/*
 * 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/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 <linux/thread_info.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_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);
}

static void print_pstate(struct pt_regs *regs)
{
        u64 pstate = regs->pstate;

        if (compat_user_mode(regs)) {
                printk("pstate: %08llx (%c%c%c%c %c %s %s %c%c%c)\n",
                        pstate,
                        pstate & COMPAT_PSR_N_BIT ? 'N' : 'n',
                        pstate & COMPAT_PSR_Z_BIT ? 'Z' : 'z',
                        pstate & COMPAT_PSR_C_BIT ? 'C' : 'c',
                        pstate & COMPAT_PSR_V_BIT ? 'V' : 'v',
                        pstate & COMPAT_PSR_Q_BIT ? 'Q' : 'q',
                        pstate & COMPAT_PSR_T_BIT ? "T32" : "A32",
                        pstate & COMPAT_PSR_E_BIT ? "BE" : "LE",
                        pstate & COMPAT_PSR_A_BIT ? 'A' : 'a',
                        pstate & COMPAT_PSR_I_BIT ? 'I' : 'i',
                        pstate & COMPAT_PSR_F_BIT ? 'F' : 'f');
        } else {
                printk("pstate: %08llx (%c%c%c%c %c%c%c%c %cPAN %cUAO)\n",
                        pstate,
                        pstate & PSR_N_BIT ? 'N' : 'n',
                        pstate & PSR_Z_BIT ? 'Z' : 'z',
                        pstate & PSR_C_BIT ? 'C' : 'c',
                        pstate & PSR_V_BIT ? 'V' : 'v',
                        pstate & PSR_D_BIT ? 'D' : 'd',
                        pstate & PSR_A_BIT ? 'A' : 'a',
                        pstate & PSR_I_BIT ? 'I' : 'i',
                        pstate & PSR_F_BIT ? 'F' : 'f',
                        pstate & PSR_PAN_BIT ? '+' : '-',
                        pstate & PSR_UAO_BIT ? '+' : '-');
        }
}

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_pstate(regs);

        if (!user_mode(regs)) {
                printk("pc : %pS\n", (void *)regs->pc);
                printk("lr : %pS\n", (void *)lr);
        } else {
                printk("pc : %016llx\n", regs->pc);
                printk("lr : %016llx\n", lr);
        }

        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.uw.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)
{
}

void arch_release_task_struct(struct task_struct *tsk)
{
        fpsimd_release_task(tsk);
}

/*
 * src and dst may temporarily have aliased sve_state after task_struct
 * is copied.  We cannot fix this properly here, because src may have
 * live SVE state and dst's thread_info may not exist yet, so tweaking
 * either src's or dst's TIF_SVE is not safe.
 *
 * The unaliasing is done in copy_thread() instead.  This works because
 * dst is not schedulable or traceable until both of these functions
 * have been called.
 */
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));

        /*
         * Unalias p->thread.sve_state (if any) from the parent task
         * and disable discard SVE state for p:
         */
        clear_tsk_thread_flag(p, TIF_SVE);
        p->thread.sve_state = NULL;

        /*
         * In case p was allocated the same task_struct pointer as some
         * other recently-exited task, make sure p is disassociated from
         * any cpu that may have run that now-exited task recently.
         * Otherwise we could erroneously skip reloading the FPSIMD
         * registers for p.
         */
        fpsimd_flush_task_state(p);

        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.uw.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)
{
        tls_preserve_current_state();

        if (is_compat_thread(task_thread_info(next)))
                write_sysreg(next->thread.uw.tp_value, tpidrro_el0);
        else if (!arm64_kernel_unmapped_at_el0())
                write_sysreg(0, tpidrro_el0);

        write_sysreg(*task_user_tls(next), tpidr_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.pc = thread_saved_pc(p);
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        frame.graph = p->curr_ret_stack;
#endif
        do {
                if (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);
}

/*
 * Called from setup_new_exec() after (COMPAT_)SET_PERSONALITY.
 */
void arch_setup_new_exec(void)
{
        current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;
}