arch/x86/kernel/process.c - arm/linux-arm64-legacy - Git at Google

 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/smp.h>
 #include <linux/prctl.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/pm.h>
 #include <linux/clockchips.h>
 #include <linux/random.h>
 #include <trace/events/power.h>
 #include <asm/system.h>
 #include <asm/apic.h>
 #include <asm/syscalls.h>
 #include <asm/idle.h>
 #include <asm/uaccess.h>
 #include <asm/i387.h>
 #include <asm/ds.h>

 unsigned long idle_halt;
 EXPORT_SYMBOL(idle_halt);
 unsigned long idle_nomwait;
 EXPORT_SYMBOL(idle_nomwait);

 struct kmem_cache *task_xstate_cachep;

 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 {
 	*dst = *src;
 	if (src->thread.xstate) {
 		dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
 						      GFP_KERNEL);
 		if (!dst->thread.xstate)
 			return -ENOMEM;
 		WARN_ON((unsigned long)dst->thread.xstate & 15);
 		memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
 	}
 	return 0;
 }

 void free_thread_xstate(struct task_struct *tsk)
 {
 	if (tsk->thread.xstate) {
 		kmem_cache_free(task_xstate_cachep, tsk->thread.xstate);
 		tsk->thread.xstate = NULL;
 	}

 	WARN(tsk->thread.ds_ctx, "leaking DS context\n");
 }

 void free_thread_info(struct thread_info *ti)
 {
 	free_thread_xstate(ti->task);
 	free_pages((unsigned long)ti, get_order(THREAD_SIZE));
 }

 void arch_task_cache_init(void)
 {
         task_xstate_cachep =
         	kmem_cache_create("task_xstate", xstate_size,
 				  __alignof__(union thread_xstate),
 				  SLAB_PANIC | SLAB_NOTRACK, NULL);
 }

 /*
  * Free current thread data structures etc..
  */
 void exit_thread(void)
 {
 	struct task_struct *me = current;
 	struct thread_struct *t = &me->thread;
 	unsigned long *bp = t->io_bitmap_ptr;

 	if (bp) {
 		struct tss_struct *tss = &per_cpu(init_tss, get_cpu());

 		t->io_bitmap_ptr = NULL;
 		clear_thread_flag(TIF_IO_BITMAP);
 		/*
 		 * Careful, clear this in the TSS too:
 		 */
 		memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
 		t->io_bitmap_max = 0;
 		put_cpu();
 		kfree(bp);
 	}
 }

 void flush_thread(void)
 {
 	struct task_struct *tsk = current;

 #ifdef CONFIG_X86_64
 	if (test_tsk_thread_flag(tsk, TIF_ABI_PENDING)) {
 		clear_tsk_thread_flag(tsk, TIF_ABI_PENDING);
 		if (test_tsk_thread_flag(tsk, TIF_IA32)) {
 			clear_tsk_thread_flag(tsk, TIF_IA32);
 		} else {
 			set_tsk_thread_flag(tsk, TIF_IA32);
 			current_thread_info()->status |= TS_COMPAT;
 		}
 	}
 #endif

 	clear_tsk_thread_flag(tsk, TIF_DEBUG);

 	tsk->thread.debugreg0 = 0;
 	tsk->thread.debugreg1 = 0;
 	tsk->thread.debugreg2 = 0;
 	tsk->thread.debugreg3 = 0;
 	tsk->thread.debugreg6 = 0;
 	tsk->thread.debugreg7 = 0;
 	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
 	/*
 	 * Forget coprocessor state..
 	 */
 	tsk->fpu_counter = 0;
 	clear_fpu(tsk);
 	clear_used_math();
 }

 static void hard_disable_TSC(void)
 {
 	write_cr4(read_cr4() | X86_CR4_TSD);
 }

 void disable_TSC(void)
 {
 	preempt_disable();
 	if (!test_and_set_thread_flag(TIF_NOTSC))
 		/*
 		 * Must flip the CPU state synchronously with
 		 * TIF_NOTSC in the current running context.
 		 */
 		hard_disable_TSC();
 	preempt_enable();
 }

 static void hard_enable_TSC(void)
 {
 	write_cr4(read_cr4() & ~X86_CR4_TSD);
 }

 static void enable_TSC(void)
 {
 	preempt_disable();
 	if (test_and_clear_thread_flag(TIF_NOTSC))
 		/*
 		 * Must flip the CPU state synchronously with
 		 * TIF_NOTSC in the current running context.
 		 */
 		hard_enable_TSC();
 	preempt_enable();
 }

 int get_tsc_mode(unsigned long adr)
 {
 	unsigned int val;

 	if (test_thread_flag(TIF_NOTSC))
 		val = PR_TSC_SIGSEGV;
 	else
 		val = PR_TSC_ENABLE;

 	return put_user(val, (unsigned int __user *)adr);
 }

 int set_tsc_mode(unsigned int val)
 {
 	if (val == PR_TSC_SIGSEGV)
 		disable_TSC();
 	else if (val == PR_TSC_ENABLE)
 		enable_TSC();
 	else
 		return -EINVAL;

 	return 0;
 }

 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 		      struct tss_struct *tss)
 {
 	struct thread_struct *prev, *next;

 	prev = &prev_p->thread;
 	next = &next_p->thread;

 	if (test_tsk_thread_flag(next_p, TIF_DS_AREA_MSR) ||
 	    test_tsk_thread_flag(prev_p, TIF_DS_AREA_MSR))
 		ds_switch_to(prev_p, next_p);
 	else if (next->debugctlmsr != prev->debugctlmsr)
 		update_debugctlmsr(next->debugctlmsr);

 	if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
 		set_debugreg(next->debugreg0, 0);
 		set_debugreg(next->debugreg1, 1);
 		set_debugreg(next->debugreg2, 2);
 		set_debugreg(next->debugreg3, 3);
 		/* no 4 and 5 */
 		set_debugreg(next->debugreg6, 6);
 		set_debugreg(next->debugreg7, 7);
 	}

 	if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
 	    test_tsk_thread_flag(next_p, TIF_NOTSC)) {
 		/* prev and next are different */
 		if (test_tsk_thread_flag(next_p, TIF_NOTSC))
 			hard_disable_TSC();
 		else
 			hard_enable_TSC();
 	}

 	if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
 		/*
 		 * Copy the relevant range of the IO bitmap.
 		 * Normally this is 128 bytes or less:
 		 */
 		memcpy(tss->io_bitmap, next->io_bitmap_ptr,
 		       max(prev->io_bitmap_max, next->io_bitmap_max));
 	} else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
 		/*
 		 * Clear any possible leftover bits:
 		 */
 		memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
 	}
 }

 int sys_fork(struct pt_regs *regs)
 {
 	return do_fork(SIGCHLD, regs->sp, regs, 0, NULL, NULL);
 }

 /*
  * This is trivial, and on the face of it looks like it
  * could equally well be done in user mode.
  *
  * Not so, for quite unobvious reasons - register pressure.
  * In user mode vfork() cannot have a stack frame, and if
  * done by calling the "clone()" system call directly, you
  * do not have enough call-clobbered registers to hold all
  * the information you need.
  */
 int sys_vfork(struct pt_regs *regs)
 {
 	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->sp, regs, 0,
 		       NULL, NULL);
 }


 /*
  * Idle related variables and functions
  */
 unsigned long boot_option_idle_override = 0;
 EXPORT_SYMBOL(boot_option_idle_override);

 /*
  * Powermanagement idle function, if any..
  */
 void (*pm_idle)(void);
 EXPORT_SYMBOL(pm_idle);

 #ifdef CONFIG_X86_32
 /*
  * This halt magic was a workaround for ancient floppy DMA
  * wreckage. It should be safe to remove.
  */
 static int hlt_counter;
 void disable_hlt(void)
 {
 	hlt_counter++;
 }
 EXPORT_SYMBOL(disable_hlt);

 void enable_hlt(void)
 {
 	hlt_counter--;
 }
 EXPORT_SYMBOL(enable_hlt);

 static inline int hlt_use_halt(void)
 {
 	return (!hlt_counter && boot_cpu_data.hlt_works_ok);
 }
 #else
 static inline int hlt_use_halt(void)
 {
 	return 1;
 }
 #endif

 /*
  * We use this if we don't have any better
  * idle routine..
  */
 void default_idle(void)
 {
 	if (hlt_use_halt()) {
 		trace_power_start(POWER_CSTATE, 1);
 		current_thread_info()->status &= ~TS_POLLING;
 		/*
 		 * TS_POLLING-cleared state must be visible before we
 		 * test NEED_RESCHED:
 		 */
 		smp_mb();

 		if (!need_resched())
 			safe_halt();	/* enables interrupts racelessly */
 		else
 			local_irq_enable();
 		current_thread_info()->status |= TS_POLLING;
 	} else {
 		local_irq_enable();
 		/* loop is done by the caller */
 		cpu_relax();
 	}
 }
 #ifdef CONFIG_APM_MODULE
 EXPORT_SYMBOL(default_idle);
 #endif

 void stop_this_cpu(void *dummy)
 {
 	local_irq_disable();
 	/*
 	 * Remove this CPU:
 	 */
 	set_cpu_online(smp_processor_id(), false);
 	disable_local_APIC();

 	for (;;) {
 		if (hlt_works(smp_processor_id()))
 			halt();
 	}
 }

 static void do_nothing(void *unused)
 {
 }

 /*
  * cpu_idle_wait - Used to ensure that all the CPUs discard old value of
  * pm_idle and update to new pm_idle value. Required while changing pm_idle
  * handler on SMP systems.
  *
  * Caller must have changed pm_idle to the new value before the call. Old
  * pm_idle value will not be used by any CPU after the return of this function.
  */
 void cpu_idle_wait(void)
 {
 	smp_mb();
 	/* kick all the CPUs so that they exit out of pm_idle */
 	smp_call_function(do_nothing, NULL, 1);
 }
 EXPORT_SYMBOL_GPL(cpu_idle_wait);

 /*
  * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
  * which can obviate IPI to trigger checking of need_resched.
  * We execute MONITOR against need_resched and enter optimized wait state
  * through MWAIT. Whenever someone changes need_resched, we would be woken
  * up from MWAIT (without an IPI).
  *
  * New with Core Duo processors, MWAIT can take some hints based on CPU
  * capability.
  */
 void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
 {
 	trace_power_start(POWER_CSTATE, (ax>>4)+1);
 	if (!need_resched()) {
 		if (cpu_has(&current_cpu_data, X86_FEATURE_CLFLUSH_MONITOR))
 			clflush((void *)&current_thread_info()->flags);

 		__monitor((void *)&current_thread_info()->flags, 0, 0);
 		smp_mb();
 		if (!need_resched())
 			__mwait(ax, cx);
 	}
 }

 /* Default MONITOR/MWAIT with no hints, used for default C1 state */
 static void mwait_idle(void)
 {
 	if (!need_resched()) {
 		trace_power_start(POWER_CSTATE, 1);
 		if (cpu_has(&current_cpu_data, X86_FEATURE_CLFLUSH_MONITOR))
 			clflush((void *)&current_thread_info()->flags);

 		__monitor((void *)&current_thread_info()->flags, 0, 0);
 		smp_mb();
 		if (!need_resched())
 			__sti_mwait(0, 0);
 		else
 			local_irq_enable();
 	} else
 		local_irq_enable();
 }

 /*
  * On SMP it's slightly faster (but much more power-consuming!)
  * to poll the ->work.need_resched flag instead of waiting for the
  * cross-CPU IPI to arrive. Use this option with caution.
  */
 static void poll_idle(void)
 {
 	trace_power_start(POWER_CSTATE, 0);
 	local_irq_enable();
 	while (!need_resched())
 		cpu_relax();
 	trace_power_end(0);
 }

 /*
  * mwait selection logic:
  *
  * It depends on the CPU. For AMD CPUs that support MWAIT this is
  * wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings
  * then depend on a clock divisor and current Pstate of the core. If
  * all cores of a processor are in halt state (C1) the processor can
  * enter the C1E (C1 enhanced) state. If mwait is used this will never
  * happen.
  *
  * idle=mwait overrides this decision and forces the usage of mwait.
  */
 static int __cpuinitdata force_mwait;

 #define MWAIT_INFO			0x05
 #define MWAIT_ECX_EXTENDED_INFO		0x01
 #define MWAIT_EDX_C1			0xf0

 static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
 {
 	u32 eax, ebx, ecx, edx;

 	if (force_mwait)
 		return 1;

 	if (c->cpuid_level < MWAIT_INFO)
 		return 0;

 	cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx);
 	/* Check, whether EDX has extended info about MWAIT */
 	if (!(ecx & MWAIT_ECX_EXTENDED_INFO))
 		return 1;

 	/*
 	 * edx enumeratios MONITOR/MWAIT extensions. Check, whether
 	 * C1  supports MWAIT
 	 */
 	return (edx & MWAIT_EDX_C1);
 }

 /*
  * Check for AMD CPUs, which have potentially C1E support
  */
 static int __cpuinit check_c1e_idle(const struct cpuinfo_x86 *c)
 {
 	if (c->x86_vendor != X86_VENDOR_AMD)
 		return 0;

 	if (c->x86 < 0x0F)
 		return 0;

 	/* Family 0x0f models < rev F do not have C1E */
 	if (c->x86 == 0x0f && c->x86_model < 0x40)
 		return 0;

 	return 1;
 }

 static cpumask_var_t c1e_mask;
 static int c1e_detected;

 void c1e_remove_cpu(int cpu)
 {
 	if (c1e_mask != NULL)
 		cpumask_clear_cpu(cpu, c1e_mask);
 }

 /*
  * C1E aware idle routine. We check for C1E active in the interrupt
  * pending message MSR. If we detect C1E, then we handle it the same
  * way as C3 power states (local apic timer and TSC stop)
  */
 static void c1e_idle(void)
 {
 	if (need_resched())
 		return;

 	if (!c1e_detected) {
 		u32 lo, hi;

 		rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
 		if (lo & K8_INTP_C1E_ACTIVE_MASK) {
 			c1e_detected = 1;
 			if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 				mark_tsc_unstable("TSC halt in AMD C1E");
 			printk(KERN_INFO "System has AMD C1E enabled\n");
 			set_cpu_cap(&boot_cpu_data, X86_FEATURE_AMDC1E);
 		}
 	}

 	if (c1e_detected) {
 		int cpu = smp_processor_id();

 		if (!cpumask_test_cpu(cpu, c1e_mask)) {
 			cpumask_set_cpu(cpu, c1e_mask);
 			/*
 			 * Force broadcast so ACPI can not interfere.
 			 */
 			clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_FORCE,
 					   &cpu);
 			printk(KERN_INFO "Switch to broadcast mode on CPU%d\n",
 			       cpu);
 		}
 		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);

 		default_idle();

 		/*
 		 * The switch back from broadcast mode needs to be
 		 * called with interrupts disabled.
 		 */
 		 local_irq_disable();
 		 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
 		 local_irq_enable();
 	} else
 		default_idle();
 }

 void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
 {
 #ifdef CONFIG_SMP
 	if (pm_idle == poll_idle && smp_num_siblings > 1) {
 		printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
 			" performance may degrade.\n");
 	}
 #endif
 	if (pm_idle)
 		return;

 	if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
 		/*
 		 * One CPU supports mwait => All CPUs supports mwait
 		 */
 		printk(KERN_INFO "using mwait in idle threads.\n");
 		pm_idle = mwait_idle;
 	} else if (check_c1e_idle(c)) {
 		printk(KERN_INFO "using C1E aware idle routine\n");
 		pm_idle = c1e_idle;
 	} else
 		pm_idle = default_idle;
 }

 void __init init_c1e_mask(void)
 {
 	/* If we're using c1e_idle, we need to allocate c1e_mask. */
 	if (pm_idle == c1e_idle) {
 		alloc_cpumask_var(&c1e_mask, GFP_KERNEL);
 		cpumask_clear(c1e_mask);
 	}
 }

 static int __init idle_setup(char *str)
 {
 	if (!str)
 		return -EINVAL;

 	if (!strcmp(str, "poll")) {
 		printk("using polling idle threads.\n");
 		pm_idle = poll_idle;
 	} else if (!strcmp(str, "mwait"))
 		force_mwait = 1;
 	else if (!strcmp(str, "halt")) {
 		/*
 		 * When the boot option of idle=halt is added, halt is
 		 * forced to be used for CPU idle. In such case CPU C2/C3
 		 * won't be used again.
 		 * To continue to load the CPU idle driver, don't touch
 		 * the boot_option_idle_override.
 		 */
 		pm_idle = default_idle;
 		idle_halt = 1;
 		return 0;
 	} else if (!strcmp(str, "nomwait")) {
 		/*
 		 * If the boot option of "idle=nomwait" is added,
 		 * it means that mwait will be disabled for CPU C2/C3
 		 * states. In such case it won't touch the variable
 		 * of boot_option_idle_override.
 		 */
 		idle_nomwait = 1;
 		return 0;
 	} else
 		return -1;

 	boot_option_idle_override = 1;
 	return 0;
 }
 early_param("idle", idle_setup);

 unsigned long arch_align_stack(unsigned long sp)
 {
 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 		sp -= get_random_int() % 8192;
 	return sp & ~0xf;
 }

 unsigned long arch_randomize_brk(struct mm_struct *mm)
 {
 	unsigned long range_end = mm->brk + 0x02000000;
 	return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
 }
	#include <linux/errno.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/smp.h>
	#include <linux/prctl.h>
	#include <linux/slab.h>
	#include <linux/sched.h>
	#include <linux/module.h>
	#include <linux/pm.h>
	#include <linux/clockchips.h>
	#include <linux/random.h>
	#include <trace/events/power.h>
	#include <asm/system.h>
	#include <asm/apic.h>
	#include <asm/syscalls.h>
	#include <asm/idle.h>
	#include <asm/uaccess.h>
	#include <asm/i387.h>
	#include <asm/ds.h>

	unsigned long idle_halt;
	EXPORT_SYMBOL(idle_halt);
	unsigned long idle_nomwait;
	EXPORT_SYMBOL(idle_nomwait);

	struct kmem_cache *task_xstate_cachep;

	int arch_dup_task_struct(struct task_struct dst, struct task_struct src)
	{
	dst = src;
	if (src->thread.xstate) {
	dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
	GFP_KERNEL);
	if (!dst->thread.xstate)
	return -ENOMEM;
	WARN_ON((unsigned long)dst->thread.xstate & 15);
	memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
	}
	return 0;
	}

	void free_thread_xstate(struct task_struct *tsk)
	{
	if (tsk->thread.xstate) {
	kmem_cache_free(task_xstate_cachep, tsk->thread.xstate);
	tsk->thread.xstate = NULL;
	}

	WARN(tsk->thread.ds_ctx, "leaking DS context\n");
	}

	void free_thread_info(struct thread_info *ti)
	{
	free_thread_xstate(ti->task);
	free_pages((unsigned long)ti, get_order(THREAD_SIZE));
	}

	void arch_task_cache_init(void)
	{
	task_xstate_cachep =
	kmem_cache_create("task_xstate", xstate_size,
	__alignof__(union thread_xstate),
	SLAB_PANIC \| SLAB_NOTRACK, NULL);
	}

	/*
	* Free current thread data structures etc..
	*/
	void exit_thread(void)
	{
	struct task_struct *me = current;
	struct thread_struct *t = &me->thread;
	unsigned long *bp = t->io_bitmap_ptr;

	if (bp) {
	struct tss_struct *tss = &per_cpu(init_tss, get_cpu());

	t->io_bitmap_ptr = NULL;
	clear_thread_flag(TIF_IO_BITMAP);
	/*
	* Careful, clear this in the TSS too:
	*/
	memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
	t->io_bitmap_max = 0;
	put_cpu();
	kfree(bp);
	}
	}

	void flush_thread(void)
	{
	struct task_struct *tsk = current;

	#ifdef CONFIG_X86_64
	if (test_tsk_thread_flag(tsk, TIF_ABI_PENDING)) {
	clear_tsk_thread_flag(tsk, TIF_ABI_PENDING);
	if (test_tsk_thread_flag(tsk, TIF_IA32)) {
	clear_tsk_thread_flag(tsk, TIF_IA32);
	} else {
	set_tsk_thread_flag(tsk, TIF_IA32);
	current_thread_info()->status \|= TS_COMPAT;
	}
	}
	#endif

	clear_tsk_thread_flag(tsk, TIF_DEBUG);

	tsk->thread.debugreg0 = 0;
	tsk->thread.debugreg1 = 0;
	tsk->thread.debugreg2 = 0;
	tsk->thread.debugreg3 = 0;
	tsk->thread.debugreg6 = 0;
	tsk->thread.debugreg7 = 0;
	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
	/*
	* Forget coprocessor state..
	*/
	tsk->fpu_counter = 0;
	clear_fpu(tsk);
	clear_used_math();
	}

	static void hard_disable_TSC(void)
	{
	write_cr4(read_cr4() \| X86_CR4_TSD);
	}

	void disable_TSC(void)
	{
	preempt_disable();
	if (!test_and_set_thread_flag(TIF_NOTSC))
	/*
	* Must flip the CPU state synchronously with
	* TIF_NOTSC in the current running context.
	*/
	hard_disable_TSC();
	preempt_enable();
	}

	static void hard_enable_TSC(void)
	{
	write_cr4(read_cr4() & ~X86_CR4_TSD);
	}

	static void enable_TSC(void)
	{
	preempt_disable();
	if (test_and_clear_thread_flag(TIF_NOTSC))
	/*
	* Must flip the CPU state synchronously with
	* TIF_NOTSC in the current running context.
	*/
	hard_enable_TSC();
	preempt_enable();
	}

	int get_tsc_mode(unsigned long adr)
	{
	unsigned int val;

	if (test_thread_flag(TIF_NOTSC))
	val = PR_TSC_SIGSEGV;
	else
	val = PR_TSC_ENABLE;

	return put_user(val, (unsigned int __user *)adr);
	}

	int set_tsc_mode(unsigned int val)
	{
	if (val == PR_TSC_SIGSEGV)
	disable_TSC();
	else if (val == PR_TSC_ENABLE)
	enable_TSC();
	else
	return -EINVAL;

	return 0;
	}

	void __switch_to_xtra(struct task_struct prev_p, struct task_struct next_p,
	struct tss_struct *tss)
	{
	struct thread_struct prev, next;

	prev = &prev_p->thread;
	next = &next_p->thread;

	if (test_tsk_thread_flag(next_p, TIF_DS_AREA_MSR) \|\|
	test_tsk_thread_flag(prev_p, TIF_DS_AREA_MSR))
	ds_switch_to(prev_p, next_p);
	else if (next->debugctlmsr != prev->debugctlmsr)
	update_debugctlmsr(next->debugctlmsr);

	if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
	set_debugreg(next->debugreg0, 0);
	set_debugreg(next->debugreg1, 1);
	set_debugreg(next->debugreg2, 2);
	set_debugreg(next->debugreg3, 3);
	/* no 4 and 5 */
	set_debugreg(next->debugreg6, 6);
	set_debugreg(next->debugreg7, 7);
	}

	if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
	test_tsk_thread_flag(next_p, TIF_NOTSC)) {
	/* prev and next are different */
	if (test_tsk_thread_flag(next_p, TIF_NOTSC))
	hard_disable_TSC();
	else
	hard_enable_TSC();
	}

	if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
	/*
	* Copy the relevant range of the IO bitmap.
	* Normally this is 128 bytes or less:
	*/
	memcpy(tss->io_bitmap, next->io_bitmap_ptr,
	max(prev->io_bitmap_max, next->io_bitmap_max));
	} else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
	/*
	* Clear any possible leftover bits:
	*/
	memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
	}
	}

	int sys_fork(struct pt_regs *regs)
	{
	return do_fork(SIGCHLD, regs->sp, regs, 0, NULL, NULL);
	}

	/*
	* This is trivial, and on the face of it looks like it
	* could equally well be done in user mode.
	*
	* Not so, for quite unobvious reasons - register pressure.
	* In user mode vfork() cannot have a stack frame, and if
	* done by calling the "clone()" system call directly, you
	* do not have enough call-clobbered registers to hold all
	* the information you need.
	*/
	int sys_vfork(struct pt_regs *regs)
	{
	return do_fork(CLONE_VFORK \| CLONE_VM \| SIGCHLD, regs->sp, regs, 0,
	NULL, NULL);
	}


	/*
	* Idle related variables and functions
	*/
	unsigned long boot_option_idle_override = 0;
	EXPORT_SYMBOL(boot_option_idle_override);

	/*
	* Powermanagement idle function, if any..
	*/
	void (*pm_idle)(void);
	EXPORT_SYMBOL(pm_idle);

	#ifdef CONFIG_X86_32
	/*
	* This halt magic was a workaround for ancient floppy DMA
	* wreckage. It should be safe to remove.
	*/
	static int hlt_counter;
	void disable_hlt(void)
	{
	hlt_counter++;
	}
	EXPORT_SYMBOL(disable_hlt);

	void enable_hlt(void)
	{
	hlt_counter--;
	}
	EXPORT_SYMBOL(enable_hlt);

	static inline int hlt_use_halt(void)
	{
	return (!hlt_counter && boot_cpu_data.hlt_works_ok);
	}
	#else
	static inline int hlt_use_halt(void)
	{
	return 1;
	}
	#endif

	/*
	* We use this if we don't have any better
	* idle routine..
	*/
	void default_idle(void)
	{
	if (hlt_use_halt()) {
	trace_power_start(POWER_CSTATE, 1);
	current_thread_info()->status &= ~TS_POLLING;
	/*
	* TS_POLLING-cleared state must be visible before we
	* test NEED_RESCHED:
	*/
	smp_mb();

	if (!need_resched())
	safe_halt(); /* enables interrupts racelessly */
	else
	local_irq_enable();
	current_thread_info()->status \|= TS_POLLING;
	} else {
	local_irq_enable();
	/* loop is done by the caller */
	cpu_relax();
	}
	}
	#ifdef CONFIG_APM_MODULE
	EXPORT_SYMBOL(default_idle);
	#endif

	void stop_this_cpu(void *dummy)
	{
	local_irq_disable();
	/*
	* Remove this CPU:
	*/
	set_cpu_online(smp_processor_id(), false);
	disable_local_APIC();

	for (;;) {
	if (hlt_works(smp_processor_id()))
	halt();
	}
	}

	static void do_nothing(void *unused)
	{
	}

	/*
	* cpu_idle_wait - Used to ensure that all the CPUs discard old value of
	* pm_idle and update to new pm_idle value. Required while changing pm_idle
	* handler on SMP systems.
	*
	* Caller must have changed pm_idle to the new value before the call. Old
	* pm_idle value will not be used by any CPU after the return of this function.
	*/
	void cpu_idle_wait(void)
	{
	smp_mb();
	/* kick all the CPUs so that they exit out of pm_idle */
	smp_call_function(do_nothing, NULL, 1);
	}
	EXPORT_SYMBOL_GPL(cpu_idle_wait);

	/*
	* This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
	* which can obviate IPI to trigger checking of need_resched.
	* We execute MONITOR against need_resched and enter optimized wait state
	* through MWAIT. Whenever someone changes need_resched, we would be woken
	* up from MWAIT (without an IPI).
	*
	* New with Core Duo processors, MWAIT can take some hints based on CPU
	* capability.
	*/
	void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
	{
	trace_power_start(POWER_CSTATE, (ax>>4)+1);
	if (!need_resched()) {
	if (cpu_has(&current_cpu_data, X86_FEATURE_CLFLUSH_MONITOR))
	clflush((void *)&current_thread_info()->flags);

	__monitor((void *)&current_thread_info()->flags, 0, 0);
	smp_mb();
	if (!need_resched())
	__mwait(ax, cx);
	}
	}

	/* Default MONITOR/MWAIT with no hints, used for default C1 state */
	static void mwait_idle(void)
	{
	if (!need_resched()) {
	trace_power_start(POWER_CSTATE, 1);
	if (cpu_has(&current_cpu_data, X86_FEATURE_CLFLUSH_MONITOR))
	clflush((void *)&current_thread_info()->flags);

	__monitor((void *)&current_thread_info()->flags, 0, 0);
	smp_mb();
	if (!need_resched())
	__sti_mwait(0, 0);
	else
	local_irq_enable();
	} else
	local_irq_enable();
	}

	/*
	* On SMP it's slightly faster (but much more power-consuming!)
	* to poll the ->work.need_resched flag instead of waiting for the
	* cross-CPU IPI to arrive. Use this option with caution.
	*/
	static void poll_idle(void)
	{
	trace_power_start(POWER_CSTATE, 0);
	local_irq_enable();
	while (!need_resched())
	cpu_relax();
	trace_power_end(0);
	}

	/*
	* mwait selection logic:
	*
	* It depends on the CPU. For AMD CPUs that support MWAIT this is
	* wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings
	* then depend on a clock divisor and current Pstate of the core. If
	* all cores of a processor are in halt state (C1) the processor can
	* enter the C1E (C1 enhanced) state. If mwait is used this will never
	* happen.
	*
	* idle=mwait overrides this decision and forces the usage of mwait.
	*/
	static int __cpuinitdata force_mwait;

	#define MWAIT_INFO 0x05
	#define MWAIT_ECX_EXTENDED_INFO 0x01
	#define MWAIT_EDX_C1 0xf0

	static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
	{
	u32 eax, ebx, ecx, edx;

	if (force_mwait)
	return 1;

	if (c->cpuid_level < MWAIT_INFO)
	return 0;

	cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx);
	/* Check, whether EDX has extended info about MWAIT */
	if (!(ecx & MWAIT_ECX_EXTENDED_INFO))
	return 1;

	/*
	* edx enumeratios MONITOR/MWAIT extensions. Check, whether
	* C1 supports MWAIT
	*/
	return (edx & MWAIT_EDX_C1);
	}

	/*
	* Check for AMD CPUs, which have potentially C1E support
	*/
	static int __cpuinit check_c1e_idle(const struct cpuinfo_x86 *c)
	{
	if (c->x86_vendor != X86_VENDOR_AMD)
	return 0;

	if (c->x86 < 0x0F)
	return 0;

	/* Family 0x0f models < rev F do not have C1E */
	if (c->x86 == 0x0f && c->x86_model < 0x40)
	return 0;

	return 1;
	}

	static cpumask_var_t c1e_mask;
	static int c1e_detected;

	void c1e_remove_cpu(int cpu)
	{
	if (c1e_mask != NULL)
	cpumask_clear_cpu(cpu, c1e_mask);
	}

	/*
	* C1E aware idle routine. We check for C1E active in the interrupt
	* pending message MSR. If we detect C1E, then we handle it the same
	* way as C3 power states (local apic timer and TSC stop)
	*/
	static void c1e_idle(void)
	{
	if (need_resched())
	return;

	if (!c1e_detected) {
	u32 lo, hi;

	rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
	if (lo & K8_INTP_C1E_ACTIVE_MASK) {
	c1e_detected = 1;
	if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
	mark_tsc_unstable("TSC halt in AMD C1E");
	printk(KERN_INFO "System has AMD C1E enabled\n");
	set_cpu_cap(&boot_cpu_data, X86_FEATURE_AMDC1E);
	}
	}

	if (c1e_detected) {
	int cpu = smp_processor_id();

	if (!cpumask_test_cpu(cpu, c1e_mask)) {
	cpumask_set_cpu(cpu, c1e_mask);
	/*
	* Force broadcast so ACPI can not interfere.
	*/
	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_FORCE,
	&cpu);
	printk(KERN_INFO "Switch to broadcast mode on CPU%d\n",
	cpu);
	}
	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);

	default_idle();

	/*
	* The switch back from broadcast mode needs to be
	* called with interrupts disabled.
	*/
	local_irq_disable();
	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
	local_irq_enable();
	} else
	default_idle();
	}

	void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
	{
	#ifdef CONFIG_SMP
	if (pm_idle == poll_idle && smp_num_siblings > 1) {
	printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
	" performance may degrade.\n");
	}
	#endif
	if (pm_idle)
	return;

	if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
	/*
	* One CPU supports mwait => All CPUs supports mwait
	*/
	printk(KERN_INFO "using mwait in idle threads.\n");
	pm_idle = mwait_idle;
	} else if (check_c1e_idle(c)) {
	printk(KERN_INFO "using C1E aware idle routine\n");
	pm_idle = c1e_idle;
	} else
	pm_idle = default_idle;
	}

	void __init init_c1e_mask(void)
	{
	/* If we're using c1e_idle, we need to allocate c1e_mask. */
	if (pm_idle == c1e_idle) {
	alloc_cpumask_var(&c1e_mask, GFP_KERNEL);
	cpumask_clear(c1e_mask);
	}
	}

	static int __init idle_setup(char *str)
	{
	if (!str)
	return -EINVAL;

	if (!strcmp(str, "poll")) {
	printk("using polling idle threads.\n");
	pm_idle = poll_idle;
	} else if (!strcmp(str, "mwait"))
	force_mwait = 1;
	else if (!strcmp(str, "halt")) {
	/*
	* When the boot option of idle=halt is added, halt is
	* forced to be used for CPU idle. In such case CPU C2/C3
	* won't be used again.
	* To continue to load the CPU idle driver, don't touch
	* the boot_option_idle_override.
	*/
	pm_idle = default_idle;
	idle_halt = 1;
	return 0;
	} else if (!strcmp(str, "nomwait")) {
	/*
	* If the boot option of "idle=nomwait" is added,
	* it means that mwait will be disabled for CPU C2/C3
	* states. In such case it won't touch the variable
	* of boot_option_idle_override.
	*/
	idle_nomwait = 1;
	return 0;
	} else
	return -1;

	boot_option_idle_override = 1;
	return 0;
	}
	early_param("idle", idle_setup);

	unsigned long arch_align_stack(unsigned long sp)
	{
	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
	sp -= get_random_int() % 8192;
	return sp & ~0xf;
	}

	unsigned long arch_randomize_brk(struct mm_struct *mm)
	{
	unsigned long range_end = mm->brk + 0x02000000;
	return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
	}