signal.c

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/*
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * Based on linux/arch/sh/kernel/signal.c
 *  Copyright (C) 1999, 2000  Niibe Yutaka & Kaz Kojima
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/tracehook.h>

#include <asm/uaccess.h>
#include <asm/ucontext.h>
#include <asm/syscalls.h>

asmlinkage int sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
                   struct pt_regs *regs)
{
    return do_sigaltstack(uss, uoss, regs->sp);
}

struct rt_sigframe
{
    struct siginfo info;
    struct ucontext uc;
    unsigned long retcode;
};

static int
restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
    int err = 0;

#define COPY(x)     err |= __get_user(regs->x, &sc->x)
    COPY(sr);
    COPY(pc);
    COPY(lr);
    COPY(sp);
    COPY(r12);
    COPY(r11);
    COPY(r10);
    COPY(r9);
    COPY(r8);
    COPY(r7);
    COPY(r6);
    COPY(r5);
    COPY(r4);
    COPY(r3);
    COPY(r2);
    COPY(r1);
    COPY(r0);
#undef  COPY

    /*
     * Don't allow anyone to pretend they're running in supervisor
     * mode or something...
     */
    err |= !valid_user_regs(regs);

    return err;
}


asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
{
    struct rt_sigframe __user *frame;
    sigset_t set;

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

    frame = (struct rt_sigframe __user *)regs->sp;
    pr_debug("SIG return: frame = %p\n", frame);

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

    if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
        goto badframe;

    set_current_blocked(&set);

    if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
        goto badframe;

    if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
        goto badframe;

    pr_debug("Context restored: pc = %08lx, lr = %08lx, sp = %08lx\n",
         regs->pc, regs->lr, regs->sp);

    return regs->r12;

badframe:
    force_sig(SIGSEGV, current);
    return 0;
}

static int
setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
{
    int err = 0;

#define COPY(x)     err |= __put_user(regs->x, &sc->x)
    COPY(sr);
    COPY(pc);
    COPY(lr);
    COPY(sp);
    COPY(r12);
    COPY(r11);
    COPY(r10);
    COPY(r9);
    COPY(r8);
    COPY(r7);
    COPY(r6);
    COPY(r5);
    COPY(r4);
    COPY(r3);
    COPY(r2);
    COPY(r1);
    COPY(r0);
#undef  COPY

    return err;
}

static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, int framesize)
{
    unsigned long sp = regs->sp;

    if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
        sp = current->sas_ss_sp + current->sas_ss_size;

    return (void __user *)((sp - framesize) & ~3);
}

static int
setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
           sigset_t *set, struct pt_regs *regs)
{
    struct rt_sigframe __user *frame;
    int err = 0;

    frame = get_sigframe(ka, regs, sizeof(*frame));
    err = -EFAULT;
    if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
        goto out;

    /*
     * Set up the return code:
     *
     *  mov r8, __NR_rt_sigreturn
     *  scall
     *
     * Note: This will blow up since we're using a non-executable
     * stack. Better use SA_RESTORER.
     */
#if __NR_rt_sigreturn > 127
# error __NR_rt_sigreturn must be < 127 to fit in a short mov
#endif
    err = __put_user(0x3008d733 | (__NR_rt_sigreturn << 20),
             &frame->retcode);

    err |= copy_siginfo_to_user(&frame->info, info);

    /* Set up the ucontext */
    err |= __put_user(0, &frame->uc.uc_flags);
    err |= __put_user(NULL, &frame->uc.uc_link);
    err |= __put_user((void __user *)current->sas_ss_sp,
              &frame->uc.uc_stack.ss_sp);
    err |= __put_user(sas_ss_flags(regs->sp),
              &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);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

    if (err)
        goto out;

    regs->r12 = sig;
    regs->r11 = (unsigned long) &frame->info;
    regs->r10 = (unsigned long) &frame->uc;
    regs->sp = (unsigned long) frame;
    if (ka->sa.sa_flags & SA_RESTORER)
        regs->lr = (unsigned long)ka->sa.sa_restorer;
    else {
        printk(KERN_NOTICE "[%s:%d] did not set SA_RESTORER\n",
               current->comm, current->pid);
        regs->lr = (unsigned long) &frame->retcode;
    }

    pr_debug("SIG deliver [%s:%d]: sig=%d sp=0x%lx pc=0x%lx->0x%p lr=0x%lx\n",
         current->comm, current->pid, sig, regs->sp,
         regs->pc, ka->sa.sa_handler, regs->lr);

    regs->pc = (unsigned long) ka->sa.sa_handler;

out:
    return err;
}

static inline void setup_syscall_restart(struct pt_regs *regs)
{
    if (regs->r12 == -ERESTART_RESTARTBLOCK)
        regs->r8 = __NR_restart_syscall;
    else
        regs->r12 = regs->r12_orig;
    regs->pc -= 2;
}

static inline void
handle_signal(unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
          struct pt_regs *regs, int syscall)
{
    int ret;

    /*
     * Set up the stack frame
     */
    ret = setup_rt_frame(sig, ka, info, sigmask_to_save(), regs);

    /*
     * Check that the resulting registers are sane
     */
    ret |= !valid_user_regs(regs);

    /*
     * Block the signal if we were successful.
     */
    if (ret != 0)
        force_sigsegv(sig, current);
    else
        signal_delivered(sig, info, ka, regs, 0);
}

/*
 * 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.
 */
static void do_signal(struct pt_regs *regs, int syscall)
{
    siginfo_t info;
    int signr;
    struct k_sigaction ka;

    /*
     * We want the common case to go fast, which is why we may in
     * certain cases get here from kernel mode. Just return
     * without doing anything if so.
     */
    if (!user_mode(regs))
        return;

    signr = get_signal_to_deliver(&info, &ka, regs, NULL);
    if (syscall) {
        switch (regs->r12) {
        case -ERESTART_RESTARTBLOCK:
        case -ERESTARTNOHAND:
            if (signr > 0) {
                regs->r12 = -EINTR;
                break;
            }
            /* fall through */
        case -ERESTARTSYS:
            if (signr > 0 && !(ka.sa.sa_flags & SA_RESTART)) {
                regs->r12 = -EINTR;
                break;
            }
            /* fall through */
        case -ERESTARTNOINTR:
            setup_syscall_restart(regs);
        }
    }

    if (signr == 0) {
        /* No signal to deliver -- put the saved sigmask back */
        restore_saved_sigmask();
        return;
    }

    handle_signal(signr, &ka, &info, regs, syscall);
}

asmlinkage void do_notify_resume(struct pt_regs *regs, struct thread_info *ti)
{
    int syscall = 0;

    if ((sysreg_read(SR) & MODE_MASK) == MODE_SUPERVISOR)
        syscall = 1;

    if (ti->flags & _TIF_SIGPENDING)
        do_signal(regs, syscall);

    if (ti->flags & _TIF_NOTIFY_RESUME) {
        clear_thread_flag(TIF_NOTIFY_RESUME);
        tracehook_notify_resume(regs);
    }
}