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

 /*
  * Based on arch/arm/kernel/process.c
  *
  * Original Copyright (C) 1995  Linus Torvalds
  * Copyright (C) 1996-2000 Russell King - Converted to ARM.
  * 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 <stdarg.h>

 #include <linux/compat.h>
 #include <linux/efi.h>
 #include <linux/export.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
 #include <linux/sched/task.h>
 #include <linux/sched/task_stack.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/stddef.h>
 #include <linux/unistd.h>
 #include <linux/user.h>
 #include <linux/delay.h>
 #include <linux/reboot.h>
 #include <linux/interrupt.h>
 #include <linux/kallsyms.h>
 #include <linux/init.h>
 #include <linux/cpu.h>
 #include <linux/elfcore.h>
 #include <linux/pm.h>
 #include <linux/tick.h>
 #include <linux/utsname.h>
 #include <linux/uaccess.h>
 #include <linux/random.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/personality.h>
 #include <linux/notifier.h>
 #include <trace/events/power.h>
 #include <linux/percpu.h>

 #include <asm/alternative.h>
 #include <asm/compat.h>
 #include <asm/cacheflush.h>
 #include <asm/exec.h>
 #include <asm/fpsimd.h>
 #include <asm/mmu_context.h>
 #include <asm/processor.h>
 #include <asm/stacktrace.h>

 #ifdef CONFIG_CC_STACKPROTECTOR
 #include <linux/stackprotector.h>
 unsigned long __stack_chk_guard __read_mostly;
 EXPORT_SYMBOL(__stack_chk_guard);
 #endif

 /*
  * Function pointers to optional machine specific functions
  */
 void (*pm_power_off)(void);
 EXPORT_SYMBOL_GPL(pm_power_off);

 void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);

 /*
  * This is our default idle handler.
  */
 void arch_cpu_idle(void)
 {
 	/*
 	 * This should do all the clock switching and wait for interrupt
 	 * tricks
 	 */
 	trace_cpu_idle_rcuidle(1, smp_processor_id());
 	cpu_do_idle();
 	local_irq_enable();
 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
 }

 #ifdef CONFIG_HOTPLUG_CPU
 void arch_cpu_idle_dead(void)
 {
        cpu_die();
 }
 #endif

 /*
  * Called by kexec, immediately prior to machine_kexec().
  *
  * This must completely disable all secondary CPUs; simply causing those CPUs
  * to execute e.g. a RAM-based pin loop is not sufficient. This allows the
  * kexec'd kernel to use any and all RAM as it sees fit, without having to
  * avoid any code or data used by any SW CPU pin loop. The CPU hotplug
  * functionality embodied in disable_nonboot_cpus() to achieve this.
  */
 void machine_shutdown(void)
 {
 	disable_nonboot_cpus();
 }

 /*
  * Halting simply requires that the secondary CPUs stop performing any
  * activity (executing tasks, handling interrupts). smp_send_stop()
  * achieves this.
  */
 void machine_halt(void)
 {
 	local_irq_disable();
 	smp_send_stop();
 	while (1);
 }

 /*
  * Power-off simply requires that the secondary CPUs stop performing any
  * activity (executing tasks, handling interrupts). smp_send_stop()
  * achieves this. When the system power is turned off, it will take all CPUs
  * with it.
  */
 void machine_power_off(void)
 {
 	local_irq_disable();
 	smp_send_stop();
 	if (pm_power_off)
 		pm_power_off();
 }

 /*
  * Restart requires that the secondary CPUs stop performing any activity
  * while the primary CPU resets the system. Systems with multiple CPUs must
  * provide a HW restart implementation, to ensure that all CPUs reset at once.
  * This is required so that any code running after reset on the primary CPU
  * doesn't have to co-ordinate with other CPUs to ensure they aren't still
  * executing pre-reset code, and using RAM that the primary CPU's code wishes
  * to use. Implementing such co-ordination would be essentially impossible.
  */
 void machine_restart(char *cmd)
 {
 	/* Disable interrupts first */
 	local_irq_disable();
 	smp_send_stop();

 	/*
 	 * UpdateCapsule() depends on the system being reset via
 	 * ResetSystem().
 	 */
 	if (efi_enabled(EFI_RUNTIME_SERVICES))
 		efi_reboot(reboot_mode, NULL);

 	/* Now call the architecture specific reboot code. */
 	if (arm_pm_restart)
 		arm_pm_restart(reboot_mode, cmd);
 	else
 		do_kernel_restart(cmd);

 	/*
 	 * Whoops - the architecture was unable to reboot.
 	 */
 	printk("Reboot failed -- System halted\n");
 	while (1);
 }

 void __show_regs(struct pt_regs *regs)
 {
 	int i, top_reg;
 	u64 lr, sp;

 	if (compat_user_mode(regs)) {
 		lr = regs->compat_lr;
 		sp = regs->compat_sp;
 		top_reg = 12;
 	} else {
 		lr = regs->regs[30];
 		sp = regs->sp;
 		top_reg = 29;
 	}

 	show_regs_print_info(KERN_DEFAULT);
 	print_symbol("PC is at %s\n", instruction_pointer(regs));
 	print_symbol("LR is at %s\n", lr);
 	printk("pc : [<%016llx>] lr : [<%016llx>] pstate: %08llx\n",
 	       regs->pc, lr, regs->pstate);
 	printk("sp : %016llx\n", sp);

 	i = top_reg;

 	while (i >= 0) {
 		printk("x%-2d: %016llx ", i, regs->regs[i]);
 		i--;

 		if (i % 2 == 0) {
 			pr_cont("x%-2d: %016llx ", i, regs->regs[i]);
 			i--;
 		}

 		pr_cont("\n");
 	}
 }

 void show_regs(struct pt_regs * regs)
 {
 	__show_regs(regs);
 	dump_backtrace(regs, NULL);
 }

 static void tls_thread_flush(void)
 {
 	write_sysreg(0, tpidr_el0);

 	if (is_compat_task()) {
 		current->thread.tp_value = 0;

 		/*
 		 * We need to ensure ordering between the shadow state and the
 		 * hardware state, so that we don't corrupt the hardware state
 		 * with a stale shadow state during context switch.
 		 */
 		barrier();
 		write_sysreg(0, tpidrro_el0);
 	}
 }

 void flush_thread(void)
 {
 	fpsimd_flush_thread();
 	tls_thread_flush();
 	flush_ptrace_hw_breakpoint(current);
 }

 void release_thread(struct task_struct *dead_task)
 {
 }

 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 {
 	if (current->mm)
 		fpsimd_preserve_current_state();
 	*dst = *src;
 	return 0;
 }

 asmlinkage void ret_from_fork(void) asm("ret_from_fork");

 int copy_thread(unsigned long clone_flags, unsigned long stack_start,
 		unsigned long stk_sz, struct task_struct *p)
 {
 	struct pt_regs *childregs = task_pt_regs(p);

 	memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));

 	if (likely(!(p->flags & PF_KTHREAD))) {
 		*childregs = *current_pt_regs();
 		childregs->regs[0] = 0;

 		/*
 		 * Read the current TLS pointer from tpidr_el0 as it may be
 		 * out-of-sync with the saved value.
 		 */
 		*task_user_tls(p) = read_sysreg(tpidr_el0);

 		if (stack_start) {
 			if (is_compat_thread(task_thread_info(p)))
 				childregs->compat_sp = stack_start;
 			else
 				childregs->sp = stack_start;
 		}

 		/*
 		 * If a TLS pointer was passed to clone (4th argument), use it
 		 * for the new thread.
 		 */
 		if (clone_flags & CLONE_SETTLS)
 			p->thread.tp_value = childregs->regs[3];
 	} else {
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->pstate = PSR_MODE_EL1h;
 		if (IS_ENABLED(CONFIG_ARM64_UAO) &&
 		    cpus_have_const_cap(ARM64_HAS_UAO))
 			childregs->pstate |= PSR_UAO_BIT;
 		p->thread.cpu_context.x19 = stack_start;
 		p->thread.cpu_context.x20 = stk_sz;
 	}
 	p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
 	p->thread.cpu_context.sp = (unsigned long)childregs;

 	ptrace_hw_copy_thread(p);

 	return 0;
 }

 void tls_preserve_current_state(void)
 {
 	*task_user_tls(current) = read_sysreg(tpidr_el0);
 }

 static void tls_thread_switch(struct task_struct *next)
 {
 	unsigned long tpidr, tpidrro;

 	tls_preserve_current_state();

 	tpidr = *task_user_tls(next);
 	tpidrro = is_compat_thread(task_thread_info(next)) ?
 		  next->thread.tp_value : 0;

 	write_sysreg(tpidr, tpidr_el0);
 	write_sysreg(tpidrro, tpidrro_el0);
 }

 /* Restore the UAO state depending on next's addr_limit */
 void uao_thread_switch(struct task_struct *next)
 {
 	if (IS_ENABLED(CONFIG_ARM64_UAO)) {
 		if (task_thread_info(next)->addr_limit == KERNEL_DS)
 			asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
 		else
 			asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO));
 	}
 }

 /*
  * We store our current task in sp_el0, which is clobbered by userspace. Keep a
  * shadow copy so that we can restore this upon entry from userspace.
  *
  * This is *only* for exception entry from EL0, and is not valid until we
  * __switch_to() a user task.
  */
 DEFINE_PER_CPU(struct task_struct *, __entry_task);

 static void entry_task_switch(struct task_struct *next)
 {
 	__this_cpu_write(__entry_task, next);
 }

 /*
  * Thread switching.
  */
 __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
 				struct task_struct *next)
 {
 	struct task_struct *last;

 	fpsimd_thread_switch(next);
 	tls_thread_switch(next);
 	hw_breakpoint_thread_switch(next);
 	contextidr_thread_switch(next);
 	entry_task_switch(next);
 	uao_thread_switch(next);

 	/*
 	 * Complete any pending TLB or cache maintenance on this CPU in case
 	 * the thread migrates to a different CPU.
 	 * This full barrier is also required by the membarrier system
 	 * call.
 	 */
 	dsb(ish);

 	/* the actual thread switch */
 	last = cpu_switch_to(prev, next);

 	return last;
 }

 unsigned long get_wchan(struct task_struct *p)
 {
 	struct stackframe frame;
 	unsigned long stack_page, ret = 0;
 	int count = 0;
 	if (!p || p == current || p->state == TASK_RUNNING)
 		return 0;

 	stack_page = (unsigned long)try_get_task_stack(p);
 	if (!stack_page)
 		return 0;

 	frame.fp = thread_saved_fp(p);
 	frame.sp = thread_saved_sp(p);
 	frame.pc = thread_saved_pc(p);
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	frame.graph = p->curr_ret_stack;
 #endif
 	do {
 		if (frame.sp < stack_page ||
 		    frame.sp >= stack_page + THREAD_SIZE ||
 		    unwind_frame(p, &frame))
 			goto out;
 		if (!in_sched_functions(frame.pc)) {
 			ret = frame.pc;
 			goto out;
 		}
 	} while (count ++ < 16);

 out:
 	put_task_stack(p);
 	return ret;
 }

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

 unsigned long arch_randomize_brk(struct mm_struct *mm)
 {
 	if (is_compat_task())
 		return randomize_page(mm->brk, SZ_32M);
 	else
 		return randomize_page(mm->brk, SZ_1G);
 }
	/*
	* Based on arch/arm/kernel/process.c
	*
	* Original Copyright (C) 1995 Linus Torvalds
	* Copyright (C) 1996-2000 Russell King - Converted to ARM.
	* 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 <stdarg.h>

	#include <linux/compat.h>
	#include <linux/efi.h>
	#include <linux/export.h>
	#include <linux/sched.h>
	#include <linux/sched/debug.h>
	#include <linux/sched/task.h>
	#include <linux/sched/task_stack.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/stddef.h>
	#include <linux/unistd.h>
	#include <linux/user.h>
	#include <linux/delay.h>
	#include <linux/reboot.h>
	#include <linux/interrupt.h>
	#include <linux/kallsyms.h>
	#include <linux/init.h>
	#include <linux/cpu.h>
	#include <linux/elfcore.h>
	#include <linux/pm.h>
	#include <linux/tick.h>
	#include <linux/utsname.h>
	#include <linux/uaccess.h>
	#include <linux/random.h>
	#include <linux/hw_breakpoint.h>
	#include <linux/personality.h>
	#include <linux/notifier.h>
	#include <trace/events/power.h>
	#include <linux/percpu.h>

	#include <asm/alternative.h>
	#include <asm/compat.h>
	#include <asm/cacheflush.h>
	#include <asm/exec.h>
	#include <asm/fpsimd.h>
	#include <asm/mmu_context.h>
	#include <asm/processor.h>
	#include <asm/stacktrace.h>

	#ifdef CONFIG_CC_STACKPROTECTOR
	#include <linux/stackprotector.h>
	unsigned long __stack_chk_guard __read_mostly;
	EXPORT_SYMBOL(__stack_chk_guard);
	#endif

	/*
	* Function pointers to optional machine specific functions
	*/
	void (*pm_power_off)(void);
	EXPORT_SYMBOL_GPL(pm_power_off);

	void (arm_pm_restart)(enum reboot_mode reboot_mode, const char cmd);

	/*
	* This is our default idle handler.
	*/
	void arch_cpu_idle(void)
	{
	/*
	* This should do all the clock switching and wait for interrupt
	* tricks
	*/
	trace_cpu_idle_rcuidle(1, smp_processor_id());
	cpu_do_idle();
	local_irq_enable();
	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
	}

	#ifdef CONFIG_HOTPLUG_CPU
	void arch_cpu_idle_dead(void)
	{
	cpu_die();
	}
	#endif

	/*
	* Called by kexec, immediately prior to machine_kexec().
	*
	* This must completely disable all secondary CPUs; simply causing those CPUs
	* to execute e.g. a RAM-based pin loop is not sufficient. This allows the
	* kexec'd kernel to use any and all RAM as it sees fit, without having to
	* avoid any code or data used by any SW CPU pin loop. The CPU hotplug
	* functionality embodied in disable_nonboot_cpus() to achieve this.
	*/
	void machine_shutdown(void)
	{
	disable_nonboot_cpus();
	}

	/*
	* Halting simply requires that the secondary CPUs stop performing any
	* activity (executing tasks, handling interrupts). smp_send_stop()
	* achieves this.
	*/
	void machine_halt(void)
	{
	local_irq_disable();
	smp_send_stop();
	while (1);
	}

	/*
	* Power-off simply requires that the secondary CPUs stop performing any
	* activity (executing tasks, handling interrupts). smp_send_stop()
	* achieves this. When the system power is turned off, it will take all CPUs
	* with it.
	*/
	void machine_power_off(void)
	{
	local_irq_disable();
	smp_send_stop();
	if (pm_power_off)
	pm_power_off();
	}

	/*
	* Restart requires that the secondary CPUs stop performing any activity
	* while the primary CPU resets the system. Systems with multiple CPUs must
	* provide a HW restart implementation, to ensure that all CPUs reset at once.
	* This is required so that any code running after reset on the primary CPU
	* doesn't have to co-ordinate with other CPUs to ensure they aren't still
	* executing pre-reset code, and using RAM that the primary CPU's code wishes
	* to use. Implementing such co-ordination would be essentially impossible.
	*/
	void machine_restart(char *cmd)
	{
	/* Disable interrupts first */
	local_irq_disable();
	smp_send_stop();

	/*
	* UpdateCapsule() depends on the system being reset via
	* ResetSystem().
	*/
	if (efi_enabled(EFI_RUNTIME_SERVICES))
	efi_reboot(reboot_mode, NULL);

	/* Now call the architecture specific reboot code. */
	if (arm_pm_restart)
	arm_pm_restart(reboot_mode, cmd);
	else
	do_kernel_restart(cmd);

	/*
	* Whoops - the architecture was unable to reboot.
	*/
	printk("Reboot failed -- System halted\n");
	while (1);
	}

	void __show_regs(struct pt_regs *regs)
	{
	int i, top_reg;
	u64 lr, sp;

	if (compat_user_mode(regs)) {
	lr = regs->compat_lr;
	sp = regs->compat_sp;
	top_reg = 12;
	} else {
	lr = regs->regs[30];
	sp = regs->sp;
	top_reg = 29;
	}

	show_regs_print_info(KERN_DEFAULT);
	print_symbol("PC is at %s\n", instruction_pointer(regs));
	print_symbol("LR is at %s\n", lr);
	printk("pc : [<%016llx>] lr : [<%016llx>] pstate: %08llx\n",
	regs->pc, lr, regs->pstate);
	printk("sp : %016llx\n", sp);

	i = top_reg;

	while (i >= 0) {
	printk("x%-2d: %016llx ", i, regs->regs[i]);
	i--;

	if (i % 2 == 0) {
	pr_cont("x%-2d: %016llx ", i, regs->regs[i]);
	i--;
	}

	pr_cont("\n");
	}
	}

	void show_regs(struct pt_regs * regs)
	{
	__show_regs(regs);
	dump_backtrace(regs, NULL);
	}

	static void tls_thread_flush(void)
	{
	write_sysreg(0, tpidr_el0);

	if (is_compat_task()) {
	current->thread.tp_value = 0;

	/*
	* We need to ensure ordering between the shadow state and the
	* hardware state, so that we don't corrupt the hardware state
	* with a stale shadow state during context switch.
	*/
	barrier();
	write_sysreg(0, tpidrro_el0);
	}
	}

	void flush_thread(void)
	{
	fpsimd_flush_thread();
	tls_thread_flush();
	flush_ptrace_hw_breakpoint(current);
	}

	void release_thread(struct task_struct *dead_task)
	{
	}

	int arch_dup_task_struct(struct task_struct dst, struct task_struct src)
	{
	if (current->mm)
	fpsimd_preserve_current_state();
	dst = src;
	return 0;
	}

	asmlinkage void ret_from_fork(void) asm("ret_from_fork");

	int copy_thread(unsigned long clone_flags, unsigned long stack_start,
	unsigned long stk_sz, struct task_struct *p)
	{
	struct pt_regs *childregs = task_pt_regs(p);

	memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));

	if (likely(!(p->flags & PF_KTHREAD))) {
	childregs = current_pt_regs();
	childregs->regs[0] = 0;

	/*
	* Read the current TLS pointer from tpidr_el0 as it may be
	* out-of-sync with the saved value.
	*/
	*task_user_tls(p) = read_sysreg(tpidr_el0);

	if (stack_start) {
	if (is_compat_thread(task_thread_info(p)))
	childregs->compat_sp = stack_start;
	else
	childregs->sp = stack_start;
	}

	/*
	* If a TLS pointer was passed to clone (4th argument), use it
	* for the new thread.
	*/
	if (clone_flags & CLONE_SETTLS)
	p->thread.tp_value = childregs->regs[3];
	} else {
	memset(childregs, 0, sizeof(struct pt_regs));
	childregs->pstate = PSR_MODE_EL1h;
	if (IS_ENABLED(CONFIG_ARM64_UAO) &&
	cpus_have_const_cap(ARM64_HAS_UAO))
	childregs->pstate \|= PSR_UAO_BIT;
	p->thread.cpu_context.x19 = stack_start;
	p->thread.cpu_context.x20 = stk_sz;
	}
	p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
	p->thread.cpu_context.sp = (unsigned long)childregs;

	ptrace_hw_copy_thread(p);

	return 0;
	}

	void tls_preserve_current_state(void)
	{
	*task_user_tls(current) = read_sysreg(tpidr_el0);
	}

	static void tls_thread_switch(struct task_struct *next)
	{
	unsigned long tpidr, tpidrro;

	tls_preserve_current_state();

	tpidr = *task_user_tls(next);
	tpidrro = is_compat_thread(task_thread_info(next)) ?
	next->thread.tp_value : 0;

	write_sysreg(tpidr, tpidr_el0);
	write_sysreg(tpidrro, tpidrro_el0);
	}

	/* Restore the UAO state depending on next's addr_limit */
	void uao_thread_switch(struct task_struct *next)
	{
	if (IS_ENABLED(CONFIG_ARM64_UAO)) {
	if (task_thread_info(next)->addr_limit == KERNEL_DS)
	asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
	else
	asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO));
	}
	}

	/*
	* We store our current task in sp_el0, which is clobbered by userspace. Keep a
	* shadow copy so that we can restore this upon entry from userspace.
	*
	* This is only for exception entry from EL0, and is not valid until we
	* __switch_to() a user task.
	*/
	DEFINE_PER_CPU(struct task_struct *, __entry_task);

	static void entry_task_switch(struct task_struct *next)
	{
	__this_cpu_write(__entry_task, next);
	}

	/*
	* Thread switching.
	*/
	__notrace_funcgraph struct task_struct __switch_to(struct task_struct prev,
	struct task_struct *next)
	{
	struct task_struct *last;

	fpsimd_thread_switch(next);
	tls_thread_switch(next);
	hw_breakpoint_thread_switch(next);
	contextidr_thread_switch(next);
	entry_task_switch(next);
	uao_thread_switch(next);

	/*
	* Complete any pending TLB or cache maintenance on this CPU in case
	* the thread migrates to a different CPU.
	* This full barrier is also required by the membarrier system
	* call.
	*/
	dsb(ish);

	/* the actual thread switch */
	last = cpu_switch_to(prev, next);

	return last;
	}

	unsigned long get_wchan(struct task_struct *p)
	{
	struct stackframe frame;
	unsigned long stack_page, ret = 0;
	int count = 0;
	if (!p \|\| p == current \|\| p->state == TASK_RUNNING)
	return 0;

	stack_page = (unsigned long)try_get_task_stack(p);
	if (!stack_page)
	return 0;

	frame.fp = thread_saved_fp(p);
	frame.sp = thread_saved_sp(p);
	frame.pc = thread_saved_pc(p);
	#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	frame.graph = p->curr_ret_stack;
	#endif
	do {
	if (frame.sp < stack_page \|\|
	frame.sp >= stack_page + THREAD_SIZE \|\|
	unwind_frame(p, &frame))
	goto out;
	if (!in_sched_functions(frame.pc)) {
	ret = frame.pc;
	goto out;
	}
	} while (count ++ < 16);

	out:
	put_task_stack(p);
	return ret;
	}

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

	unsigned long arch_randomize_brk(struct mm_struct *mm)
	{
	if (is_compat_task())
	return randomize_page(mm->brk, SZ_32M);
	else
	return randomize_page(mm->brk, SZ_1G);
	}