alistair23-linux/arch/x86/include/asm/orc_types.h

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
 */

#ifndef _ORC_TYPES_H
#define _ORC_TYPES_H

#include <linux/types.h>
#include <linux/compiler.h>

/*
 * The ORC_REG_* registers are base registers which are used to find other
 * registers on the stack.
 *
 * ORC_REG_PREV_SP, also known as DWARF Call Frame Address (CFA), is the
 * address of the previous frame: the caller's SP before it called the current
 * function.
 *
 * ORC_REG_UNDEFINED means the corresponding register's value didn't change in
 * the current frame.
 *
 * The most commonly used base registers are SP and BP -- which the previous SP
 * is usually based on -- and PREV_SP and UNDEFINED -- which the previous BP is
 * usually based on.
 *
 * The rest of the base registers are needed for special cases like entry code
 * and GCC realigned stacks.
 */
#define ORC_REG_UNDEFINED		0
#define ORC_REG_PREV_SP			1
#define ORC_REG_DX			2
#define ORC_REG_DI			3
#define ORC_REG_BP			4
#define ORC_REG_SP			5
#define ORC_REG_R10			6
#define ORC_REG_R13			7
#define ORC_REG_BP_INDIRECT		8
#define ORC_REG_SP_INDIRECT		9
#define ORC_REG_MAX			15

/*
 * ORC_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP (the
 * caller's SP right before it made the call).  Used for all callable
 * functions, i.e. all C code and all callable asm functions.
 *
 * ORC_TYPE_REGS: Used in entry code to indicate that sp_reg+sp_offset points
 * to a fully populated pt_regs from a syscall, interrupt, or exception.
 *
 * ORC_TYPE_REGS_IRET: Used in entry code to indicate that sp_reg+sp_offset
 * points to the iret return frame.
 *
 * The UNWIND_HINT macros are used only for the unwind_hint struct.  They
 * aren't used in struct orc_entry due to size and complexity constraints.
 * Objtool converts them to real types when it converts the hints to orc
 * entries.
 */
#define ORC_TYPE_CALL			0
#define ORC_TYPE_REGS			1
#define ORC_TYPE_REGS_IRET		2
#define UNWIND_HINT_TYPE_SAVE		3
#define UNWIND_HINT_TYPE_RESTORE	4

#ifndef __ASSEMBLY__
/*
 * This struct is more or less a vastly simplified version of the DWARF Call
 * Frame Information standard.  It contains only the necessary parts of DWARF
 * CFI, simplified for ease of access by the in-kernel unwinder.  It tells the
 * unwinder how to find the previous SP and BP (and sometimes entry regs) on
 * the stack for a given code address.  Each instance of the struct corresponds
 * to one or more code locations.
 */
struct orc_entry {
	s16		sp_offset;
	s16		bp_offset;
	unsigned	sp_reg:4;
	unsigned	bp_reg:4;
	unsigned	type:2;
	unsigned	end:1;
} __packed;

/*
 * This struct is used by asm and inline asm code to manually annotate the
 * location of registers on the stack for the ORC unwinder.
 *
 * Type can be either ORC_TYPE_* or UNWIND_HINT_TYPE_*.
 */
struct unwind_hint {
	u32		ip;
	s16		sp_offset;
	u8		sp_reg;
	u8		type;
	u8		end;
};
#endif /* __ASSEMBLY__ */

#endif /* _ORC_TYPES_H */