xref: /linux/arch/riscv/include/asm/module.h (revision b2105aa2c6481fda72c1825800b753a0bf614517)
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 
9 struct module;
10 unsigned long module_emit_got_entry(struct module *mod, unsigned long val);
11 unsigned long module_emit_plt_entry(struct module *mod, unsigned long val);
12 
13 #ifdef CONFIG_MODULE_SECTIONS
14 struct mod_section {
15 	Elf_Shdr *shdr;
16 	int num_entries;
17 	int max_entries;
18 };
19 
20 struct mod_arch_specific {
21 	struct mod_section got;
22 	struct mod_section plt;
23 	struct mod_section got_plt;
24 };
25 
26 struct got_entry {
27 	unsigned long symbol_addr;	/* the real variable address */
28 };
29 
30 static inline struct got_entry emit_got_entry(unsigned long val)
31 {
32 	return (struct got_entry) {val};
33 }
34 
35 static inline struct got_entry *get_got_entry(unsigned long val,
36 					      const struct mod_section *sec)
37 {
38 	struct got_entry *got = (struct got_entry *)(sec->shdr->sh_addr);
39 	int i;
40 	for (i = 0; i < sec->num_entries; i++) {
41 		if (got[i].symbol_addr == val)
42 			return &got[i];
43 	}
44 	return NULL;
45 }
46 
47 struct plt_entry {
48 	/*
49 	 * Trampoline code to real target address. The return address
50 	 * should be the original (pc+4) before entring plt entry.
51 	 */
52 	u32 insn_auipc;		/* auipc t0, 0x0                       */
53 	u32 insn_ld;		/* ld    t1, 0x10(t0)                  */
54 	u32 insn_jr;		/* jr    t1                            */
55 };
56 
57 #define OPC_AUIPC  0x0017
58 #define OPC_LD     0x3003
59 #define OPC_JALR   0x0067
60 #define REG_T0     0x5
61 #define REG_T1     0x6
62 
63 static inline struct plt_entry emit_plt_entry(unsigned long val,
64 					      unsigned long plt,
65 					      unsigned long got_plt)
66 {
67 	/*
68 	 * U-Type encoding:
69 	 * +------------+----------+----------+
70 	 * | imm[31:12] | rd[11:7] | opc[6:0] |
71 	 * +------------+----------+----------+
72 	 *
73 	 * I-Type encoding:
74 	 * +------------+------------+--------+----------+----------+
75 	 * | imm[31:20] | rs1[19:15] | funct3 | rd[11:7] | opc[6:0] |
76 	 * +------------+------------+--------+----------+----------+
77 	 *
78 	 */
79 	unsigned long offset = got_plt - plt;
80 	u32 hi20 = (offset + 0x800) & 0xfffff000;
81 	u32 lo12 = (offset - hi20);
82 	return (struct plt_entry) {
83 		OPC_AUIPC | (REG_T0 << 7) | hi20,
84 		OPC_LD | (lo12 << 20) | (REG_T0 << 15) | (REG_T1 << 7),
85 		OPC_JALR | (REG_T1 << 15)
86 	};
87 }
88 
89 static inline int get_got_plt_idx(unsigned long val, const struct mod_section *sec)
90 {
91 	struct got_entry *got_plt = (struct got_entry *)sec->shdr->sh_addr;
92 	int i;
93 	for (i = 0; i < sec->num_entries; i++) {
94 		if (got_plt[i].symbol_addr == val)
95 			return i;
96 	}
97 	return -1;
98 }
99 
100 static inline struct plt_entry *get_plt_entry(unsigned long val,
101 					      const struct mod_section *sec_plt,
102 					      const struct mod_section *sec_got_plt)
103 {
104 	struct plt_entry *plt = (struct plt_entry *)sec_plt->shdr->sh_addr;
105 	int got_plt_idx = get_got_plt_idx(val, sec_got_plt);
106 	if (got_plt_idx >= 0)
107 		return plt + got_plt_idx;
108 	else
109 		return NULL;
110 }
111 
112 #endif /* CONFIG_MODULE_SECTIONS */
113 
114 #endif /* _ASM_RISCV_MODULE_H */
115