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
10 struct module;
11 unsigned long module_emit_got_entry(struct module *mod, unsigned long val);
12 unsigned long module_emit_plt_entry(struct module *mod, unsigned long val);
13
14 #ifdef CONFIG_MODULE_SECTIONS
15 struct mod_section {
16 Elf_Shdr *shdr;
17 int num_entries;
18 int max_entries;
19 };
20
21 struct mod_arch_specific {
22 struct mod_section got;
23 struct mod_section plt;
24 struct mod_section got_plt;
25 };
26
27 struct got_entry {
28 unsigned long symbol_addr; /* the real variable address */
29 };
30
31 static inline struct got_entry emit_got_entry(unsigned long val)
32 {
33 return (struct got_entry) {val};
34 }
35
36 static 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
48 struct 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
64 static 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
90 static 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
101 static 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
115 static 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 */
131
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