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signal.c

/*
 *  linux/arch/sh/kernel/signal.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 *  SuperH version:  Copyright (C) 1999, 2000  Niibe Yutaka & Kaz Kojima
 *
 */
#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/elf.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/freezer.h>
#include <linux/io.h>
#include <asm/system.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/cacheflush.h>

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

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
asmlinkage int
sys_sigsuspend(old_sigset_t mask,
             unsigned long r5, unsigned long r6, unsigned long r7,
             struct pt_regs __regs)
{
      mask &= _BLOCKABLE;
      spin_lock_irq(&current->sighand->siglock);
      current->saved_sigmask = current->blocked;
      siginitset(&current->blocked, mask);
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

      current->state = TASK_INTERRUPTIBLE;
      schedule();
      set_thread_flag(TIF_RESTORE_SIGMASK);
      return -ERESTARTNOHAND;
}

asmlinkage int
sys_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))
                  return -EFAULT;
            __get_user(new_ka.sa.sa_flags, &act->sa_flags);
            __get_user(mask, &act->sa_mask);
            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))
                  return -EFAULT;
            __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
            __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
      }

      return ret;
}

asmlinkage int
sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
            unsigned long r6, unsigned long r7,
            struct pt_regs __regs)
{
      struct pt_regs *regs = RELOC_HIDE(&__regs, 0);

      return do_sigaltstack(uss, uoss, regs->regs[15]);
}


/*
 * Do a signal return; undo the signal stack.
 */

#define MOVW(n)    (0x9300|((n)-2)) /* Move mem word at PC+n to R3 */
#if defined(CONFIG_CPU_SH2)
#define TRAP_NOARG 0xc320           /* Syscall w/no args (NR in R3) */
#else
#define TRAP_NOARG 0xc310           /* Syscall w/no args (NR in R3) */
#endif
#define OR_R0_R0 0x200b             /* or r0,r0 (insert to avoid hardware bug) */

struct sigframe
{
      struct sigcontext sc;
      unsigned long extramask[_NSIG_WORDS-1];
      u16 retcode[8];
};

struct rt_sigframe
{
      struct siginfo info;
      struct ucontext uc;
      u16 retcode[8];
};

#ifdef CONFIG_SH_FPU
static inline int restore_sigcontext_fpu(struct sigcontext __user *sc)
{
      struct task_struct *tsk = current;

      if (!(current_cpu_data.flags & CPU_HAS_FPU))
            return 0;

      set_used_math();
      return __copy_from_user(&tsk->thread.fpu.hard, &sc->sc_fpregs[0],
                        sizeof(long)*(16*2+2));
}

static inline int save_sigcontext_fpu(struct sigcontext __user *sc,
                              struct pt_regs *regs)
{
      struct task_struct *tsk = current;

      if (!(current_cpu_data.flags & CPU_HAS_FPU))
            return 0;

      if (!used_math()) {
            __put_user(0, &sc->sc_ownedfp);
            return 0;
      }

      __put_user(1, &sc->sc_ownedfp);

      /* This will cause a "finit" to be triggered by the next
         attempted FPU operation by the 'current' process.
         */
      clear_used_math();

      unlazy_fpu(tsk, regs);
      return __copy_to_user(&sc->sc_fpregs[0], &tsk->thread.fpu.hard,
                        sizeof(long)*(16*2+2));
}
#endif /* CONFIG_SH_FPU */

static int
restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, int *r0_p)
{
      unsigned int err = 0;

#define COPY(x)         err |= __get_user(regs->x, &sc->sc_##x)
                  COPY(regs[1]);
      COPY(regs[2]);    COPY(regs[3]);
      COPY(regs[4]);    COPY(regs[5]);
      COPY(regs[6]);    COPY(regs[7]);
      COPY(regs[8]);    COPY(regs[9]);
      COPY(regs[10]);   COPY(regs[11]);
      COPY(regs[12]);   COPY(regs[13]);
      COPY(regs[14]);   COPY(regs[15]);
      COPY(gbr);  COPY(mach);
      COPY(macl); COPY(pr);
      COPY(sr);   COPY(pc);
#undef COPY

#ifdef CONFIG_SH_FPU
      if (current_cpu_data.flags & CPU_HAS_FPU) {
            int owned_fp;
            struct task_struct *tsk = current;

            regs->sr |= SR_FD; /* Release FPU */
            clear_fpu(tsk, regs);
            clear_used_math();
            __get_user (owned_fp, &sc->sc_ownedfp);
            if (owned_fp)
                  err |= restore_sigcontext_fpu(sc);
      }
#endif

      regs->tra = -1;         /* disable syscall checks */
      err |= __get_user(*r0_p, &sc->sc_regs[0]);
      return err;
}

asmlinkage int sys_sigreturn(unsigned long r4, unsigned long r5,
                       unsigned long r6, unsigned long r7,
                       struct pt_regs __regs)
{
      struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
      struct sigframe __user *frame = (struct sigframe __user *)regs->regs[15];
      sigset_t set;
      int r0;

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

      if (__get_user(set.sig[0], &frame->sc.oldmask)
          || (_NSIG_WORDS > 1
            && __copy_from_user(&set.sig[1], &frame->extramask,
                            sizeof(frame->extramask))))
            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->sc, &r0))
            goto badframe;
      return r0;

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

asmlinkage int sys_rt_sigreturn(unsigned long r4, unsigned long r5,
                        unsigned long r6, unsigned long r7,
                        struct pt_regs __regs)
{
      struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
      struct rt_sigframe __user *frame = (struct rt_sigframe __user *)regs->regs[15];
      sigset_t set;
      stack_t st;
      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;

      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, &r0))
            goto badframe;

      if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
            goto badframe;
      /* It is more difficult to avoid calling this function than to
         call it and ignore errors.  */
      do_sigaltstack((const stack_t __user *)&st, NULL, (unsigned long)frame);

      return r0;

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->sc_##x)
      COPY(regs[0]);    COPY(regs[1]);
      COPY(regs[2]);    COPY(regs[3]);
      COPY(regs[4]);    COPY(regs[5]);
      COPY(regs[6]);    COPY(regs[7]);
      COPY(regs[8]);    COPY(regs[9]);
      COPY(regs[10]);   COPY(regs[11]);
      COPY(regs[12]);   COPY(regs[13]);
      COPY(regs[14]);   COPY(regs[15]);
      COPY(gbr);  COPY(mach);
      COPY(macl); COPY(pr);
      COPY(sr);   COPY(pc);
#undef COPY

#ifdef CONFIG_SH_FPU
      err |= save_sigcontext_fpu(sc, regs);
#endif

      /* non-iBCS2 extensions.. */
      err |= __put_user(mask, &sc->oldmask);

      return err;
}

/*
 * Determine which stack to use..
 */
static inline void __user *
get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
{
      if (ka->sa.sa_flags & SA_ONSTACK) {
            if (sas_ss_flags(sp) == 0)
                  sp = current->sas_ss_sp + current->sas_ss_size;
      }

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

/* These symbols are defined with the addresses in the vsyscall page.
   See vsyscall-trapa.S.  */
extern void __user __kernel_sigreturn;
extern void __user __kernel_rt_sigreturn;

static int setup_frame(int sig, struct k_sigaction *ka,
                  sigset_t *set, struct pt_regs *regs)
{
      struct sigframe __user *frame;
      int err = 0;
      int signal;

      frame = get_sigframe(ka, regs->regs[15], 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;

      err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);

      if (_NSIG_WORDS > 1)
            err |= __copy_to_user(frame->extramask, &set->sig[1],
                              sizeof(frame->extramask));

      /* Set up to return from userspace.  If provided, use a stub
         already in userspace.  */
      if (ka->sa.sa_flags & SA_RESTORER) {
            regs->pr = (unsigned long) ka->sa.sa_restorer;
#ifdef CONFIG_VSYSCALL
      } else if (likely(current->mm->context.vdso)) {
            regs->pr = VDSO_SYM(&__kernel_sigreturn);
#endif
      } else {
            /* Generate return code (system call to sigreturn) */
            err |= __put_user(MOVW(7), &frame->retcode[0]);
            err |= __put_user(TRAP_NOARG, &frame->retcode[1]);
            err |= __put_user(OR_R0_R0, &frame->retcode[2]);
            err |= __put_user(OR_R0_R0, &frame->retcode[3]);
            err |= __put_user(OR_R0_R0, &frame->retcode[4]);
            err |= __put_user(OR_R0_R0, &frame->retcode[5]);
            err |= __put_user(OR_R0_R0, &frame->retcode[6]);
            err |= __put_user((__NR_sigreturn), &frame->retcode[7]);
            regs->pr = (unsigned long) frame->retcode;
      }

      if (err)
            goto give_sigsegv;

      /* Set up registers for signal handler */
      regs->regs[15] = (unsigned long) frame;
      regs->regs[4] = signal; /* Arg for signal handler */
      regs->regs[5] = 0;
      regs->regs[6] = (unsigned long) &frame->sc;
      regs->pc = (unsigned long) ka->sa.sa_handler;

      set_fs(USER_DS);

      pr_debug("SIG deliver (%s:%d): sp=%p pc=%08lx pr=%08lx\n",
             current->comm, task_pid_nr(current), frame, regs->pc, regs->pr);

      flush_cache_sigtramp(regs->pr);

      if ((-regs->pr & (L1_CACHE_BYTES-1)) < sizeof(frame->retcode))
            flush_cache_sigtramp(regs->pr + L1_CACHE_BYTES);

      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)
{
      struct rt_sigframe __user *frame;
      int err = 0;
      int signal;

      frame = get_sigframe(ka, regs->regs[15], 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;

      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->regs[15]),
                    &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.  */
      if (ka->sa.sa_flags & SA_RESTORER) {
            regs->pr = (unsigned long) ka->sa.sa_restorer;
#ifdef CONFIG_VSYSCALL
      } else if (likely(current->mm->context.vdso)) {
            regs->pr = VDSO_SYM(&__kernel_rt_sigreturn);
#endif
      } else {
            /* Generate return code (system call to rt_sigreturn) */
            err |= __put_user(MOVW(7), &frame->retcode[0]);
            err |= __put_user(TRAP_NOARG, &frame->retcode[1]);
            err |= __put_user(OR_R0_R0, &frame->retcode[2]);
            err |= __put_user(OR_R0_R0, &frame->retcode[3]);
            err |= __put_user(OR_R0_R0, &frame->retcode[4]);
            err |= __put_user(OR_R0_R0, &frame->retcode[5]);
            err |= __put_user(OR_R0_R0, &frame->retcode[6]);
            err |= __put_user((__NR_rt_sigreturn), &frame->retcode[7]);
            regs->pr = (unsigned long) frame->retcode;
      }

      if (err)
            goto give_sigsegv;

      /* Set up registers for signal handler */
      regs->regs[15] = (unsigned long) frame;
      regs->regs[4] = signal; /* Arg for signal handler */
      regs->regs[5] = (unsigned long) &frame->info;
      regs->regs[6] = (unsigned long) &frame->uc;
      regs->pc = (unsigned long) ka->sa.sa_handler;

      set_fs(USER_DS);

      pr_debug("SIG deliver (%s:%d): sp=%p pc=%08lx pr=%08lx\n",
             current->comm, task_pid_nr(current), frame, regs->pc, regs->pr);

      flush_cache_sigtramp(regs->pr);

      if ((-regs->pr & (L1_CACHE_BYTES-1)) < sizeof(frame->retcode))
            flush_cache_sigtramp(regs->pr + L1_CACHE_BYTES);

      return 0;

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

/*
 * 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, unsigned int save_r0)
{
      int ret;

      /* Are we from a system call? */
      if (regs->tra >= 0) {
            /* If so, check system call restarting.. */
            switch (regs->regs[0]) {
                  case -ERESTART_RESTARTBLOCK:
                  case -ERESTARTNOHAND:
                        regs->regs[0] = -EINTR;
                        break;

                  case -ERESTARTSYS:
                        if (!(ka->sa.sa_flags & SA_RESTART)) {
                              regs->regs[0] = -EINTR;
                              break;
                        }
                  /* fallthrough */
                  case -ERESTARTNOINTR:
                        regs->regs[0] = save_r0;
                        regs->pc -= instruction_size(
                                    ctrl_inw(regs->pc - 4));
                        break;
            }
#ifdef CONFIG_GUSA
      } else {
            /* gUSA handling */
            preempt_disable();

            if (regs->regs[15] >= 0xc0000000) {
                  int offset = (int)regs->regs[15];

                  /* Reset stack pointer: clear critical region mark */
                  regs->regs[15] = regs->regs[1];
                  if (regs->pc < regs->regs[0])
                        /* Go to rewind point #1 */
                        regs->pc = regs->regs[0] + offset -
                              instruction_size(ctrl_inw(regs->pc-4));
            }

            preempt_enable_no_resched();
#endif
      }

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

      if (ret == 0) {
            spin_lock_irq(&current->sighand->siglock);
            sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
            if (!(ka->sa.sa_flags & SA_NODEFER))
                  sigaddset(&current->blocked,sig);
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);
      }

      return ret;
}

/*
 * 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, unsigned int save_r0)
{
      siginfo_t info;
      int signr;
      struct k_sigaction ka;
      sigset_t *oldset;

      /*
       * 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 (!user_mode(regs))
            return;

      if (try_to_freeze())
            goto no_signal;

      if (test_thread_flag(TIF_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 (handle_signal(signr, &ka, &info, oldset,
                          regs, save_r0) == 0) {
                  /* 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 TIF_RESTORE_SIGMASK flag */
                  if (test_thread_flag(TIF_RESTORE_SIGMASK))
                        clear_thread_flag(TIF_RESTORE_SIGMASK);
            }

            return;
      }

 no_signal:
      /* Did we come from a system call? */
      if (regs->tra >= 0) {
            /* Restart the system call - no handlers present */
            if (regs->regs[0] == -ERESTARTNOHAND ||
                regs->regs[0] == -ERESTARTSYS ||
                regs->regs[0] == -ERESTARTNOINTR) {
                  regs->regs[0] = save_r0;
                  regs->pc -= instruction_size(ctrl_inw(regs->pc - 4));
            } else if (regs->regs[0] == -ERESTART_RESTARTBLOCK) {
                  regs->pc -= instruction_size(ctrl_inw(regs->pc - 4));
                  regs->regs[3] = __NR_restart_syscall;
            }
      }

      /* if there's no signal to deliver, we just put the saved sigmask
       * back */
      if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
            clear_thread_flag(TIF_RESTORE_SIGMASK);
            sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
      }
}

asmlinkage void do_notify_resume(struct pt_regs *regs, unsigned int save_r0,
                         __u32 thread_info_flags)
{
      /* deal with pending signal delivery */
      if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
            do_signal(regs, save_r0);
}

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