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