arch/tile/kernel/process.c - linux - Git at Google

 /*
  * Copyright 2010 Tilera Corporation. All Rights Reserved.
  *
  *   This program is free software; you can redistribute it and/or
  *   modify it under the terms of the GNU General Public License
  *   as published by the Free Software Foundation, version 2.
  *
  *   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, GOOD TITLE or
  *   NON INFRINGEMENT.  See the GNU General Public License for
  *   more details.
  */

 #include <linux/sched.h>
 #include <linux/preempt.h>
 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/kprobes.h>
 #include <linux/elfcore.h>
 #include <linux/tick.h>
 #include <linux/init.h>
 #include <linux/mm.h>
 #include <linux/compat.h>
 #include <linux/hardirq.h>
 #include <linux/syscalls.h>
 #include <linux/kernel.h>
 #include <linux/tracehook.h>
 #include <linux/signal.h>
 #include <asm/stack.h>
 #include <asm/switch_to.h>
 #include <asm/homecache.h>
 #include <asm/syscalls.h>
 #include <asm/traps.h>
 #include <asm/setup.h>
 #ifdef CONFIG_HARDWALL
 #include <asm/hardwall.h>
 #endif
 #include <arch/chip.h>
 #include <arch/abi.h>
 #include <arch/sim_def.h>


 /*
  * Use the (x86) "idle=poll" option to prefer low latency when leaving the
  * idle loop over low power while in the idle loop, e.g. if we have
  * one thread per core and we want to get threads out of futex waits fast.
  */
 static int no_idle_nap;
 static int __init idle_setup(char *str)
 {
 	if (!str)
 		return -EINVAL;

 	if (!strcmp(str, "poll")) {
 		pr_info("using polling idle threads.\n");
 		no_idle_nap = 1;
 	} else if (!strcmp(str, "halt"))
 		no_idle_nap = 0;
 	else
 		return -1;

 	return 0;
 }
 early_param("idle", idle_setup);

 /*
  * The idle thread. There's no useful work to be
  * done, so just try to conserve power and have a
  * low exit latency (ie sit in a loop waiting for
  * somebody to say that they'd like to reschedule)
  */
 void cpu_idle(void)
 {
 	int cpu = smp_processor_id();


 	current_thread_info()->status |= TS_POLLING;

 	if (no_idle_nap) {
 		while (1) {
 			while (!need_resched())
 				cpu_relax();
 			schedule();
 		}
 	}

 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_idle_enter();
 		rcu_idle_enter();
 		while (!need_resched()) {
 			if (cpu_is_offline(cpu))
 				BUG();  /* no HOTPLUG_CPU */

 			local_irq_disable();
 			__get_cpu_var(irq_stat).idle_timestamp = jiffies;
 			current_thread_info()->status &= ~TS_POLLING;
 			/*
 			 * TS_POLLING-cleared state must be visible before we
 			 * test NEED_RESCHED:
 			 */
 			smp_mb();

 			if (!need_resched())
 				_cpu_idle();
 			else
 				local_irq_enable();
 			current_thread_info()->status |= TS_POLLING;
 		}
 		rcu_idle_exit();
 		tick_nohz_idle_exit();
 		schedule_preempt_disabled();
 	}
 }

 /*
  * Release a thread_info structure
  */
 void arch_release_thread_info(struct thread_info *info)
 {
 	struct single_step_state *step_state = info->step_state;

 #ifdef CONFIG_HARDWALL
 	/*
 	 * We free a thread_info from the context of the task that has
 	 * been scheduled next, so the original task is already dead.
 	 * Calling deactivate here just frees up the data structures.
 	 * If the task we're freeing held the last reference to a
 	 * hardwall fd, it would have been released prior to this point
 	 * anyway via exit_files(), and the hardwall_task.info pointers
 	 * would be NULL by now.
 	 */
 	hardwall_deactivate_all(info->task);
 #endif

 	if (step_state) {

 		/*
 		 * FIXME: we don't munmap step_state->buffer
 		 * because the mm_struct for this process (info->task->mm)
 		 * has already been zeroed in exit_mm().  Keeping a
 		 * reference to it here seems like a bad move, so this
 		 * means we can't munmap() the buffer, and therefore if we
 		 * ptrace multiple threads in a process, we will slowly
 		 * leak user memory.  (Note that as soon as the last
 		 * thread in a process dies, we will reclaim all user
 		 * memory including single-step buffers in the usual way.)
 		 * We should either assign a kernel VA to this buffer
 		 * somehow, or we should associate the buffer(s) with the
 		 * mm itself so we can clean them up that way.
 		 */
 		kfree(step_state);
 	}
 }

 static void save_arch_state(struct thread_struct *t);

 int copy_thread(unsigned long clone_flags, unsigned long sp,
 		unsigned long stack_size,
 		struct task_struct *p, struct pt_regs *regs)
 {
 	struct pt_regs *childregs;
 	unsigned long ksp;

 	/*
 	 * When creating a new kernel thread we pass sp as zero.
 	 * Assign it to a reasonable value now that we have the stack.
 	 */
 	if (sp == 0 && regs->ex1 == PL_ICS_EX1(KERNEL_PL, 0))
 		sp = KSTK_TOP(p);

 	/*
 	 * Do not clone step state from the parent; each thread
 	 * must make its own lazily.
 	 */
 	task_thread_info(p)->step_state = NULL;

 	/*
 	 * Start new thread in ret_from_fork so it schedules properly
 	 * and then return from interrupt like the parent.
 	 */
 	p->thread.pc = (unsigned long) ret_from_fork;

 	/* Save user stack top pointer so we can ID the stack vm area later. */
 	p->thread.usp0 = sp;

 	/* Record the pid of the process that created this one. */
 	p->thread.creator_pid = current->pid;

 	/*
 	 * Copy the registers onto the kernel stack so the
 	 * return-from-interrupt code will reload it into registers.
 	 */
 	childregs = task_pt_regs(p);
 	*childregs = *regs;
 	childregs->regs[0] = 0;         /* return value is zero */
 	childregs->sp = sp;  /* override with new user stack pointer */

 	/*
 	 * If CLONE_SETTLS is set, set "tp" in the new task to "r4",
 	 * which is passed in as arg #5 to sys_clone().
 	 */
 	if (clone_flags & CLONE_SETTLS)
 		childregs->tp = regs->regs[4];

 	/*
 	 * Copy the callee-saved registers from the passed pt_regs struct
 	 * into the context-switch callee-saved registers area.
 	 * This way when we start the interrupt-return sequence, the
 	 * callee-save registers will be correctly in registers, which
 	 * is how we assume the compiler leaves them as we start doing
 	 * the normal return-from-interrupt path after calling C code.
 	 * Zero out the C ABI save area to mark the top of the stack.
 	 */
 	ksp = (unsigned long) childregs;
 	ksp -= C_ABI_SAVE_AREA_SIZE;   /* interrupt-entry save area */
 	((long *)ksp)[0] = ((long *)ksp)[1] = 0;
 	ksp -= CALLEE_SAVED_REGS_COUNT * sizeof(unsigned long);
 	memcpy((void *)ksp, &regs->regs[CALLEE_SAVED_FIRST_REG],
 	       CALLEE_SAVED_REGS_COUNT * sizeof(unsigned long));
 	ksp -= C_ABI_SAVE_AREA_SIZE;   /* __switch_to() save area */
 	((long *)ksp)[0] = ((long *)ksp)[1] = 0;
 	p->thread.ksp = ksp;

 #if CHIP_HAS_TILE_DMA()
 	/*
 	 * No DMA in the new thread.  We model this on the fact that
 	 * fork() clears the pending signals, alarms, and aio for the child.
 	 */
 	memset(&p->thread.tile_dma_state, 0, sizeof(struct tile_dma_state));
 	memset(&p->thread.dma_async_tlb, 0, sizeof(struct async_tlb));
 #endif

 #if CHIP_HAS_SN_PROC()
 	/* Likewise, the new thread is not running static processor code. */
 	p->thread.sn_proc_running = 0;
 	memset(&p->thread.sn_async_tlb, 0, sizeof(struct async_tlb));
 #endif

 #if CHIP_HAS_PROC_STATUS_SPR()
 	/* New thread has its miscellaneous processor state bits clear. */
 	p->thread.proc_status = 0;
 #endif

 #ifdef CONFIG_HARDWALL
 	/* New thread does not own any networks. */
 	memset(&p->thread.hardwall[0], 0,
 	       sizeof(struct hardwall_task) * HARDWALL_TYPES);
 #endif


 	/*
 	 * Start the new thread with the current architecture state
 	 * (user interrupt masks, etc.).
 	 */
 	save_arch_state(&p->thread);

 	return 0;
 }

 /*
  * Return "current" if it looks plausible, or else a pointer to a dummy.
  * This can be helpful if we are just trying to emit a clean panic.
  */
 struct task_struct *validate_current(void)
 {
 	static struct task_struct corrupt = { .comm = "<corrupt>" };
 	struct task_struct *tsk = current;
 	if (unlikely((unsigned long)tsk < PAGE_OFFSET ||
 		     (high_memory && (void *)tsk > high_memory) ||
 		     ((unsigned long)tsk & (__alignof__(*tsk) - 1)) != 0)) {
 		pr_err("Corrupt 'current' %p (sp %#lx)\n", tsk, stack_pointer);
 		tsk = &corrupt;
 	}
 	return tsk;
 }

 /* Take and return the pointer to the previous task, for schedule_tail(). */
 struct task_struct *sim_notify_fork(struct task_struct *prev)
 {
 	struct task_struct *tsk = current;
 	__insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_FORK_PARENT |
 		     (tsk->thread.creator_pid << _SIM_CONTROL_OPERATOR_BITS));
 	__insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_FORK |
 		     (tsk->pid << _SIM_CONTROL_OPERATOR_BITS));
 	return prev;
 }

 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 {
 	struct pt_regs *ptregs = task_pt_regs(tsk);
 	elf_core_copy_regs(regs, ptregs);
 	return 1;
 }

 #if CHIP_HAS_TILE_DMA()

 /* Allow user processes to access the DMA SPRs */
 void grant_dma_mpls(void)
 {
 #if CONFIG_KERNEL_PL == 2
 	__insn_mtspr(SPR_MPL_DMA_CPL_SET_1, 1);
 	__insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_1, 1);
 #else
 	__insn_mtspr(SPR_MPL_DMA_CPL_SET_0, 1);
 	__insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_0, 1);
 #endif
 }

 /* Forbid user processes from accessing the DMA SPRs */
 void restrict_dma_mpls(void)
 {
 #if CONFIG_KERNEL_PL == 2
 	__insn_mtspr(SPR_MPL_DMA_CPL_SET_2, 1);
 	__insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_2, 1);
 #else
 	__insn_mtspr(SPR_MPL_DMA_CPL_SET_1, 1);
 	__insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_1, 1);
 #endif
 }

 /* Pause the DMA engine, then save off its state registers. */
 static void save_tile_dma_state(struct tile_dma_state *dma)
 {
 	unsigned long state = __insn_mfspr(SPR_DMA_USER_STATUS);
 	unsigned long post_suspend_state;

 	/* If we're running, suspend the engine. */
 	if ((state & DMA_STATUS_MASK) == SPR_DMA_STATUS__RUNNING_MASK)
 		__insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__SUSPEND_MASK);

 	/*
 	 * Wait for the engine to idle, then save regs.  Note that we
 	 * want to record the "running" bit from before suspension,
 	 * and the "done" bit from after, so that we can properly
 	 * distinguish a case where the user suspended the engine from
 	 * the case where the kernel suspended as part of the context
 	 * swap.
 	 */
 	do {
 		post_suspend_state = __insn_mfspr(SPR_DMA_USER_STATUS);
 	} while (post_suspend_state & SPR_DMA_STATUS__BUSY_MASK);

 	dma->src = __insn_mfspr(SPR_DMA_SRC_ADDR);
 	dma->src_chunk = __insn_mfspr(SPR_DMA_SRC_CHUNK_ADDR);
 	dma->dest = __insn_mfspr(SPR_DMA_DST_ADDR);
 	dma->dest_chunk = __insn_mfspr(SPR_DMA_DST_CHUNK_ADDR);
 	dma->strides = __insn_mfspr(SPR_DMA_STRIDE);
 	dma->chunk_size = __insn_mfspr(SPR_DMA_CHUNK_SIZE);
 	dma->byte = __insn_mfspr(SPR_DMA_BYTE);
 	dma->status = (state & SPR_DMA_STATUS__RUNNING_MASK) |
 		(post_suspend_state & SPR_DMA_STATUS__DONE_MASK);
 }

 /* Restart a DMA that was running before we were context-switched out. */
 static void restore_tile_dma_state(struct thread_struct *t)
 {
 	const struct tile_dma_state *dma = &t->tile_dma_state;

 	/*
 	 * The only way to restore the done bit is to run a zero
 	 * length transaction.
 	 */
 	if ((dma->status & SPR_DMA_STATUS__DONE_MASK) &&
 	    !(__insn_mfspr(SPR_DMA_USER_STATUS) & SPR_DMA_STATUS__DONE_MASK)) {
 		__insn_mtspr(SPR_DMA_BYTE, 0);
 		__insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
 		while (__insn_mfspr(SPR_DMA_USER_STATUS) &
 		       SPR_DMA_STATUS__BUSY_MASK)
 			;
 	}

 	__insn_mtspr(SPR_DMA_SRC_ADDR, dma->src);
 	__insn_mtspr(SPR_DMA_SRC_CHUNK_ADDR, dma->src_chunk);
 	__insn_mtspr(SPR_DMA_DST_ADDR, dma->dest);
 	__insn_mtspr(SPR_DMA_DST_CHUNK_ADDR, dma->dest_chunk);
 	__insn_mtspr(SPR_DMA_STRIDE, dma->strides);
 	__insn_mtspr(SPR_DMA_CHUNK_SIZE, dma->chunk_size);
 	__insn_mtspr(SPR_DMA_BYTE, dma->byte);

 	/*
 	 * Restart the engine if we were running and not done.
 	 * Clear a pending async DMA fault that we were waiting on return
 	 * to user space to execute, since we expect the DMA engine
 	 * to regenerate those faults for us now.  Note that we don't
 	 * try to clear the TIF_ASYNC_TLB flag, since it's relatively
 	 * harmless if set, and it covers both DMA and the SN processor.
 	 */
 	if ((dma->status & DMA_STATUS_MASK) == SPR_DMA_STATUS__RUNNING_MASK) {
 		t->dma_async_tlb.fault_num = 0;
 		__insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
 	}
 }

 #endif

 static void save_arch_state(struct thread_struct *t)
 {
 #if CHIP_HAS_SPLIT_INTR_MASK()
 	t->interrupt_mask = __insn_mfspr(SPR_INTERRUPT_MASK_0_0) |
 		((u64)__insn_mfspr(SPR_INTERRUPT_MASK_0_1) << 32);
 #else
 	t->interrupt_mask = __insn_mfspr(SPR_INTERRUPT_MASK_0);
 #endif
 	t->ex_context[0] = __insn_mfspr(SPR_EX_CONTEXT_0_0);
 	t->ex_context[1] = __insn_mfspr(SPR_EX_CONTEXT_0_1);
 	t->system_save[0] = __insn_mfspr(SPR_SYSTEM_SAVE_0_0);
 	t->system_save[1] = __insn_mfspr(SPR_SYSTEM_SAVE_0_1);
 	t->system_save[2] = __insn_mfspr(SPR_SYSTEM_SAVE_0_2);
 	t->system_save[3] = __insn_mfspr(SPR_SYSTEM_SAVE_0_3);
 	t->intctrl_0 = __insn_mfspr(SPR_INTCTRL_0_STATUS);
 #if CHIP_HAS_PROC_STATUS_SPR()
 	t->proc_status = __insn_mfspr(SPR_PROC_STATUS);
 #endif
 #if !CHIP_HAS_FIXED_INTVEC_BASE()
 	t->interrupt_vector_base = __insn_mfspr(SPR_INTERRUPT_VECTOR_BASE_0);
 #endif
 #if CHIP_HAS_TILE_RTF_HWM()
 	t->tile_rtf_hwm = __insn_mfspr(SPR_TILE_RTF_HWM);
 #endif
 #if CHIP_HAS_DSTREAM_PF()
 	t->dstream_pf = __insn_mfspr(SPR_DSTREAM_PF);
 #endif
 }

 static void restore_arch_state(const struct thread_struct *t)
 {
 #if CHIP_HAS_SPLIT_INTR_MASK()
 	__insn_mtspr(SPR_INTERRUPT_MASK_0_0, (u32) t->interrupt_mask);
 	__insn_mtspr(SPR_INTERRUPT_MASK_0_1, t->interrupt_mask >> 32);
 #else
 	__insn_mtspr(SPR_INTERRUPT_MASK_0, t->interrupt_mask);
 #endif
 	__insn_mtspr(SPR_EX_CONTEXT_0_0, t->ex_context[0]);
 	__insn_mtspr(SPR_EX_CONTEXT_0_1, t->ex_context[1]);
 	__insn_mtspr(SPR_SYSTEM_SAVE_0_0, t->system_save[0]);
 	__insn_mtspr(SPR_SYSTEM_SAVE_0_1, t->system_save[1]);
 	__insn_mtspr(SPR_SYSTEM_SAVE_0_2, t->system_save[2]);
 	__insn_mtspr(SPR_SYSTEM_SAVE_0_3, t->system_save[3]);
 	__insn_mtspr(SPR_INTCTRL_0_STATUS, t->intctrl_0);
 #if CHIP_HAS_PROC_STATUS_SPR()
 	__insn_mtspr(SPR_PROC_STATUS, t->proc_status);
 #endif
 #if !CHIP_HAS_FIXED_INTVEC_BASE()
 	__insn_mtspr(SPR_INTERRUPT_VECTOR_BASE_0, t->interrupt_vector_base);
 #endif
 #if CHIP_HAS_TILE_RTF_HWM()
 	__insn_mtspr(SPR_TILE_RTF_HWM, t->tile_rtf_hwm);
 #endif
 #if CHIP_HAS_DSTREAM_PF()
 	__insn_mtspr(SPR_DSTREAM_PF, t->dstream_pf);
 #endif
 }


 void _prepare_arch_switch(struct task_struct *next)
 {
 #if CHIP_HAS_SN_PROC()
 	int snctl;
 #endif
 #if CHIP_HAS_TILE_DMA()
 	struct tile_dma_state *dma = &current->thread.tile_dma_state;
 	if (dma->enabled)
 		save_tile_dma_state(dma);
 #endif
 #if CHIP_HAS_SN_PROC()
 	/*
 	 * Suspend the static network processor if it was running.
 	 * We do not suspend the fabric itself, just like we don't
 	 * try to suspend the UDN.
 	 */
 	snctl = __insn_mfspr(SPR_SNCTL);
 	current->thread.sn_proc_running =
 		(snctl & SPR_SNCTL__FRZPROC_MASK) == 0;
 	if (current->thread.sn_proc_running)
 		__insn_mtspr(SPR_SNCTL, snctl | SPR_SNCTL__FRZPROC_MASK);
 #endif
 }


 struct task_struct *__sched _switch_to(struct task_struct *prev,
 				       struct task_struct *next)
 {
 	/* DMA state is already saved; save off other arch state. */
 	save_arch_state(&prev->thread);

 #if CHIP_HAS_TILE_DMA()
 	/*
 	 * Restore DMA in new task if desired.
 	 * Note that it is only safe to restart here since interrupts
 	 * are disabled, so we can't take any DMATLB miss or access
 	 * interrupts before we have finished switching stacks.
 	 */
 	if (next->thread.tile_dma_state.enabled) {
 		restore_tile_dma_state(&next->thread);
 		grant_dma_mpls();
 	} else {
 		restrict_dma_mpls();
 	}
 #endif

 	/* Restore other arch state. */
 	restore_arch_state(&next->thread);

 #if CHIP_HAS_SN_PROC()
 	/*
 	 * Restart static network processor in the new process
 	 * if it was running before.
 	 */
 	if (next->thread.sn_proc_running) {
 		int snctl = __insn_mfspr(SPR_SNCTL);
 		__insn_mtspr(SPR_SNCTL, snctl & ~SPR_SNCTL__FRZPROC_MASK);
 	}
 #endif

 #ifdef CONFIG_HARDWALL
 	/* Enable or disable access to the network registers appropriately. */
 	hardwall_switch_tasks(prev, next);
 #endif

 	/*
 	 * Switch kernel SP, PC, and callee-saved registers.
 	 * In the context of the new task, return the old task pointer
 	 * (i.e. the task that actually called __switch_to).
 	 * Pass the value to use for SYSTEM_SAVE_K_0 when we reset our sp.
 	 */
 	return __switch_to(prev, next, next_current_ksp0(next));
 }

 /*
  * This routine is called on return from interrupt if any of the
  * TIF_WORK_MASK flags are set in thread_info->flags.  It is
  * entered with interrupts disabled so we don't miss an event
  * that modified the thread_info flags.  If any flag is set, we
  * handle it and return, and the calling assembly code will
  * re-disable interrupts, reload the thread flags, and call back
  * if more flags need to be handled.
  *
  * We return whether we need to check the thread_info flags again
  * or not.  Note that we don't clear TIF_SINGLESTEP here, so it's
  * important that it be tested last, and then claim that we don't
  * need to recheck the flags.
  */
 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
 {
 	/* If we enter in kernel mode, do nothing and exit the caller loop. */
 	if (!user_mode(regs))
 		return 0;

 	if (thread_info_flags & _TIF_NEED_RESCHED) {
 		schedule();
 		return 1;
 	}
 #if CHIP_HAS_TILE_DMA() || CHIP_HAS_SN_PROC()
 	if (thread_info_flags & _TIF_ASYNC_TLB) {
 		do_async_page_fault(regs);
 		return 1;
 	}
 #endif
 	if (thread_info_flags & _TIF_SIGPENDING) {
 		do_signal(regs);
 		return 1;
 	}
 	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 		clear_thread_flag(TIF_NOTIFY_RESUME);
 		tracehook_notify_resume(regs);
 		return 1;
 	}
 	if (thread_info_flags & _TIF_SINGLESTEP) {
 		single_step_once(regs);
 		return 0;
 	}
 	panic("work_pending: bad flags %#x\n", thread_info_flags);
 }

 /* Note there is an implicit fifth argument if (clone_flags & CLONE_SETTLS). */
 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
 		void __user *, parent_tidptr, void __user *, child_tidptr,
 		struct pt_regs *, regs)
 {
 	if (!newsp)
 		newsp = regs->sp;
 	return do_fork(clone_flags, newsp, regs, 0,
 		       parent_tidptr, child_tidptr);
 }

 /*
  * sys_execve() executes a new program.
  */
 SYSCALL_DEFINE4(execve, const char __user *, path,
 		const char __user *const __user *, argv,
 		const char __user *const __user *, envp,
 		struct pt_regs *, regs)
 {
 	long error;
 	struct filename *filename;

 	filename = getname(path);
 	error = PTR_ERR(filename);
 	if (IS_ERR(filename))
 		goto out;
 	error = do_execve(filename->name, argv, envp, regs);
 	putname(filename);
 	if (error == 0)
 		single_step_execve();
 out:
 	return error;
 }

 #ifdef CONFIG_COMPAT
 long compat_sys_execve(const char __user *path,
 		       compat_uptr_t __user *argv,
 		       compat_uptr_t __user *envp,
 		       struct pt_regs *regs)
 {
 	long error;
 	struct filename *filename;

 	filename = getname(path);
 	error = PTR_ERR(filename);
 	if (IS_ERR(filename))
 		goto out;
 	error = compat_do_execve(filename->name, argv, envp, regs);
 	putname(filename);
 	if (error == 0)
 		single_step_execve();
 out:
 	return error;
 }
 #endif

 unsigned long get_wchan(struct task_struct *p)
 {
 	struct KBacktraceIterator kbt;

 	if (!p || p == current || p->state == TASK_RUNNING)
 		return 0;

 	for (KBacktraceIterator_init(&kbt, p, NULL);
 	     !KBacktraceIterator_end(&kbt);
 	     KBacktraceIterator_next(&kbt)) {
 		if (!in_sched_functions(kbt.it.pc))
 			return kbt.it.pc;
 	}

 	return 0;
 }

 /*
  * We pass in lr as zero (cleared in kernel_thread) and the caller
  * part of the backtrace ABI on the stack also zeroed (in copy_thread)
  * so that backtraces will stop with this function.
  * Note that we don't use r0, since copy_thread() clears it.
  */
 static void start_kernel_thread(int dummy, int (*fn)(int), int arg)
 {
 	do_exit(fn(arg));
 }

 /*
  * Create a kernel thread
  */
 int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
 {
 	struct pt_regs regs;

 	memset(&regs, 0, sizeof(regs));
 	regs.ex1 = PL_ICS_EX1(KERNEL_PL, 0);  /* run at kernel PL, no ICS */
 	regs.pc = (long) start_kernel_thread;
 	regs.flags = PT_FLAGS_CALLER_SAVES;   /* need to restore r1 and r2 */
 	regs.regs[1] = (long) fn;             /* function pointer */
 	regs.regs[2] = (long) arg;            /* parameter register */

 	/* Ok, create the new process.. */
 	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs,
 		       0, NULL, NULL);
 }
 EXPORT_SYMBOL(kernel_thread);

 /* Flush thread state. */
 void flush_thread(void)
 {
 	/* Nothing */
 }

 /*
  * Free current thread data structures etc..
  */
 void exit_thread(void)
 {
 	/* Nothing */
 }

 void show_regs(struct pt_regs *regs)
 {
 	struct task_struct *tsk = validate_current();
 	int i;

 	pr_err("\n");
 	pr_err(" Pid: %d, comm: %20s, CPU: %d\n",
 	       tsk->pid, tsk->comm, smp_processor_id());
 #ifdef __tilegx__
 	for (i = 0; i < 51; i += 3)
 		pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
 		       i, regs->regs[i], i+1, regs->regs[i+1],
 		       i+2, regs->regs[i+2]);
 	pr_err(" r51: "REGFMT" r52: "REGFMT" tp : "REGFMT"\n",
 	       regs->regs[51], regs->regs[52], regs->tp);
 	pr_err(" sp : "REGFMT" lr : "REGFMT"\n", regs->sp, regs->lr);
 #else
 	for (i = 0; i < 52; i += 4)
 		pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT
 		       " r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
 		       i, regs->regs[i], i+1, regs->regs[i+1],
 		       i+2, regs->regs[i+2], i+3, regs->regs[i+3]);
 	pr_err(" r52: "REGFMT" tp : "REGFMT" sp : "REGFMT" lr : "REGFMT"\n",
 	       regs->regs[52], regs->tp, regs->sp, regs->lr);
 #endif
 	pr_err(" pc : "REGFMT" ex1: %ld     faultnum: %ld\n",
 	       regs->pc, regs->ex1, regs->faultnum);

 	dump_stack_regs(regs);
 }
	/*
	* Copyright 2010 Tilera Corporation. All Rights Reserved.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation, version 2.
	*
	* 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, GOOD TITLE or
	* NON INFRINGEMENT. See the GNU General Public License for
	* more details.
	*/

	#include <linux/sched.h>
	#include <linux/preempt.h>
	#include <linux/module.h>
	#include <linux/fs.h>
	#include <linux/kprobes.h>
	#include <linux/elfcore.h>
	#include <linux/tick.h>
	#include <linux/init.h>
	#include <linux/mm.h>
	#include <linux/compat.h>
	#include <linux/hardirq.h>
	#include <linux/syscalls.h>
	#include <linux/kernel.h>
	#include <linux/tracehook.h>
	#include <linux/signal.h>
	#include <asm/stack.h>
	#include <asm/switch_to.h>
	#include <asm/homecache.h>
	#include <asm/syscalls.h>
	#include <asm/traps.h>
	#include <asm/setup.h>
	#ifdef CONFIG_HARDWALL
	#include <asm/hardwall.h>
	#endif
	#include <arch/chip.h>
	#include <arch/abi.h>
	#include <arch/sim_def.h>


	/*
	* Use the (x86) "idle=poll" option to prefer low latency when leaving the
	* idle loop over low power while in the idle loop, e.g. if we have
	* one thread per core and we want to get threads out of futex waits fast.
	*/
	static int no_idle_nap;
	static int __init idle_setup(char *str)
	{
	if (!str)
	return -EINVAL;

	if (!strcmp(str, "poll")) {
	pr_info("using polling idle threads.\n");
	no_idle_nap = 1;
	} else if (!strcmp(str, "halt"))
	no_idle_nap = 0;
	else
	return -1;

	return 0;
	}
	early_param("idle", idle_setup);

	/*
	* The idle thread. There's no useful work to be
	* done, so just try to conserve power and have a
	* low exit latency (ie sit in a loop waiting for
	* somebody to say that they'd like to reschedule)
	*/
	void cpu_idle(void)
	{
	int cpu = smp_processor_id();


	current_thread_info()->status \|= TS_POLLING;

	if (no_idle_nap) {
	while (1) {
	while (!need_resched())
	cpu_relax();
	schedule();
	}
	}

	/* endless idle loop with no priority at all */
	while (1) {
	tick_nohz_idle_enter();
	rcu_idle_enter();
	while (!need_resched()) {
	if (cpu_is_offline(cpu))
	BUG(); /* no HOTPLUG_CPU */

	local_irq_disable();
	__get_cpu_var(irq_stat).idle_timestamp = jiffies;
	current_thread_info()->status &= ~TS_POLLING;
	/*
	* TS_POLLING-cleared state must be visible before we
	* test NEED_RESCHED:
	*/
	smp_mb();

	if (!need_resched())
	_cpu_idle();
	else
	local_irq_enable();
	current_thread_info()->status \|= TS_POLLING;
	}
	rcu_idle_exit();
	tick_nohz_idle_exit();
	schedule_preempt_disabled();
	}
	}

	/*
	* Release a thread_info structure
	*/
	void arch_release_thread_info(struct thread_info *info)
	{
	struct single_step_state *step_state = info->step_state;

	#ifdef CONFIG_HARDWALL
	/*
	* We free a thread_info from the context of the task that has
	* been scheduled next, so the original task is already dead.
	* Calling deactivate here just frees up the data structures.
	* If the task we're freeing held the last reference to a
	* hardwall fd, it would have been released prior to this point
	* anyway via exit_files(), and the hardwall_task.info pointers
	* would be NULL by now.
	*/
	hardwall_deactivate_all(info->task);
	#endif

	if (step_state) {

	/*
	* FIXME: we don't munmap step_state->buffer
	* because the mm_struct for this process (info->task->mm)
	* has already been zeroed in exit_mm(). Keeping a
	* reference to it here seems like a bad move, so this
	* means we can't munmap() the buffer, and therefore if we
	* ptrace multiple threads in a process, we will slowly
	* leak user memory. (Note that as soon as the last
	* thread in a process dies, we will reclaim all user
	* memory including single-step buffers in the usual way.)
	* We should either assign a kernel VA to this buffer
	* somehow, or we should associate the buffer(s) with the
	* mm itself so we can clean them up that way.
	*/
	kfree(step_state);
	}
	}

	static void save_arch_state(struct thread_struct *t);

	int copy_thread(unsigned long clone_flags, unsigned long sp,
	unsigned long stack_size,
	struct task_struct p, struct pt_regs regs)
	{
	struct pt_regs *childregs;
	unsigned long ksp;

	/*
	* When creating a new kernel thread we pass sp as zero.
	* Assign it to a reasonable value now that we have the stack.
	*/
	if (sp == 0 && regs->ex1 == PL_ICS_EX1(KERNEL_PL, 0))
	sp = KSTK_TOP(p);

	/*
	* Do not clone step state from the parent; each thread
	* must make its own lazily.
	*/
	task_thread_info(p)->step_state = NULL;

	/*
	* Start new thread in ret_from_fork so it schedules properly
	* and then return from interrupt like the parent.
	*/
	p->thread.pc = (unsigned long) ret_from_fork;

	/* Save user stack top pointer so we can ID the stack vm area later. */
	p->thread.usp0 = sp;

	/* Record the pid of the process that created this one. */
	p->thread.creator_pid = current->pid;

	/*
	* Copy the registers onto the kernel stack so the
	* return-from-interrupt code will reload it into registers.
	*/
	childregs = task_pt_regs(p);
	childregs = regs;
	childregs->regs[0] = 0; /* return value is zero */
	childregs->sp = sp; /* override with new user stack pointer */

	/*
	* If CLONE_SETTLS is set, set "tp" in the new task to "r4",
	* which is passed in as arg #5 to sys_clone().
	*/
	if (clone_flags & CLONE_SETTLS)
	childregs->tp = regs->regs[4];

	/*
	* Copy the callee-saved registers from the passed pt_regs struct
	* into the context-switch callee-saved registers area.
	* This way when we start the interrupt-return sequence, the
	* callee-save registers will be correctly in registers, which
	* is how we assume the compiler leaves them as we start doing
	* the normal return-from-interrupt path after calling C code.
	* Zero out the C ABI save area to mark the top of the stack.
	*/
	ksp = (unsigned long) childregs;
	ksp -= C_ABI_SAVE_AREA_SIZE; /* interrupt-entry save area */
	((long )ksp)[0] = ((long )ksp)[1] = 0;
	ksp -= CALLEE_SAVED_REGS_COUNT * sizeof(unsigned long);
	memcpy((void *)ksp, &regs->regs[CALLEE_SAVED_FIRST_REG],
	CALLEE_SAVED_REGS_COUNT * sizeof(unsigned long));
	ksp -= C_ABI_SAVE_AREA_SIZE; /* __switch_to() save area */
	((long )ksp)[0] = ((long )ksp)[1] = 0;
	p->thread.ksp = ksp;

	#if CHIP_HAS_TILE_DMA()
	/*
	* No DMA in the new thread. We model this on the fact that
	* fork() clears the pending signals, alarms, and aio for the child.
	*/
	memset(&p->thread.tile_dma_state, 0, sizeof(struct tile_dma_state));
	memset(&p->thread.dma_async_tlb, 0, sizeof(struct async_tlb));
	#endif

	#if CHIP_HAS_SN_PROC()
	/* Likewise, the new thread is not running static processor code. */
	p->thread.sn_proc_running = 0;
	memset(&p->thread.sn_async_tlb, 0, sizeof(struct async_tlb));
	#endif

	#if CHIP_HAS_PROC_STATUS_SPR()
	/* New thread has its miscellaneous processor state bits clear. */
	p->thread.proc_status = 0;
	#endif

	#ifdef CONFIG_HARDWALL
	/* New thread does not own any networks. */
	memset(&p->thread.hardwall[0], 0,
	sizeof(struct hardwall_task) * HARDWALL_TYPES);
	#endif


	/*
	* Start the new thread with the current architecture state
	* (user interrupt masks, etc.).
	*/
	save_arch_state(&p->thread);

	return 0;
	}

	/*
	* Return "current" if it looks plausible, or else a pointer to a dummy.
	* This can be helpful if we are just trying to emit a clean panic.
	*/
	struct task_struct *validate_current(void)
	{
	static struct task_struct corrupt = { .comm = "<corrupt>" };
	struct task_struct *tsk = current;
	if (unlikely((unsigned long)tsk < PAGE_OFFSET \|\|
	(high_memory && (void *)tsk > high_memory) \|\|
	((unsigned long)tsk & (__alignof__(*tsk) - 1)) != 0)) {
	pr_err("Corrupt 'current' %p (sp %#lx)\n", tsk, stack_pointer);
	tsk = &corrupt;
	}
	return tsk;
	}

	/* Take and return the pointer to the previous task, for schedule_tail(). */
	struct task_struct sim_notify_fork(struct task_struct prev)
	{
	struct task_struct *tsk = current;
	__insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_FORK_PARENT \|
	(tsk->thread.creator_pid << _SIM_CONTROL_OPERATOR_BITS));
	__insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_FORK \|
	(tsk->pid << _SIM_CONTROL_OPERATOR_BITS));
	return prev;
	}

	int dump_task_regs(struct task_struct tsk, elf_gregset_t regs)
	{
	struct pt_regs *ptregs = task_pt_regs(tsk);
	elf_core_copy_regs(regs, ptregs);
	return 1;
	}

	#if CHIP_HAS_TILE_DMA()

	/* Allow user processes to access the DMA SPRs */
	void grant_dma_mpls(void)
	{
	#if CONFIG_KERNEL_PL == 2
	__insn_mtspr(SPR_MPL_DMA_CPL_SET_1, 1);
	__insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_1, 1);
	#else
	__insn_mtspr(SPR_MPL_DMA_CPL_SET_0, 1);
	__insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_0, 1);
	#endif
	}

	/* Forbid user processes from accessing the DMA SPRs */
	void restrict_dma_mpls(void)
	{
	#if CONFIG_KERNEL_PL == 2
	__insn_mtspr(SPR_MPL_DMA_CPL_SET_2, 1);
	__insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_2, 1);
	#else
	__insn_mtspr(SPR_MPL_DMA_CPL_SET_1, 1);
	__insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_1, 1);
	#endif
	}

	/* Pause the DMA engine, then save off its state registers. */
	static void save_tile_dma_state(struct tile_dma_state *dma)
	{
	unsigned long state = __insn_mfspr(SPR_DMA_USER_STATUS);
	unsigned long post_suspend_state;

	/* If we're running, suspend the engine. */
	if ((state & DMA_STATUS_MASK) == SPR_DMA_STATUS__RUNNING_MASK)
	__insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__SUSPEND_MASK);

	/*
	* Wait for the engine to idle, then save regs. Note that we
	* want to record the "running" bit from before suspension,
	* and the "done" bit from after, so that we can properly
	* distinguish a case where the user suspended the engine from
	* the case where the kernel suspended as part of the context
	* swap.
	*/
	do {
	post_suspend_state = __insn_mfspr(SPR_DMA_USER_STATUS);
	} while (post_suspend_state & SPR_DMA_STATUS__BUSY_MASK);

	dma->src = __insn_mfspr(SPR_DMA_SRC_ADDR);
	dma->src_chunk = __insn_mfspr(SPR_DMA_SRC_CHUNK_ADDR);
	dma->dest = __insn_mfspr(SPR_DMA_DST_ADDR);
	dma->dest_chunk = __insn_mfspr(SPR_DMA_DST_CHUNK_ADDR);
	dma->strides = __insn_mfspr(SPR_DMA_STRIDE);
	dma->chunk_size = __insn_mfspr(SPR_DMA_CHUNK_SIZE);
	dma->byte = __insn_mfspr(SPR_DMA_BYTE);
	dma->status = (state & SPR_DMA_STATUS__RUNNING_MASK) \|
	(post_suspend_state & SPR_DMA_STATUS__DONE_MASK);
	}

	/* Restart a DMA that was running before we were context-switched out. */
	static void restore_tile_dma_state(struct thread_struct *t)
	{
	const struct tile_dma_state *dma = &t->tile_dma_state;

	/*
	* The only way to restore the done bit is to run a zero
	* length transaction.
	*/
	if ((dma->status & SPR_DMA_STATUS__DONE_MASK) &&
	!(__insn_mfspr(SPR_DMA_USER_STATUS) & SPR_DMA_STATUS__DONE_MASK)) {
	__insn_mtspr(SPR_DMA_BYTE, 0);
	__insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
	while (__insn_mfspr(SPR_DMA_USER_STATUS) &
	SPR_DMA_STATUS__BUSY_MASK)
	;
	}

	__insn_mtspr(SPR_DMA_SRC_ADDR, dma->src);
	__insn_mtspr(SPR_DMA_SRC_CHUNK_ADDR, dma->src_chunk);
	__insn_mtspr(SPR_DMA_DST_ADDR, dma->dest);
	__insn_mtspr(SPR_DMA_DST_CHUNK_ADDR, dma->dest_chunk);
	__insn_mtspr(SPR_DMA_STRIDE, dma->strides);
	__insn_mtspr(SPR_DMA_CHUNK_SIZE, dma->chunk_size);
	__insn_mtspr(SPR_DMA_BYTE, dma->byte);

	/*
	* Restart the engine if we were running and not done.
	* Clear a pending async DMA fault that we were waiting on return
	* to user space to execute, since we expect the DMA engine
	* to regenerate those faults for us now. Note that we don't
	* try to clear the TIF_ASYNC_TLB flag, since it's relatively
	* harmless if set, and it covers both DMA and the SN processor.
	*/
	if ((dma->status & DMA_STATUS_MASK) == SPR_DMA_STATUS__RUNNING_MASK) {
	t->dma_async_tlb.fault_num = 0;
	__insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
	}
	}

	#endif

	static void save_arch_state(struct thread_struct *t)
	{
	#if CHIP_HAS_SPLIT_INTR_MASK()
	t->interrupt_mask = __insn_mfspr(SPR_INTERRUPT_MASK_0_0) \|
	((u64)__insn_mfspr(SPR_INTERRUPT_MASK_0_1) << 32);
	#else
	t->interrupt_mask = __insn_mfspr(SPR_INTERRUPT_MASK_0);
	#endif
	t->ex_context[0] = __insn_mfspr(SPR_EX_CONTEXT_0_0);
	t->ex_context[1] = __insn_mfspr(SPR_EX_CONTEXT_0_1);
	t->system_save[0] = __insn_mfspr(SPR_SYSTEM_SAVE_0_0);
	t->system_save[1] = __insn_mfspr(SPR_SYSTEM_SAVE_0_1);
	t->system_save[2] = __insn_mfspr(SPR_SYSTEM_SAVE_0_2);
	t->system_save[3] = __insn_mfspr(SPR_SYSTEM_SAVE_0_3);
	t->intctrl_0 = __insn_mfspr(SPR_INTCTRL_0_STATUS);
	#if CHIP_HAS_PROC_STATUS_SPR()
	t->proc_status = __insn_mfspr(SPR_PROC_STATUS);
	#endif
	#if !CHIP_HAS_FIXED_INTVEC_BASE()
	t->interrupt_vector_base = __insn_mfspr(SPR_INTERRUPT_VECTOR_BASE_0);
	#endif
	#if CHIP_HAS_TILE_RTF_HWM()
	t->tile_rtf_hwm = __insn_mfspr(SPR_TILE_RTF_HWM);
	#endif
	#if CHIP_HAS_DSTREAM_PF()
	t->dstream_pf = __insn_mfspr(SPR_DSTREAM_PF);
	#endif
	}

	static void restore_arch_state(const struct thread_struct *t)
	{
	#if CHIP_HAS_SPLIT_INTR_MASK()
	__insn_mtspr(SPR_INTERRUPT_MASK_0_0, (u32) t->interrupt_mask);
	__insn_mtspr(SPR_INTERRUPT_MASK_0_1, t->interrupt_mask >> 32);
	#else
	__insn_mtspr(SPR_INTERRUPT_MASK_0, t->interrupt_mask);
	#endif
	__insn_mtspr(SPR_EX_CONTEXT_0_0, t->ex_context[0]);
	__insn_mtspr(SPR_EX_CONTEXT_0_1, t->ex_context[1]);
	__insn_mtspr(SPR_SYSTEM_SAVE_0_0, t->system_save[0]);
	__insn_mtspr(SPR_SYSTEM_SAVE_0_1, t->system_save[1]);
	__insn_mtspr(SPR_SYSTEM_SAVE_0_2, t->system_save[2]);
	__insn_mtspr(SPR_SYSTEM_SAVE_0_3, t->system_save[3]);
	__insn_mtspr(SPR_INTCTRL_0_STATUS, t->intctrl_0);
	#if CHIP_HAS_PROC_STATUS_SPR()
	__insn_mtspr(SPR_PROC_STATUS, t->proc_status);
	#endif
	#if !CHIP_HAS_FIXED_INTVEC_BASE()
	__insn_mtspr(SPR_INTERRUPT_VECTOR_BASE_0, t->interrupt_vector_base);
	#endif
	#if CHIP_HAS_TILE_RTF_HWM()
	__insn_mtspr(SPR_TILE_RTF_HWM, t->tile_rtf_hwm);
	#endif
	#if CHIP_HAS_DSTREAM_PF()
	__insn_mtspr(SPR_DSTREAM_PF, t->dstream_pf);
	#endif
	}


	void _prepare_arch_switch(struct task_struct *next)
	{
	#if CHIP_HAS_SN_PROC()
	int snctl;
	#endif
	#if CHIP_HAS_TILE_DMA()
	struct tile_dma_state *dma = &current->thread.tile_dma_state;
	if (dma->enabled)
	save_tile_dma_state(dma);
	#endif
	#if CHIP_HAS_SN_PROC()
	/*
	* Suspend the static network processor if it was running.
	* We do not suspend the fabric itself, just like we don't
	* try to suspend the UDN.
	*/
	snctl = __insn_mfspr(SPR_SNCTL);
	current->thread.sn_proc_running =
	(snctl & SPR_SNCTL__FRZPROC_MASK) == 0;
	if (current->thread.sn_proc_running)
	__insn_mtspr(SPR_SNCTL, snctl \| SPR_SNCTL__FRZPROC_MASK);
	#endif
	}


	struct task_struct __sched _switch_to(struct task_struct prev,
	struct task_struct *next)
	{
	/* DMA state is already saved; save off other arch state. */
	save_arch_state(&prev->thread);

	#if CHIP_HAS_TILE_DMA()
	/*
	* Restore DMA in new task if desired.
	* Note that it is only safe to restart here since interrupts
	* are disabled, so we can't take any DMATLB miss or access
	* interrupts before we have finished switching stacks.
	*/
	if (next->thread.tile_dma_state.enabled) {
	restore_tile_dma_state(&next->thread);
	grant_dma_mpls();
	} else {
	restrict_dma_mpls();
	}
	#endif

	/* Restore other arch state. */
	restore_arch_state(&next->thread);

	#if CHIP_HAS_SN_PROC()
	/*
	* Restart static network processor in the new process
	* if it was running before.
	*/
	if (next->thread.sn_proc_running) {
	int snctl = __insn_mfspr(SPR_SNCTL);
	__insn_mtspr(SPR_SNCTL, snctl & ~SPR_SNCTL__FRZPROC_MASK);
	}
	#endif

	#ifdef CONFIG_HARDWALL
	/* Enable or disable access to the network registers appropriately. */
	hardwall_switch_tasks(prev, next);
	#endif

	/*
	* Switch kernel SP, PC, and callee-saved registers.
	* In the context of the new task, return the old task pointer
	* (i.e. the task that actually called __switch_to).
	* Pass the value to use for SYSTEM_SAVE_K_0 when we reset our sp.
	*/
	return __switch_to(prev, next, next_current_ksp0(next));
	}

	/*
	* This routine is called on return from interrupt if any of the
	* TIF_WORK_MASK flags are set in thread_info->flags. It is
	* entered with interrupts disabled so we don't miss an event
	* that modified the thread_info flags. If any flag is set, we
	* handle it and return, and the calling assembly code will
	* re-disable interrupts, reload the thread flags, and call back
	* if more flags need to be handled.
	*
	* We return whether we need to check the thread_info flags again
	* or not. Note that we don't clear TIF_SINGLESTEP here, so it's
	* important that it be tested last, and then claim that we don't
	* need to recheck the flags.
	*/
	int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
	{
	/* If we enter in kernel mode, do nothing and exit the caller loop. */
	if (!user_mode(regs))
	return 0;

	if (thread_info_flags & _TIF_NEED_RESCHED) {
	schedule();
	return 1;
	}
	#if CHIP_HAS_TILE_DMA() \|\| CHIP_HAS_SN_PROC()
	if (thread_info_flags & _TIF_ASYNC_TLB) {
	do_async_page_fault(regs);
	return 1;
	}
	#endif
	if (thread_info_flags & _TIF_SIGPENDING) {
	do_signal(regs);
	return 1;
	}
	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
	clear_thread_flag(TIF_NOTIFY_RESUME);
	tracehook_notify_resume(regs);
	return 1;
	}
	if (thread_info_flags & _TIF_SINGLESTEP) {
	single_step_once(regs);
	return 0;
	}
	panic("work_pending: bad flags %#x\n", thread_info_flags);
	}

	/* Note there is an implicit fifth argument if (clone_flags & CLONE_SETTLS). */
	SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
	void __user , parent_tidptr, void __user , child_tidptr,
	struct pt_regs *, regs)
	{
	if (!newsp)
	newsp = regs->sp;
	return do_fork(clone_flags, newsp, regs, 0,
	parent_tidptr, child_tidptr);
	}

	/*
	* sys_execve() executes a new program.
	*/
	SYSCALL_DEFINE4(execve, const char __user *, path,
	const char __user const __user , argv,
	const char __user const __user , envp,
	struct pt_regs *, regs)
	{
	long error;
	struct filename *filename;

	filename = getname(path);
	error = PTR_ERR(filename);
	if (IS_ERR(filename))
	goto out;
	error = do_execve(filename->name, argv, envp, regs);
	putname(filename);
	if (error == 0)
	single_step_execve();
	out:
	return error;
	}

	#ifdef CONFIG_COMPAT
	long compat_sys_execve(const char __user *path,
	compat_uptr_t __user *argv,
	compat_uptr_t __user *envp,
	struct pt_regs *regs)
	{
	long error;
	struct filename *filename;

	filename = getname(path);
	error = PTR_ERR(filename);
	if (IS_ERR(filename))
	goto out;
	error = compat_do_execve(filename->name, argv, envp, regs);
	putname(filename);
	if (error == 0)
	single_step_execve();
	out:
	return error;
	}
	#endif

	unsigned long get_wchan(struct task_struct *p)
	{
	struct KBacktraceIterator kbt;

	if (!p \|\| p == current \|\| p->state == TASK_RUNNING)
	return 0;

	for (KBacktraceIterator_init(&kbt, p, NULL);
	!KBacktraceIterator_end(&kbt);
	KBacktraceIterator_next(&kbt)) {
	if (!in_sched_functions(kbt.it.pc))
	return kbt.it.pc;
	}

	return 0;
	}

	/*
	* We pass in lr as zero (cleared in kernel_thread) and the caller
	* part of the backtrace ABI on the stack also zeroed (in copy_thread)
	* so that backtraces will stop with this function.
	* Note that we don't use r0, since copy_thread() clears it.
	*/
	static void start_kernel_thread(int dummy, int (*fn)(int), int arg)
	{
	do_exit(fn(arg));
	}

	/*
	* Create a kernel thread
	*/
	int kernel_thread(int (fn)(void ), void * arg, unsigned long flags)
	{
	struct pt_regs regs;

	memset(&regs, 0, sizeof(regs));
	regs.ex1 = PL_ICS_EX1(KERNEL_PL, 0); /* run at kernel PL, no ICS */
	regs.pc = (long) start_kernel_thread;
	regs.flags = PT_FLAGS_CALLER_SAVES; /* need to restore r1 and r2 */
	regs.regs[1] = (long) fn; /* function pointer */
	regs.regs[2] = (long) arg; /* parameter register */

	/* Ok, create the new process.. */
	return do_fork(flags \| CLONE_VM \| CLONE_UNTRACED, 0, &regs,
	0, NULL, NULL);
	}
	EXPORT_SYMBOL(kernel_thread);

	/* Flush thread state. */
	void flush_thread(void)
	{
	/* Nothing */
	}

	/*
	* Free current thread data structures etc..
	*/
	void exit_thread(void)
	{
	/* Nothing */
	}

	void show_regs(struct pt_regs *regs)
	{
	struct task_struct *tsk = validate_current();
	int i;

	pr_err("\n");
	pr_err(" Pid: %d, comm: %20s, CPU: %d\n",
	tsk->pid, tsk->comm, smp_processor_id());
	#ifdef __tilegx__
	for (i = 0; i < 51; i += 3)
	pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
	i, regs->regs[i], i+1, regs->regs[i+1],
	i+2, regs->regs[i+2]);
	pr_err(" r51: "REGFMT" r52: "REGFMT" tp : "REGFMT"\n",
	regs->regs[51], regs->regs[52], regs->tp);
	pr_err(" sp : "REGFMT" lr : "REGFMT"\n", regs->sp, regs->lr);
	#else
	for (i = 0; i < 52; i += 4)
	pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT
	" r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
	i, regs->regs[i], i+1, regs->regs[i+1],
	i+2, regs->regs[i+2], i+3, regs->regs[i+3]);
	pr_err(" r52: "REGFMT" tp : "REGFMT" sp : "REGFMT" lr : "REGFMT"\n",
	regs->regs[52], regs->tp, regs->sp, regs->lr);
	#endif
	pr_err(" pc : "REGFMT" ex1: %ld faultnum: %ld\n",
	regs->pc, regs->ex1, regs->faultnum);

	dump_stack_regs(regs);
	}