/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * 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/errno.h>
#include <linux/sched.h>
#include <linux/tick.h>
#include <linux/kernel.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/init.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/random.h>
#include <linux/prctl.h>

#include <asm/asm.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
#include <asm/dsemul.h>
#include <asm/dsp.h>
#include <asm/fpu.h>
#include <asm/msa.h>
#include <asm/pgtable.h>
#include <asm/mipsregs.h>
#include <asm/processor.h>
#include <asm/reg.h>
#include <linux/uaccess.h>
#include <asm/io.h>
#include <asm/elf.h>
#include <asm/isadep.h>
#include <asm/inst.h>
#include <asm/stacktrace.h>
#include <asm/irq_regs.h>

#ifdef CONFIG_HOTPLUG_CPU
void arch_cpu_idle_dead(void)
{
        /* What the heck is this check doing ? */
        if (!cpumask_test_cpu(smp_processor_id(), &cpu_callin_map))
                play_dead();
}
#endif

asmlinkage void ret_from_fork(void);
asmlinkage void ret_from_kernel_thread(void);

void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
{
        unsigned long status;

        /* New thread loses kernel privileges. */
        status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
        status |= KU_USER;
        regs->cp0_status = status;
        lose_fpu(0);
        clear_thread_flag(TIF_MSA_CTX_LIVE);
        clear_used_math();
        atomic_set(&current->thread.bd_emu_frame, BD_EMUFRAME_NONE);
        init_dsp();
        regs->cp0_epc = pc;
        regs->regs[29] = sp;
}

void exit_thread(struct task_struct *tsk)
{
        /*
         * User threads may have allocated a delay slot emulation frame.
         * If so, clean up that allocation.
         */
        if (!(current->flags & PF_KTHREAD))
                dsemul_thread_cleanup(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_msa_enabled())
                save_msa(current);
        else if (is_fpu_owner())
                _save_fp(current);

        save_dsp(current);

        preempt_enable();

        *dst = *src;
        return 0;
}

/*
 * Copy architecture-specific thread state
 */
int copy_thread(unsigned long clone_flags, unsigned long usp,
        unsigned long kthread_arg, struct task_struct *p)
{
        struct thread_info *ti = task_thread_info(p);
        struct pt_regs *childregs, *regs = current_pt_regs();
        unsigned long childksp;
        p->set_child_tid = p->clear_child_tid = NULL;

        childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;

        /* set up new TSS. */
        childregs = (struct pt_regs *) childksp - 1;
        /*  Put the stack after the struct pt_regs.  */
        childksp = (unsigned long) childregs;
        p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
        if (unlikely(p->flags & PF_KTHREAD)) {
                /* kernel thread */
                unsigned long status = p->thread.cp0_status;
                memset(childregs, 0, sizeof(struct pt_regs));
                ti->addr_limit = KERNEL_DS;
                p->thread.reg16 = usp; /* fn */
                p->thread.reg17 = kthread_arg;
                p->thread.reg29 = childksp;
                p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
                status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
                         ((status & (ST0_KUC | ST0_IEC)) << 2);
#else
                status |= ST0_EXL;
#endif
                childregs->cp0_status = status;
                return 0;
        }

        /* user thread */
        *childregs = *regs;
        childregs->regs[7] = 0; /* Clear error flag */
        childregs->regs[2] = 0; /* Child gets zero as return value */
        if (usp)
                childregs->regs[29] = usp;
        ti->addr_limit = USER_DS;

        p->thread.reg29 = (unsigned long) childregs;
        p->thread.reg31 = (unsigned long) ret_from_fork;

        /*
         * New tasks lose permission to use the fpu. This accelerates context
         * switching for most programs since they don't use the fpu.
         */
        childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);

        clear_tsk_thread_flag(p, TIF_USEDFPU);
        clear_tsk_thread_flag(p, TIF_USEDMSA);
        clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);

#ifdef CONFIG_MIPS_MT_FPAFF
        clear_tsk_thread_flag(p, TIF_FPUBOUND);
#endif /* CONFIG_MIPS_MT_FPAFF */

        atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE);

        if (clone_flags & CLONE_SETTLS)
                ti->tp_value = regs->regs[7];

        return 0;
}

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

struct mips_frame_info {
        void            *func;
        unsigned long   func_size;
        int             frame_size;
        int             pc_offset;
};

#define J_TARGET(pc,target)     \
                (((unsigned long)(pc) & 0xf0000000) | ((target) << 2))

static inline int is_ra_save_ins(union mips_instruction *ip)
{
#ifdef CONFIG_CPU_MICROMIPS
        union mips_instruction mmi;

        /*
         * swsp ra,offset
         * swm16 reglist,offset(sp)
         * swm32 reglist,offset(sp)
         * sw32 ra,offset(sp)
         * jradiussp - NOT SUPPORTED
         *
         * microMIPS is way more fun...
         */
        if (mm_insn_16bit(ip->halfword[0])) {
                mmi.word = (ip->halfword[0] << 16);
                return (mmi.mm16_r5_format.opcode == mm_swsp16_op &&
                        mmi.mm16_r5_format.rt == 31) ||
                       (mmi.mm16_m_format.opcode == mm_pool16c_op &&
                        mmi.mm16_m_format.func == mm_swm16_op);
        }
        else {
                mmi.halfword[0] = ip->halfword[1];
                mmi.halfword[1] = ip->halfword[0];
                return (mmi.mm_m_format.opcode == mm_pool32b_op &&
                        mmi.mm_m_format.rd > 9 &&
                        mmi.mm_m_format.base == 29 &&
                        mmi.mm_m_format.func == mm_swm32_func) ||
                       (mmi.i_format.opcode == mm_sw32_op &&
                        mmi.i_format.rs == 29 &&
                        mmi.i_format.rt == 31);
        }
#else
        /* sw / sd $ra, offset($sp) */
        return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
                ip->i_format.rs == 29 &&
                ip->i_format.rt == 31;
#endif
}

static inline int is_jump_ins(union mips_instruction *ip)
{
#ifdef CONFIG_CPU_MICROMIPS
        /*
         * jr16,jrc,jalr16,jalr16
         * jal
         * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
         * jraddiusp - NOT SUPPORTED
         *
         * microMIPS is kind of more fun...
         */
        union mips_instruction mmi;

        mmi.word = (ip->halfword[0] << 16);

        if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
            (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
            ip->j_format.opcode == mm_jal32_op)
                return 1;
        if (ip->r_format.opcode != mm_pool32a_op ||
                        ip->r_format.func != mm_pool32axf_op)
                return 0;
        return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
#else
        if (ip->j_format.opcode == j_op)
                return 1;
        if (ip->j_format.opcode == jal_op)
                return 1;
        if (ip->r_format.opcode != spec_op)
                return 0;
        return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
#endif
}

static inline int is_sp_move_ins(union mips_instruction *ip)
{
#ifdef CONFIG_CPU_MICROMIPS
        /*
         * addiusp -imm
         * addius5 sp,-imm
         * addiu32 sp,sp,-imm
         * jradiussp - NOT SUPPORTED
         *
         * microMIPS is not more fun...
         */
        if (mm_insn_16bit(ip->halfword[0])) {
                union mips_instruction mmi;

                mmi.word = (ip->halfword[0] << 16);
                return (mmi.mm16_r3_format.opcode == mm_pool16d_op &&
                        mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
                       (mmi.mm16_r5_format.opcode == mm_pool16d_op &&
                        mmi.mm16_r5_format.rt == 29);
        }
        return ip->mm_i_format.opcode == mm_addiu32_op &&
               ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
#else
        /* addiu/daddiu sp,sp,-imm */
        if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
                return 0;
        if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
                return 1;
#endif
        return 0;
}

static int get_frame_info(struct mips_frame_info *info)
{
#ifdef CONFIG_CPU_MICROMIPS
        union mips_instruction *ip = (void *) (((char *) info->func) - 1);
#else
        union mips_instruction *ip = info->func;
#endif
        unsigned max_insns = info->func_size / sizeof(union mips_instruction);
        unsigned i;

        info->pc_offset = -1;
        info->frame_size = 0;

        if (!ip)
                goto err;

        if (max_insns == 0)
                max_insns = 128U;       /* unknown function size */
        max_insns = min(128U, max_insns);

        for (i = 0; i < max_insns; i++, ip++) {

                if (is_jump_ins(ip))
                        break;
                if (!info->frame_size) {
                        if (is_sp_move_ins(ip))
                        {
#ifdef CONFIG_CPU_MICROMIPS
                                if (mm_insn_16bit(ip->halfword[0]))
                                {
                                        unsigned short tmp;

                                        if (ip->halfword[0] & mm_addiusp_func)
                                        {
                                                tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
                                                info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
                                        } else {
                                                tmp = (ip->halfword[0] >> 1);
                                                info->frame_size = -(signed short)(tmp & 0xf);
                                        }
                                        ip = (void *) &ip->halfword[1];
                                        ip--;
                                } else
#endif
                                info->frame_size = - ip->i_format.simmediate;
                        }
                        continue;
                }
                if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
                        info->pc_offset =
                                ip->i_format.simmediate / sizeof(long);
                        break;
                }
        }
        if (info->frame_size && info->pc_offset >= 0) /* nested */
                return 0;
        if (info->pc_offset < 0) /* leaf */
                return 1;
        /* prologue seems bogus... */
err:
        return -1;
}

static struct mips_frame_info schedule_mfi __read_mostly;

#ifdef CONFIG_KALLSYMS
static unsigned long get___schedule_addr(void)
{
        return kallsyms_lookup_name("__schedule");
}
#else
static unsigned long get___schedule_addr(void)
{
        union mips_instruction *ip = (void *)schedule;
        int max_insns = 8;
        int i;

        for (i = 0; i < max_insns; i++, ip++) {
                if (ip->j_format.opcode == j_op)
                        return J_TARGET(ip, ip->j_format.target);
        }
        return 0;
}
#endif

static int __init frame_info_init(void)
{
        unsigned long size = 0;
#ifdef CONFIG_KALLSYMS
        unsigned long ofs;
#endif
        unsigned long addr;

        addr = get___schedule_addr();
        if (!addr)
                addr = (unsigned long)schedule;

#ifdef CONFIG_KALLSYMS
        kallsyms_lookup_size_offset(addr, &size, &ofs);
#endif
        schedule_mfi.func = (void *)addr;
        schedule_mfi.func_size = size;

        get_frame_info(&schedule_mfi);

        /*
         * Without schedule() frame info, result given by
         * thread_saved_pc() and get_wchan() are not reliable.
         */
        if (schedule_mfi.pc_offset < 0)
                printk("Can't analyze schedule() prologue at %p\n", schedule);

        return 0;
}

arch_initcall(frame_info_init);

/*
 * Return saved PC of a blocked thread.
 */
unsigned long thread_saved_pc(struct task_struct *tsk)
{
        struct thread_struct *t = &tsk->thread;

        /* New born processes are a special case */
        if (t->reg31 == (unsigned long) ret_from_fork)
                return t->reg31;
        if (schedule_mfi.pc_offset < 0)
                return 0;
        return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
}


#ifdef CONFIG_KALLSYMS
/* generic stack unwinding function */
unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
                                              unsigned long *sp,
                                              unsigned long pc,
                                              unsigned long *ra)
{
        struct mips_frame_info info;
        unsigned long size, ofs;
        int leaf;
        extern void ret_from_irq(void);
        extern void ret_from_exception(void);

        if (!stack_page)
                return 0;

        /*
         * If we reached the bottom of interrupt context,
         * return saved pc in pt_regs.
         */
        if (pc == (unsigned long)ret_from_irq ||
            pc == (unsigned long)ret_from_exception) {
                struct pt_regs *regs;
                if (*sp >= stack_page &&
                    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
                        regs = (struct pt_regs *)*sp;
                        pc = regs->cp0_epc;
                        if (!user_mode(regs) && __kernel_text_address(pc)) {
                                *sp = regs->regs[29];
                                *ra = regs->regs[31];
                                return pc;
                        }
                }
                return 0;
        }
        if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
                return 0;
        /*
         * Return ra if an exception occurred at the first instruction
         */
        if (unlikely(ofs == 0)) {
                pc = *ra;
                *ra = 0;
                return pc;
        }

        info.func = (void *)(pc - ofs);
        info.func_size = ofs;   /* analyze from start to ofs */
        leaf = get_frame_info(&info);
        if (leaf < 0)
                return 0;

        if (*sp < stack_page ||
            *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
                return 0;

        if (leaf)
                /*
                 * For some extreme cases, get_frame_info() can
                 * consider wrongly a nested function as a leaf
                 * one. In that cases avoid to return always the
                 * same value.
                 */
                pc = pc != *ra ? *ra : 0;
        else
                pc = ((unsigned long *)(*sp))[info.pc_offset];

        *sp += info.frame_size;
        *ra = 0;
        return __kernel_text_address(pc) ? pc : 0;
}
EXPORT_SYMBOL(unwind_stack_by_address);

/* used by show_backtrace() */
unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
                           unsigned long pc, unsigned long *ra)
{
        unsigned long stack_page = (unsigned long)task_stack_page(task);
        return unwind_stack_by_address(stack_page, sp, pc, ra);
}
#endif

/*
 * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 */
unsigned long get_wchan(struct task_struct *task)
{
        unsigned long pc = 0;
#ifdef CONFIG_KALLSYMS
        unsigned long sp;
        unsigned long ra = 0;
#endif

        if (!task || task == current || task->state == TASK_RUNNING)
                goto out;
        if (!task_stack_page(task))
                goto out;

        pc = thread_saved_pc(task);

#ifdef CONFIG_KALLSYMS
        sp = task->thread.reg29 + schedule_mfi.frame_size;

        while (in_sched_functions(pc))
                pc = unwind_stack(task, &sp, pc, &ra);
#endif

out:
        return pc;
}

/*
 * 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_int() & ~PAGE_MASK;

        return sp & ALMASK;
}

static void arch_dump_stack(void *info)
{
        struct pt_regs *regs;

        regs = get_irq_regs();

        if (regs)
                show_regs(regs);

        dump_stack();
}

void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
{
        long this_cpu = get_cpu();

        if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
                dump_stack();

        smp_call_function_many(mask, arch_dump_stack, NULL, 1);

        put_cpu();
}

int mips_get_process_fp_mode(struct task_struct *task)
{
        int value = 0;

        if (!test_tsk_thread_flag(task, TIF_32BIT_FPREGS))
                value |= PR_FP_MODE_FR;
        if (test_tsk_thread_flag(task, TIF_HYBRID_FPREGS))
                value |= PR_FP_MODE_FRE;

        return value;
}

static void prepare_for_fp_mode_switch(void *info)
{
        struct mm_struct *mm = info;

        if (current->mm == mm)
                lose_fpu(1);
}

int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
{
        const unsigned int known_bits = PR_FP_MODE_FR | PR_FP_MODE_FRE;
        struct task_struct *t;
        int max_users;

        /* Check the value is valid */
        if (value & ~known_bits)
                return -EOPNOTSUPP;

        /* Avoid inadvertently triggering emulation */
        if ((value & PR_FP_MODE_FR) && raw_cpu_has_fpu &&
            !(raw_current_cpu_data.fpu_id & MIPS_FPIR_F64))
                return -EOPNOTSUPP;
        if ((value & PR_FP_MODE_FRE) && raw_cpu_has_fpu && !cpu_has_fre)
                return -EOPNOTSUPP;

        /* FR = 0 not supported in MIPS R6 */
        if (!(value & PR_FP_MODE_FR) && raw_cpu_has_fpu && cpu_has_mips_r6)
                return -EOPNOTSUPP;

        /* Proceed with the mode switch */
        preempt_disable();

        /* Save FP & vector context, then disable FPU & MSA */
        if (task->signal == current->signal)
                lose_fpu(1);

        /* Prevent any threads from obtaining live FP context */
        atomic_set(&task->mm->context.fp_mode_switching, 1);
        smp_mb__after_atomic();

        /*
         * If there are multiple online CPUs then force any which are running
         * threads in this process to lose their FPU context, which they can't
         * regain until fp_mode_switching is cleared later.
         */
        if (num_online_cpus() > 1) {
                /* No need to send an IPI for the local CPU */
                max_users = (task->mm == current->mm) ? 1 : 0;

                if (atomic_read(&current->mm->mm_users) > max_users)
                        smp_call_function(prepare_for_fp_mode_switch,
                                          (void *)current->mm, 1);
        }

        /*
         * There are now no threads of the process with live FP context, so it
         * is safe to proceed with the FP mode switch.
         */
        for_each_thread(task, t) {
                /* Update desired FP register width */
                if (value & PR_FP_MODE_FR) {
                        clear_tsk_thread_flag(t, TIF_32BIT_FPREGS);
                } else {
                        set_tsk_thread_flag(t, TIF_32BIT_FPREGS);
                        clear_tsk_thread_flag(t, TIF_MSA_CTX_LIVE);
                }

                /* Update desired FP single layout */
                if (value & PR_FP_MODE_FRE)
                        set_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
                else
                        clear_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
        }

        /* Allow threads to use FP again */
        atomic_set(&task->mm->context.fp_mode_switching, 0);
        preempt_enable();

        return 0;
}