signal.c

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/*
 * Copyright 2004-2010 Analog Devices Inc.
 *
 * Licensed under the GPL-2 or later
 */

#include <linux/signal.h>
#include <linux/syscalls.h>
#include <linux/ptrace.h>
#include <linux/tty.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/uaccess.h>
#include <linux/tracehook.h>

#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/fixed_code.h>
#include <asm/syscall.h>

/* Location of the trace bit in SYSCFG. */
#define TRACE_BITS 0x0001

struct fdpic_func_descriptor {
    unsigned long   text;
    unsigned long   GOT;
};

struct rt_sigframe {
    int sig;
    struct siginfo *pinfo;
    void *puc;
    /* This is no longer needed by the kernel, but unfortunately userspace
     * code expects it to be there.  */
    char retcode[8];
    struct siginfo info;
    struct ucontext uc;
};

asmlinkage int sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
{
    return do_sigaltstack(uss, uoss, rdusp());
}

static inline int
rt_restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, int *pr0)
{
    unsigned long usp = 0;
    int err = 0;

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

#define RESTORE(x) err |= __get_user(regs->x, &sc->sc_##x)

    /* restore passed registers */
    RESTORE(r0); RESTORE(r1); RESTORE(r2); RESTORE(r3);
    RESTORE(r4); RESTORE(r5); RESTORE(r6); RESTORE(r7);
    RESTORE(p0); RESTORE(p1); RESTORE(p2); RESTORE(p3);
    RESTORE(p4); RESTORE(p5);
    err |= __get_user(usp, &sc->sc_usp);
    wrusp(usp);
    RESTORE(a0w); RESTORE(a1w);
    RESTORE(a0x); RESTORE(a1x);
    RESTORE(astat);
    RESTORE(rets);
    RESTORE(pc);
    RESTORE(retx);
    RESTORE(fp);
    RESTORE(i0); RESTORE(i1); RESTORE(i2); RESTORE(i3);
    RESTORE(m0); RESTORE(m1); RESTORE(m2); RESTORE(m3);
    RESTORE(l0); RESTORE(l1); RESTORE(l2); RESTORE(l3);
    RESTORE(b0); RESTORE(b1); RESTORE(b2); RESTORE(b3);
    RESTORE(lc0); RESTORE(lc1);
    RESTORE(lt0); RESTORE(lt1);
    RESTORE(lb0); RESTORE(lb1);
    RESTORE(seqstat);

    regs->orig_p0 = -1; /* disable syscall checks */

    *pr0 = regs->r0;
    return err;
}

asmlinkage int do_rt_sigreturn(unsigned long __unused)
{
    struct pt_regs *regs = (struct pt_regs *)__unused;
    unsigned long usp = rdusp();
    struct rt_sigframe *frame = (struct rt_sigframe *)(usp);
    sigset_t set;
    int r0;

    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 (rt_restore_sigcontext(regs, &frame->uc.uc_mcontext, &r0))
        goto badframe;

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

    return r0;

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

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

#define SETUP(x) err |= __put_user(regs->x, &sc->sc_##x)

    SETUP(r0); SETUP(r1); SETUP(r2); SETUP(r3);
    SETUP(r4); SETUP(r5); SETUP(r6); SETUP(r7);
    SETUP(p0); SETUP(p1); SETUP(p2); SETUP(p3);
    SETUP(p4); SETUP(p5);
    err |= __put_user(rdusp(), &sc->sc_usp);
    SETUP(a0w); SETUP(a1w);
    SETUP(a0x); SETUP(a1x);
    SETUP(astat);
    SETUP(rets);
    SETUP(pc);
    SETUP(retx);
    SETUP(fp);
    SETUP(i0); SETUP(i1); SETUP(i2); SETUP(i3);
    SETUP(m0); SETUP(m1); SETUP(m2); SETUP(m3);
    SETUP(l0); SETUP(l1); SETUP(l2); SETUP(l3);
    SETUP(b0); SETUP(b1); SETUP(b2); SETUP(b3);
    SETUP(lc0); SETUP(lc1);
    SETUP(lt0); SETUP(lt1);
    SETUP(lb0); SETUP(lb1);
    SETUP(seqstat);

    return err;
}

static inline void *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
                 size_t frame_size)
{
    unsigned long usp;

    /* Default to using normal stack.  */
    usp = rdusp();

    /* This is the X/Open sanctioned signal stack switching.  */
    if (ka->sa.sa_flags & SA_ONSTACK) {
        if (!on_sig_stack(usp))
            usp = current->sas_ss_sp + current->sas_ss_size;
    }
    return (void *)((usp - frame_size) & -8UL);
}

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

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

    err |= __put_user((current_thread_info()->exec_domain
               && current_thread_info()->exec_domain->signal_invmap
               && sig < 32
               ? current_thread_info()->exec_domain->
               signal_invmap[sig] : sig), &frame->sig);

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

    /* Create the ucontext.  */
    err |= __put_user(0, &frame->uc.uc_flags);
    err |= __put_user(0, &frame->uc.uc_link);
    err |=
        __put_user((void *)current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
    err |= __put_user(sas_ss_flags(rdusp()), &frame->uc.uc_stack.ss_flags);
    err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
    err |= rt_setup_sigcontext(&frame->uc.uc_mcontext, regs);
    err |= copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

    if (err)
        return -EFAULT;

    /* Set up registers for signal handler */
    if (current->personality & FDPIC_FUNCPTRS) {
        struct fdpic_func_descriptor __user *funcptr =
            (struct fdpic_func_descriptor *) ka->sa.sa_handler;
        u32 pc, p3;
        err |= __get_user(pc, &funcptr->text);
        err |= __get_user(p3, &funcptr->GOT);
        if (err)
            return -EFAULT;
        regs->pc = pc;
        regs->p3 = p3;
    } else
        regs->pc = (unsigned long)ka->sa.sa_handler;
    wrusp((unsigned long)frame);
    regs->rets = SIGRETURN_STUB;

    regs->r0 = frame->sig;
    regs->r1 = (unsigned long)(&frame->info);
    regs->r2 = (unsigned long)(&frame->uc);

    return 0;
}

static inline void
handle_restart(struct pt_regs *regs, struct k_sigaction *ka, int has_handler)
{
    switch (regs->r0) {
    case -ERESTARTNOHAND:
        if (!has_handler)
            goto do_restart;
        regs->r0 = -EINTR;
        break;

    case -ERESTARTSYS:
        if (has_handler && !(ka->sa.sa_flags & SA_RESTART)) {
            regs->r0 = -EINTR;
            break;
        }
        /* fallthrough */
    case -ERESTARTNOINTR:
 do_restart:
        regs->p0 = regs->orig_p0;
        regs->r0 = regs->orig_r0;
        regs->pc -= 2;
        break;

    case -ERESTART_RESTARTBLOCK:
        regs->p0 = __NR_restart_syscall;
        regs->pc -= 2;
        break;
    }
}

/*
 * OK, we're invoking a handler
 */
static void
handle_signal(int sig, siginfo_t *info, struct k_sigaction *ka,
          struct pt_regs *regs)
{
    /* are we from a system call? to see pt_regs->orig_p0 */
    if (regs->orig_p0 >= 0)
        /* If so, check system call restarting.. */
        handle_restart(regs, ka, 1);

    /* set up the stack frame */
    if (setup_rt_frame(sig, ka, info, sigmask_to_save(), regs) < 0)
        force_sigsegv(sig, current);
    else 
        signal_delivered(sig, info, ka, regs,
                test_thread_flag(TIF_SINGLESTEP));
}

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

    current->thread.esp0 = (unsigned long)regs;

    signr = get_signal_to_deliver(&info, &ka, regs, NULL);
    if (signr > 0) {
        /* Whee!  Actually deliver the signal.  */
        handle_signal(signr, &info, &ka, regs);
        return;
    }

    /* Did we come from a system call? */
    if (regs->orig_p0 >= 0)
        /* Restart the system call - no handlers present */
        handle_restart(regs, NULL, 0);

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

/*
 * notification of userspace execution resumption
 */
asmlinkage void do_notify_resume(struct pt_regs *regs)
{
    if (test_thread_flag(TIF_SIGPENDING))
        do_signal(regs);

    if (test_thread_flag(TIF_NOTIFY_RESUME)) {
        clear_thread_flag(TIF_NOTIFY_RESUME);
        tracehook_notify_resume(regs);
    }
}