// SPDX-License-Identifier: GPL-2.0
/*
 * Author: Huacai Chen <chenhuacai@loongson.cn>
 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
 *
 * Derived from MIPS:
 * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
 * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 * Copyright (C) 2004 Thiemo Seufer
 * Copyright (C) 2013  Imagination Technologies Ltd.
 */
#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/entry-common.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/hw_breakpoint.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/export.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/personality.h>
#include <linux/sys.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/random.h>
#include <linux/prctl.h>
#include <linux/nmi.h>

#include <asm/asm.h>
#include <asm/asm-prototypes.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
#include <asm/elf.h>
#include <asm/exec.h>
#include <asm/fpu.h>
#include <asm/lbt.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/irq_regs.h>
#include <asm/loongarch.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/reg.h>
#include <asm/switch_to.h>
#include <asm/unwind.h>
#include <asm/vdso.h>

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

/*
 * Idle related variables and functions
 */

unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
EXPORT_SYMBOL(boot_option_idle_override);

asmlinkage void restore_and_ret(void);
asmlinkage void ret_from_fork_asm(void);
asmlinkage void ret_from_kernel_thread_asm(void);

void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
{
        unsigned long crmd;
        unsigned long prmd;
        unsigned long euen;

        /* New thread loses kernel privileges. */
        crmd = regs->csr_crmd & ~(PLV_MASK);
        crmd |= PLV_USER;
        regs->csr_crmd = crmd;

        prmd = regs->csr_prmd & ~(PLV_MASK);
        prmd |= PLV_USER;
        regs->csr_prmd = prmd;

        euen = regs->csr_euen & ~(CSR_EUEN_FPEN);
        regs->csr_euen = euen;
        lose_fpu(0);
        lose_lbt(0);
        current->thread.fpu.fcsr = boot_cpu_data.fpu_csr0;

        clear_thread_flag(TIF_LSX_CTX_LIVE);
        clear_thread_flag(TIF_LASX_CTX_LIVE);
        clear_thread_flag(TIF_LBT_CTX_LIVE);
        clear_used_math();
        regs->csr_era = pc;
        regs->regs[3] = sp;
}

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

void exit_thread(struct task_struct *tsk)
{
}

int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
        /*
         * Save any process state which is live in hardware registers to the
         * parent context prior to duplication. This prevents the new child
         * state becoming stale if the parent is preempted before copy_thread()
         * gets a chance to save the parent's live hardware registers to the
         * child context.
         */
        preempt_disable();

        if (is_fpu_owner()) {
                if (is_lasx_enabled())
                        save_lasx(current);
                else if (is_lsx_enabled())
                        save_lsx(current);
                else
                        save_fp(current);
        }

        preempt_enable();

        if (IS_ENABLED(CONFIG_RANDSTRUCT)) {
                memcpy(dst, src, sizeof(struct task_struct));
                return 0;
        }

        if (!used_math())
                memcpy(dst, src, offsetof(struct task_struct, thread.fpu.fpr));
        else
                memcpy(dst, src, offsetof(struct task_struct, thread.lbt.scr0));

#ifdef CONFIG_CPU_HAS_LBT
        memcpy(&dst->thread.lbt, &src->thread.lbt, sizeof(struct loongarch_lbt));
#endif

        return 0;
}

asmlinkage void noinstr __no_stack_protector ret_from_fork(struct task_struct *prev,
                                                           struct pt_regs *regs)
{
        schedule_tail(prev);
        syscall_exit_to_user_mode(regs);
}

asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev,
                                                                    struct pt_regs *regs,
                                                                    int (*fn)(void *),
                                                                    void *fn_arg)
{
        schedule_tail(prev);
        fn(fn_arg);
        syscall_exit_to_user_mode(regs);
}

/*
 * Copy architecture-specific thread state
 */
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
        unsigned long childksp;
        unsigned long tls = args->tls;
        unsigned long usp = args->stack;
        u64 clone_flags = args->flags;
        struct pt_regs *childregs, *regs = current_pt_regs();

        childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE;

        /* set up new TSS. */
        childregs = (struct pt_regs *) childksp - 1;
        /*  Put the stack after the struct pt_regs.  */
        childksp = (unsigned long) childregs;
        p->thread.sched_cfa = 0;
        p->thread.csr_euen = 0;
        p->thread.csr_crmd = csr_read32(LOONGARCH_CSR_CRMD);
        p->thread.csr_prmd = csr_read32(LOONGARCH_CSR_PRMD);
        p->thread.csr_ecfg = csr_read32(LOONGARCH_CSR_ECFG);
        if (unlikely(args->fn)) {
                /* kernel thread */
                p->thread.reg03 = childksp;
                p->thread.reg23 = (unsigned long)args->fn;
                p->thread.reg24 = (unsigned long)args->fn_arg;
                p->thread.reg01 = (unsigned long)ret_from_kernel_thread_asm;
                p->thread.sched_ra = (unsigned long)ret_from_kernel_thread_asm;
                memset(childregs, 0, sizeof(struct pt_regs));
                childregs->csr_euen = p->thread.csr_euen;
                childregs->csr_crmd = p->thread.csr_crmd;
                childregs->csr_prmd = p->thread.csr_prmd;
                childregs->csr_ecfg = p->thread.csr_ecfg;
                goto out;
        }

        /* user thread */
        *childregs = *regs;
        childregs->regs[4] = 0; /* Child gets zero as return value */
        if (usp)
                childregs->regs[3] = usp;

        p->thread.reg03 = (unsigned long) childregs;
        p->thread.reg01 = (unsigned long) ret_from_fork_asm;
        p->thread.sched_ra = (unsigned long) ret_from_fork_asm;

        /*
         * New tasks lose permission to use the fpu. This accelerates context
         * switching for most programs since they don't use the fpu.
         */
        childregs->csr_euen = 0;

        if (clone_flags & CLONE_SETTLS)
                childregs->regs[2] = tls;

out:
        ptrace_hw_copy_thread(p);
        clear_tsk_thread_flag(p, TIF_USEDFPU);
        clear_tsk_thread_flag(p, TIF_USEDSIMD);
        clear_tsk_thread_flag(p, TIF_USEDLBT);
        clear_tsk_thread_flag(p, TIF_LSX_CTX_LIVE);
        clear_tsk_thread_flag(p, TIF_LASX_CTX_LIVE);
        clear_tsk_thread_flag(p, TIF_LBT_CTX_LIVE);

        return 0;
}

unsigned long __get_wchan(struct task_struct *task)
{
        unsigned long pc = 0;
        struct unwind_state state;

        if (!try_get_task_stack(task))
                return 0;

        for (unwind_start(&state, task, NULL);
             !unwind_done(&state); unwind_next_frame(&state)) {
                pc = unwind_get_return_address(&state);
                if (!pc)
                        break;
                if (in_sched_functions(pc))
                        continue;
                break;
        }

        put_task_stack(task);

        return pc;
}

bool in_irq_stack(unsigned long stack, struct stack_info *info)
{
        unsigned long nextsp;
        unsigned long begin = (unsigned long)this_cpu_read(irq_stack);
        unsigned long end = begin + IRQ_STACK_START;

        if (stack < begin || stack >= end)
                return false;

        nextsp = *(unsigned long *)end;
        if (nextsp & (SZREG - 1))
                return false;

        info->begin = begin;
        info->end = end;
        info->next_sp = nextsp;
        info->type = STACK_TYPE_IRQ;

        return true;
}

bool in_task_stack(unsigned long stack, struct task_struct *task,
                        struct stack_info *info)
{
        unsigned long begin = (unsigned long)task_stack_page(task);
        unsigned long end = begin + THREAD_SIZE;

        if (stack < begin || stack >= end)
                return false;

        info->begin = begin;
        info->end = end;
        info->next_sp = 0;
        info->type = STACK_TYPE_TASK;

        return true;
}

int get_stack_info(unsigned long stack, struct task_struct *task,
                   struct stack_info *info)
{
        task = task ? : current;

        if (!stack || stack & (SZREG - 1))
                goto unknown;

        if (in_task_stack(stack, task, info))
                return 0;

        if (task != current)
                goto unknown;

        if (in_irq_stack(stack, info))
                return 0;

unknown:
        info->type = STACK_TYPE_UNKNOWN;
        return -EINVAL;
}

unsigned long stack_top(void)
{
        unsigned long top = TASK_SIZE & PAGE_MASK;

        if (current->thread.vdso) {
                /* Space for the VDSO & data page */
                top -= PAGE_ALIGN(current->thread.vdso->size);
                top -= VVAR_SIZE;

                /* Space to randomize the VDSO base */
                if (current->flags & PF_RANDOMIZE)
                        top -= VDSO_RANDOMIZE_SIZE;
        }

        return top;
}

/*
 * Don't forget that the stack pointer must be aligned on a 8 bytes
 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 */
unsigned long arch_align_stack(unsigned long sp)
{
        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
                sp -= get_random_u32_below(PAGE_SIZE);

        return sp & STACK_ALIGN;
}

static DEFINE_PER_CPU(call_single_data_t, backtrace_csd);
static struct cpumask backtrace_csd_busy;

static void handle_backtrace(void *info)
{
        nmi_cpu_backtrace(get_irq_regs());
        cpumask_clear_cpu(smp_processor_id(), &backtrace_csd_busy);
}

static void raise_backtrace(cpumask_t *mask)
{
        call_single_data_t *csd;
        int cpu;

        for_each_cpu(cpu, mask) {
                /*
                 * If we previously sent an IPI to the target CPU & it hasn't
                 * cleared its bit in the busy cpumask then it didn't handle
                 * our previous IPI & it's not safe for us to reuse the
                 * call_single_data_t.
                 */
                if (cpumask_test_and_set_cpu(cpu, &backtrace_csd_busy)) {
                        pr_warn("Unable to send backtrace IPI to CPU%u - perhaps it hung?\n",
                                cpu);
                        continue;
                }

                csd = &per_cpu(backtrace_csd, cpu);
                csd->func = handle_backtrace;
                smp_call_function_single_async(cpu, csd);
        }
}

void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
{
        nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace);
}

#ifdef CONFIG_32BIT
void loongarch_dump_regs32(u32 *uregs, const struct pt_regs *regs)
#else
void loongarch_dump_regs64(u64 *uregs, const struct pt_regs *regs)
#endif
{
        unsigned int i;

        for (i = LOONGARCH_EF_R1; i <= LOONGARCH_EF_R31; i++) {
                uregs[i] = regs->regs[i - LOONGARCH_EF_R0];
        }

        uregs[LOONGARCH_EF_ORIG_A0] = regs->orig_a0;
        uregs[LOONGARCH_EF_CSR_ERA] = regs->csr_era;
        uregs[LOONGARCH_EF_CSR_BADV] = regs->csr_badvaddr;
        uregs[LOONGARCH_EF_CSR_CRMD] = regs->csr_crmd;
        uregs[LOONGARCH_EF_CSR_PRMD] = regs->csr_prmd;
        uregs[LOONGARCH_EF_CSR_EUEN] = regs->csr_euen;
        uregs[LOONGARCH_EF_CSR_ECFG] = regs->csr_ecfg;
        uregs[LOONGARCH_EF_CSR_ESTAT] = regs->csr_estat;
}