arch/arm64/kernel/signal.c - arm/linux-arm-legacy - Git at Google

 /*
  * Based on arch/arm/kernel/signal.c
  *
  * Copyright (C) 1995-2009 Russell King
  * Copyright (C) 2012 ARM Ltd.
  *
  * 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.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */

 #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 <linux/ratelimit.h>

 #include <asm/compat.h>
 #include <asm/debug-monitors.h>
 #include <asm/elf.h>
 #include <asm/cacheflush.h>
 #include <asm/ucontext.h>
 #include <asm/unistd.h>
 #include <asm/fpsimd.h>
 #include <asm/signal32.h>
 #include <asm/vdso.h>

 /*
  * Do a signal return; undo the signal stack. These are aligned to 128-bit.
  */
 struct rt_sigframe {
 	struct siginfo info;
 	struct ucontext uc;
 	u64 fp;
 	u64 lr;
 };

 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
 {
 	struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
 	int err;

 	/* dump the hardware registers to the fpsimd_state structure */
 	fpsimd_save_state(fpsimd);

 	/* copy the FP and status/control registers */
 	err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
 	__put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
 	__put_user_error(fpsimd->fpcr, &ctx->fpcr, err);

 	/* copy the magic/size information */
 	__put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
 	__put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);

 	return err ? -EFAULT : 0;
 }

 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
 {
 	struct fpsimd_state fpsimd;
 	__u32 magic, size;
 	int err = 0;

 	/* check the magic/size information */
 	__get_user_error(magic, &ctx->head.magic, err);
 	__get_user_error(size, &ctx->head.size, err);
 	if (err)
 		return -EFAULT;
 	if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
 		return -EINVAL;

 	/* copy the FP and status/control registers */
 	err = __copy_from_user(fpsimd.vregs, ctx->vregs,
 			       sizeof(fpsimd.vregs));
 	__get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
 	__get_user_error(fpsimd.fpcr, &ctx->fpcr, err);

 	/* load the hardware registers from the fpsimd_state structure */
 	if (!err) {
 		preempt_disable();
 		fpsimd_load_state(&fpsimd);
 		preempt_enable();
 	}

 	return err ? -EFAULT : 0;
 }

 static int restore_sigframe(struct pt_regs *regs,
 			    struct rt_sigframe __user *sf)
 {
 	sigset_t set;
 	int i, err;
 	struct aux_context __user *aux =
 		(struct aux_context __user *)sf->uc.uc_mcontext.__reserved;

 	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 	if (err == 0)
 		set_current_blocked(&set);

 	for (i = 0; i < 31; i++)
 		__get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 				 err);
 	__get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 	__get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 	__get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);

 	/*
 	 * Avoid sys_rt_sigreturn() restarting.
 	 */
 	regs->syscallno = ~0UL;

 	err |= !valid_user_regs(&regs->user_regs);

 	if (err == 0)
 		err |= restore_fpsimd_context(&aux->fpsimd);

 	return err;
 }

 asmlinkage long 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 128-bit boundary, then 'sp' should
 	 * be word aligned here.
 	 */
 	if (regs->sp & 15)
 		goto badframe;

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

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

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

 	if (restore_altstack(&frame->uc.uc_stack))
 		goto badframe;

 	return regs->regs[0];

 badframe:
 	if (show_unhandled_signals)
 		pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
 				    current->comm, task_pid_nr(current), __func__,
 				    regs->pc, regs->sp);
 	force_sig(SIGSEGV, current);
 	return 0;
 }

 static int setup_sigframe(struct rt_sigframe __user *sf,
 			  struct pt_regs *regs, sigset_t *set)
 {
 	int i, err = 0;
 	struct aux_context __user *aux =
 		(struct aux_context __user *)sf->uc.uc_mcontext.__reserved;

 	/* set up the stack frame for unwinding */
 	__put_user_error(regs->regs[29], &sf->fp, err);
 	__put_user_error(regs->regs[30], &sf->lr, err);

 	for (i = 0; i < 31; i++)
 		__put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 				 err);
 	__put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 	__put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 	__put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);

 	__put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);

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

 	if (err == 0)
 		err |= preserve_fpsimd_context(&aux->fpsimd);

 	/* set the "end" magic */
 	__put_user_error(0, &aux->end.magic, err);
 	__put_user_error(0, &aux->end.size, err);

 	return err;
 }

 static struct rt_sigframe __user *get_sigframe(struct k_sigaction *ka,
 					       struct pt_regs *regs)
 {
 	unsigned long sp, sp_top;
 	struct rt_sigframe __user *frame;

 	sp = sp_top = regs->sp;

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

 	sp = (sp - sizeof(struct rt_sigframe)) & ~15;
 	frame = (struct rt_sigframe __user *)sp;

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

 	return frame;
 }

 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 			 void __user *frame, int usig)
 {
 	__sigrestore_t sigtramp;

 	regs->regs[0] = usig;
 	regs->sp = (unsigned long)frame;
 	regs->regs[29] = regs->sp + offsetof(struct rt_sigframe, fp);
 	regs->pc = (unsigned long)ka->sa.sa_handler;

 	if (ka->sa.sa_flags & SA_RESTORER)
 		sigtramp = ka->sa.sa_restorer;
 	else
 		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);

 	regs->regs[30] = (unsigned long)sigtramp;
 }

 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;
 	int err = 0;

 	frame = get_sigframe(ka, regs);
 	if (!frame)
 		return 1;

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

 	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 	err |= setup_sigframe(frame, regs, set);
 	if (err == 0) {
 		setup_return(regs, ka, frame, usig);
 		if (ka->sa.sa_flags & SA_SIGINFO) {
 			err |= copy_siginfo_to_user(&frame->info, info);
 			regs->regs[1] = (unsigned long)&frame->info;
 			regs->regs[2] = (unsigned long)&frame->uc;
 		}
 	}

 	return err;
 }

 static void setup_restart_syscall(struct pt_regs *regs)
 {
 	if (is_compat_task())
 		compat_setup_restart_syscall(regs);
 	else
 		regs->regs[8] = __NR_restart_syscall;
 }

 /*
  * OK, we're invoking a handler
  */
 static void handle_signal(unsigned long sig, struct k_sigaction *ka,
 			  siginfo_t *info, struct pt_regs *regs)
 {
 	struct thread_info *thread = current_thread_info();
 	struct task_struct *tsk = current;
 	sigset_t *oldset = sigmask_to_save();
 	int usig = sig;
 	int ret;

 	/*
 	 * 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 (is_compat_task()) {
 		if (ka->sa.sa_flags & SA_SIGINFO)
 			ret = compat_setup_rt_frame(usig, ka, info, oldset,
 						    regs);
 		else
 			ret = compat_setup_frame(usig, ka, oldset, regs);
 	} else {
 		ret = setup_rt_frame(usig, ka, info, oldset, regs);
 	}

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

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

 	/*
 	 * Fast forward the stepping logic so we step into the signal
 	 * handler.
 	 */
 	user_fastforward_single_step(tsk);

 	signal_delivered(sig, info, ka, regs, 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)
 {
 	unsigned long continue_addr = 0, restart_addr = 0;
 	struct k_sigaction ka;
 	siginfo_t info;
 	int signr, retval = 0;
 	int syscall = (int)regs->syscallno;

 	/*
 	 * If we were from a system call, check for system call restarting...
 	 */
 	if (syscall >= 0) {
 		continue_addr = regs->pc;
 		restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 		retval = regs->regs[0];

 		/*
 		 * Avoid additional syscall restarting via ret_to_user.
 		 */
 		regs->syscallno = ~0UL;

 		/*
 		 * Prepare for system call restart. We do this here so that a
 		 * debugger will see the already changed PC.
 		 */
 		switch (retval) {
 		case -ERESTARTNOHAND:
 		case -ERESTARTSYS:
 		case -ERESTARTNOINTR:
 		case -ERESTART_RESTARTBLOCK:
 			regs->regs[0] = regs->orig_x0;
 			regs->pc = restart_addr;
 			break;
 		}
 	}

 	/*
 	 * Get the signal to deliver. When running under ptrace, at this point
 	 * the debugger may change all of our registers.
 	 */
 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 	if (signr > 0) {
 		/*
 		 * Depending on the signal settings, we may need to revert the
 		 * decision to restart the system call, but skip this if a
 		 * debugger has chosen to restart at a different PC.
 		 */
 		if (regs->pc == restart_addr &&
 		    (retval == -ERESTARTNOHAND ||
 		     retval == -ERESTART_RESTARTBLOCK ||
 		     (retval == -ERESTARTSYS &&
 		      !(ka.sa.sa_flags & SA_RESTART)))) {
 			regs->regs[0] = -EINTR;
 			regs->pc = continue_addr;
 		}

 		handle_signal(signr, &ka, &info, regs);
 		return;
 	}

 	/*
 	 * Handle restarting a different system call. As above, if a debugger
 	 * has chosen to restart at a different PC, ignore the restart.
 	 */
 	if (syscall >= 0 && regs->pc == restart_addr) {
 		if (retval == -ERESTART_RESTARTBLOCK)
 			setup_restart_syscall(regs);
 		user_rewind_single_step(current);
 	}

 	restore_saved_sigmask();
 }

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

 	if (thread_flags & _TIF_NOTIFY_RESUME) {
 		clear_thread_flag(TIF_NOTIFY_RESUME);
 		tracehook_notify_resume(regs);
 	}
 }
	/*
	* Based on arch/arm/kernel/signal.c
	*
	* Copyright (C) 1995-2009 Russell King
	* Copyright (C) 2012 ARM Ltd.
	*
	* 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.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	*/

	#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 <linux/ratelimit.h>

	#include <asm/compat.h>
	#include <asm/debug-monitors.h>
	#include <asm/elf.h>
	#include <asm/cacheflush.h>
	#include <asm/ucontext.h>
	#include <asm/unistd.h>
	#include <asm/fpsimd.h>
	#include <asm/signal32.h>
	#include <asm/vdso.h>

	/*
	* Do a signal return; undo the signal stack. These are aligned to 128-bit.
	*/
	struct rt_sigframe {
	struct siginfo info;
	struct ucontext uc;
	u64 fp;
	u64 lr;
	};

	static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
	{
	struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
	int err;

	/* dump the hardware registers to the fpsimd_state structure */
	fpsimd_save_state(fpsimd);

	/* copy the FP and status/control registers */
	err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
	__put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
	__put_user_error(fpsimd->fpcr, &ctx->fpcr, err);

	/* copy the magic/size information */
	__put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
	__put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);

	return err ? -EFAULT : 0;
	}

	static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
	{
	struct fpsimd_state fpsimd;
	__u32 magic, size;
	int err = 0;

	/* check the magic/size information */
	__get_user_error(magic, &ctx->head.magic, err);
	__get_user_error(size, &ctx->head.size, err);
	if (err)
	return -EFAULT;
	if (magic != FPSIMD_MAGIC \|\| size != sizeof(struct fpsimd_context))
	return -EINVAL;

	/* copy the FP and status/control registers */
	err = __copy_from_user(fpsimd.vregs, ctx->vregs,
	sizeof(fpsimd.vregs));
	__get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
	__get_user_error(fpsimd.fpcr, &ctx->fpcr, err);

	/* load the hardware registers from the fpsimd_state structure */
	if (!err) {
	preempt_disable();
	fpsimd_load_state(&fpsimd);
	preempt_enable();
	}

	return err ? -EFAULT : 0;
	}

	static int restore_sigframe(struct pt_regs *regs,
	struct rt_sigframe __user *sf)
	{
	sigset_t set;
	int i, err;
	struct aux_context __user *aux =
	(struct aux_context __user *)sf->uc.uc_mcontext.__reserved;

	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
	if (err == 0)
	set_current_blocked(&set);

	for (i = 0; i < 31; i++)
	__get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
	err);
	__get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
	__get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
	__get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);

	/*
	* Avoid sys_rt_sigreturn() restarting.
	*/
	regs->syscallno = ~0UL;

	err \|= !valid_user_regs(&regs->user_regs);

	if (err == 0)
	err \|= restore_fpsimd_context(&aux->fpsimd);

	return err;
	}

	asmlinkage long 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 128-bit boundary, then 'sp' should
	* be word aligned here.
	*/
	if (regs->sp & 15)
	goto badframe;

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

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

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

	if (restore_altstack(&frame->uc.uc_stack))
	goto badframe;

	return regs->regs[0];

	badframe:
	if (show_unhandled_signals)
	pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
	current->comm, task_pid_nr(current), __func__,
	regs->pc, regs->sp);
	force_sig(SIGSEGV, current);
	return 0;
	}

	static int setup_sigframe(struct rt_sigframe __user *sf,
	struct pt_regs regs, sigset_t set)
	{
	int i, err = 0;
	struct aux_context __user *aux =
	(struct aux_context __user *)sf->uc.uc_mcontext.__reserved;

	/* set up the stack frame for unwinding */
	__put_user_error(regs->regs[29], &sf->fp, err);
	__put_user_error(regs->regs[30], &sf->lr, err);

	for (i = 0; i < 31; i++)
	__put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
	err);
	__put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
	__put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
	__put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);

	__put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);

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

	if (err == 0)
	err \|= preserve_fpsimd_context(&aux->fpsimd);

	/* set the "end" magic */
	__put_user_error(0, &aux->end.magic, err);
	__put_user_error(0, &aux->end.size, err);

	return err;
	}

	static struct rt_sigframe __user get_sigframe(struct k_sigaction ka,
	struct pt_regs *regs)
	{
	unsigned long sp, sp_top;
	struct rt_sigframe __user *frame;

	sp = sp_top = regs->sp;

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

	sp = (sp - sizeof(struct rt_sigframe)) & ~15;
	frame = (struct rt_sigframe __user *)sp;

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

	return frame;
	}

	static void setup_return(struct pt_regs regs, struct k_sigaction ka,
	void __user *frame, int usig)
	{
	__sigrestore_t sigtramp;

	regs->regs[0] = usig;
	regs->sp = (unsigned long)frame;
	regs->regs[29] = regs->sp + offsetof(struct rt_sigframe, fp);
	regs->pc = (unsigned long)ka->sa.sa_handler;

	if (ka->sa.sa_flags & SA_RESTORER)
	sigtramp = ka->sa.sa_restorer;
	else
	sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);

	regs->regs[30] = (unsigned long)sigtramp;
	}

	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;
	int err = 0;

	frame = get_sigframe(ka, regs);
	if (!frame)
	return 1;

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

	err \|= __save_altstack(&frame->uc.uc_stack, regs->sp);
	err \|= setup_sigframe(frame, regs, set);
	if (err == 0) {
	setup_return(regs, ka, frame, usig);
	if (ka->sa.sa_flags & SA_SIGINFO) {
	err \|= copy_siginfo_to_user(&frame->info, info);
	regs->regs[1] = (unsigned long)&frame->info;
	regs->regs[2] = (unsigned long)&frame->uc;
	}
	}

	return err;
	}

	static void setup_restart_syscall(struct pt_regs *regs)
	{
	if (is_compat_task())
	compat_setup_restart_syscall(regs);
	else
	regs->regs[8] = __NR_restart_syscall;
	}

	/*
	* OK, we're invoking a handler
	*/
	static void handle_signal(unsigned long sig, struct k_sigaction *ka,
	siginfo_t info, struct pt_regs regs)
	{
	struct thread_info *thread = current_thread_info();
	struct task_struct *tsk = current;
	sigset_t *oldset = sigmask_to_save();
	int usig = sig;
	int ret;

	/*
	* 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 (is_compat_task()) {
	if (ka->sa.sa_flags & SA_SIGINFO)
	ret = compat_setup_rt_frame(usig, ka, info, oldset,
	regs);
	else
	ret = compat_setup_frame(usig, ka, oldset, regs);
	} else {
	ret = setup_rt_frame(usig, ka, info, oldset, regs);
	}

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

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

	/*
	* Fast forward the stepping logic so we step into the signal
	* handler.
	*/
	user_fastforward_single_step(tsk);

	signal_delivered(sig, info, ka, regs, 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)
	{
	unsigned long continue_addr = 0, restart_addr = 0;
	struct k_sigaction ka;
	siginfo_t info;
	int signr, retval = 0;
	int syscall = (int)regs->syscallno;

	/*
	* If we were from a system call, check for system call restarting...
	*/
	if (syscall >= 0) {
	continue_addr = regs->pc;
	restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
	retval = regs->regs[0];

	/*
	* Avoid additional syscall restarting via ret_to_user.
	*/
	regs->syscallno = ~0UL;

	/*
	* Prepare for system call restart. We do this here so that a
	* debugger will see the already changed PC.
	*/
	switch (retval) {
	case -ERESTARTNOHAND:
	case -ERESTARTSYS:
	case -ERESTARTNOINTR:
	case -ERESTART_RESTARTBLOCK:
	regs->regs[0] = regs->orig_x0;
	regs->pc = restart_addr;
	break;
	}
	}

	/*
	* Get the signal to deliver. When running under ptrace, at this point
	* the debugger may change all of our registers.
	*/
	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
	if (signr > 0) {
	/*
	* Depending on the signal settings, we may need to revert the
	* decision to restart the system call, but skip this if a
	* debugger has chosen to restart at a different PC.
	*/
	if (regs->pc == restart_addr &&
	(retval == -ERESTARTNOHAND \|\|
	retval == -ERESTART_RESTARTBLOCK \|\|
	(retval == -ERESTARTSYS &&
	!(ka.sa.sa_flags & SA_RESTART)))) {
	regs->regs[0] = -EINTR;
	regs->pc = continue_addr;
	}

	handle_signal(signr, &ka, &info, regs);
	return;
	}

	/*
	* Handle restarting a different system call. As above, if a debugger
	* has chosen to restart at a different PC, ignore the restart.
	*/
	if (syscall >= 0 && regs->pc == restart_addr) {
	if (retval == -ERESTART_RESTARTBLOCK)
	setup_restart_syscall(regs);
	user_rewind_single_step(current);
	}

	restore_saved_sigmask();
	}

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

	if (thread_flags & _TIF_NOTIFY_RESUME) {
	clear_thread_flag(TIF_NOTIFY_RESUME);
	tracehook_notify_resume(regs);
	}
	}