projects/linux·blob master · refs

211 lines · 5.8 KiB

1/* SPDX-License-Identifier: GPL-2.0
2 *
3 * Copyright (C) 2014-2017 Linaro Ltd. <[email protected]>
4 *
5 * Copyright (C) 2018 Andes Technology Corporation <[email protected]>
6 */
7
8#include <linux/elf.h>
9#include <linux/kernel.h>
10#include <linux/module.h>
11#include <linux/moduleloader.h>
12#include <linux/sort.h>
13
14unsigned long module_emit_got_entry(struct module *mod, unsigned long val)
15{
16 struct mod_section *got_sec = &mod->arch.got;
17 int i = got_sec->num_entries;
18 struct got_entry *got = get_got_entry(val, got_sec);
19
20 if (got)
21 return (unsigned long)got;
22
23 /* There is no duplicate entry, create a new one */
24 got = (struct got_entry *)got_sec->shdr->sh_addr;
25 got[i] = emit_got_entry(val);
26
27 got_sec->num_entries++;
28 BUG_ON(got_sec->num_entries > got_sec->max_entries);
29
30 return (unsigned long)&got[i];
31}
32
33unsigned long module_emit_plt_entry(struct module *mod, unsigned long val)
34{
35 struct mod_section *got_plt_sec = &mod->arch.got_plt;
36 struct got_entry *got_plt;
37 struct mod_section *plt_sec = &mod->arch.plt;
38 struct plt_entry *plt = get_plt_entry(val, plt_sec, got_plt_sec);
39 int i = plt_sec->num_entries;
40
41 if (plt)
42 return (unsigned long)plt;
43
44 /* There is no duplicate entry, create a new one */
45 got_plt = (struct got_entry *)got_plt_sec->shdr->sh_addr;
46 got_plt[i] = emit_got_entry(val);
47 plt = (struct plt_entry *)plt_sec->shdr->sh_addr;
48 plt[i] = emit_plt_entry(val,
49 (unsigned long)&plt[i],
50 (unsigned long)&got_plt[i]);
51
52 plt_sec->num_entries++;
53 got_plt_sec->num_entries++;
54 BUG_ON(plt_sec->num_entries > plt_sec->max_entries);
55
56 return (unsigned long)&plt[i];
57}
58
59static int cmp_rela(const void *a, const void *b)
60{
61 const Elf_Rela *x = a, *y = b;
62 int i;
63
64 /* sort by type, symbol index and addend */
65 i = cmp_int(x->r_info, y->r_info);
66 if (i == 0)
67 i = cmp_int(x->r_addend, y->r_addend);
68 return i;
69}
70
71static bool duplicate_rela(const Elf_Rela *rela, int idx)
72{
73 /*
74 * Entries are sorted by type, symbol index and addend. That means
75 * that, if a duplicate entry exists, it must be in the preceding slot.
76 */
77 return idx > 0 && cmp_rela(rela + idx, rela + idx - 1) == 0;
78}
79
80static void count_max_entries(const Elf_Rela *relas, size_t num,
81 unsigned int *plts, unsigned int *gots)
82{
83 for (size_t i = 0; i < num; i++) {
84 if (duplicate_rela(relas, i))
85 continue;
86
87 switch (ELF_R_TYPE(relas[i].r_info)) {
88 case R_RISCV_CALL_PLT:
89 case R_RISCV_PLT32:
90 (*plts)++;
91 break;
92 case R_RISCV_GOT_HI20:
93 (*gots)++;
94 break;
95 default:
96 unreachable();
97 }
98 }
99}
100
101static bool rela_needs_plt_got_entry(const Elf_Rela *rela)
102{
103 switch (ELF_R_TYPE(rela->r_info)) {
104 case R_RISCV_CALL_PLT:
105 case R_RISCV_GOT_HI20:
106 case R_RISCV_PLT32:
107 return true;
108 default:
109 return false;
110 }
111}
112
113int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
114 char *secstrings, struct module *mod)
115{
116 size_t num_scratch_relas = 0;
117 unsigned int num_plts = 0;
118 unsigned int num_gots = 0;
119 Elf_Rela *scratch = NULL;
120 Elf_Rela *new_scratch;
121 size_t scratch_size = 0;
122 int i;
123
124 /*
125 * Find the empty .got and .plt sections.
126 */
127 for (i = 0; i < ehdr->e_shnum; i++) {
128 if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
129 mod->arch.plt.shdr = sechdrs + i;
130 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got"))
131 mod->arch.got.shdr = sechdrs + i;
132 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got.plt"))
133 mod->arch.got_plt.shdr = sechdrs + i;
134 }
135
136 if (!mod->arch.plt.shdr) {
137 pr_err("%s: module PLT section(s) missing\n", mod->name);
138 return -ENOEXEC;
139 }
140 if (!mod->arch.got.shdr) {
141 pr_err("%s: module GOT section(s) missing\n", mod->name);
142 return -ENOEXEC;
143 }
144 if (!mod->arch.got_plt.shdr) {
145 pr_err("%s: module GOT.PLT section(s) missing\n", mod->name);
146 return -ENOEXEC;
147 }
148
149 /* Calculate the maximum number of entries */
150 for (i = 0; i < ehdr->e_shnum; i++) {
151 size_t num_relas = sechdrs[i].sh_size / sizeof(Elf_Rela);
152 Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset;
153 Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info;
154 size_t scratch_size_needed;
155
156 if (sechdrs[i].sh_type != SHT_RELA)
157 continue;
158
159 /* ignore relocations that operate on non-exec sections */
160 if (!(dst_sec->sh_flags & SHF_EXECINSTR))
161 continue;
162
163 /*
164 * apply_relocate_add() relies on HI20 and LO12 relocation pairs being
165 * close together, so sort a copy of the section to avoid interfering.
166 */
167 scratch_size_needed = (num_scratch_relas + num_relas) * sizeof(*scratch);
168 if (scratch_size_needed > scratch_size) {
169 scratch_size = scratch_size_needed;
170 new_scratch = kvrealloc(scratch, scratch_size, GFP_KERNEL);
171 if (!new_scratch) {
172 kvfree(scratch);
173 return -ENOMEM;
174 }
175 scratch = new_scratch;
176 }
177
178 for (size_t j = 0; j < num_relas; j++)
179 if (rela_needs_plt_got_entry(&relas[j]))
180 scratch[num_scratch_relas++] = relas[j];
181 }
182
183 if (scratch) {
184 /* sort the accumulated PLT/GOT relocations so duplicates are adjacent */
185 sort(scratch, num_scratch_relas, sizeof(*scratch), cmp_rela, NULL);
186 count_max_entries(scratch, num_scratch_relas, &num_plts, &num_gots);
187 kvfree(scratch);
188 }
189
190 mod->arch.plt.shdr->sh_type = SHT_NOBITS;
191 mod->arch.plt.shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
192 mod->arch.plt.shdr->sh_addralign = L1_CACHE_BYTES;
193 mod->arch.plt.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_entry);
194 mod->arch.plt.num_entries = 0;
195 mod->arch.plt.max_entries = num_plts;
196
197 mod->arch.got.shdr->sh_type = SHT_NOBITS;
198 mod->arch.got.shdr->sh_flags = SHF_ALLOC;
199 mod->arch.got.shdr->sh_addralign = L1_CACHE_BYTES;
200 mod->arch.got.shdr->sh_size = (num_gots + 1) * sizeof(struct got_entry);
201 mod->arch.got.num_entries = 0;
202 mod->arch.got.max_entries = num_gots;
203
204 mod->arch.got_plt.shdr->sh_type = SHT_NOBITS;
205 mod->arch.got_plt.shdr->sh_flags = SHF_ALLOC;
206 mod->arch.got_plt.shdr->sh_addralign = L1_CACHE_BYTES;
207 mod->arch.got_plt.shdr->sh_size = (num_plts + 1) * sizeof(struct got_entry);
208 mod->arch.got_plt.num_entries = 0;
209 mod->arch.got_plt.max_entries = num_plts;
210 return 0;
211}