signal.c

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/*
 * Common signal handling code for both 32 and 64 bits
 *
 *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Coproration
 *    Extracted from signal_32.c and signal_64.c
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License.  See the file README.legal in the main directory of
 * this archive for more details.
 */

#include <linux/tracehook.h>
#include <linux/signal.h>
#include <linux/uprobes.h>
#include <linux/key.h>
#include <asm/hw_breakpoint.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/debug.h>

#include "signal.h"

/* Log an error when sending an unhandled signal to a process. Controlled
 * through debug.exception-trace sysctl.
 */

int show_unhandled_signals = 0;

/*
 * Allocate space for the signal frame
 */
void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
               size_t frame_size, int is_32)
{
        unsigned long oldsp, newsp;

        /* Default to using normal stack */
        oldsp = get_clean_sp(regs, is_32);

    /* Check for alt stack */
    if ((ka->sa.sa_flags & SA_ONSTACK) &&
        current->sas_ss_size && !on_sig_stack(oldsp))
        oldsp = (current->sas_ss_sp + current->sas_ss_size);

    /* Get aligned frame */
    newsp = (oldsp - frame_size) & ~0xFUL;

    /* Check access */
    if (!access_ok(VERIFY_WRITE, (void __user *)newsp, oldsp - newsp))
        return NULL;

        return (void __user *)newsp;
}

static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
                  int has_handler)
{
    unsigned long ret = regs->gpr[3];
    int restart = 1;

    /* syscall ? */
    if (TRAP(regs) != 0x0C00)
        return;

    /* error signalled ? */
    if (!(regs->ccr & 0x10000000))
        return;

    switch (ret) {
    case ERESTART_RESTARTBLOCK:
    case ERESTARTNOHAND:
        /* ERESTARTNOHAND means that the syscall should only be
         * restarted if there was no handler for the signal, and since
         * we only get here if there is a handler, we dont restart.
         */
        restart = !has_handler;
        break;
    case ERESTARTSYS:
        /* ERESTARTSYS means to restart the syscall if there is no
         * handler or the handler was registered with SA_RESTART
         */
        restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
        break;
    case ERESTARTNOINTR:
        /* ERESTARTNOINTR means that the syscall should be
         * called again after the signal handler returns.
         */
        break;
    default:
        return;
    }
    if (restart) {
        if (ret == ERESTART_RESTARTBLOCK)
            regs->gpr[0] = __NR_restart_syscall;
        else
            regs->gpr[3] = regs->orig_gpr3;
        regs->nip -= 4;
        regs->result = 0;
    } else {
        regs->result = -EINTR;
        regs->gpr[3] = EINTR;
        regs->ccr |= 0x10000000;
    }
}

static int do_signal(struct pt_regs *regs)
{
    sigset_t *oldset = sigmask_to_save();
    siginfo_t info;
    int signr;
    struct k_sigaction ka;
    int ret;
    int is32 = is_32bit_task();

    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) {
        /* No signal to deliver -- put the saved sigmask back */
        restore_saved_sigmask();
        regs->trap = 0;
        return 0;               /* no signals delivered */
    }

#ifndef CONFIG_PPC_ADV_DEBUG_REGS
        /*
     * 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, current->thread.dabrx);
#endif
    /* Re-enable the breakpoints for the signal stack */
    thread_change_pc(current, regs);

    if (is32) {
            if (ka.sa.sa_flags & SA_SIGINFO)
            ret = handle_rt_signal32(signr, &ka, &info, oldset,
                    regs);
        else
            ret = handle_signal32(signr, &ka, &info, oldset,
                    regs);
    } else {
        ret = handle_rt_signal64(signr, &ka, &info, oldset, regs);
    }

    regs->trap = 0;
    if (ret) {
        signal_delivered(signr, &info, &ka, regs,
                     test_thread_flag(TIF_SINGLESTEP));
    }

    return ret;
}

void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
{
    if (thread_info_flags & _TIF_UPROBE) {
        clear_thread_flag(TIF_UPROBE);
        uprobe_notify_resume(regs);
    }

    if (thread_info_flags & _TIF_SIGPENDING)
        do_signal(regs);

    if (thread_info_flags & _TIF_NOTIFY_RESUME) {
        clear_thread_flag(TIF_NOTIFY_RESUME);
        tracehook_notify_resume(regs);
    }
}

long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
        unsigned long r5, unsigned long r6, unsigned long r7,
        unsigned long r8, struct pt_regs *regs)
{
    return do_sigaltstack(uss, uoss, regs->gpr[1]);
}