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signal.c

/*
 * Signal handling
 *
 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
 * Copyright (C) 2008-2009 PetaLogix
 * Copyright (C) 2003,2004 John Williams <jwilliams@itee.uq.edu.au>
 * Copyright (C) 2001 NEC Corporation
 * Copyright (C) 2001 Miles Bader <miles@gnu.org>
 * 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 <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>

#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

asmlinkage int do_signal(struct pt_regs *regs, sigset_t *oldset, int in_sycall);


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 + STATE_SAVE_ARG_SPACE);

      sigset_t set;
      int rval;

      if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
            goto badframe;

      if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
            goto badframe;

      sigdelsetmask(&set, ~_BLOCKABLE);
      spin_lock_irq(&current->sighand->siglock);
      current->blocked = set;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

      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))
            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 void 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;

      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(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(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;

      __invalidate_cache_sigtramp((unsigned long)frame->tramp);

      if (err)
            goto give_sigsegv;

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

      /* 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;

give_sigsegv:
      if (sig == SIGSEGV)
            ka->sa.sa_handler = SIG_DFL;
      force_sig(SIGSEGV, current);
}

/* 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 */
#ifndef CONFIG_MMU
            regs->pc -= 4;
#else
            /* offset of 8 bytes required = 4 for rtbd
               offset, plus 4 for size of
                  "brki r14,8"
               instruction. */
            regs->pc -= 8;
#endif
            break;
      }
}

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

static int
handle_signal(unsigned long sig, struct k_sigaction *ka,
            siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
{
      /* Set up the stack frame */
      if (ka->sa.sa_flags & SA_SIGINFO)
            setup_rt_frame(sig, ka, info, oldset, regs);
      else
            setup_rt_frame(sig, ka, NULL, oldset, regs);

      if (ka->sa.sa_flags & SA_ONESHOT)
            ka->sa.sa_handler = SIG_DFL;

      if (!(ka->sa.sa_flags & SA_NODEFER)) {
            spin_lock_irq(&current->sighand->siglock);
            sigorsets(&current->blocked,
                        &current->blocked, &ka->sa.sa_mask);
            sigaddset(&current->blocked, sig);
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);
      }
      return 1;
}

/*
 * 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.
 */
int do_signal(struct pt_regs *regs, sigset_t *oldset, int in_syscall)
{
      siginfo_t info;
      int signr;
      struct k_sigaction ka;
#ifdef DEBUG_SIG
      printk(KERN_INFO "do signal: %p %p %d\n", regs, oldset, in_syscall);
      printk(KERN_INFO "do signal2: %lx %lx %ld [%lx]\n", regs->pc, regs->r1,
                  regs->r12, current_thread_info()->flags);
#endif
      /*
       * 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 1;

      if (current_thread_info()->status & TS_RESTORE_SIGMASK)
            oldset = &current->saved_sigmask;
      else
            oldset = &current->blocked;

      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);
            if (handle_signal(signr, &ka, &info, oldset, regs)) {
                  /*
                   * A signal was successfully delivered; the saved
                   * sigmask will have been stored in the signal frame,
                   * and will be restored by sigreturn, so we can simply
                   * clear the TS_RESTORE_SIGMASK flag.
                   */
                  current_thread_info()->status &=
                      ~TS_RESTORE_SIGMASK;
            }
            return 1;
      }

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

      /*
       * If there's no signal to deliver, we just put the saved sigmask
       * back.
       */
      if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
            current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
            sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
      }

      /* Did we come from a system call? */
      return 0;
}

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