siginfo).
 */
static void
handle_rt_signal(unsigned long sig, struct k_sigaction *ka,
		 siginfo_t *info, sigset_t *oldset, struct pt_regs * regs,
		 unsigned long newsp)
{
	struct rt_sigframe *rt_sf;
	struct mcontext *frame;
	unsigned long origsp = newsp;

	/* Set up Signal Frame */
	/* Put a Real Time Context onto stack */
	newsp -= sizeof(*rt_sf);
	rt_sf = (struct rt_sigframe *) newsp;

	/* create a stack frame for the caller of the handler */
	newsp -= __SIGNAL_FRAMESIZE + 16;

	if (verify_area(VERIFY_WRITE, (void *) newsp, origsp - newsp))
		goto badframe;

	/* Put the siginfo & fill in most of the ucontext */
	if (__copy_to_user(&rt_sf->info, info, sizeof(*info))
	    || __put_user(0, &rt_sf->uc.uc_flags)
	    || __put_user(0, &rt_sf->uc.uc_link)
	    || __put_user(current->sas_ss_sp, &rt_sf->uc.uc_stack.ss_sp)
	    || __put_user(sas_ss_flags(regs->gpr[1]), 
			  &rt_sf->uc.uc_stack.ss_flags)
	    || __put_user(current->sas_ss_size, &rt_sf->uc.uc_stack.ss_size)
	    || __put_user(&rt_sf->uc.uc_mcontext, &rt_sf->uc.uc_regs)