module.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2/* Copyright (C) 2017 Andes Technology Corporation */
  3
  4#ifndef _ASM_RISCV_MODULE_H
  5#define _ASM_RISCV_MODULE_H
  6
  7#include <asm-generic/module.h>
  8#include <linux/elf.h>
  9
 10struct module;
 11unsigned long module_emit_got_entry(struct module *mod, unsigned long val);
 12unsigned long module_emit_plt_entry(struct module *mod, unsigned long val);
 13
 14#ifdef CONFIG_MODULE_SECTIONS
 15struct mod_section {
 16	Elf_Shdr *shdr;
 17	int num_entries;
 18	int max_entries;
 19};
 20
 21struct mod_arch_specific {
 22	struct mod_section got;
 23	struct mod_section plt;
 24	struct mod_section got_plt;
 25};
 26
 27struct got_entry {
 28	unsigned long symbol_addr;	/* the real variable address */
 29};
 30
 31static inline struct got_entry emit_got_entry(unsigned long val)
 32{
 33	return (struct got_entry) {val};
 34}
 35
 36static inline struct got_entry *get_got_entry(unsigned long val,
 37					      const struct mod_section *sec)
 38{
 39	struct got_entry *got = (struct got_entry *)(sec->shdr->sh_addr);
 40	int i;
 41	for (i = 0; i < sec->num_entries; i++) {
 42		if (got[i].symbol_addr == val)
 43			return &got[i];
 44	}
 45	return NULL;
 46}
 47
 48struct plt_entry {
 49	/*
 50	 * Trampoline code to real target address. The return address
 51	 * should be the original (pc+4) before entring plt entry.
 52	 */
 53	u32 insn_auipc;		/* auipc t0, 0x0                       */
 54	u32 insn_ld;		/* ld    t1, 0x10(t0)                  */
 55	u32 insn_jr;		/* jr    t1                            */
 56};
 57
 58#define OPC_AUIPC  0x0017
 59#define OPC_LD     0x3003
 60#define OPC_JALR   0x0067
 61#define REG_T0     0x5
 62#define REG_T1     0x6
 63
 64static inline struct plt_entry emit_plt_entry(unsigned long val,
 65					      unsigned long plt,
 66					      unsigned long got_plt)
 67{
 68	/*
 69	 * U-Type encoding:
 70	 * +------------+----------+----------+
 71	 * | imm[31:12] | rd[11:7] | opc[6:0] |
 72	 * +------------+----------+----------+
 73	 *
 74	 * I-Type encoding:
 75	 * +------------+------------+--------+----------+----------+
 76	 * | imm[31:20] | rs1[19:15] | funct3 | rd[11:7] | opc[6:0] |
 77	 * +------------+------------+--------+----------+----------+
 78	 *
 79	 */
 80	unsigned long offset = got_plt - plt;
 81	u32 hi20 = (offset + 0x800) & 0xfffff000;
 82	u32 lo12 = (offset - hi20);
 83	return (struct plt_entry) {
 84		OPC_AUIPC | (REG_T0 << 7) | hi20,
 85		OPC_LD | (lo12 << 20) | (REG_T0 << 15) | (REG_T1 << 7),
 86		OPC_JALR | (REG_T1 << 15)
 87	};
 88}
 89
 90static inline int get_got_plt_idx(unsigned long val, const struct mod_section *sec)
 91{
 92	struct got_entry *got_plt = (struct got_entry *)sec->shdr->sh_addr;
 93	int i;
 94	for (i = 0; i < sec->num_entries; i++) {
 95		if (got_plt[i].symbol_addr == val)
 96			return i;
 97	}
 98	return -1;
 99}
100
101static inline struct plt_entry *get_plt_entry(unsigned long val,
102					      const struct mod_section *sec_plt,
103					      const struct mod_section *sec_got_plt)
104{
105	struct plt_entry *plt = (struct plt_entry *)sec_plt->shdr->sh_addr;
106	int got_plt_idx = get_got_plt_idx(val, sec_got_plt);
107	if (got_plt_idx >= 0)
108		return plt + got_plt_idx;
109	else
110		return NULL;
111}
112
113#endif /* CONFIG_MODULE_SECTIONS */
114
115static inline const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
116					   const Elf_Shdr *sechdrs,
117					   const char *name)
118{
119	const Elf_Shdr *s, *se;
120	const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
121
122	for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++) {
123		if (strcmp(name, secstrs + s->sh_name) == 0)
124			return s;
125	}
126
127	return NULL;
128}
129
130#endif /* _ASM_RISCV_MODULE_H */