1 /* SPDX-License-Identifier: GPL-2.0
2  *
3  * Copyright (C) 2014-2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
4  *
5  * Copyright (C) 2018 Andes Technology Corporation <zong@andestech.com>
6  */
7 
8 #include <linux/elf.h>
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/moduleloader.h>
12 
13 unsigned long module_emit_got_entry(struct module *mod, unsigned long val)
14 {
15 	struct mod_section *got_sec = &mod->arch.got;
16 	int i = got_sec->num_entries;
17 	struct got_entry *got = get_got_entry(val, got_sec);
18 
19 	if (got)
20 		return (unsigned long)got;
21 
22 	/* There is no duplicate entry, create a new one */
23 	got = (struct got_entry *)got_sec->shdr->sh_addr;
24 	got[i] = emit_got_entry(val);
25 
26 	got_sec->num_entries++;
27 	BUG_ON(got_sec->num_entries > got_sec->max_entries);
28 
29 	return (unsigned long)&got[i];
30 }
31 
32 unsigned long module_emit_plt_entry(struct module *mod, unsigned long val)
33 {
34 	struct mod_section *got_plt_sec = &mod->arch.got_plt;
35 	struct got_entry *got_plt;
36 	struct mod_section *plt_sec = &mod->arch.plt;
37 	struct plt_entry *plt = get_plt_entry(val, plt_sec, got_plt_sec);
38 	int i = plt_sec->num_entries;
39 
40 	if (plt)
41 		return (unsigned long)plt;
42 
43 	/* There is no duplicate entry, create a new one */
44 	got_plt = (struct got_entry *)got_plt_sec->shdr->sh_addr;
45 	got_plt[i] = emit_got_entry(val);
46 	plt = (struct plt_entry *)plt_sec->shdr->sh_addr;
47 	plt[i] = emit_plt_entry(val,
48 				(unsigned long)&plt[i],
49 				(unsigned long)&got_plt[i]);
50 
51 	plt_sec->num_entries++;
52 	got_plt_sec->num_entries++;
53 	BUG_ON(plt_sec->num_entries > plt_sec->max_entries);
54 
55 	return (unsigned long)&plt[i];
56 }
57 
58 static int is_rela_equal(const Elf_Rela *x, const Elf_Rela *y)
59 {
60 	return x->r_info == y->r_info && x->r_addend == y->r_addend;
61 }
62 
63 static bool duplicate_rela(const Elf_Rela *rela, int idx)
64 {
65 	int i;
66 	for (i = 0; i < idx; i++) {
67 		if (is_rela_equal(&rela[i], &rela[idx]))
68 			return true;
69 	}
70 	return false;
71 }
72 
73 static void count_max_entries(Elf_Rela *relas, int num,
74 			      unsigned int *plts, unsigned int *gots)
75 {
76 	unsigned int type, i;
77 
78 	for (i = 0; i < num; i++) {
79 		type = ELF_RISCV_R_TYPE(relas[i].r_info);
80 		if (type == R_RISCV_CALL_PLT) {
81 			if (!duplicate_rela(relas, i))
82 				(*plts)++;
83 		} else if (type == R_RISCV_GOT_HI20) {
84 			if (!duplicate_rela(relas, i))
85 				(*gots)++;
86 		}
87 	}
88 }
89 
90 int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
91 			      char *secstrings, struct module *mod)
92 {
93 	unsigned int num_plts = 0;
94 	unsigned int num_gots = 0;
95 	int i;
96 
97 	/*
98 	 * Find the empty .got and .plt sections.
99 	 */
100 	for (i = 0; i < ehdr->e_shnum; i++) {
101 		if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
102 			mod->arch.plt.shdr = sechdrs + i;
103 		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got"))
104 			mod->arch.got.shdr = sechdrs + i;
105 		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got.plt"))
106 			mod->arch.got_plt.shdr = sechdrs + i;
107 	}
108 
109 	if (!mod->arch.plt.shdr) {
110 		pr_err("%s: module PLT section(s) missing\n", mod->name);
111 		return -ENOEXEC;
112 	}
113 	if (!mod->arch.got.shdr) {
114 		pr_err("%s: module GOT section(s) missing\n", mod->name);
115 		return -ENOEXEC;
116 	}
117 	if (!mod->arch.got_plt.shdr) {
118 		pr_err("%s: module GOT.PLT section(s) missing\n", mod->name);
119 		return -ENOEXEC;
120 	}
121 
122 	/* Calculate the maxinum number of entries */
123 	for (i = 0; i < ehdr->e_shnum; i++) {
124 		Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset;
125 		int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela);
126 		Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info;
127 
128 		if (sechdrs[i].sh_type != SHT_RELA)
129 			continue;
130 
131 		/* ignore relocations that operate on non-exec sections */
132 		if (!(dst_sec->sh_flags & SHF_EXECINSTR))
133 			continue;
134 
135 		count_max_entries(relas, num_rela, &num_plts, &num_gots);
136 	}
137 
138 	mod->arch.plt.shdr->sh_type = SHT_NOBITS;
139 	mod->arch.plt.shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
140 	mod->arch.plt.shdr->sh_addralign = L1_CACHE_BYTES;
141 	mod->arch.plt.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_entry);
142 	mod->arch.plt.num_entries = 0;
143 	mod->arch.plt.max_entries = num_plts;
144 
145 	mod->arch.got.shdr->sh_type = SHT_NOBITS;
146 	mod->arch.got.shdr->sh_flags = SHF_ALLOC;
147 	mod->arch.got.shdr->sh_addralign = L1_CACHE_BYTES;
148 	mod->arch.got.shdr->sh_size = (num_gots + 1) * sizeof(struct got_entry);
149 	mod->arch.got.num_entries = 0;
150 	mod->arch.got.max_entries = num_gots;
151 
152 	mod->arch.got_plt.shdr->sh_type = SHT_NOBITS;
153 	mod->arch.got_plt.shdr->sh_flags = SHF_ALLOC;
154 	mod->arch.got_plt.shdr->sh_addralign = L1_CACHE_BYTES;
155 	mod->arch.got_plt.shdr->sh_size = (num_plts + 1) * sizeof(struct got_entry);
156 	mod->arch.got_plt.num_entries = 0;
157 	mod->arch.got_plt.max_entries = num_plts;
158 	return 0;
159 }
160