process.c

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/*
 * 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;

    *childregs = *regs;
    childregs->regs[0] = 0;

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

    memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
    p->thread.cpu_context.sp = (unsigned long)childregs;
    p->thread.cpu_context.pc = (unsigned long)ret_from_fork;

    /* If a TLS pointer was passed to clone, use that for the new thread. */
    if (clone_flags & CLONE_SETTLS)
        tls = regs->regs[3];
    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;
}

/*
 * Shuffle the argument into the correct register before calling the
 * thread function.  x1 is the thread argument, x2 is the pointer to
 * the thread function, and x3 points to the exit function.
 */
extern void kernel_thread_helper(void);
asm(    ".section .text\n"
"   .align\n"
"   .type   kernel_thread_helper, #function\n"
"kernel_thread_helper:\n"
"   mov x0, x1\n"
"   mov x30, x3\n"
"   br  x2\n"
"   .size   kernel_thread_helper, . - kernel_thread_helper\n"
"   .previous");

#define kernel_thread_exit  do_exit

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

    memset(&regs, 0, sizeof(regs));

    regs.regs[1] = (unsigned long)arg;
    regs.regs[2] = (unsigned long)fn;
    regs.regs[3] = (unsigned long)kernel_thread_exit;
    regs.pc = (unsigned long)kernel_thread_helper;
    regs.pstate = PSR_MODE_EL1h;

    return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
}
EXPORT_SYMBOL(kernel_thread);

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);
}