// SPDX-License-Identifier: GPL-2.0
/*
 * 'traps.c' handles hardware traps and faults after we have saved some
 * state in 'entry.S'.
 *
 *  SuperH version: Copyright (C) 1999 Niibe Yutaka
 *                  Copyright (C) 2000 Philipp Rumpf
 *                  Copyright (C) 2000 David Howells
 *                  Copyright (C) 2002 - 2010 Paul Mundt
 */
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/hardirq.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/kallsyms.h>
#include <linux/io.h>
#include <linux/bug.h>
#include <linux/debug_locks.h>
#include <linux/kdebug.h>
#include <linux/limits.h>
#include <linux/sysfs.h>
#include <linux/uaccess.h>
#include <linux/perf_event.h>
#include <linux/sched/task_stack.h>

#include <asm/alignment.h>
#include <asm/fpu.h>
#include <asm/kprobes.h>
#include <asm/traps.h>
#include <asm/bl_bit.h>

#ifdef CONFIG_CPU_SH2
# define TRAP_RESERVED_INST     4
# define TRAP_ILLEGAL_SLOT_INST 6
# define TRAP_ADDRESS_ERROR     9
# ifdef CONFIG_CPU_SH2A
#  define TRAP_UBC              12
#  define TRAP_FPU_ERROR        13
#  define TRAP_DIVZERO_ERROR    17
#  define TRAP_DIVOVF_ERROR     18
# endif
#else
#define TRAP_RESERVED_INST      12
#define TRAP_ILLEGAL_SLOT_INST  13
#endif

static inline void sign_extend(unsigned int count, unsigned char *dst)
{
#ifdef __LITTLE_ENDIAN__
        if ((count == 1) && dst[0] & 0x80) {
                dst[1] = 0xff;
                dst[2] = 0xff;
                dst[3] = 0xff;
        }
        if ((count == 2) && dst[1] & 0x80) {
                dst[2] = 0xff;
                dst[3] = 0xff;
        }
#else
        if ((count == 1) && dst[3] & 0x80) {
                dst[2] = 0xff;
                dst[1] = 0xff;
                dst[0] = 0xff;
        }
        if ((count == 2) && dst[2] & 0x80) {
                dst[1] = 0xff;
                dst[0] = 0xff;
        }
#endif
}

static struct mem_access user_mem_access = {
        copy_from_user,
        copy_to_user,
};

/*
 * handle an instruction that does an unaligned memory access by emulating the
 * desired behaviour
 * - note that PC _may not_ point to the faulting instruction
 *   (if that instruction is in a branch delay slot)
 * - return 0 if emulation okay, -EFAULT on existential error
 */
static int handle_unaligned_ins(insn_size_t instruction, struct pt_regs *regs,
                                struct mem_access *ma)
{
        int ret, index, count;
        unsigned long *rm, *rn;
        unsigned char *src, *dst;
        unsigned char __user *srcu, *dstu;

        index = (instruction>>8)&15;    /* 0x0F00 */
        rn = &regs->regs[index];

        index = (instruction>>4)&15;    /* 0x00F0 */
        rm = &regs->regs[index];

        count = 1<<(instruction&3);

        switch (count) {
        case 1: inc_unaligned_byte_access(); break;
        case 2: inc_unaligned_word_access(); break;
        case 4: inc_unaligned_dword_access(); break;
        case 8: inc_unaligned_multi_access(); break;
        }

        ret = -EFAULT;
        switch (instruction>>12) {
        case 0: /* mov.[bwl] to/from memory via r0+rn */
                if (instruction & 8) {
                        /* from memory */
                        srcu = (unsigned char __user *)*rm;
                        srcu += regs->regs[0];
                        dst = (unsigned char *)rn;
                        *(unsigned long *)dst = 0;

#if !defined(__LITTLE_ENDIAN__)
                        dst += 4-count;
#endif
                        if (ma->from(dst, srcu, count))
                                goto fetch_fault;

                        sign_extend(count, dst);
                } else {
                        /* to memory */
                        src = (unsigned char *)rm;
#if !defined(__LITTLE_ENDIAN__)
                        src += 4-count;
#endif
                        dstu = (unsigned char __user *)*rn;
                        dstu += regs->regs[0];

                        if (ma->to(dstu, src, count))
                                goto fetch_fault;
                }
                ret = 0;
                break;

        case 1: /* mov.l Rm,@(disp,Rn) */
                src = (unsigned char*) rm;
                dstu = (unsigned char __user *)*rn;
                dstu += (instruction&0x000F)<<2;

                if (ma->to(dstu, src, 4))
                        goto fetch_fault;
                ret = 0;
                break;

        case 2: /* mov.[bwl] to memory, possibly with pre-decrement */
                if (instruction & 4)
                        *rn -= count;
                src = (unsigned char*) rm;
                dstu = (unsigned char __user *)*rn;
#if !defined(__LITTLE_ENDIAN__)
                src += 4-count;
#endif
                if (ma->to(dstu, src, count))
                        goto fetch_fault;
                ret = 0;
                break;

        case 5: /* mov.l @(disp,Rm),Rn */
                srcu = (unsigned char __user *)*rm;
                srcu += (instruction & 0x000F) << 2;
                dst = (unsigned char *)rn;
                *(unsigned long *)dst = 0;

                if (ma->from(dst, srcu, 4))
                        goto fetch_fault;
                ret = 0;
                break;

        case 6: /* mov.[bwl] from memory, possibly with post-increment */
                srcu = (unsigned char __user *)*rm;
                if (instruction & 4)
                        *rm += count;
                dst = (unsigned char*) rn;
                *(unsigned long*)dst = 0;

#if !defined(__LITTLE_ENDIAN__)
                dst += 4-count;
#endif
                if (ma->from(dst, srcu, count))
                        goto fetch_fault;
                sign_extend(count, dst);
                ret = 0;
                break;

        case 8:
                switch ((instruction&0xFF00)>>8) {
                case 0x81: /* mov.w R0,@(disp,Rn) */
                        src = (unsigned char *) &regs->regs[0];
#if !defined(__LITTLE_ENDIAN__)
                        src += 2;
#endif
                        dstu = (unsigned char __user *)*rm; /* called Rn in the spec */
                        dstu += (instruction & 0x000F) << 1;

                        if (ma->to(dstu, src, 2))
                                goto fetch_fault;
                        ret = 0;
                        break;

                case 0x85: /* mov.w @(disp,Rm),R0 */
                        srcu = (unsigned char __user *)*rm;
                        srcu += (instruction & 0x000F) << 1;
                        dst = (unsigned char *) &regs->regs[0];
                        *(unsigned long *)dst = 0;

#if !defined(__LITTLE_ENDIAN__)
                        dst += 2;
#endif
                        if (ma->from(dst, srcu, 2))
                                goto fetch_fault;
                        sign_extend(2, dst);
                        ret = 0;
                        break;
                }
                break;

        case 9: /* mov.w @(disp,PC),Rn */
                srcu = (unsigned char __user *)regs->pc;
                srcu += 4;
                srcu += (instruction & 0x00FF) << 1;
                dst = (unsigned char *)rn;
                *(unsigned long *)dst = 0;

#if !defined(__LITTLE_ENDIAN__)
                dst += 2;
#endif

                if (ma->from(dst, srcu, 2))
                        goto fetch_fault;
                sign_extend(2, dst);
                ret = 0;
                break;

        case 0xd: /* mov.l @(disp,PC),Rn */
                srcu = (unsigned char __user *)(regs->pc & ~0x3);
                srcu += 4;
                srcu += (instruction & 0x00FF) << 2;
                dst = (unsigned char *)rn;
                *(unsigned long *)dst = 0;

                if (ma->from(dst, srcu, 4))
                        goto fetch_fault;
                ret = 0;
                break;
        }
        return ret;

 fetch_fault:
        /* Argh. Address not only misaligned but also non-existent.
         * Raise an EFAULT and see if it's trapped
         */
        die_if_no_fixup("Fault in unaligned fixup", regs, 0);
        return -EFAULT;
}

/*
 * emulate the instruction in the delay slot
 * - fetches the instruction from PC+2
 */
static inline int handle_delayslot(struct pt_regs *regs,
                                   insn_size_t old_instruction,
                                   struct mem_access *ma)
{
        insn_size_t instruction;
        void __user *addr = (void __user *)(regs->pc +
                instruction_size(old_instruction));

        if (copy_from_user(&instruction, addr, sizeof(instruction))) {
                /* the instruction-fetch faulted */
                if (user_mode(regs))
                        return -EFAULT;

                /* kernel */
                die("delay-slot-insn faulting in handle_unaligned_delayslot",
                    regs, 0);
        }

        return handle_unaligned_ins(instruction, regs, ma);
}

/*
 * handle an instruction that does an unaligned memory access
 * - have to be careful of branch delay-slot instructions that fault
 *  SH3:
 *   - if the branch would be taken PC points to the branch
 *   - if the branch would not be taken, PC points to delay-slot
 *  SH4:
 *   - PC always points to delayed branch
 * - return 0 if handled, -EFAULT if failed (may not return if in kernel)
 */

/* Macros to determine offset from current PC for branch instructions */
/* Explicit type coercion is used to force sign extension where needed */
#define SH_PC_8BIT_OFFSET(instr) ((((signed char)(instr))*2) + 4)
#define SH_PC_12BIT_OFFSET(instr) ((((signed short)(instr<<4))>>3) + 4)

int handle_unaligned_access(insn_size_t instruction, struct pt_regs *regs,
                            struct mem_access *ma, int expected,
                            unsigned long address)
{
        u_int rm;
        int ret, index;

        /*
         * XXX: We can't handle mixed 16/32-bit instructions yet
         */
        if (instruction_size(instruction) != 2)
                return -EINVAL;

        index = (instruction>>8)&15;    /* 0x0F00 */
        rm = regs->regs[index];

        /*
         * Log the unexpected fixups, and then pass them on to perf.
         *
         * We intentionally don't report the expected cases to perf as
         * otherwise the trapped I/O case will skew the results too much
         * to be useful.
         */
        if (!expected) {
                unaligned_fixups_notify(current, instruction, regs);
                perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1,
                              regs, address);
        }

        ret = -EFAULT;
        switch (instruction&0xF000) {
        case 0x0000:
                if (instruction==0x000B) {
                        /* rts */
                        ret = handle_delayslot(regs, instruction, ma);
                        if (ret==0)
                                regs->pc = regs->pr;
                }
                else if ((instruction&0x00FF)==0x0023) {
                        /* braf @Rm */
                        ret = handle_delayslot(regs, instruction, ma);
                        if (ret==0)
                                regs->pc += rm + 4;
                }
                else if ((instruction&0x00FF)==0x0003) {
                        /* bsrf @Rm */
                        ret = handle_delayslot(regs, instruction, ma);
                        if (ret==0) {
                                regs->pr = regs->pc + 4;
                                regs->pc += rm + 4;
                        }
                }
                else {
                        /* mov.[bwl] to/from memory via r0+rn */
                        goto simple;
                }
                break;

        case 0x1000: /* mov.l Rm,@(disp,Rn) */
                goto simple;

        case 0x2000: /* mov.[bwl] to memory, possibly with pre-decrement */
                goto simple;

        case 0x4000:
                if ((instruction&0x00FF)==0x002B) {
                        /* jmp @Rm */
                        ret = handle_delayslot(regs, instruction, ma);
                        if (ret==0)
                                regs->pc = rm;
                }
                else if ((instruction&0x00FF)==0x000B) {
                        /* jsr @Rm */
                        ret = handle_delayslot(regs, instruction, ma);
                        if (ret==0) {
                                regs->pr = regs->pc + 4;
                                regs->pc = rm;
                        }
                }
                else {
                        /* mov.[bwl] to/from memory via r0+rn */
                        goto simple;
                }
                break;

        case 0x5000: /* mov.l @(disp,Rm),Rn */
                goto simple;

        case 0x6000: /* mov.[bwl] from memory, possibly with post-increment */
                goto simple;

        case 0x8000: /* bf lab, bf/s lab, bt lab, bt/s lab */
                switch (instruction&0x0F00) {
                case 0x0100: /* mov.w R0,@(disp,Rm) */
                        goto simple;
                case 0x0500: /* mov.w @(disp,Rm),R0 */
                        goto simple;
                case 0x0B00: /* bf   lab - no delayslot*/
                        ret = 0;
                        break;
                case 0x0F00: /* bf/s lab */
                        ret = handle_delayslot(regs, instruction, ma);
                        if (ret==0) {
#if defined(CONFIG_CPU_SH4) || defined(CONFIG_SH7705_CACHE_32KB)
                                if ((regs->sr & 0x00000001) != 0)
                                        regs->pc += 4; /* next after slot */
                                else
#endif
                                        regs->pc += SH_PC_8BIT_OFFSET(instruction);
                        }
                        break;
                case 0x0900: /* bt   lab - no delayslot */
                        ret = 0;
                        break;
                case 0x0D00: /* bt/s lab */
                        ret = handle_delayslot(regs, instruction, ma);
                        if (ret==0) {
#if defined(CONFIG_CPU_SH4) || defined(CONFIG_SH7705_CACHE_32KB)
                                if ((regs->sr & 0x00000001) == 0)
                                        regs->pc += 4; /* next after slot */
                                else
#endif
                                        regs->pc += SH_PC_8BIT_OFFSET(instruction);
                        }
                        break;
                }
                break;

        case 0x9000: /* mov.w @(disp,Rm),Rn */
                goto simple;

        case 0xA000: /* bra label */
                ret = handle_delayslot(regs, instruction, ma);
                if (ret==0)
                        regs->pc += SH_PC_12BIT_OFFSET(instruction);
                break;

        case 0xB000: /* bsr label */
                ret = handle_delayslot(regs, instruction, ma);
                if (ret==0) {
                        regs->pr = regs->pc + 4;
                        regs->pc += SH_PC_12BIT_OFFSET(instruction);
                }
                break;

        case 0xD000: /* mov.l @(disp,Rm),Rn */
                goto simple;
        }
        return ret;

        /* handle non-delay-slot instruction */
 simple:
        ret = handle_unaligned_ins(instruction, regs, ma);
        if (ret==0)
                regs->pc += instruction_size(instruction);
        return ret;
}

/*
 * Handle various address error exceptions:
 *  - instruction address error:
 *       misaligned PC
 *       PC >= 0x80000000 in user mode
 *  - data address error (read and write)
 *       misaligned data access
 *       access to >= 0x80000000 is user mode
 * Unfortuntaly we can't distinguish between instruction address error
 * and data address errors caused by read accesses.
 */
asmlinkage void do_address_error(struct pt_regs *regs,
                                 unsigned long writeaccess,
                                 unsigned long address)
{
        unsigned long error_code = 0;
        mm_segment_t oldfs;
        insn_size_t instruction;
        int tmp;

        /* Intentional ifdef */
#ifdef CONFIG_CPU_HAS_SR_RB
        error_code = lookup_exception_vector();
#endif

        if (user_mode(regs)) {
                int si_code = BUS_ADRERR;
                unsigned int user_action;

                local_irq_enable();
                inc_unaligned_user_access();

                oldfs = force_uaccess_begin();
                if (copy_from_user(&instruction, (insn_size_t *)(regs->pc & ~1),
                                   sizeof(instruction))) {
                        force_uaccess_end(oldfs);
                        goto uspace_segv;
                }
                force_uaccess_end(oldfs);

                /* shout about userspace fixups */
                unaligned_fixups_notify(current, instruction, regs);

                user_action = unaligned_user_action();
                if (user_action & UM_FIXUP)
                        goto fixup;
                if (user_action & UM_SIGNAL)
                        goto uspace_segv;
                else {
                        /* ignore */
                        regs->pc += instruction_size(instruction);
                        return;
                }

fixup:
                /* bad PC is not something we can fix */
                if (regs->pc & 1) {
                        si_code = BUS_ADRALN;
                        goto uspace_segv;
                }

                oldfs = force_uaccess_begin();
                tmp = handle_unaligned_access(instruction, regs,
                                              &user_mem_access, 0,
                                              address);
                force_uaccess_end(oldfs);

                if (tmp == 0)
                        return; /* sorted */
uspace_segv:
                printk(KERN_NOTICE "Sending SIGBUS to \"%s\" due to unaligned "
                       "access (PC %lx PR %lx)\n", current->comm, regs->pc,
                       regs->pr);

                force_sig_fault(SIGBUS, si_code, (void __user *)address);
        } else {
                inc_unaligned_kernel_access();

                if (regs->pc & 1)
                        die("unaligned program counter", regs, error_code);

                set_fs(KERNEL_DS);
                if (copy_from_user(&instruction, (void __user *)(regs->pc),
                                   sizeof(instruction))) {
                        /* Argh. Fault on the instruction itself.
                           This should never happen non-SMP
                        */
                        set_fs(oldfs);
                        die("insn faulting in do_address_error", regs, 0);
                }

                unaligned_fixups_notify(current, instruction, regs);

                handle_unaligned_access(instruction, regs, &user_mem_access,
                                        0, address);
                set_fs(oldfs);
        }
}

#ifdef CONFIG_SH_DSP
/*
 *      SH-DSP support gerg@snapgear.com.
 */
int is_dsp_inst(struct pt_regs *regs)
{
        unsigned short inst = 0;

        /*
         * Safe guard if DSP mode is already enabled or we're lacking
         * the DSP altogether.
         */
        if (!(current_cpu_data.flags & CPU_HAS_DSP) || (regs->sr & SR_DSP))
                return 0;

        get_user(inst, ((unsigned short *) regs->pc));

        inst &= 0xf000;

        /* Check for any type of DSP or support instruction */
        if ((inst == 0xf000) || (inst == 0x4000))
                return 1;

        return 0;
}
#else
#define is_dsp_inst(regs)       (0)
#endif /* CONFIG_SH_DSP */

#ifdef CONFIG_CPU_SH2A
asmlinkage void do_divide_error(unsigned long r4)
{
        int code;

        switch (r4) {
        case TRAP_DIVZERO_ERROR:
                code = FPE_INTDIV;
                break;
        case TRAP_DIVOVF_ERROR:
                code = FPE_INTOVF;
                break;
        default:
                /* Let gcc know unhandled cases don't make it past here */
                return;
        }
        force_sig_fault(SIGFPE, code, NULL);
}
#endif

asmlinkage void do_reserved_inst(void)
{
        struct pt_regs *regs = current_pt_regs();
        unsigned long error_code;

#ifdef CONFIG_SH_FPU_EMU
        unsigned short inst = 0;
        int err;

        get_user(inst, (unsigned short*)regs->pc);

        err = do_fpu_inst(inst, regs);
        if (!err) {
                regs->pc += instruction_size(inst);
                return;
        }
        /* not a FPU inst. */
#endif

#ifdef CONFIG_SH_DSP
        /* Check if it's a DSP instruction */
        if (is_dsp_inst(regs)) {
                /* Enable DSP mode, and restart instruction. */
                regs->sr |= SR_DSP;
                /* Save DSP mode */
                current->thread.dsp_status.status |= SR_DSP;
                return;
        }
#endif

        error_code = lookup_exception_vector();

        local_irq_enable();
        force_sig(SIGILL);
        die_if_no_fixup("reserved instruction", regs, error_code);
}

#ifdef CONFIG_SH_FPU_EMU
static int emulate_branch(unsigned short inst, struct pt_regs *regs)
{
        /*
         * bfs: 8fxx: PC+=d*2+4;
         * bts: 8dxx: PC+=d*2+4;
         * bra: axxx: PC+=D*2+4;
         * bsr: bxxx: PC+=D*2+4  after PR=PC+4;
         * braf:0x23: PC+=Rn*2+4;
         * bsrf:0x03: PC+=Rn*2+4 after PR=PC+4;
         * jmp: 4x2b: PC=Rn;
         * jsr: 4x0b: PC=Rn      after PR=PC+4;
         * rts: 000b: PC=PR;
         */
        if (((inst & 0xf000) == 0xb000)  ||     /* bsr */
            ((inst & 0xf0ff) == 0x0003)  ||     /* bsrf */
            ((inst & 0xf0ff) == 0x400b))        /* jsr */
                regs->pr = regs->pc + 4;

        if ((inst & 0xfd00) == 0x8d00) {        /* bfs, bts */
                regs->pc += SH_PC_8BIT_OFFSET(inst);
                return 0;
        }

        if ((inst & 0xe000) == 0xa000) {        /* bra, bsr */
                regs->pc += SH_PC_12BIT_OFFSET(inst);
                return 0;
        }

        if ((inst & 0xf0df) == 0x0003) {        /* braf, bsrf */
                regs->pc += regs->regs[(inst & 0x0f00) >> 8] + 4;
                return 0;
        }

        if ((inst & 0xf0df) == 0x400b) {        /* jmp, jsr */
                regs->pc = regs->regs[(inst & 0x0f00) >> 8];
                return 0;
        }

        if ((inst & 0xffff) == 0x000b) {        /* rts */
                regs->pc = regs->pr;
                return 0;
        }

        return 1;
}
#endif

asmlinkage void do_illegal_slot_inst(void)
{
        struct pt_regs *regs = current_pt_regs();
        unsigned long inst;

        if (kprobe_handle_illslot(regs->pc) == 0)
                return;

#ifdef CONFIG_SH_FPU_EMU
        get_user(inst, (unsigned short *)regs->pc + 1);
        if (!do_fpu_inst(inst, regs)) {
                get_user(inst, (unsigned short *)regs->pc);
                if (!emulate_branch(inst, regs))
                        return;
                /* fault in branch.*/
        }
        /* not a FPU inst. */
#endif

        inst = lookup_exception_vector();

        local_irq_enable();
        force_sig(SIGILL);
        die_if_no_fixup("illegal slot instruction", regs, inst);
}

asmlinkage void do_exception_error(void)
{
        long ex;

        ex = lookup_exception_vector();
        die_if_kernel("exception", current_pt_regs(), ex);
}

void per_cpu_trap_init(void)
{
        extern void *vbr_base;

        /* NOTE: The VBR value should be at P1
           (or P2, virtural "fixed" address space).
           It's definitely should not in physical address.  */

        asm volatile("ldc       %0, vbr"
                     : /* no output */
                     : "r" (&vbr_base)
                     : "memory");

        /* disable exception blocking now when the vbr has been setup */
        clear_bl_bit();
}

void *set_exception_table_vec(unsigned int vec, void *handler)
{
        extern void *exception_handling_table[];
        void *old_handler;

        old_handler = exception_handling_table[vec];
        exception_handling_table[vec] = handler;
        return old_handler;
}

void __init trap_init(void)
{
        set_exception_table_vec(TRAP_RESERVED_INST, do_reserved_inst);
        set_exception_table_vec(TRAP_ILLEGAL_SLOT_INST, do_illegal_slot_inst);

#if defined(CONFIG_CPU_SH4) && !defined(CONFIG_SH_FPU) || \
    defined(CONFIG_SH_FPU_EMU)
        /*
         * For SH-4 lacking an FPU, treat floating point instructions as
         * reserved. They'll be handled in the math-emu case, or faulted on
         * otherwise.
         */
        set_exception_table_evt(0x800, do_reserved_inst);
        set_exception_table_evt(0x820, do_illegal_slot_inst);
#elif defined(CONFIG_SH_FPU)
        set_exception_table_evt(0x800, fpu_state_restore_trap_handler);
        set_exception_table_evt(0x820, fpu_state_restore_trap_handler);
#endif

#ifdef CONFIG_CPU_SH2
        set_exception_table_vec(TRAP_ADDRESS_ERROR, address_error_trap_handler);
#endif
#ifdef CONFIG_CPU_SH2A
        set_exception_table_vec(TRAP_DIVZERO_ERROR, do_divide_error);
        set_exception_table_vec(TRAP_DIVOVF_ERROR, do_divide_error);
#ifdef CONFIG_SH_FPU
        set_exception_table_vec(TRAP_FPU_ERROR, fpu_error_trap_handler);
#endif
#endif

#ifdef TRAP_UBC
        set_exception_table_vec(TRAP_UBC, breakpoint_trap_handler);
#endif
}