1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
4 */
5
6#include <linux/elf.h>
7#include <linux/kernel.h>
8#include <linux/module.h>
9#include <linux/moduleloader.h>
10#include <linux/ftrace.h>
11#include <linux/sort.h>
12
13Elf_Addr module_emit_got_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr 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, sechdrs, got_sec);
18
19 if (got)
20 return (Elf_Addr)got;
21
22 /* There is no GOT entry for val yet, create a new one. */
23 got = (struct got_entry *)sechdrs[got_sec->shndx].sh_addr;
24 got[i] = emit_got_entry(val);
25
26 got_sec->num_entries++;
27 if (got_sec->num_entries > got_sec->max_entries) {
28 /*
29 * This may happen when the module contains a GOT_HI20 without
30 * a paired GOT_LO12. Such a module is broken, reject it.
31 */
32 pr_err("%s: module contains bad GOT relocation\n", mod->name);
33 return 0;
34 }
35
36 return (Elf_Addr)&got[i];
37}
38
39Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val)
40{
41 int nr;
42 struct mod_section *plt_sec = &mod->arch.plt;
43 struct mod_section *plt_idx_sec = &mod->arch.plt_idx;
44 struct plt_entry *plt = get_plt_entry(val, sechdrs, plt_sec, plt_idx_sec);
45 struct plt_idx_entry *plt_idx;
46
47 if (plt)
48 return (Elf_Addr)plt;
49
50 nr = plt_sec->num_entries;
51
52 /* There is no duplicate entry, create a new one */
53 plt = (struct plt_entry *)sechdrs[plt_sec->shndx].sh_addr;
54 plt[nr] = emit_plt_entry(val);
55 plt_idx = (struct plt_idx_entry *)sechdrs[plt_idx_sec->shndx].sh_addr;
56 plt_idx[nr] = emit_plt_idx_entry(val);
57
58 plt_sec->num_entries++;
59 plt_idx_sec->num_entries++;
60 BUG_ON(plt_sec->num_entries > plt_sec->max_entries);
61
62 return (Elf_Addr)&plt[nr];
63}
64
65#define cmp_3way(a, b) ((a) < (b) ? -1 : (a) > (b))
66
67static int compare_rela(const void *x, const void *y)
68{
69 int ret;
70 const Elf_Rela *rela_x = x, *rela_y = y;
71
72 ret = cmp_3way(rela_x->r_info, rela_y->r_info);
73 if (ret == 0)
74 ret = cmp_3way(rela_x->r_addend, rela_y->r_addend);
75
76 return ret;
77}
78
79static void count_max_entries(Elf_Rela *relas, int num,
80 unsigned int *plts, unsigned int *gots)
81{
82 unsigned int i;
83
84 sort(base: relas, num, size: sizeof(Elf_Rela), cmp_func: compare_rela, NULL);
85
86 for (i = 0; i < num; i++) {
87 if (i && !compare_rela(x: &relas[i-1], y: &relas[i]))
88 continue;
89
90 switch (ELF_R_TYPE(relas[i].r_info)) {
91 case R_LARCH_SOP_PUSH_PLT_PCREL:
92 case R_LARCH_B26:
93 (*plts)++;
94 break;
95 case R_LARCH_GOT_PC_HI20:
96 case R_LARCH_GOT_PCADD_HI20:
97 (*gots)++;
98 break;
99 default:
100 break; /* Do nothing. */
101 }
102 }
103}
104
105int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
106 char *secstrings, struct module *mod)
107{
108 unsigned int i, num_plts = 0, num_gots = 0;
109 Elf_Shdr *got_sec, *plt_sec, *plt_idx_sec, *tramp = NULL;
110
111 /*
112 * Find the empty .plt sections.
113 */
114 for (i = 0; i < ehdr->e_shnum; i++) {
115 if (!strcmp(secstrings + sechdrs[i].sh_name, ".got"))
116 mod->arch.got.shndx = i;
117 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
118 mod->arch.plt.shndx = i;
119 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx"))
120 mod->arch.plt_idx.shndx = i;
121 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".ftrace_trampoline"))
122 tramp = sechdrs + i;
123 }
124
125 if (!mod->arch.got.shndx) {
126 pr_err("%s: module GOT section(s) missing\n", mod->name);
127 return -ENOEXEC;
128 }
129 if (!mod->arch.plt.shndx) {
130 pr_err("%s: module PLT section(s) missing\n", mod->name);
131 return -ENOEXEC;
132 }
133 if (!mod->arch.plt_idx.shndx) {
134 pr_err("%s: module PLT.IDX section(s) missing\n", mod->name);
135 return -ENOEXEC;
136 }
137
138 /* Calculate the maxinum number of entries */
139 for (i = 0; i < ehdr->e_shnum; i++) {
140 int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela);
141 Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset;
142 Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info;
143
144 if (sechdrs[i].sh_type != SHT_RELA)
145 continue;
146
147 /* ignore relocations that operate on non-exec sections */
148 if (!(dst_sec->sh_flags & SHF_EXECINSTR))
149 continue;
150
151 count_max_entries(relas, num: num_rela, plts: &num_plts, gots: &num_gots);
152 }
153
154 got_sec = sechdrs + mod->arch.got.shndx;
155 got_sec->sh_type = SHT_NOBITS;
156 got_sec->sh_flags = SHF_ALLOC;
157 got_sec->sh_addralign = L1_CACHE_BYTES;
158 got_sec->sh_size = (num_gots + 1) * sizeof(struct got_entry);
159 mod->arch.got.num_entries = 0;
160 mod->arch.got.max_entries = num_gots;
161
162 plt_sec = sechdrs + mod->arch.plt.shndx;
163 plt_sec->sh_type = SHT_NOBITS;
164 plt_sec->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
165 plt_sec->sh_addralign = L1_CACHE_BYTES;
166 plt_sec->sh_size = (num_plts + 1) * sizeof(struct plt_entry);
167 mod->arch.plt.num_entries = 0;
168 mod->arch.plt.max_entries = num_plts;
169
170 plt_idx_sec = sechdrs + mod->arch.plt_idx.shndx;
171 plt_idx_sec->sh_type = SHT_NOBITS;
172 plt_idx_sec->sh_flags = SHF_ALLOC;
173 plt_idx_sec->sh_addralign = L1_CACHE_BYTES;
174 plt_idx_sec->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry);
175 mod->arch.plt_idx.num_entries = 0;
176 mod->arch.plt_idx.max_entries = num_plts;
177
178 if (tramp) {
179 tramp->sh_type = SHT_NOBITS;
180 tramp->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
181 tramp->sh_addralign = __alignof__(struct plt_entry);
182 tramp->sh_size = NR_FTRACE_PLTS * sizeof(struct plt_entry);
183 }
184
185 return 0;
186}
187

source code of linux/arch/loongarch/kernel/module-sections.c