xref: /arch/mips/kernel/jump_label.c

/*
 * 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>

#ifdef HAVE_JUMP_LABEL

/*
 * 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;

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

	/* Jump only works within an aligned region its delay slot is in. */
	BUG_ON((e->target & ~J_RANGE_MASK) != ((e->code + 4) & ~J_RANGE_MASK));

	/* 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_ENABLE) {
		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 */
	}

	get_online_cpus();
	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);
	put_online_cpus();
}

#endif /* HAVE_JUMP_LABEL */