text: /*
   *  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/random.h>
  #include <linux/signal.h>
  #include <linux/personality.h>
  #include <linux/uaccess.h>
  #include <linux/tracehook.h>
  #include <linux/uprobes.h>
  #include <linux/syscalls.h>
  
  #include <asm/elf.h>
  #include <asm/cacheflush.h>
  #include <asm/traps.h>
  #include <asm/ucontext.h>
  #include <asm/unistd.h>
  #include <asm/vfp.h>
  
  extern const unsigned long sigreturn_codes[7];
  
  static unsigned long signal_return_offset;
  
  #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(char __user **auxp)
  {
  	struct crunch_sigframe __user *frame =
  		(struct crunch_sigframe __user *)*auxp;
  	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;
  	*auxp += CRUNCH_STORAGE_SIZE;
  	crunch_task_restore(current_thread_info(), &kframe->storage);
  	return 0;
  }
  #endif
  
  #ifdef CONFIG_IWMMXT
  
  static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
  {
  	char kbuf[sizeof(*frame) + 8];
  	struct iwmmxt_sigframe *kframe;
  	int err = 0;
  
  	/* the iWMMXt context must be 64 bit aligned */
  	kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
  
  	if (test_thread_flag(TIF_USING_IWMMXT)) {
  		kframe->magic = IWMMXT_MAGIC;
  		kframe->size = IWMMXT_STORAGE_SIZE;
  		iwmmxt_task_copy(current_thread_info(), &kframe->storage);
  
  		err = __copy_to_user(frame, kframe, sizeof(*frame));
  	} else {
  		/*
  		 * For bug-compatibility with older kernels, some space
  		 * has to be reserved for iWMMXt even if it's not used.
  		 * Set the magic and size appropriately so that properly
  		 * written userspace can skip it reliably:
  		 */
  		__put_user_error(DUMMY_MAGIC, &frame->magic, err);
  		__put_user_error(IWMMXT_STORAGE_SIZE, &frame->size, err);
  	}
  
  	return err;
  }
  
  static int restore_iwmmxt_context(char __user **auxp)
  {
  	struct iwmmxt_sigframe __user *frame =
  		(struct iwmmxt_sigframe __user *)*auxp;
  	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;
  
  	/*
  	 * For non-iWMMXt threads: a single iwmmxt_sigframe-sized dummy
  	 * block is discarded for compatibility with setup_sigframe() if
  	 * present, but we don't mandate its presence.  If some other
  	 * magic is here, it's not for us:
  	 */
  	if (!test_thread_flag(TIF_USING_IWMMXT) &&
  	    kframe->magic != DUMMY_MAGIC)
  		return 0;
  
  	if (kframe->size != IWMMXT_STORAGE_SIZE)
  		return -1;
  
  	if (test_thread_flag(TIF_USING_IWMMXT)) {
  		if (kframe->magic != IWMMXT_MAGIC)
  			return -1;
  
  		iwmmxt_task_restore(current_thread_info(), &kframe->storage);
  	}
  
  	*auxp += IWMMXT_STORAGE_SIZE;
  	return 0;
  }
  
  #endif
  
  #ifdef CONFIG_VFP
  
  static int preserve_vfp_context(struct vfp_sigframe __user *frame)
  {
  	const unsigned long magic = VFP_MAGIC;
  	const unsigned long size = VFP_STORAGE_SIZE;
  	int err = 0;
  
  	__put_user_error(magic, &frame->magic, err);
  	__put_user_error(size, &frame->size, err);
  
  	if (err)
  		return -EFAULT;
  
  	return vfp_preserve_user_clear_hwstate(&frame->ufp, &frame->ufp_exc);
  }
  
  static int restore_vfp_context(char __user **auxp)
  {
  	struct vfp_sigframe frame;
  	int err;
  
  	err = __copy_from_user(&frame, *auxp, sizeof(frame));
  	if (err)
  		return err;
  
  	if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE)
  		return -EINVAL;
  
  	*auxp += sizeof(frame);
  	return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc);
  }
  
  #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 sigcontext context;
  	char __user *aux;
  	sigset_t set;
  	int err;
  
  	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
  	if (err == 0)
  		set_current_blocked(&set);
  
  	err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
  	if (err == 0) {
  		regs->ARM_r0 = context.arm_r0;
  		regs->ARM_r1 = context.arm_r1;
  		regs->ARM_r2 = context.arm_r2;
  		regs->ARM_r3 = context.arm_r3;
  		regs->ARM_r4 = context.arm_r4;
  		regs->ARM_r5 = context.arm_r5;
  		regs->ARM_r6 = context.arm_r6;
  		regs->ARM_r7 = context.arm_r7;
  		regs->ARM_r8 = context.arm_r8;
  		regs->ARM_r9 = context.arm_r9;
  		regs->ARM_r10 = context.arm_r10;
  		regs->ARM_fp = context.arm_fp;
  		regs->ARM_ip = context.arm_ip;
  		regs->ARM_sp = context.arm_sp;
  		regs->ARM_lr = context.arm_lr;
  		regs->ARM_pc = context.arm_pc;
  		regs->ARM_cpsr = context.arm_cpsr;
  	}
  
  	err |= !valid_user_regs(regs);
  
  	aux = (char __user *) sf->uc.uc_regspace;
  #ifdef CONFIG_CRUNCH
  	if (err == 0)
  		err |= restore_crunch_context(&aux);
  #endif
  #ifdef CONFIG_IWMMXT
  	if (err == 0)
  		err |= restore_iwmmxt_context(&aux);
  #endif
  #ifdef CONFIG_VFP
  	if (err == 0)
  		err |= restore_vfp_context(&aux);
  #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->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;
  
  	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->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 (restore_altstack(&frame->sig.uc.uc_stack))
  		goto badframe;
  
  	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)
  		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 ksignal *ksig, struct pt_regs *regs, int framesize)
  {
  	unsigned long sp = sigsp(regs->ARM_sp, ksig);
  	void __user *frame;
  
  	/*
  	 * 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 ksignal *ksig,
  	     unsigned long __user *rc, void __user *frame)
  {
  	unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
  	unsigned long retcode;
  	int thumb = 0;
  	unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
  
  	cpsr |= PSR_ENDSTATE;
  
  	/*
  	 * Maybe we need to deliver a 32-bit signal to a 26-bit task.
  	 */
  	if (ksig->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;
  
  		/*
  		 * Clear the If-Then Thumb-2 execution state.  ARM spec
  		 * requires this to be all 000s in ARM mode.  Snapdragon
  		 * S4/Krait misbehaves on a Thumb=>ARM signal transition
  		 * without this.
  		 *
  		 * We must do this whenever we are running on a Thumb-2
  		 * capable CPU, which includes ARMv6T2.  However, we elect
  		 * to always do this to simplify the code; this field is
  		 * marked UNK/SBZP for older architectures.
  		 */
  		cpsr &= ~PSR_IT_MASK;
  
  		if (thumb) {
  			cpsr |= PSR_T_BIT;
  		} else
  			cpsr &= ~PSR_T_BIT;
  	}
  #endif
  
  	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
  		retcode = (unsigned long)ksig->ka.sa.sa_restorer;
  	} else {
  		unsigned int idx = thumb << 1;
  
  		if (ksig->ka.sa.sa_flags & SA_SIGINFO)
  			idx += 3;
  
  		/*
  		 * Put the sigreturn code on the stack no matter which return
  		 * mechanism we use in order to remain ABI compliant
  		 */
  		if (__put_user(sigreturn_codes[idx],   rc) ||
  		    __put_user(sigreturn_codes[idx+1], rc+1))
  			return 1;
  
  #ifdef CONFIG_MMU
  		if (cpsr & MODE32_BIT) {
  			struct mm_struct *mm = current->mm;
  
  			/*
  			 * 32-bit code can use the signal return page
  			 * except when the MPU has protected the vectors
  			 * page from PL0
  			 */
  			retcode = mm->context.sigpage + signal_return_offset +
  				  (idx << 2) + thumb;
  		} else
  #endif
  		{
  			/*
  			 * 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 = ksig->sig;
  	regs->ARM_sp = (unsigned long)frame;
  	regs->ARM_lr = retcode;
  	regs->ARM_pc = handler;
  	regs->ARM_cpsr = cpsr;
  
  	return 0;
  }
  
  static int
  setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
  {
  	struct sigframe __user *frame = get_sigframe(ksig, 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, ksig, frame->retcode, frame);
  
  	return err;
  }
  
  static int
  setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
  {
  	struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
  	int err = 0;
  
  	if (!frame)
  		return 1;
  
  	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
  
  	__put_user_error(0, &frame->sig.uc.uc_flags, err);
  	__put_user_error(NULL, &frame->sig.uc.uc_link, err);
  
  	err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
  	err |= setup_sigframe(&frame->sig, regs, set);
  	if (err == 0)
  		err = setup_return(regs, ksig, frame->sig.retcode, frame);
  
  	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;
  }
  
  /*
   * OK, we're invoking a handler
   */	
  static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
  {
  	sigset_t *oldset = sigmask_to_save();
  	int ret;
  
  	/*
  	 * Set up the stack frame
  	 */
  	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
  		ret = setup_rt_frame(ksig, oldset, regs);
  	else
  		ret = setup_frame(ksig, oldset, regs);
  
  	/*
  	 * Check that the resulting registers are actually sane.
  	 */
  	ret |= !valid_user_regs(regs);
  
  	signal_setup_done(ret, ksig, 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 int do_signal(struct pt_regs *regs, int syscall)
  {
  	unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
  	struct ksignal ksig;
  	int restart = 0;
  
  	/*
  	 * If we were from a system call, check for system call restarting...
  	 */
  	if (syscall) {
  		continue_addr = regs->ARM_pc;
  		restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
  		retval = regs->ARM_r0;
  
  		/*
  		 * Prepare for system call restart.  We do this here so that a
  		 * debugger will see the already changed PSW.
  		 */
  		switch (retval) {
  		case -ERESTART_RESTARTBLOCK:
  			restart -= 2;
  		case -ERESTARTNOHAND:
  		case -ERESTARTSYS:
  		case -ERESTARTNOINTR:
  			restart++;
  			regs->ARM_r0 = regs->ARM_ORIG_r0;
  			regs->ARM_pc = restart_addr;
  			break;
  		}
  	}
  
  	/*
  	 * Get the signal to deliver.  When running under ptrace, at this
  	 * point the debugger may change all our registers ...
  	 */
  	/*
  	 * 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 (get_signal(&ksig)) {
  		/* handler */
  		if (unlikely(restart) && regs->ARM_pc == restart_addr) {
  			if (retval == -ERESTARTNOHAND ||
  			    retval == -ERESTART_RESTARTBLOCK
  			    || (retval == -ERESTARTSYS
  				&& !(ksig.ka.sa.sa_flags & SA_RESTART))) {
  				regs->ARM_r0 = -EINTR;
  				regs->ARM_pc = continue_addr;
  			}
  		}
  		handle_signal(&ksig, regs);
  	} else {
  		/* no handler */
  		restore_saved_sigmask();
  		if (unlikely(restart) && regs->ARM_pc == restart_addr) {
  			regs->ARM_pc = continue_addr;
  			return restart;
  		}
  	}
  	return 0;
  }
  
  asmlinkage int
  do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
  {
  	/*
  	 * The assembly code enters us with IRQs off, but it hasn't
  	 * informed the tracing code of that for efficiency reasons.
  	 * Update the trace code with the current status.
  	 */
  	trace_hardirqs_off();
  	do {
  		if (likely(thread_flags & _TIF_NEED_RESCHED)) {
  			schedule();
  		} else {
  			if (unlikely(!user_mode(regs)))
  				return 0;
  			local_irq_enable();
  			if (thread_flags & _TIF_SIGPENDING) {
  				int restart = do_signal(regs, syscall);
  				if (unlikely(restart)) {
  					/*
  					 * Restart without handlers.
  					 * Deal with it without leaving
  					 * the kernel space.
  					 */
  					return restart;
  				}
  				syscall = 0;
  			} else if (thread_flags & _TIF_UPROBE) {
  				uprobe_notify_resume(regs);
  			} else {
  				clear_thread_flag(TIF_NOTIFY_RESUME);
  				tracehook_notify_resume(regs);
  			}
  		}
  		local_irq_disable();
  		thread_flags = current_thread_info()->flags;
  	} while (thread_flags & _TIF_WORK_MASK);
  	return 0;
  }
  
  struct page *get_signal_page(void)
  {
  	unsigned long ptr;
  	unsigned offset;
  	struct page *page;
  	void *addr;
  
  	page = alloc_pages(GFP_KERNEL, 0);
  
  	if (!page)
  		return NULL;
  
  	addr = page_address(page);
  
  	/* Give the signal return code some randomness */
  	offset = 0x200 + (get_random_int() & 0x7fc);
  	signal_return_offset = offset;
  
  	/*
  	 * Copy signal return handlers into the vector page, and
  	 * set sigreturn to be a pointer to these.
  	 */
  	memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
  
  	ptr = (unsigned long)addr + offset;
  	flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
  
  	return page;
  }
  
  /* Defer to generic check */
  asmlinkage void addr_limit_check_failed(void)
  {
  	addr_limit_user_check();
  }
  