/*
 * 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/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 <asm/alternative.h>
#include <asm/compat.h>
#include <asm/cacheflush.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);
        for (i = top_reg; 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");
        __show_regs(regs);
}

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

static void tls_thread_flush(void)
{
        asm ("msr tpidr_el0, xzr");

        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();
                asm ("msr tpidrro_el0, xzr");
        }
}

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.
                 */
                asm("mrs %0, tpidr_el0" : "=r" (*task_user_tls(p)));

                if (stack_start) {
                        if (is_compat_thread(task_thread_info(p)))
                                childregs->compat_sp = stack_start;
                        /* 16-byte aligned stack mandatory on AArch64 */
                        else if (stack_start & 15)
                                return -EINVAL;
                        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_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;
}

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

        asm("mrs %0, tpidr_el0" : "=r" (tpidr));
        *task_user_tls(current) = tpidr;

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

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

/* Restore the UAO state depending on next's addr_limit */
static 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));
        }
}

/*
 * 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);
        contextidr_thread_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.
         */
        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;
        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);
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        frame.graph = p->curr_ret_stack;
#endif
        stack_page = (unsigned long)task_stack_page(p);
        do {
                if (frame.sp < stack_page ||
                    frame.sp >= stack_page + THREAD_SIZE ||
                    unwind_frame(p, &frame))
                        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);
}