signal.c

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/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <asm/siginfo.h>
#include <asm/signal.h>
#include <asm/unistd.h>
#include <frame_kern.h>
#include <kern_util.h>

EXPORT_SYMBOL(block_signals);
EXPORT_SYMBOL(unblock_signals);

/*
 * OK, we're invoking a handler
 */
static void handle_signal(struct pt_regs *regs, unsigned long signr,
             struct k_sigaction *ka, siginfo_t *info)
{
    sigset_t *oldset = sigmask_to_save();
    int singlestep = 0;
    unsigned long sp;
    int err;

    if ((current->ptrace & PT_DTRACE) && (current->ptrace & PT_PTRACED))
        singlestep = 1;

    /* Did we come from a system call? */
    if (PT_REGS_SYSCALL_NR(regs) >= 0) {
        /* If so, check system call restarting.. */
        switch (PT_REGS_SYSCALL_RET(regs)) {
        case -ERESTART_RESTARTBLOCK:
        case -ERESTARTNOHAND:
            PT_REGS_SYSCALL_RET(regs) = -EINTR;
            break;

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

    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;

#ifdef CONFIG_ARCH_HAS_SC_SIGNALS
    if (!(ka->sa.sa_flags & SA_SIGINFO))
        err = setup_signal_stack_sc(sp, signr, ka, regs, oldset);
    else
#endif
        err = setup_signal_stack_si(sp, signr, ka, regs, info, oldset);

    if (err)
        force_sigsegv(signr, current);
    else
        signal_delivered(signr, info, ka, regs, singlestep);
}

static int kern_do_signal(struct pt_regs *regs)
{
    struct k_sigaction ka_copy;
    siginfo_t info;
    int sig, handled_sig = 0;

    while ((sig = get_signal_to_deliver(&info, &ka_copy, regs, NULL)) > 0) {
        handled_sig = 1;
        /* Whee!  Actually deliver the signal.  */
        handle_signal(regs, sig, &ka_copy, &info);
    }

    /* Did we come from a system call? */
    if (!handled_sig && (PT_REGS_SYSCALL_NR(regs) >= 0)) {
        /* Restart the system call - no handlers present */
        switch (PT_REGS_SYSCALL_RET(regs)) {
        case -ERESTARTNOHAND:
        case -ERESTARTSYS:
        case -ERESTARTNOINTR:
            PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);
            PT_REGS_RESTART_SYSCALL(regs);
            break;
        case -ERESTART_RESTARTBLOCK:
            PT_REGS_ORIG_SYSCALL(regs) = __NR_restart_syscall;
            PT_REGS_RESTART_SYSCALL(regs);
            break;
        }
    }

    /*
     * 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)
        current->thread.singlestep_syscall =
            is_syscall(PT_REGS_IP(&current->thread.regs));

    /*
     * if there's no signal to deliver, we just put the saved sigmask
     * back
     */
    if (!handled_sig)
        restore_saved_sigmask();
    return handled_sig;
}

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

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
long sys_sigsuspend(int history0, int history1, old_sigset_t mask)
{
    sigset_t blocked;
    siginitset(&blocked, mask);
    return sigsuspend(&blocked);
}

long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
{
    return do_sigaltstack(uss, uoss, PT_REGS_SP(&current->thread.regs));
}