xref: /openbmc/linux/arch/riscv/include/asm/module.h (revision e0c267e0)
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 
emit_got_entry(unsigned long val)31 static inline struct got_entry emit_got_entry(unsigned long val)
32 {
33 	return (struct got_entry) {val};
34 }
35 
get_got_entry(unsigned long val,const struct mod_section * sec)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 
emit_plt_entry(unsigned long val,unsigned long plt,unsigned long got_plt)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 
get_got_plt_idx(unsigned long val,const struct mod_section * sec)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 
get_plt_entry(unsigned long val,const struct mod_section * sec_plt,const struct mod_section * sec_got_plt)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 
find_section(const Elf_Ehdr * hdr,const Elf_Shdr * sechdrs,const char * name)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