signal.c

Go to the documentation of this file.

/*
 *    Copyright IBM Corp. 1999, 2006
 *    Author(s): Denis Joseph Barrow ([email protected],[email protected])
 *
 *    Based on Intel version
 * 
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 */

#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/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/tty.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/tracehook.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/lowcore.h>
#include <asm/switch_to.h>
#include "entry.h"

typedef struct 
{
    __u8 callee_used_stack[__SIGNAL_FRAMESIZE];
    struct sigcontext sc;
    _sigregs sregs;
    int signo;
    __u8 retcode[S390_SYSCALL_SIZE];
} sigframe;

typedef struct 
{
    __u8 callee_used_stack[__SIGNAL_FRAMESIZE];
    __u8 retcode[S390_SYSCALL_SIZE];
    struct siginfo info;
    struct ucontext uc;
} rt_sigframe;

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
SYSCALL_DEFINE3(sigsuspend, int, history0, int, history1, old_sigset_t, mask)
{
    sigset_t blocked;
    siginitset(&blocked, mask);
    return sigsuspend(&blocked);
}

SYSCALL_DEFINE3(sigaction, int, sig, const struct old_sigaction __user *, act,
        struct old_sigaction __user *, oact)
{
    struct k_sigaction new_ka, old_ka;
    int ret;

    if (act) {
        old_sigset_t mask;
        if (!access_ok(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) ||
            __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
            __get_user(mask, &act->sa_mask))
            return -EFAULT;
        siginitset(&new_ka.sa.sa_mask, mask);
    }

    ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);

    if (!ret && oact) {
        if (!access_ok(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) ||
            __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
            __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
            return -EFAULT;
    }

    return ret;
}

SYSCALL_DEFINE2(sigaltstack, const stack_t __user *, uss,
        stack_t __user *, uoss)
{
    struct pt_regs *regs = task_pt_regs(current);
    return do_sigaltstack(uss, uoss, regs->gprs[15]);
}

/* Returns non-zero on fault. */
static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
{
    _sigregs user_sregs;

    save_access_regs(current->thread.acrs);

    /* Copy a 'clean' PSW mask to the user to avoid leaking
       information about whether PER is currently on.  */
    user_sregs.regs.psw.mask = psw_user_bits |
        (regs->psw.mask & PSW_MASK_USER);
    user_sregs.regs.psw.addr = regs->psw.addr;
    memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
    memcpy(&user_sregs.regs.acrs, current->thread.acrs,
           sizeof(sregs->regs.acrs));
    /* 
     * We have to store the fp registers to current->thread.fp_regs
     * to merge them with the emulated registers.
     */
    save_fp_regs(&current->thread.fp_regs);
    memcpy(&user_sregs.fpregs, &current->thread.fp_regs,
           sizeof(s390_fp_regs));
    return __copy_to_user(sregs, &user_sregs, sizeof(_sigregs));
}

/* Returns positive number on error */
static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
{
    int err;
    _sigregs user_sregs;

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

    err = __copy_from_user(&user_sregs, sregs, sizeof(_sigregs));
    if (err)
        return err;
    /* Use regs->psw.mask instead of psw_user_bits to preserve PER bit. */
    regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
        (user_sregs.regs.psw.mask & PSW_MASK_USER);
    /* Check for invalid user address space control. */
    if ((regs->psw.mask & PSW_MASK_ASC) >= (psw_kernel_bits & PSW_MASK_ASC))
        regs->psw.mask = (psw_user_bits & PSW_MASK_ASC) |
            (regs->psw.mask & ~PSW_MASK_ASC);
    /* Check for invalid amode */
    if (regs->psw.mask & PSW_MASK_EA)
        regs->psw.mask |= PSW_MASK_BA;
    regs->psw.addr = user_sregs.regs.psw.addr;
    memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
    memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
           sizeof(sregs->regs.acrs));
    restore_access_regs(current->thread.acrs);

    memcpy(&current->thread.fp_regs, &user_sregs.fpregs,
           sizeof(s390_fp_regs));
    current->thread.fp_regs.fpc &= FPC_VALID_MASK;

    restore_fp_regs(&current->thread.fp_regs);
    clear_thread_flag(TIF_SYSCALL); /* No longer in a system call */
    return 0;
}

SYSCALL_DEFINE0(sigreturn)
{
    struct pt_regs *regs = task_pt_regs(current);
    sigframe __user *frame = (sigframe __user *)regs->gprs[15];
    sigset_t set;

    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE))
        goto badframe;
    set_current_blocked(&set);
    if (restore_sigregs(regs, &frame->sregs))
        goto badframe;
    return regs->gprs[2];
badframe:
    force_sig(SIGSEGV, current);
    return 0;
}

SYSCALL_DEFINE0(rt_sigreturn)
{
    struct pt_regs *regs = task_pt_regs(current);
    rt_sigframe __user *frame = (rt_sigframe __user *)regs->gprs[15];
    sigset_t set;

    if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
        goto badframe;
    if (__copy_from_user(&set.sig, &frame->uc.uc_sigmask, sizeof(set)))
        goto badframe;
    set_current_blocked(&set);
    if (restore_sigregs(regs, &frame->uc.uc_mcontext))
        goto badframe;
    if (do_sigaltstack(&frame->uc.uc_stack, NULL,
               regs->gprs[15]) == -EFAULT)
        goto badframe;
    return regs->gprs[2];
badframe:
    force_sig(SIGSEGV, current);
    return 0;
}

/*
 * Set up a signal frame.
 */


/*
 * Determine which stack to use..
 */
static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
{
    unsigned long sp;

    /* Default to using normal stack */
    sp = regs->gprs[15];

    /* Overflow on alternate signal stack gives SIGSEGV. */
    if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
        return (void __user *) -1UL;

    /* This is the X/Open sanctioned signal stack switching.  */
    if (ka->sa.sa_flags & SA_ONSTACK) {
        if (! sas_ss_flags(sp))
            sp = current->sas_ss_sp + current->sas_ss_size;
    }

    return (void __user *)((sp - frame_size) & -8ul);
}

static inline int map_signal(int sig)
{
    if (current_thread_info()->exec_domain
        && current_thread_info()->exec_domain->signal_invmap
        && sig < 32)
        return current_thread_info()->exec_domain->signal_invmap[sig];
    else
        return sig;
}

static int setup_frame(int sig, struct k_sigaction *ka,
               sigset_t *set, struct pt_regs * regs)
{
    sigframe __user *frame;

    frame = get_sigframe(ka, regs, sizeof(sigframe));
    if (!access_ok(VERIFY_WRITE, frame, sizeof(sigframe)))
        goto give_sigsegv;

    if (frame == (void __user *) -1UL)
        goto give_sigsegv;

    if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE))
        goto give_sigsegv;

    if (save_sigregs(regs, &frame->sregs))
        goto give_sigsegv;
    if (__put_user(&frame->sregs, &frame->sc.sregs))
        goto give_sigsegv;

    /* Set up to return from userspace.  If provided, use a stub
       already in userspace.  */
    if (ka->sa.sa_flags & SA_RESTORER) {
                regs->gprs[14] = (unsigned long)
            ka->sa.sa_restorer | PSW_ADDR_AMODE;
    } else {
                regs->gprs[14] = (unsigned long)
            frame->retcode | PSW_ADDR_AMODE;
        if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn,
                           (u16 __user *)(frame->retcode)))
            goto give_sigsegv;
    }

    /* Set up backchain. */
    if (__put_user(regs->gprs[15], (addr_t __user *) frame))
        goto give_sigsegv;

    /* Set up registers for signal handler */
    regs->gprs[15] = (unsigned long) frame;
    /* Force default amode and default user address space control. */
    regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
        (psw_user_bits & PSW_MASK_ASC) |
        (regs->psw.mask & ~PSW_MASK_ASC);
    regs->psw.addr = (unsigned long) ka->sa.sa_handler | PSW_ADDR_AMODE;

    regs->gprs[2] = map_signal(sig);
    regs->gprs[3] = (unsigned long) &frame->sc;

    /* We forgot to include these in the sigcontext.
       To avoid breaking binary compatibility, they are passed as args. */
    if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
        sig == SIGTRAP || sig == SIGFPE) {
        /* set extra registers only for synchronous signals */
        regs->gprs[4] = regs->int_code & 127;
        regs->gprs[5] = regs->int_parm_long;
        regs->gprs[6] = task_thread_info(current)->last_break;
    }

    /* Place signal number on stack to allow backtrace from handler.  */
    if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
        goto give_sigsegv;
    return 0;

give_sigsegv:
    force_sigsegv(sig, current);
    return -EFAULT;
}

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

    frame = get_sigframe(ka, regs, sizeof(rt_sigframe));
    if (!access_ok(VERIFY_WRITE, frame, sizeof(rt_sigframe)))
        goto give_sigsegv;

    if (frame == (void __user *) -1UL)
        goto give_sigsegv;

    if (copy_siginfo_to_user(&frame->info, info))
        goto give_sigsegv;

    /* Create 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->gprs[15]),
              &frame->uc.uc_stack.ss_flags);
    err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
    err |= save_sigregs(regs, &frame->uc.uc_mcontext);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
    if (err)
        goto give_sigsegv;

    /* Set up to return from userspace.  If provided, use a stub
       already in userspace.  */
    if (ka->sa.sa_flags & SA_RESTORER) {
                regs->gprs[14] = (unsigned long)
            ka->sa.sa_restorer | PSW_ADDR_AMODE;
    } else {
                regs->gprs[14] = (unsigned long)
            frame->retcode | PSW_ADDR_AMODE;
        if (__put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn,
                   (u16 __user *)(frame->retcode)))
            goto give_sigsegv;
    }

    /* Set up backchain. */
    if (__put_user(regs->gprs[15], (addr_t __user *) frame))
        goto give_sigsegv;

    /* Set up registers for signal handler */
    regs->gprs[15] = (unsigned long) frame;
    /* Force default amode and default user address space control. */
    regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
        (psw_user_bits & PSW_MASK_ASC) |
        (regs->psw.mask & ~PSW_MASK_ASC);
    regs->psw.addr = (unsigned long) ka->sa.sa_handler | PSW_ADDR_AMODE;

    regs->gprs[2] = map_signal(sig);
    regs->gprs[3] = (unsigned long) &frame->info;
    regs->gprs[4] = (unsigned long) &frame->uc;
    regs->gprs[5] = task_thread_info(current)->last_break;
    return 0;

give_sigsegv:
    force_sigsegv(sig, current);
    return -EFAULT;
}

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

    /* Set up the stack frame */
    if (ka->sa.sa_flags & SA_SIGINFO)
        ret = setup_rt_frame(sig, ka, info, oldset, regs);
    else
        ret = setup_frame(sig, ka, oldset, regs);
    if (ret)
        return;
    signal_delivered(sig, info, ka, regs,
                 test_thread_flag(TIF_SINGLE_STEP));
}

/*
 * 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.
 *
 * Note that we go through the signals twice: once to check the signals that
 * the kernel can handle, and then we build all the user-level signal handling
 * stack-frames in one go after that.
 */
void do_signal(struct pt_regs *regs)
{
    siginfo_t info;
    int signr;
    struct k_sigaction ka;
    sigset_t *oldset = sigmask_to_save();

    /*
     * Get signal to deliver. When running under ptrace, at this point
     * the debugger may change all our registers, including the system
     * call information.
     */
    current_thread_info()->system_call =
        test_thread_flag(TIF_SYSCALL) ? regs->int_code : 0;
    signr = get_signal_to_deliver(&info, &ka, regs, NULL);

    if (signr > 0) {
        /* Whee!  Actually deliver the signal.  */
        if (current_thread_info()->system_call) {
            regs->int_code = current_thread_info()->system_call;
            /* Check for system call restarting. */
            switch (regs->gprs[2]) {
            case -ERESTART_RESTARTBLOCK:
            case -ERESTARTNOHAND:
                regs->gprs[2] = -EINTR;
                break;
            case -ERESTARTSYS:
                if (!(ka.sa.sa_flags & SA_RESTART)) {
                    regs->gprs[2] = -EINTR;
                    break;
                }
            /* fallthrough */
            case -ERESTARTNOINTR:
                regs->gprs[2] = regs->orig_gpr2;
                regs->psw.addr =
                    __rewind_psw(regs->psw,
                             regs->int_code >> 16);
                break;
            }
        }
        /* No longer in a system call */
        clear_thread_flag(TIF_SYSCALL);

        if (is_compat_task())
            handle_signal32(signr, &ka, &info, oldset, regs);
        else
            handle_signal(signr, &ka, &info, oldset, regs);
        return;
    }

    /* No handlers present - check for system call restart */
    clear_thread_flag(TIF_SYSCALL);
    if (current_thread_info()->system_call) {
        regs->int_code = current_thread_info()->system_call;
        switch (regs->gprs[2]) {
        case -ERESTART_RESTARTBLOCK:
            /* Restart with sys_restart_syscall */
            regs->int_code = __NR_restart_syscall;
        /* fallthrough */
        case -ERESTARTNOHAND:
        case -ERESTARTSYS:
        case -ERESTARTNOINTR:
            /* Restart system call with magic TIF bit. */
            regs->gprs[2] = regs->orig_gpr2;
            set_thread_flag(TIF_SYSCALL);
            break;
        }
    }

    /*
     * If there's no signal to deliver, we just put the saved sigmask back.
     */
    restore_saved_sigmask();
}

void do_notify_resume(struct pt_regs *regs)
{
    clear_thread_flag(TIF_NOTIFY_RESUME);
    tracehook_notify_resume(regs);
}