linux_kernel/arch/arm64/include/asm/module.h

/*
 * Copyright (C) 2012 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef __ASM_MODULE_H
#define __ASM_MODULE_H

#include <asm-generic/module.h>

#define MODULE_ARCH_VERMAGIC	"aarch64"

#ifdef CONFIG_ARM64_MODULE_PLTS
struct mod_plt_sec {
	struct elf64_shdr	*plt;
	int			plt_num_entries;
	int			plt_max_entries;
};

struct mod_arch_specific {
	struct mod_plt_sec	core;
	struct mod_plt_sec	init;

	/* for CONFIG_DYNAMIC_FTRACE */
	struct plt_entry 	*ftrace_trampoline;
};
#endif

u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela *rela,
			  Elf64_Sym *sym);

u64 module_emit_veneer_for_adrp(struct module *mod, void *loc, u64 val);

#ifdef CONFIG_RANDOMIZE_BASE
extern u64 module_alloc_base;
#else
#define module_alloc_base	((u64)_etext - MODULES_VSIZE)
#endif

struct plt_entry {
	/*
	 * A program that conforms to the AArch64 Procedure Call Standard
	 * (AAPCS64) must assume that a veneer that alters IP0 (x16) and/or
	 * IP1 (x17) may be inserted at any branch instruction that is
	 * exposed to a relocation that supports long branches. Since that
	 * is exactly what we are dealing with here, we are free to use x16
	 * as a scratch register in the PLT veneers.
	 */
	__le32	mov0;	/* movn	x16, #0x....			*/
	__le32	mov1;	/* movk	x16, #0x...., lsl #16		*/
	__le32	mov2;	/* movk	x16, #0x...., lsl #32		*/
	__le32	br;	/* br	x16				*/
};

static inline struct plt_entry get_plt_entry(u64 val)
{
	/*
	 * MOVK/MOVN/MOVZ opcode:
	 * +--------+------------+--------+-----------+-------------+---------+
	 * | sf[31] | opc[30:29] | 100101 | hw[22:21] | imm16[20:5] | Rd[4:0] |
	 * +--------+------------+--------+-----------+-------------+---------+
	 *
	 * Rd     := 0x10 (x16)
	 * hw     := 0b00 (no shift), 0b01 (lsl #16), 0b10 (lsl #32)
	 * opc    := 0b11 (MOVK), 0b00 (MOVN), 0b10 (MOVZ)
	 * sf     := 1 (64-bit variant)
	 */
	return (struct plt_entry){
		cpu_to_le32(0x92800010 | (((~val      ) & 0xffff)) << 5),
		cpu_to_le32(0xf2a00010 | ((( val >> 16) & 0xffff)) << 5),
		cpu_to_le32(0xf2c00010 | ((( val >> 32) & 0xffff)) << 5),
		cpu_to_le32(0xd61f0200)
	};
}

static inline bool plt_entries_equal(const struct plt_entry *a,
				     const struct plt_entry *b)
{
	return a->mov0 == b->mov0 &&
	       a->mov1 == b->mov1 &&
	       a->mov2 == b->mov2;
}

#endif /* __ASM_MODULE_H */