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signal_32.c

/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
 */

#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/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/suspend.h>
#include <linux/ptrace.h>
#include <linux/elf.h>
#include <linux/binfmts.h>
#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/i387.h>
#include "sigframe_32.h"

#define DEBUG_SIG 0

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

/*
 * 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 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(unsigned long ebx)
{
      /* This is needed to make gcc realize it doesn't own the "struct pt_regs" */
      struct pt_regs *regs = (struct pt_regs *)&ebx;
      const stack_t __user *uss = (const stack_t __user *)ebx;
      stack_t __user *uoss = (stack_t __user *)regs->ecx;

      return do_sigaltstack(uss, uoss, regs->esp);
}


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

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

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

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

#define COPY_SEG(seg)                                       \
      { unsigned short tmp;                                 \
        err |= __get_user(tmp, &sc->seg);                   \
        regs->x##seg = tmp; }

#define COPY_SEG_STRICT(seg)                                \
      { unsigned short tmp;                                 \
        err |= __get_user(tmp, &sc->seg);                   \
        regs->x##seg = tmp|3; }

#define GET_SEG(seg)                                        \
      { unsigned short tmp;                                 \
        err |= __get_user(tmp, &sc->seg);                   \
        loadsegment(seg,tmp); }

#define     FIX_EFLAGS  (X86_EFLAGS_AC | X86_EFLAGS_RF |           \
                   X86_EFLAGS_OF | X86_EFLAGS_DF |           \
                   X86_EFLAGS_TF | X86_EFLAGS_SF | X86_EFLAGS_ZF | \
                   X86_EFLAGS_AF | X86_EFLAGS_PF | X86_EFLAGS_CF)

      GET_SEG(gs);
      COPY_SEG(fs);
      COPY_SEG(es);
      COPY_SEG(ds);
      COPY(edi);
      COPY(esi);
      COPY(ebp);
      COPY(esp);
      COPY(ebx);
      COPY(edx);
      COPY(ecx);
      COPY(eip);
      COPY_SEG_STRICT(cs);
      COPY_SEG_STRICT(ss);
      
      {
            unsigned int tmpflags;
            err |= __get_user(tmpflags, &sc->eflags);
            regs->eflags = (regs->eflags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
            regs->orig_eax = -1;          /* disable syscall checks */
      }

      {
            struct _fpstate __user * buf;
            err |= __get_user(buf, &sc->fpstate);
            if (buf) {
                  if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
                        goto badframe;
                  err |= restore_i387(buf);
            } else {
                  struct task_struct *me = current;
                  if (used_math()) {
                        clear_fpu(me);
                        clear_used_math();
                  }
            }
      }

      err |= __get_user(*peax, &sc->eax);
      return err;

badframe:
      return 1;
}

asmlinkage int sys_sigreturn(unsigned long __unused)
{
      struct pt_regs *regs = (struct pt_regs *) &__unused;
      struct sigframe __user *frame = (struct sigframe __user *)(regs->esp - 8);
      sigset_t set;
      int eax;

      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, &eax))
            goto badframe;
      return eax;

badframe:
      if (show_unhandled_signals && printk_ratelimit())
            printk("%s%s[%d] bad frame in sigreturn frame:%p eip:%lx"
                   " esp:%lx oeax:%lx\n",
                task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
                current->comm, task_pid_nr(current), frame, regs->eip,
                regs->esp, regs->orig_eax);

      force_sig(SIGSEGV, current);
      return 0;
}     

asmlinkage int sys_rt_sigreturn(unsigned long __unused)
{
      struct pt_regs *regs = (struct pt_regs *) &__unused;
      struct rt_sigframe __user *frame = (struct rt_sigframe __user *)(regs->esp - 4);
      sigset_t set;
      int eax;

      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, &eax))
            goto badframe;

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

      return eax;

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

/*
 * Set up a signal frame.
 */

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

      err |= __put_user(regs->xfs, (unsigned int __user *)&sc->fs);
      savesegment(gs, tmp);
      err |= __put_user(tmp, (unsigned int __user *)&sc->gs);

      err |= __put_user(regs->xes, (unsigned int __user *)&sc->es);
      err |= __put_user(regs->xds, (unsigned int __user *)&sc->ds);
      err |= __put_user(regs->edi, &sc->edi);
      err |= __put_user(regs->esi, &sc->esi);
      err |= __put_user(regs->ebp, &sc->ebp);
      err |= __put_user(regs->esp, &sc->esp);
      err |= __put_user(regs->ebx, &sc->ebx);
      err |= __put_user(regs->edx, &sc->edx);
      err |= __put_user(regs->ecx, &sc->ecx);
      err |= __put_user(regs->eax, &sc->eax);
      err |= __put_user(current->thread.trap_no, &sc->trapno);
      err |= __put_user(current->thread.error_code, &sc->err);
      err |= __put_user(regs->eip, &sc->eip);
      err |= __put_user(regs->xcs, (unsigned int __user *)&sc->cs);
      err |= __put_user(regs->eflags, &sc->eflags);
      err |= __put_user(regs->esp, &sc->esp_at_signal);
      err |= __put_user(regs->xss, (unsigned int __user *)&sc->ss);

      tmp = save_i387(fpstate);
      if (tmp < 0)
        err = 1;
      else
        err |= __put_user(tmp ? fpstate : NULL, &sc->fpstate);

      /* non-iBCS2 extensions.. */
      err |= __put_user(mask, &sc->oldmask);
      err |= __put_user(current->thread.cr2, &sc->cr2);

      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)
{
      unsigned long esp;

      /* Default to using normal stack */
      esp = regs->esp;

      /* This is the X/Open sanctioned signal stack switching.  */
      if (ka->sa.sa_flags & SA_ONSTACK) {
            if (sas_ss_flags(esp) == 0)
                  esp = current->sas_ss_sp + current->sas_ss_size;
      }

      /* This is the legacy signal stack switching. */
      else if ((regs->xss & 0xffff) != __USER_DS &&
             !(ka->sa.sa_flags & SA_RESTORER) &&
             ka->sa.sa_restorer) {
            esp = (unsigned long) ka->sa.sa_restorer;
      }

      esp -= frame_size;
      /* Align the stack pointer according to the i386 ABI,
       * i.e. so that on function entry ((sp + 4) & 15) == 0. */
      esp = ((esp + 4) & -16ul) - 4;
      return (void __user *) esp;
}

/* These symbols are defined with the addresses in the vsyscall page.
   See vsyscall-sigreturn.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)
{
      void __user *restorer;
      struct sigframe __user *frame;
      int err = 0;
      int usig;

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

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

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

      err = __put_user(usig, &frame->sig);
      if (err)
            goto give_sigsegv;

      err = setup_sigcontext(&frame->sc, &frame->fpstate, regs, set->sig[0]);
      if (err)
            goto give_sigsegv;

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

      if (current->binfmt->hasvdso)
            restorer = (void *)VDSO_SYM(&__kernel_sigreturn);
      else
            restorer = (void *)&frame->retcode;
      if (ka->sa.sa_flags & SA_RESTORER)
            restorer = ka->sa.sa_restorer;

      /* Set up to return from userspace.  */
      err |= __put_user(restorer, &frame->pretcode);
       
      /*
       * This is popl %eax ; movl $,%eax ; int $0x80
       *
       * WE DO NOT USE IT ANY MORE! It's only left here for historical
       * reasons and because gdb uses it as a signature to notice
       * signal handler stack frames.
       */
      err |= __put_user(0xb858, (short __user *)(frame->retcode+0));
      err |= __put_user(__NR_sigreturn, (int __user *)(frame->retcode+2));
      err |= __put_user(0x80cd, (short __user *)(frame->retcode+6));

      if (err)
            goto give_sigsegv;

      /* Set up registers for signal handler */
      regs->esp = (unsigned long) frame;
      regs->eip = (unsigned long) ka->sa.sa_handler;
      regs->eax = (unsigned long) sig;
      regs->edx = (unsigned long) 0;
      regs->ecx = (unsigned long) 0;

      regs->xds = __USER_DS;
      regs->xes = __USER_DS;
      regs->xss = __USER_DS;
      regs->xcs = __USER_CS;

      /*
       * Clear TF when entering the signal handler, but
       * notify any tracer that was single-stepping it.
       * The tracer may want to single-step inside the
       * handler too.
       */
      regs->eflags &= ~TF_MASK;
      if (test_thread_flag(TIF_SINGLESTEP))
            ptrace_notify(SIGTRAP);

#if DEBUG_SIG
      printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
            current->comm, current->pid, frame, regs->eip, frame->pretcode);
#endif

      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)
{
      void __user *restorer;
      struct rt_sigframe __user *frame;
      int err = 0;
      int usig;

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

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

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

      err |= __put_user(usig, &frame->sig);
      err |= __put_user(&frame->info, &frame->pinfo);
      err |= __put_user(&frame->uc, &frame->puc);
      err |= copy_siginfo_to_user(&frame->info, info);
      if (err)
            goto give_sigsegv;

      /* Create the ucontext.  */
      err |= __put_user(0, &frame->uc.uc_flags);
      err |= __put_user(0, &frame->uc.uc_link);
      err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
      err |= __put_user(sas_ss_flags(regs->esp),
                    &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, &frame->fpstate,
                          regs, set->sig[0]);
      err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
      if (err)
            goto give_sigsegv;

      /* Set up to return from userspace.  */
      restorer = (void *)VDSO_SYM(&__kernel_rt_sigreturn);
      if (ka->sa.sa_flags & SA_RESTORER)
            restorer = ka->sa.sa_restorer;
      err |= __put_user(restorer, &frame->pretcode);
       
      /*
       * This is movl $,%eax ; int $0x80
       *
       * WE DO NOT USE IT ANY MORE! It's only left here for historical
       * reasons and because gdb uses it as a signature to notice
       * signal handler stack frames.
       */
      err |= __put_user(0xb8, (char __user *)(frame->retcode+0));
      err |= __put_user(__NR_rt_sigreturn, (int __user *)(frame->retcode+1));
      err |= __put_user(0x80cd, (short __user *)(frame->retcode+5));

      if (err)
            goto give_sigsegv;

      /* Set up registers for signal handler */
      regs->esp = (unsigned long) frame;
      regs->eip = (unsigned long) ka->sa.sa_handler;
      regs->eax = (unsigned long) usig;
      regs->edx = (unsigned long) &frame->info;
      regs->ecx = (unsigned long) &frame->uc;

      regs->xds = __USER_DS;
      regs->xes = __USER_DS;
      regs->xss = __USER_DS;
      regs->xcs = __USER_CS;

      /*
       * Clear TF when entering the signal handler, but
       * notify any tracer that was single-stepping it.
       * The tracer may want to single-step inside the
       * handler too.
       */
      regs->eflags &= ~TF_MASK;
      if (test_thread_flag(TIF_SINGLESTEP))
            ptrace_notify(SIGTRAP);

#if DEBUG_SIG
      printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
            current->comm, current->pid, frame, regs->eip, frame->pretcode);
#endif

      return 0;

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

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

static int
handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
            sigset_t *oldset, struct pt_regs * regs)
{
      int ret;

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

                  case -ERESTARTSYS:
                        if (!(ka->sa.sa_flags & SA_RESTART)) {
                              regs->eax = -EINTR;
                              break;
                        }
                  /* fallthrough */
                  case -ERESTARTNOINTR:
                        regs->eax = regs->orig_eax;
                        regs->eip -= 2;
            }
      }

      /*
       * If TF is set due to a debugger (PT_DTRACE), clear the TF flag so
       * that register information in the sigcontext is correct.
       */
      if (unlikely(regs->eflags & TF_MASK)
          && likely(current->ptrace & PT_DTRACE)) {
            current->ptrace &= ~PT_DTRACE;
            regs->eflags &= ~TF_MASK;
      }

      /* 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.
 */
static void fastcall do_signal(struct pt_regs *regs)
{
      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.  vm86 regs switched out by assembly code
       * before reaching here, so testing against kernel
       * CS suffices.
       */
      if (!user_mode(regs))
            return;

      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) {
            /* Re-enable any watchpoints before delivering the
             * signal to user space. The processor register will
             * have been cleared if the watchpoint triggered
             * inside the kernel.
             */
            if (unlikely(current->thread.debugreg[7]))
                  set_debugreg(current->thread.debugreg[7], 7);

            /* Whee!  Actually deliver the signal.  */
            if (handle_signal(signr, &info, &ka, oldset, regs) == 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;
      }

      /* Did we come from a system call? */
      if (regs->orig_eax >= 0) {
            /* Restart the system call - no handlers present */
            switch (regs->eax) {
            case -ERESTARTNOHAND:
            case -ERESTARTSYS:
            case -ERESTARTNOINTR:
                  regs->eax = regs->orig_eax;
                  regs->eip -= 2;
                  break;

            case -ERESTART_RESTARTBLOCK:
                  regs->eax = __NR_restart_syscall;
                  regs->eip -= 2;
                  break;
            }
      }

      /* 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);
      }
}

/*
 * notification of userspace execution resumption
 * - triggered by the TIF_WORK_MASK flags
 */
__attribute__((regparm(3)))
void do_notify_resume(struct pt_regs *regs, void *_unused,
                  __u32 thread_info_flags)
{
      /* Pending single-step? */
      if (thread_info_flags & _TIF_SINGLESTEP) {
            regs->eflags |= TF_MASK;
            clear_thread_flag(TIF_SINGLESTEP);
      }

      /* deal with pending signal delivery */
      if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
            do_signal(regs);
      
      clear_thread_flag(TIF_IRET);
}

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