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signal.c

/*
 *  arch/s390/kernel/signal.c
 *
 *    Copyright (C) IBM Corp. 1999,2006
 *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
 *
 *    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 <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/lowcore.h>
#include "entry.h"

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


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.
 */
asmlinkage int
sys_sigsuspend(int history0, int history1, old_sigset_t mask)
{
      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 long
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) ||
                __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;
}

asmlinkage long
sys_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_MASK_MERGE(psw_user_bits, regs->psw.mask);
      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;
      regs->psw.mask = PSW_MASK_MERGE(regs->psw.mask,
                              user_sregs.regs.psw.mask);
      regs->psw.addr = PSW_ADDR_AMODE | 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);
      regs->trap = -1;  /* disable syscall checks */
      return 0;
}

asmlinkage long sys_sigreturn(void)
{
      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;

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

      if (restore_sigregs(regs, &frame->sregs))
            goto badframe;

      return regs->gprs[2];

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

asmlinkage long sys_rt_sigreturn(void)
{
      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;

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

      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;
      }

      /* This is the legacy signal stack switching. */
      else if (!user_mode(regs) &&
             !(ka->sa.sa_flags & SA_RESTORER) &&
             ka->sa.sa_restorer) {
            sp = (unsigned long) ka->sa.sa_restorer;
      }

      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;
      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. */
      regs->gprs[4] = current->thread.trap_no;
      regs->gprs[5] = current->thread.prot_addr;

      /* 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;
      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;
      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)
{
      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 == 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.
 */
void do_signal(struct pt_regs *regs)
{
      unsigned long retval = 0, continue_addr = 0, restart_addr = 0;
      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 (test_thread_flag(TIF_RESTORE_SIGMASK))
            oldset = &current->saved_sigmask;
      else
            oldset = &current->blocked;

      /* Are we from a system call? */
      if (regs->trap == __LC_SVC_OLD_PSW) {
            continue_addr = regs->psw.addr;
            restart_addr = continue_addr - regs->ilc;
            retval = regs->gprs[2];

            /* Prepare for system call restart.  We do this here so that a
               debugger will see the already changed PSW. */
            switch (retval) {
            case -ERESTARTNOHAND:
            case -ERESTARTSYS:
            case -ERESTARTNOINTR:
                  regs->gprs[2] = regs->orig_gpr2;
                  regs->psw.addr = restart_addr;
                  break;
            case -ERESTART_RESTARTBLOCK:
                  regs->gprs[2] = -EINTR;
            }
            regs->trap = -1;  /* Don't deal with this again. */
      }

      /* Get signal to deliver.  When running under ptrace, at this point
         the debugger may change all our registers ... */
      signr = get_signal_to_deliver(&info, &ka, regs, NULL);

      /* Depending on the signal settings we may need to revert the
         decision to restart the system call. */
      if (signr > 0 && regs->psw.addr == restart_addr) {
            if (retval == -ERESTARTNOHAND
                || (retval == -ERESTARTSYS
                   && !(current->sighand->action[signr-1].sa.sa_flags
                        & SA_RESTART))) {
                  regs->gprs[2] = -EINTR;
                  regs->psw.addr = continue_addr;
            }
      }

      if (signr > 0) {
            /* Whee!  Actually deliver the signal.  */
            int ret;
#ifdef CONFIG_COMPAT
            if (test_thread_flag(TIF_31BIT)) {
                  ret = handle_signal32(signr, &ka, &info, oldset, regs);
              }
            else
#endif
                  ret = handle_signal(signr, &ka, &info, oldset, regs);
            if (!ret) {
                  /*
                   * 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);

                  /*
                   * If we would have taken a single-step trap
                   * for a normal instruction, act like we took
                   * one for the handler setup.
                   */
                  if (current->thread.per_info.single_step)
                        set_thread_flag(TIF_SINGLE_STEP);
            }
            return;
      }

      /*
       * 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);
      }

      /* Restart a different system call. */
      if (retval == -ERESTART_RESTARTBLOCK
          && regs->psw.addr == continue_addr) {
            regs->gprs[2] = __NR_restart_syscall;
            set_thread_flag(TIF_RESTART_SVC);
      }
}

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