/*
 * 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) 2010 Cavium Networks, Inc.
 */

#include <linux/jump_label.h>
#include <linux/kernel.h>
#include <linux/memory.h>
#include <linux/mutex.h>
#include <linux/types.h>
#include <linux/cpu.h>

#include <asm/cacheflush.h>
#include <asm/inst.h>

/*
 * Define parameters for the standard MIPS and the microMIPS jump
 * instruction encoding respectively:
 *
 * - the ISA bit of the target, either 0 or 1 respectively,
 *
 * - the amount the jump target address is shifted right to fit in the
 *   immediate field of the machine instruction, either 2 or 1,
 *
 * - the mask determining the size of the jump region relative to the
 *   delay-slot instruction, either 256MB or 128MB,
 *
 * - the jump target alignment, either 4 or 2 bytes.
 */
#define J_ISA_BIT       IS_ENABLED(CONFIG_CPU_MICROMIPS)
#define J_RANGE_SHIFT   (2 - J_ISA_BIT)
#define J_RANGE_MASK    ((1ul << (26 + J_RANGE_SHIFT)) - 1)
#define J_ALIGN_MASK    ((1ul << J_RANGE_SHIFT) - 1)

void arch_jump_label_transform(struct jump_entry *e,
                               enum jump_label_type type)
{
        union mips_instruction *insn_p;
        union mips_instruction insn;
        long offset;

        insn_p = (union mips_instruction *)msk_isa16_mode(e->code);

        /* Target must have the right alignment and ISA must be preserved. */
        BUG_ON((e->target & J_ALIGN_MASK) != J_ISA_BIT);

        if (type == JUMP_LABEL_JMP) {
                if (!IS_ENABLED(CONFIG_CPU_MICROMIPS) && MIPS_ISA_REV >= 6) {
                        offset = e->target - ((unsigned long)insn_p + 4);
                        offset >>= 2;

                        /*
                         * The branch offset must fit in the instruction's 26
                         * bit field.
                         */
                        WARN_ON((offset >= (long)BIT(25)) ||
                                (offset < -(long)BIT(25)));

                        insn.j_format.opcode = bc6_op;
                        insn.j_format.target = offset;
                } else {
                        /*
                         * Jump only works within an aligned region its delay
                         * slot is in.
                         */
                        WARN_ON((e->target & ~J_RANGE_MASK) !=
                                ((e->code + 4) & ~J_RANGE_MASK));

                        insn.j_format.opcode = J_ISA_BIT ? mm_j32_op : j_op;
                        insn.j_format.target = e->target >> J_RANGE_SHIFT;
                }
        } else {
                insn.word = 0; /* nop */
        }

        mutex_lock(&text_mutex);
        if (IS_ENABLED(CONFIG_CPU_MICROMIPS)) {
                insn_p->halfword[0] = insn.word >> 16;
                insn_p->halfword[1] = insn.word;
        } else
                *insn_p = insn;

        flush_icache_range((unsigned long)insn_p,
                           (unsigned long)insn_p + sizeof(*insn_p));

        mutex_unlock(&text_mutex);
}

#ifdef CONFIG_MODULES
void jump_label_apply_nops(struct module *mod)
{
        struct jump_entry *iter_start = mod->jump_entries;
        struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
        struct jump_entry *iter;

        /* if the module doesn't have jump label entries, just return */
        if (iter_start == iter_stop)
                return;

        for (iter = iter_start; iter < iter_stop; iter++) {
                /* Only write NOPs for arch_branch_static(). */
                if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
                        arch_jump_label_transform(iter, JUMP_LABEL_NOP);
        }
}
#endif