signal.c

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/*
 * Signal handling
 *
 * Copyright (C) 2008-2009 Michal Simek <[email protected]>
 * Copyright (C) 2008-2009 PetaLogix
 * Copyright (C) 2003,2004 John Williams <[email protected]>
 * Copyright (C) 2001 NEC Corporation
 * Copyright (C) 2001 Miles Bader <[email protected]>
 * Copyright (C) 1999,2000 Niibe Yutaka & Kaz Kojima
 * Copyright (C) 1991,1992 Linus Torvalds
 *
 * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
 *
 * This file was was derived from the sh version, arch/sh/kernel/signal.c
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License. See the file COPYING in the main directory of this
 * archive for more details.
 */

#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/personality.h>
#include <linux/percpu.h>
#include <linux/linkage.h>
#include <linux/tracehook.h>
#include <asm/entry.h>
#include <asm/ucontext.h>
#include <linux/uaccess.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <linux/syscalls.h>
#include <asm/cacheflush.h>
#include <asm/syscalls.h>

asmlinkage long
sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
        struct pt_regs *regs)
{
    return do_sigaltstack(uss, uoss, regs->r1);
}

/*
 * Do a signal return; undo the signal stack.
 */
struct sigframe {
    struct sigcontext sc;
    unsigned long extramask[_NSIG_WORDS-1];
    unsigned long tramp[2]; /* signal trampoline */
};

struct rt_sigframe {
    struct siginfo info;
    struct ucontext uc;
    unsigned long tramp[2]; /* signal trampoline */
};

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

#define COPY(x)     {err |= __get_user(regs->x, &sc->regs.x); }
    COPY(r0);
    COPY(r1);
    COPY(r2);   COPY(r3);   COPY(r4);   COPY(r5);
    COPY(r6);   COPY(r7);   COPY(r8);   COPY(r9);
    COPY(r10);  COPY(r11);  COPY(r12);  COPY(r13);
    COPY(r14);  COPY(r15);  COPY(r16);  COPY(r17);
    COPY(r18);  COPY(r19);  COPY(r20);  COPY(r21);
    COPY(r22);  COPY(r23);  COPY(r24);  COPY(r25);
    COPY(r26);  COPY(r27);  COPY(r28);  COPY(r29);
    COPY(r30);  COPY(r31);
    COPY(pc);   COPY(ear);  COPY(esr);  COPY(fsr);
#undef COPY

    *rval_p = regs->r3;

    return err;
}

asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
{
    struct rt_sigframe __user *frame =
        (struct rt_sigframe __user *)(regs->r1);

    sigset_t set;
    int rval;

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

    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, &rval))
        goto badframe;

    /* It is more difficult to avoid calling this function than to
     call it and ignore errors. */
    if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->r1) == -EFAULT)
        goto badframe;

    return rval;

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

/*
 * Set up a signal frame.
 */

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

#define COPY(x)     {err |= __put_user(regs->x, &sc->regs.x); }
    COPY(r0);
    COPY(r1);
    COPY(r2);   COPY(r3);   COPY(r4);   COPY(r5);
    COPY(r6);   COPY(r7);   COPY(r8);   COPY(r9);
    COPY(r10);  COPY(r11);  COPY(r12);  COPY(r13);
    COPY(r14);  COPY(r15);  COPY(r16);  COPY(r17);
    COPY(r18);  COPY(r19);  COPY(r20);  COPY(r21);
    COPY(r22);  COPY(r23);  COPY(r24);  COPY(r25);
    COPY(r26);  COPY(r27);  COPY(r28);  COPY(r29);
    COPY(r30);  COPY(r31);
    COPY(pc);   COPY(ear);  COPY(esr);  COPY(fsr);
#undef COPY

    err |= __put_user(mask, &sc->oldmask);

    return err;
}

/*
 * Determine which stack to use..
 */
static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size)
{
    /* Default to using normal stack */
    unsigned long sp = regs->r1;

    if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && !on_sig_stack(sp))
        sp = current->sas_ss_sp + current->sas_ss_size;

    return (void __user *)((sp - 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 __user *frame;
    int err = 0;
    int signal;
    unsigned long address = 0;
#ifdef CONFIG_MMU
    pmd_t *pmdp;
    pte_t *ptep;
#endif

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

    if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
        goto give_sigsegv;

    signal = current_thread_info()->exec_domain
        && current_thread_info()->exec_domain->signal_invmap
        && sig < 32
        ? current_thread_info()->exec_domain->signal_invmap[sig]
        : sig;

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

    /* 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->r1),
            &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, set->sig[0]);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

    /* Set up to return from userspace. If provided, use a stub
     already in userspace. */
    /* minus 8 is offset to cater for "rtsd r15,8" */
    /* addi r12, r0, __NR_sigreturn */
    err |= __put_user(0x31800000 | __NR_rt_sigreturn ,
            frame->tramp + 0);
    /* brki r14, 0x8 */
    err |= __put_user(0xb9cc0008, frame->tramp + 1);

    /* Return from sighandler will jump to the tramp.
     Negative 8 offset because return is rtsd r15, 8 */
    regs->r15 = ((unsigned long)frame->tramp)-8;

    address = ((unsigned long)frame->tramp);
#ifdef CONFIG_MMU
    pmdp = pmd_offset(pud_offset(
            pgd_offset(current->mm, address),
                    address), address);

    preempt_disable();
    ptep = pte_offset_map(pmdp, address);
    if (pte_present(*ptep)) {
        address = (unsigned long) page_address(pte_page(*ptep));
        /* MS: I need add offset in page */
        address += ((unsigned long)frame->tramp) & ~PAGE_MASK;
        /* MS address is virtual */
        address = virt_to_phys(address);
        invalidate_icache_range(address, address + 8);
        flush_dcache_range(address, address + 8);
    }
    pte_unmap(ptep);
    preempt_enable();
#else
    flush_icache_range(address, address + 8);
    flush_dcache_range(address, address + 8);
#endif
    if (err)
        goto give_sigsegv;

    /* Set up registers for signal handler */
    regs->r1 = (unsigned long) frame;

    /* Signal handler args: */
    regs->r5 = signal; /* arg 0: signum */
    regs->r6 = (unsigned long) &frame->info; /* arg 1: siginfo */
    regs->r7 = (unsigned long) &frame->uc; /* arg2: ucontext */
    /* Offset to handle microblaze rtid r14, 0 */
    regs->pc = (unsigned long)ka->sa.sa_handler;

    set_fs(USER_DS);

#ifdef DEBUG_SIG
    printk(KERN_INFO "SIG deliver (%s:%d): sp=%p pc=%08lx\n",
        current->comm, current->pid, frame, regs->pc);
#endif

    return 0;

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

/* Handle restarting system calls */
static inline void
handle_restart(struct pt_regs *regs, struct k_sigaction *ka, int has_handler)
{
    switch (regs->r3) {
    case -ERESTART_RESTARTBLOCK:
    case -ERESTARTNOHAND:
        if (!has_handler)
            goto do_restart;
        regs->r3 = -EINTR;
        break;
    case -ERESTARTSYS:
        if (has_handler && !(ka->sa.sa_flags & SA_RESTART)) {
            regs->r3 = -EINTR;
            break;
    }
    /* fallthrough */
    case -ERESTARTNOINTR:
do_restart:
        /* offset of 4 bytes to re-execute trap (brki) instruction */
        regs->pc -= 4;
        break;
    }
}

/*
 * OK, we're invoking a handler
 */

static void
handle_signal(unsigned long sig, struct k_sigaction *ka,
        siginfo_t *info, struct pt_regs *regs)
{
    sigset_t *oldset = sigmask_to_save();
    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_rt_frame(sig, ka, NULL, oldset, regs);

    if (ret)
        return;

    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.
 */
static void do_signal(struct pt_regs *regs, int in_syscall)
{
    siginfo_t info;
    int signr;
    struct k_sigaction ka;
#ifdef DEBUG_SIG
    printk(KERN_INFO "do signal: %p %d\n", regs, in_syscall);
    printk(KERN_INFO "do signal2: %lx %lx %ld [%lx]\n", regs->pc, regs->r1,
            regs->r12, current_thread_info()->flags);
#endif

    signr = get_signal_to_deliver(&info, &ka, regs, NULL);
    if (signr > 0) {
        /* Whee! Actually deliver the signal. */
        if (in_syscall)
            handle_restart(regs, &ka, 1);
        handle_signal(signr, &ka, &info, regs);
        return;
    }

    if (in_syscall)
        handle_restart(regs, NULL, 0);

    /*
     * 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, int in_syscall)
{
    /*
     * 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 (kernel_mode(regs))
        return;

    if (test_thread_flag(TIF_SIGPENDING))
        do_signal(regs, in_syscall);

    if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
        tracehook_notify_resume(regs);
}