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signal.c

/*
 *  linux/arch/arm/kernel/signal.c
 *
 *  Copyright (C) 1995-2009 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/personality.h>
#include <linux/freezer.h>
#include <linux/uaccess.h>
#include <linux/tracehook.h>

#include <asm/elf.h>
#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/unistd.h>
#include <asm/vfp.h>

#include "ptrace.h"
#include "signal.h"

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

/*
 * For ARM syscalls, we encode the syscall number into the instruction.
 */
#define SWI_SYS_SIGRETURN     (0xef000000|(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE))
#define SWI_SYS_RT_SIGRETURN  (0xef000000|(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE))
#define SWI_SYS_RESTART       (0xef000000|__NR_restart_syscall|__NR_OABI_SYSCALL_BASE)

/*
 * With EABI, the syscall number has to be loaded into r7.
 */
#define MOV_R7_NR_SIGRETURN   (0xe3a07000 | (__NR_sigreturn - __NR_SYSCALL_BASE))
#define MOV_R7_NR_RT_SIGRETURN      (0xe3a07000 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))

/*
 * For Thumb syscalls, we pass the syscall number via r7.  We therefore
 * need two 16-bit instructions.
 */
#define SWI_THUMB_SIGRETURN   (0xdf00 << 16 | 0x2700 | (__NR_sigreturn - __NR_SYSCALL_BASE))
#define SWI_THUMB_RT_SIGRETURN      (0xdf00 << 16 | 0x2700 | (__NR_rt_sigreturn - __NR_SYSCALL_BASE))

const unsigned long sigreturn_codes[7] = {
      MOV_R7_NR_SIGRETURN,    SWI_SYS_SIGRETURN,    SWI_THUMB_SIGRETURN,
      MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN,
};

/*
 * Either we support OABI only, or we have EABI with the OABI
 * compat layer enabled.  In the later case we don't know if
 * user space is EABI or not, and if not we must not clobber r7.
 * Always using the OABI syscall solves that issue and works for
 * all those cases.
 */
const unsigned long syscall_restart_code[2] = {
      SWI_SYS_RESTART,  /* swi      __NR_restart_syscall */
      0xe49df004,       /* ldr      pc, [sp], #4 */
};

/*
 * atomically swap in the new signal mask, and wait for a signal.
 */
asmlinkage int sys_sigsuspend(int restart, unsigned long oldmask, 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_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;
}

#ifdef CONFIG_CRUNCH
static int preserve_crunch_context(struct crunch_sigframe __user *frame)
{
      char kbuf[sizeof(*frame) + 8];
      struct crunch_sigframe *kframe;

      /* the crunch context must be 64 bit aligned */
      kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
      kframe->magic = CRUNCH_MAGIC;
      kframe->size = CRUNCH_STORAGE_SIZE;
      crunch_task_copy(current_thread_info(), &kframe->storage);
      return __copy_to_user(frame, kframe, sizeof(*frame));
}

static int restore_crunch_context(struct crunch_sigframe __user *frame)
{
      char kbuf[sizeof(*frame) + 8];
      struct crunch_sigframe *kframe;

      /* the crunch context must be 64 bit aligned */
      kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
      if (__copy_from_user(kframe, frame, sizeof(*frame)))
            return -1;
      if (kframe->magic != CRUNCH_MAGIC ||
          kframe->size != CRUNCH_STORAGE_SIZE)
            return -1;
      crunch_task_restore(current_thread_info(), &kframe->storage);
      return 0;
}
#endif

#ifdef CONFIG_IWMMXT

static int preserve_iwmmxt_context(struct iwmmxt_sigframe *frame)
{
      char kbuf[sizeof(*frame) + 8];
      struct iwmmxt_sigframe *kframe;

      /* the iWMMXt context must be 64 bit aligned */
      kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
      kframe->magic = IWMMXT_MAGIC;
      kframe->size = IWMMXT_STORAGE_SIZE;
      iwmmxt_task_copy(current_thread_info(), &kframe->storage);
      return __copy_to_user(frame, kframe, sizeof(*frame));
}

static int restore_iwmmxt_context(struct iwmmxt_sigframe *frame)
{
      char kbuf[sizeof(*frame) + 8];
      struct iwmmxt_sigframe *kframe;

      /* the iWMMXt context must be 64 bit aligned */
      kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
      if (__copy_from_user(kframe, frame, sizeof(*frame)))
            return -1;
      if (kframe->magic != IWMMXT_MAGIC ||
          kframe->size != IWMMXT_STORAGE_SIZE)
            return -1;
      iwmmxt_task_restore(current_thread_info(), &kframe->storage);
      return 0;
}

#endif

#ifdef CONFIG_VFP

static int preserve_vfp_context(struct vfp_sigframe __user *frame)
{
      struct thread_info *thread = current_thread_info();
      struct vfp_hard_struct *h = &thread->vfpstate.hard;
      const unsigned long magic = VFP_MAGIC;
      const unsigned long size = VFP_STORAGE_SIZE;
      int err = 0;

      vfp_sync_hwstate(thread);
      __put_user_error(magic, &frame->magic, err);
      __put_user_error(size, &frame->size, err);

      /*
       * Copy the floating point registers. There can be unused
       * registers see asm/hwcap.h for details.
       */
      err |= __copy_to_user(&frame->ufp.fpregs, &h->fpregs,
                        sizeof(h->fpregs));
      /*
       * Copy the status and control register.
       */
      __put_user_error(h->fpscr, &frame->ufp.fpscr, err);

      /*
       * Copy the exception registers.
       */
      __put_user_error(h->fpexc, &frame->ufp_exc.fpexc, err);
      __put_user_error(h->fpinst, &frame->ufp_exc.fpinst, err);
      __put_user_error(h->fpinst2, &frame->ufp_exc.fpinst2, err);

      return err ? -EFAULT : 0;
}

static int restore_vfp_context(struct vfp_sigframe __user *frame)
{
      struct thread_info *thread = current_thread_info();
      struct vfp_hard_struct *h = &thread->vfpstate.hard;
      unsigned long magic;
      unsigned long size;
      unsigned long fpexc;
      int err = 0;

      __get_user_error(magic, &frame->magic, err);
      __get_user_error(size, &frame->size, err);

      if (err)
            return -EFAULT;
      if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
            return -EINVAL;

      /*
       * Copy the floating point registers. There can be unused
       * registers see asm/hwcap.h for details.
       */
      err |= __copy_from_user(&h->fpregs, &frame->ufp.fpregs,
                        sizeof(h->fpregs));
      /*
       * Copy the status and control register.
       */
      __get_user_error(h->fpscr, &frame->ufp.fpscr, err);

      /*
       * Sanitise and restore the exception registers.
       */
      __get_user_error(fpexc, &frame->ufp_exc.fpexc, err);
      /* Ensure the VFP is enabled. */
      fpexc |= FPEXC_EN;
      /* Ensure FPINST2 is invalid and the exception flag is cleared. */
      fpexc &= ~(FPEXC_EX | FPEXC_FP2V);
      h->fpexc = fpexc;

      __get_user_error(h->fpinst, &frame->ufp_exc.fpinst, err);
      __get_user_error(h->fpinst2, &frame->ufp_exc.fpinst2, err);

      if (!err)
            vfp_flush_hwstate(thread);

      return err ? -EFAULT : 0;
}

#endif

/*
 * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
 */
struct sigframe {
      struct ucontext uc;
      unsigned long retcode[2];
};

struct rt_sigframe {
      struct siginfo info;
      struct sigframe sig;
};

static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
{
      struct aux_sigframe __user *aux;
      sigset_t set;
      int err;

      err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
      if (err == 0) {
            sigdelsetmask(&set, ~_BLOCKABLE);
            spin_lock_irq(&current->sighand->siglock);
            current->blocked = set;
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);
      }

      __get_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
      __get_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
      __get_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
      __get_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
      __get_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
      __get_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
      __get_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
      __get_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
      __get_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
      __get_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
      __get_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
      __get_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
      __get_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
      __get_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
      __get_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
      __get_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
      __get_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);

      err |= !valid_user_regs(regs);

      aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
#ifdef CONFIG_CRUNCH
      if (err == 0)
            err |= restore_crunch_context(&aux->crunch);
#endif
#ifdef CONFIG_IWMMXT
      if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
            err |= restore_iwmmxt_context(&aux->iwmmxt);
#endif
#ifdef CONFIG_VFP
      if (err == 0)
            err |= restore_vfp_context(&aux->vfp);
#endif

      return err;
}

asmlinkage int sys_sigreturn(struct pt_regs *regs)
{
      struct sigframe __user *frame;

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

      /*
       * Since we stacked the signal on a 64-bit boundary,
       * then 'sp' should be word aligned here.  If it's
       * not, then the user is trying to mess with us.
       */
      if (regs->ARM_sp & 7)
            goto badframe;

      frame = (struct sigframe __user *)regs->ARM_sp;

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

      if (restore_sigframe(regs, frame))
            goto badframe;

      single_step_trap(current);

      return regs->ARM_r0;

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

asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
{
      struct rt_sigframe __user *frame;

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

      /*
       * Since we stacked the signal on a 64-bit boundary,
       * then 'sp' should be word aligned here.  If it's
       * not, then the user is trying to mess with us.
       */
      if (regs->ARM_sp & 7)
            goto badframe;

      frame = (struct rt_sigframe __user *)regs->ARM_sp;

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

      if (restore_sigframe(regs, &frame->sig))
            goto badframe;

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

      single_step_trap(current);

      return regs->ARM_r0;

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

static int
setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
{
      struct aux_sigframe __user *aux;
      int err = 0;

      __put_user_error(regs->ARM_r0, &sf->uc.uc_mcontext.arm_r0, err);
      __put_user_error(regs->ARM_r1, &sf->uc.uc_mcontext.arm_r1, err);
      __put_user_error(regs->ARM_r2, &sf->uc.uc_mcontext.arm_r2, err);
      __put_user_error(regs->ARM_r3, &sf->uc.uc_mcontext.arm_r3, err);
      __put_user_error(regs->ARM_r4, &sf->uc.uc_mcontext.arm_r4, err);
      __put_user_error(regs->ARM_r5, &sf->uc.uc_mcontext.arm_r5, err);
      __put_user_error(regs->ARM_r6, &sf->uc.uc_mcontext.arm_r6, err);
      __put_user_error(regs->ARM_r7, &sf->uc.uc_mcontext.arm_r7, err);
      __put_user_error(regs->ARM_r8, &sf->uc.uc_mcontext.arm_r8, err);
      __put_user_error(regs->ARM_r9, &sf->uc.uc_mcontext.arm_r9, err);
      __put_user_error(regs->ARM_r10, &sf->uc.uc_mcontext.arm_r10, err);
      __put_user_error(regs->ARM_fp, &sf->uc.uc_mcontext.arm_fp, err);
      __put_user_error(regs->ARM_ip, &sf->uc.uc_mcontext.arm_ip, err);
      __put_user_error(regs->ARM_sp, &sf->uc.uc_mcontext.arm_sp, err);
      __put_user_error(regs->ARM_lr, &sf->uc.uc_mcontext.arm_lr, err);
      __put_user_error(regs->ARM_pc, &sf->uc.uc_mcontext.arm_pc, err);
      __put_user_error(regs->ARM_cpsr, &sf->uc.uc_mcontext.arm_cpsr, err);

      __put_user_error(current->thread.trap_no, &sf->uc.uc_mcontext.trap_no, err);
      __put_user_error(current->thread.error_code, &sf->uc.uc_mcontext.error_code, err);
      __put_user_error(current->thread.address, &sf->uc.uc_mcontext.fault_address, err);
      __put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);

      err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));

      aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
#ifdef CONFIG_CRUNCH
      if (err == 0)
            err |= preserve_crunch_context(&aux->crunch);
#endif
#ifdef CONFIG_IWMMXT
      if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
            err |= preserve_iwmmxt_context(&aux->iwmmxt);
#endif
#ifdef CONFIG_VFP
      if (err == 0)
            err |= preserve_vfp_context(&aux->vfp);
#endif
      __put_user_error(0, &aux->end_magic, err);

      return err;
}

static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, int framesize)
{
      unsigned long sp = regs->ARM_sp;
      void __user *frame;

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

      /*
       * ATPCS B01 mandates 8-byte alignment
       */
      frame = (void __user *)((sp - framesize) & ~7);

      /*
       * Check that we can actually write to the signal frame.
       */
      if (!access_ok(VERIFY_WRITE, frame, framesize))
            frame = NULL;

      return frame;
}

static int
setup_return(struct pt_regs *regs, struct k_sigaction *ka,
           unsigned long __user *rc, void __user *frame, int usig)
{
      unsigned long handler = (unsigned long)ka->sa.sa_handler;
      unsigned long retcode;
      int thumb = 0;
      unsigned long cpsr = regs->ARM_cpsr & ~PSR_f;

      /*
       * Maybe we need to deliver a 32-bit signal to a 26-bit task.
       */
      if (ka->sa.sa_flags & SA_THIRTYTWO)
            cpsr = (cpsr & ~MODE_MASK) | USR_MODE;

#ifdef CONFIG_ARM_THUMB
      if (elf_hwcap & HWCAP_THUMB) {
            /*
             * The LSB of the handler determines if we're going to
             * be using THUMB or ARM mode for this signal handler.
             */
            thumb = handler & 1;

            if (thumb) {
                  cpsr |= PSR_T_BIT;
#if __LINUX_ARM_ARCH__ >= 7
                  /* clear the If-Then Thumb-2 execution state */
                  cpsr &= ~PSR_IT_MASK;
#endif
            } else
                  cpsr &= ~PSR_T_BIT;
      }
#endif

      if (ka->sa.sa_flags & SA_RESTORER) {
            retcode = (unsigned long)ka->sa.sa_restorer;
      } else {
            unsigned int idx = thumb << 1;

            if (ka->sa.sa_flags & SA_SIGINFO)
                  idx += 3;

            if (__put_user(sigreturn_codes[idx],   rc) ||
                __put_user(sigreturn_codes[idx+1], rc+1))
                  return 1;

            if (cpsr & MODE32_BIT) {
                  /*
                   * 32-bit code can use the new high-page
                   * signal return code support.
                   */
                  retcode = KERN_SIGRETURN_CODE + (idx << 2) + thumb;
            } else {
                  /*
                   * Ensure that the instruction cache sees
                   * the return code written onto the stack.
                   */
                  flush_icache_range((unsigned long)rc,
                                 (unsigned long)(rc + 2));

                  retcode = ((unsigned long)rc) + thumb;
            }
      }

      regs->ARM_r0 = usig;
      regs->ARM_sp = (unsigned long)frame;
      regs->ARM_lr = retcode;
      regs->ARM_pc = handler;
      regs->ARM_cpsr = cpsr;

      return 0;
}

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

      if (!frame)
            return 1;

      /*
       * Set uc.uc_flags to a value which sc.trap_no would never have.
       */
      __put_user_error(0x5ac3c35a, &frame->uc.uc_flags, err);

      err |= setup_sigframe(frame, regs, set);
      if (err == 0)
            err = setup_return(regs, ka, frame->retcode, frame, usig);

      return err;
}

static int
setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
             sigset_t *set, struct pt_regs *regs)
{
      struct rt_sigframe __user *frame = get_sigframe(ka, regs, sizeof(*frame));
      stack_t stack;
      int err = 0;

      if (!frame)
            return 1;

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

      __put_user_error(0, &frame->sig.uc.uc_flags, err);
      __put_user_error(NULL, &frame->sig.uc.uc_link, err);

      memset(&stack, 0, sizeof(stack));
      stack.ss_sp = (void __user *)current->sas_ss_sp;
      stack.ss_flags = sas_ss_flags(regs->ARM_sp);
      stack.ss_size = current->sas_ss_size;
      err |= __copy_to_user(&frame->sig.uc.uc_stack, &stack, sizeof(stack));

      err |= setup_sigframe(&frame->sig, regs, set);
      if (err == 0)
            err = setup_return(regs, ka, frame->sig.retcode, frame, usig);

      if (err == 0) {
            /*
             * For realtime signals we must also set the second and third
             * arguments for the signal handler.
             *   -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
             */
            regs->ARM_r1 = (unsigned long)&frame->info;
            regs->ARM_r2 = (unsigned long)&frame->sig.uc;
      }

      return err;
}

static inline void setup_syscall_restart(struct pt_regs *regs)
{
      regs->ARM_r0 = regs->ARM_ORIG_r0;
      regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
}

/*
 * 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 syscall)
{
      struct thread_info *thread = current_thread_info();
      struct task_struct *tsk = current;
      int usig = sig;
      int ret;

      /*
       * If we were from a system call, check for system call restarting...
       */
      if (syscall) {
            switch (regs->ARM_r0) {
            case -ERESTART_RESTARTBLOCK:
            case -ERESTARTNOHAND:
                  regs->ARM_r0 = -EINTR;
                  break;
            case -ERESTARTSYS:
                  if (!(ka->sa.sa_flags & SA_RESTART)) {
                        regs->ARM_r0 = -EINTR;
                        break;
                  }
                  /* fallthrough */
            case -ERESTARTNOINTR:
                  setup_syscall_restart(regs);
            }
      }

      /*
       * translate the signal
       */
      if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
            usig = thread->exec_domain->signal_invmap[usig];

      /*
       * Set up the stack frame
       */
      if (ka->sa.sa_flags & SA_SIGINFO)
            ret = setup_rt_frame(usig, ka, info, oldset, regs);
      else
            ret = setup_frame(usig, ka, oldset, regs);

      /*
       * Check that the resulting registers are actually sane.
       */
      ret |= !valid_user_regs(regs);

      if (ret != 0) {
            force_sigsegv(sig, tsk);
            return ret;
      }

      /*
       * Block the signal if we were successful.
       */
      spin_lock_irq(&tsk->sighand->siglock);
      sigorsets(&tsk->blocked, &tsk->blocked,
              &ka->sa.sa_mask);
      if (!(ka->sa.sa_flags & SA_NODEFER))
            sigaddset(&tsk->blocked, sig);
      recalc_sigpending();
      spin_unlock_irq(&tsk->sighand->siglock);

      return 0;
}

/*
 * 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 syscall)
{
      struct k_sigaction ka;
      siginfo_t info;
      int signr;

      /*
       * 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;

      single_step_clear(current);

      signr = get_signal_to_deliver(&info, &ka, regs, NULL);
      if (signr > 0) {
            sigset_t *oldset;

            if (test_thread_flag(TIF_RESTORE_SIGMASK))
                  oldset = &current->saved_sigmask;
            else
                  oldset = &current->blocked;
            if (handle_signal(signr, &ka, &info, oldset, regs, syscall) == 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);
            }
            single_step_set(current);
            return;
      }

 no_signal:
      /*
       * No signal to deliver to the process - restart the syscall.
       */
      if (syscall) {
            if (regs->ARM_r0 == -ERESTART_RESTARTBLOCK) {
                  if (thumb_mode(regs)) {
                        regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE;
                        regs->ARM_pc -= 2;
                  } else {
#if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT)
                        regs->ARM_r7 = __NR_restart_syscall;
                        regs->ARM_pc -= 4;
#else
                        u32 __user *usp;

                        regs->ARM_sp -= 4;
                        usp = (u32 __user *)regs->ARM_sp;

                        if (put_user(regs->ARM_pc, usp) == 0) {
                              regs->ARM_pc = KERN_RESTART_CODE;
                        } else {
                              regs->ARM_sp += 4;
                              force_sigsegv(0, current);
                        }
#endif
                  }
            }
            if (regs->ARM_r0 == -ERESTARTNOHAND ||
                regs->ARM_r0 == -ERESTARTSYS ||
                regs->ARM_r0 == -ERESTARTNOINTR) {
                  setup_syscall_restart(regs);
            }

            /* 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);
            }
      }
      single_step_set(current);
}

asmlinkage void
do_notify_resume(struct pt_regs *regs, unsigned int thread_flags, int syscall)
{
      if (thread_flags & _TIF_SIGPENDING)
            do_signal(regs, syscall);

      if (thread_flags & _TIF_NOTIFY_RESUME) {
            clear_thread_flag(TIF_NOTIFY_RESUME);
            tracehook_notify_resume(regs);
            if (current->replacement_session_keyring)
                  key_replace_session_keyring();
      }
}

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