process.c

/*
 * 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/export.h>
#include <linux/sched.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 <asm/compat.h>
#include <asm/cacheflush.h>
#include <asm/processor.h>
#include <asm/stacktrace.h>
#include <asm/fpsimd.h>

static void setup_restart(void)
{
	/*
	 * Tell the mm system that we are going to reboot -
	 * we may need it to insert some 1:1 mappings so that
	 * soft boot works.
	 */
	setup_mm_for_reboot();

	/* Clean and invalidate caches */
	flush_cache_all();

	/* Turn D-cache off */
	cpu_cache_off();

	/* Push out any further dirty data, and ensure cache is empty */
	flush_cache_all();
}

void soft_restart(unsigned long addr)
{
	setup_restart();
	cpu_reset(addr);
}

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

void (*pm_restart)(const char *cmd);
EXPORT_SYMBOL_GPL(pm_restart);


/*
 * This is our default idle handler.
 */
static void default_idle(void)
{
	/*
	 * This should do all the clock switching and wait for interrupt
	 * tricks
	 */
	cpu_do_idle();
	local_irq_enable();
}

void (*pm_idle)(void) = default_idle;
EXPORT_SYMBOL_GPL(pm_idle);

/*
 * The idle thread, has rather strange semantics for calling pm_idle,
 * but this is what x86 does and we need to do the same, so that
 * things like cpuidle get called in the same way.  The only difference
 * is that we always respect 'hlt_counter' to prevent low power idle.
 */
void cpu_idle(void)
{
	local_fiq_enable();

	/* endless idle loop with no priority at all */
	while (1) {
		tick_nohz_idle_enter();
		rcu_idle_enter();
		while (!need_resched()) {
			/*
			 * We need to disable interrupts here to ensure
			 * we don't miss a wakeup call.
			 */
			local_irq_disable();
			if (!need_resched()) {
				stop_critical_timings();
				pm_idle();
				start_critical_timings();
				/*
				 * pm_idle functions should always return
				 * with IRQs enabled.
				 */
				WARN_ON(irqs_disabled());
			} else {
				local_irq_enable();
			}
		}
		rcu_idle_exit();
		tick_nohz_idle_exit();
		schedule_preempt_disabled();
	}
}

void machine_shutdown(void)
{
#ifdef CONFIG_SMP
	smp_send_stop();
#endif
}

void machine_halt(void)
{
	machine_shutdown();
	while (1);
}

void machine_power_off(void)
{
	machine_shutdown();
	if (pm_power_off)
		pm_power_off();
}

void machine_restart(char *cmd)
{
	machine_shutdown();

	/* Disable interrupts first */
	local_irq_disable();
	local_fiq_disable();

	/* Now call the architecture specific reboot code. */
	if (pm_restart)
		pm_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;

	printk("CPU: %d    %s  (%s %.*s)\n",
		raw_smp_processor_id(), print_tainted(),
		init_utsname()->release,
		(int)strcspn(init_utsname()->version, " "),
		init_utsname()->version);
	print_symbol("PC is at %s\n", instruction_pointer(regs));
	print_symbol("LR is at %s\n", regs->regs[30]);
	printk("pc : [<%016llx>] lr : [<%016llx>] pstate: %08llx\n",
	       regs->pc, regs->regs[30], regs->pstate);
	printk("sp : %016llx\n", regs->sp);
	for (i = 29; i >= 0; i--) {
		printk("x%-2d: %016llx ", i, regs->regs[i]);
		if (i % 2 == 0)
			printk("\n");
	}
	printk("\n");
}

void show_regs(struct pt_regs * regs)
{
	printk("\n");
	printk("Pid: %d, comm: %20s\n", task_pid_nr(current), current->comm);
	__show_regs(regs);
}

/*
 * Free current thread data structures etc..
 */
void exit_thread(void)
{
}

void flush_thread(void)
{
	fpsimd_flush_thread();
	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)
{
	fpsimd_save_state(&current->thread.fpsimd_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 *regs)
{
	struct pt_regs *childregs = task_pt_regs(p);
	unsigned long tls = p->thread.tp_value;

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

	if (likely(regs)) {
		*childregs = *regs;
		childregs->regs[0] = 0;
		if (is_compat_thread(task_thread_info(p))) {
			if (stack_start)
				childregs->compat_sp = stack_start;
		} else {
			/*
			 * Read the current TLS pointer from tpidr_el0 as it may be
			 * out-of-sync with the saved value.
			 */
			asm("mrs %0, tpidr_el0" : "=r" (tls));
			if (stack_start) {
				/* 16-byte aligned stack mandatory on AArch64 */
				if (stack_start & 15)
					return -EINVAL;
				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)
			tls = regs->regs[3];
	} else {
		memset(childregs, 0, sizeof(struct pt_regs));
		childregs->pstate = PSR_MODE_EL1h;
		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;
	p->thread.tp_value = tls;

	ptrace_hw_copy_thread(p);

	return 0;
}

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

	if (!is_compat_task()) {
		asm("mrs %0, tpidr_el0" : "=r" (tpidr));
		current->thread.tp_value = tpidr;
	}

	if (is_compat_thread(task_thread_info(next))) {
		tpidr = 0;
		tpidrro = next->thread.tp_value;
	} else {
		tpidr = next->thread.tp_value;
		tpidrro = 0;
	}

	asm(
	"	msr	tpidr_el0, %0\n"
	"	msr	tpidrro_el0, %1"
	: : "r" (tpidr), "r" (tpidrro));
}

/*
 * Thread switching.
 */
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);

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

	return last;
}

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

	frame.fp = thread_saved_fp(p);
	frame.sp = thread_saved_sp(p);
	frame.pc = thread_saved_pc(p);
	do {
		int ret = unwind_frame(&frame);
		if (ret < 0)
			return 0;
		if (!in_sched_functions(frame.pc))
			return frame.pc;
	} while (count ++ < 16);
	return 0;
}

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;
}

static unsigned long randomize_base(unsigned long base)
{
	unsigned long range_end = base + (STACK_RND_MASK << PAGE_SHIFT) + 1;
	return randomize_range(base, range_end, 0) ? : base;
}

unsigned long arch_randomize_brk(struct mm_struct *mm)
{
	return randomize_base(mm->brk);
}

unsigned long randomize_et_dyn(unsigned long base)
{
	return randomize_base(base);
}