/*
 * 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/user.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/random.h>

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

#ifdef CONFIG_HOTPLUG_CPU
void arch_cpu_idle_dead(void)
{
        /* What the heck is this check doing ? */
        if (!cpu_isset(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);
#ifdef CONFIG_64BIT
        status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
#endif
        status |= KU_USER;
        regs->cp0_status = status;
        clear_used_math();
        clear_fpu_owner();
        if (cpu_has_dsp)
                __init_dsp();
        regs->cp0_epc = pc;
        regs->regs[29] = sp;
}

void exit_thread(void)
{
}

void flush_thread(void)
{
}

int copy_thread(unsigned long clone_flags, unsigned long usp,
        unsigned long 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;

        preempt_disable();

        if (is_fpu_owner())
                save_fp(p);

        if (cpu_has_dsp)
                save_dsp(p);

        preempt_enable();

        /* 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)) {
                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 = 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;
        }
        *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);

#ifdef CONFIG_MIPS_MT_SMTC
        /*
         * SMTC restores TCStatus after Status, and the CU bits
         * are aliased there.
         */
        childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
#endif
        clear_tsk_thread_flag(p, TIF_USEDFPU);

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

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

        return 0;
}

/* Fill in the fpu structure for a core dump.. */
int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
{
        memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));

        return 1;
}

void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
{
        int i;

        for (i = 0; i < EF_R0; i++)
                gp[i] = 0;
        gp[EF_R0] = 0;
        for (i = 1; i <= 31; i++)
                gp[EF_R0 + i] = regs->regs[i];
        gp[EF_R26] = 0;
        gp[EF_R27] = 0;
        gp[EF_LO] = regs->lo;
        gp[EF_HI] = regs->hi;
        gp[EF_CP0_EPC] = regs->cp0_epc;
        gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
        gp[EF_CP0_STATUS] = regs->cp0_status;
        gp[EF_CP0_CAUSE] = regs->cp0_cause;
#ifdef EF_UNUSED0
        gp[EF_UNUSED0] = 0;
#endif
}

int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
{
        elf_dump_regs(*regs, task_pt_regs(tsk));
        return 1;
}

int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
{
        memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));

        return 1;
}

/*
 *
 */
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 boggus... */
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 (__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;
}