[POWERPC] Consolidate sys_sigaltstack

[deliverable/linux.git] / arch / powerpc / kernel / signal_64.c

/*
 *  PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  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/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/elf.h>
#include <linux/ptrace.h>
#include <linux/module.h>

#include <asm/sigcontext.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>
#include <asm/syscalls.h>
#include <asm/vdso.h>

#include "signal.h"

#define DEBUG_SIG 0

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

#define GP_REGS_SIZE    min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
#define FP_REGS_SIZE    sizeof(elf_fpregset_t)

#define TRAMP_TRACEBACK 3
#define TRAMP_SIZE      6

/*
 * When we have signals to deliver, we set up on the user stack,
 * going down from the original stack pointer:
 *      1) a rt_sigframe struct which contains the ucontext     
 *      2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
 *         frame for the signal handler.
 */

struct rt_sigframe {
        /* sys_rt_sigreturn requires the ucontext be the first field */
        struct ucontext uc;
        unsigned long _unused[2];
        unsigned int tramp[TRAMP_SIZE];
        struct siginfo __user *pinfo;
        void __user *puc;
        struct siginfo info;
        /* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
        char abigap[288];
} __attribute__ ((aligned (16)));

/*
 * Set up the sigcontext for the signal frame.
 */

static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
                 int signr, sigset_t *set, unsigned long handler)
{
        /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
         * process never used altivec yet (MSR_VEC is zero in pt_regs of
         * the context). This is very important because we must ensure we
         * don't lose the VRSAVE content that may have been set prior to
         * the process doing its first vector operation
         * Userland shall check AT_HWCAP to know wether it can rely on the
         * v_regs pointer or not
         */
#ifdef CONFIG_ALTIVEC
        elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
#endif
        long err = 0;

        flush_fp_to_thread(current);

#ifdef CONFIG_ALTIVEC
        err |= __put_user(v_regs, &sc->v_regs);

        /* save altivec registers */
        if (current->thread.used_vr) {
                flush_altivec_to_thread(current);
                /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
                err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
                /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
                 * contains valid data.
                 */
                regs->msr |= MSR_VEC;
        }
        /* We always copy to/from vrsave, it's 0 if we don't have or don't
         * use altivec.
         */
        err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
#else /* CONFIG_ALTIVEC */
        err |= __put_user(0, &sc->v_regs);
#endif /* CONFIG_ALTIVEC */
        err |= __put_user(&sc->gp_regs, &sc->regs);
        WARN_ON(!FULL_REGS(regs));
        err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
        err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
        err |= __put_user(signr, &sc->signal);
        err |= __put_user(handler, &sc->handler);
        if (set != NULL)
                err |=  __put_user(set->sig[0], &sc->oldmask);

        return err;
}

/*
 * Restore the sigcontext from the signal frame.
 */

static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
                              struct sigcontext __user *sc)
{
#ifdef CONFIG_ALTIVEC
        elf_vrreg_t __user *v_regs;
#endif
        unsigned long err = 0;
        unsigned long save_r13 = 0;
        elf_greg_t *gregs = (elf_greg_t *)regs;
        unsigned long msr;
        int i;

        /* If this is not a signal return, we preserve the TLS in r13 */
        if (!sig)
                save_r13 = regs->gpr[13];

        /* copy everything before MSR */
        err |= __copy_from_user(regs, &sc->gp_regs,
                                PT_MSR*sizeof(unsigned long));

        /* get MSR separately, transfer the LE bit if doing signal return */
        err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
        if (sig)
                regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);

        /* skip SOFTE */
        for (i = PT_MSR+1; i <= PT_RESULT; i++) {
                if (i == PT_SOFTE)
                        continue;
                err |= __get_user(gregs[i], &sc->gp_regs[i]);
        }

        if (!sig)
                regs->gpr[13] = save_r13;
        if (set != NULL)
                err |=  __get_user(set->sig[0], &sc->oldmask);

        /*
         * Do this before updating the thread state in
         * current->thread.fpr/vr.  That way, if we get preempted
         * and another task grabs the FPU/Altivec, it won't be
         * tempted to save the current CPU state into the thread_struct
         * and corrupt what we are writing there.
         */
        discard_lazy_cpu_state();

        err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);

#ifdef CONFIG_ALTIVEC
        err |= __get_user(v_regs, &sc->v_regs);
        if (err)
                return err;
        if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
                return -EFAULT;
        /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
        if (v_regs != 0 && (msr & MSR_VEC) != 0)
                err |= __copy_from_user(current->thread.vr, v_regs,
                                        33 * sizeof(vector128));
        else if (current->thread.used_vr)
                memset(current->thread.vr, 0, 33 * sizeof(vector128));
        /* Always get VRSAVE back */
        if (v_regs != 0)
                err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
        else
                current->thread.vrsave = 0;
#endif /* CONFIG_ALTIVEC */

        /* Force reload of FP/VEC */
        regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);

        return err;
}

/*
 * Allocate space for the signal frame
 */
static inline void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
                                  size_t frame_size)
{
        unsigned long newsp;

        /* Default to using normal stack */
        newsp = regs->gpr[1];

        if ((ka->sa.sa_flags & SA_ONSTACK) && current->sas_ss_size) {
                if (! on_sig_stack(regs->gpr[1]))
                        newsp = (current->sas_ss_sp + current->sas_ss_size);
        }

        return (void __user *)((newsp - frame_size) & -16ul);
}

/*
 * Setup the trampoline code on the stack
 */
static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
{
        int i;
        long err = 0;

        /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
        err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
        /* li r0, __NR_[rt_]sigreturn| */
        err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
        /* sc */
        err |= __put_user(0x44000002UL, &tramp[2]);

        /* Minimal traceback info */
        for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
                err |= __put_user(0, &tramp[i]);

        if (!err)
                flush_icache_range((unsigned long) &tramp[0],
                           (unsigned long) &tramp[TRAMP_SIZE]);

        return err;
}

/*
 * Restore the user process's signal mask (also used by signal32.c)
 */
void restore_sigmask(sigset_t *set)
{
        sigdelsetmask(set, ~_BLOCKABLE);
        spin_lock_irq(&current->sighand->siglock);
        current->blocked = *set;
        recalc_sigpending();
        spin_unlock_irq(&current->sighand->siglock);
}


/*
 * Handle {get,set,swap}_context operations
 */
int sys_swapcontext(struct ucontext __user *old_ctx,
                    struct ucontext __user *new_ctx,
                    long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
{
        unsigned char tmp;
        sigset_t set;

        /* Context size is for future use. Right now, we only make sure
         * we are passed something we understand
         */
        if (ctx_size < sizeof(struct ucontext))
                return -EINVAL;

        if (old_ctx != NULL) {
                if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
                    || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
                    || __copy_to_user(&old_ctx->uc_sigmask,
                                      &current->blocked, sizeof(sigset_t)))
                        return -EFAULT;
        }
        if (new_ctx == NULL)
                return 0;
        if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
            || __get_user(tmp, (u8 __user *) new_ctx)
            || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
                return -EFAULT;

        /*
         * If we get a fault copying the context into the kernel's
         * image of the user's registers, we can't just return -EFAULT
         * because the user's registers will be corrupted.  For instance
         * the NIP value may have been updated but not some of the
         * other registers.  Given that we have done the access_ok
         * and successfully read the first and last bytes of the region
         * above, this should only happen in an out-of-memory situation
         * or if another thread unmaps the region containing the context.
         * We kill the task with a SIGSEGV in this situation.
         */

        if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
                do_exit(SIGSEGV);
        restore_sigmask(&set);
        if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
                do_exit(SIGSEGV);

        /* This returns like rt_sigreturn */
        set_thread_flag(TIF_RESTOREALL);
        return 0;
}


/*
 * Do a signal return; undo the signal stack.
 */

int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
                     unsigned long r6, unsigned long r7, unsigned long r8,
                     struct pt_regs *regs)
{
        struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
        sigset_t set;

        /* Always make any pending restarted system calls return -EINTR */
        current_thread_info()->restart_block.fn = do_no_restart_syscall;

        if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
                goto badframe;

        if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
                goto badframe;
        restore_sigmask(&set);
        if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
                goto badframe;

        /* do_sigaltstack expects a __user pointer and won't modify
         * what's in there anyway
         */
        do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);

        set_thread_flag(TIF_RESTOREALL);
        return 0;

badframe:
#if DEBUG_SIG
        printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
               regs, uc, &uc->uc_mcontext);
#endif
        force_sig(SIGSEGV, current);
        return 0;
}

static int setup_rt_frame(int signr, struct k_sigaction *ka, siginfo_t *info,
                sigset_t *set, struct pt_regs *regs)
{
        /* Handler is *really* a pointer to the function descriptor for
         * the signal routine.  The first entry in the function
         * descriptor is the entry address of signal and the second
         * entry is the TOC value we need to use.
         */
        func_descr_t __user *funct_desc_ptr;
        struct rt_sigframe __user *frame;
        unsigned long newsp = 0;
        long err = 0;

        frame = get_sigframe(ka, regs, sizeof(*frame));

        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                goto badframe;

        err |= __put_user(&frame->info, &frame->pinfo);
        err |= __put_user(&frame->uc, &frame->puc);
        err |= copy_siginfo_to_user(&frame->info, info);
        if (err)
                goto badframe;

        /* 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->gpr[1]),
                          &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, signr, NULL,
                                (unsigned long)ka->sa.sa_handler);
        err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
        if (err)
                goto badframe;

        /* Make sure signal handler doesn't get spurious FP exceptions */
        current->thread.fpscr.val = 0;

        /* Set up to return from userspace. */
        if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
                regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
        } else {
                err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
                if (err)
                        goto badframe;
                regs->link = (unsigned long) &frame->tramp[0];
        }
        funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;

        /* Allocate a dummy caller frame for the signal handler. */
        newsp = (unsigned long)frame - __SIGNAL_FRAMESIZE;
        err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);

        /* Set up "regs" so we "return" to the signal handler. */
        err |= get_user(regs->nip, &funct_desc_ptr->entry);
        /* enter the signal handler in big-endian mode */
        regs->msr &= ~MSR_LE;
        regs->gpr[1] = newsp;
        err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
        regs->gpr[3] = signr;
        regs->result = 0;
        if (ka->sa.sa_flags & SA_SIGINFO) {
                err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
                err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
                regs->gpr[6] = (unsigned long) frame;
        } else {
                regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
        }
        if (err)
                goto badframe;

        return 1;

badframe:
#if DEBUG_SIG
        printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
               regs, frame, newsp);
#endif
        force_sigsegv(signr, current);
        return 0;
}


/*
 * OK, we're invoking a handler
 */
static int handle_signal(unsigned long sig, struct k_sigaction *ka,
                         siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
{
        int ret;

        /* Set up Signal Frame */
        ret = setup_rt_frame(sig, ka, info, oldset, regs);

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

        return ret;
}

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

        /*
         * If the current thread is 32 bit - invoke the
         * 32 bit signal handling code
         */
        if (test_thread_flag(TIF_32BIT))
                return do_signal32(oldset, regs);

        if (test_thread_flag(TIF_RESTORE_SIGMASK))
                oldset = &current->saved_sigmask;
        else if (!oldset)
                oldset = &current->blocked;

        signr = get_signal_to_deliver(&info, &ka, regs, NULL);

        /* Is there any syscall restart business here ? */
        check_syscall_restart(regs, &ka, signr > 0);

        if (signr > 0) {
                int ret;

                /*
                 * Reenable the DABR before delivering the signal to
                 * user space. The DABR will have been cleared if it
                 * triggered inside the kernel.
                 */
                if (current->thread.dabr)
                        set_dabr(current->thread.dabr);

                /* Whee!  Actually deliver the signal.  */
                ret = handle_signal(signr, &ka, &info, oldset, regs);

                /* If a signal was successfully delivered, the saved sigmask is in
                   its frame, and we can clear the TIF_RESTORE_SIGMASK flag */
                if (ret && test_thread_flag(TIF_RESTORE_SIGMASK))
                        clear_thread_flag(TIF_RESTORE_SIGMASK);

                return ret;
        }

        /* No signal to deliver -- put the saved sigmask back */
        if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
                clear_thread_flag(TIF_RESTORE_SIGMASK);
                sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
        }

        return 0;
}
EXPORT_SYMBOL(do_signal);