/*
 * SPDX-License-Identifier: CDDL 1.0
 *
 * Copyright 2022 Christos Margiolis <christos@FreeBSD.org>
 * Copyright 2022 Mark Johnston <markj@FreeBSD.org>
 */

#ifndef _KINST_ISA_H_
#define _KINST_ISA_H_

#include <sys/types.h>

#define KINST_PATCHVAL		0xcc

/*
 * Each trampoline is 32 bytes long and contains [instruction, jmp]. Since we
 * have 2 instructions stored in the trampoline, and each of them can take up
 * to 16 bytes, 32 bytes is enough to cover even the worst case scenario.
 */
#define	KINST_TRAMP_SIZE	32
#define	KINST_TRAMPCHUNK_SIZE	PAGE_SIZE

/*
 * Fill the trampolines with breakpoint instructions so that the kernel will
 * crash cleanly if things somehow go wrong.
 */
#define	KINST_TRAMP_INIT(t, s)	memset((t), KINST_PATCHVAL, (s))

typedef uint8_t kinst_patchval_t;

struct kinst_probe_md {
	int			flags;
	int			instlen;	/* original instr len */
	int			tinstlen;	/* trampoline instr len */
	uint8_t			template[16];	/* copied into thread tramps */
	int			dispoff;	/* offset of rip displacement */

	/* operands to "call" instruction branch target */
	int			reg1;
	int			reg2;
	int			scale;
	int64_t			disp;
};

#endif /* _KINST_ISA_H_ */