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 | |
12 | Elf_Addr module_emit_got_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr 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, sechdrs, got_sec); |
17 | |
18 | if (got) |
19 | return (Elf_Addr)got; |
20 | |
21 | /* There is no GOT entry for val yet, create a new one. */ |
22 | got = (struct got_entry *)sechdrs[got_sec->shndx].sh_addr; |
23 | got[i] = emit_got_entry(val); |
24 | |
25 | got_sec->num_entries++; |
26 | if (got_sec->num_entries > got_sec->max_entries) { |
27 | /* |
28 | * This may happen when the module contains a GOT_HI20 without |
29 | * a paired GOT_LO12. Such a module is broken, reject it. |
30 | */ |
31 | pr_err("%s: module contains bad GOT relocation\n" , mod->name); |
32 | return 0; |
33 | } |
34 | |
35 | return (Elf_Addr)&got[i]; |
36 | } |
37 | |
38 | Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val) |
39 | { |
40 | int nr; |
41 | struct mod_section *plt_sec = &mod->arch.plt; |
42 | struct mod_section *plt_idx_sec = &mod->arch.plt_idx; |
43 | struct plt_entry *plt = get_plt_entry(val, sechdrs, plt_sec, plt_idx_sec); |
44 | struct plt_idx_entry *plt_idx; |
45 | |
46 | if (plt) |
47 | return (Elf_Addr)plt; |
48 | |
49 | nr = plt_sec->num_entries; |
50 | |
51 | /* There is no duplicate entry, create a new one */ |
52 | plt = (struct plt_entry *)sechdrs[plt_sec->shndx].sh_addr; |
53 | plt[nr] = emit_plt_entry(val); |
54 | plt_idx = (struct plt_idx_entry *)sechdrs[plt_idx_sec->shndx].sh_addr; |
55 | plt_idx[nr] = emit_plt_idx_entry(val); |
56 | |
57 | plt_sec->num_entries++; |
58 | plt_idx_sec->num_entries++; |
59 | BUG_ON(plt_sec->num_entries > plt_sec->max_entries); |
60 | |
61 | return (Elf_Addr)&plt[nr]; |
62 | } |
63 | |
64 | static int is_rela_equal(const Elf_Rela *x, const Elf_Rela *y) |
65 | { |
66 | return x->r_info == y->r_info && x->r_addend == y->r_addend; |
67 | } |
68 | |
69 | static bool duplicate_rela(const Elf_Rela *rela, int idx) |
70 | { |
71 | int i; |
72 | |
73 | for (i = 0; i < idx; i++) { |
74 | if (is_rela_equal(x: &rela[i], y: &rela[idx])) |
75 | return true; |
76 | } |
77 | |
78 | return false; |
79 | } |
80 | |
81 | static void count_max_entries(Elf_Rela *relas, int num, |
82 | unsigned int *plts, unsigned int *gots) |
83 | { |
84 | unsigned int i, type; |
85 | |
86 | for (i = 0; i < num; i++) { |
87 | type = ELF_R_TYPE(relas[i].r_info); |
88 | switch (type) { |
89 | case R_LARCH_SOP_PUSH_PLT_PCREL: |
90 | case R_LARCH_B26: |
91 | if (!duplicate_rela(rela: relas, idx: i)) |
92 | (*plts)++; |
93 | break; |
94 | case R_LARCH_GOT_PC_HI20: |
95 | if (!duplicate_rela(rela: relas, idx: i)) |
96 | (*gots)++; |
97 | break; |
98 | default: |
99 | break; /* Do nothing. */ |
100 | } |
101 | } |
102 | } |
103 | |
104 | int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, |
105 | char *secstrings, struct module *mod) |
106 | { |
107 | unsigned int i, num_plts = 0, num_gots = 0; |
108 | Elf_Shdr *got_sec, *plt_sec, *plt_idx_sec, *tramp = NULL; |
109 | |
110 | /* |
111 | * Find the empty .plt sections. |
112 | */ |
113 | for (i = 0; i < ehdr->e_shnum; i++) { |
114 | if (!strcmp(secstrings + sechdrs[i].sh_name, ".got" )) |
115 | mod->arch.got.shndx = i; |
116 | else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt" )) |
117 | mod->arch.plt.shndx = i; |
118 | else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx" )) |
119 | mod->arch.plt_idx.shndx = i; |
120 | else if (!strcmp(secstrings + sechdrs[i].sh_name, ".ftrace_trampoline" )) |
121 | tramp = sechdrs + i; |
122 | } |
123 | |
124 | if (!mod->arch.got.shndx) { |
125 | pr_err("%s: module GOT section(s) missing\n" , mod->name); |
126 | return -ENOEXEC; |
127 | } |
128 | if (!mod->arch.plt.shndx) { |
129 | pr_err("%s: module PLT section(s) missing\n" , mod->name); |
130 | return -ENOEXEC; |
131 | } |
132 | if (!mod->arch.plt_idx.shndx) { |
133 | pr_err("%s: module PLT.IDX section(s) missing\n" , mod->name); |
134 | return -ENOEXEC; |
135 | } |
136 | |
137 | /* Calculate the maxinum number of entries */ |
138 | for (i = 0; i < ehdr->e_shnum; i++) { |
139 | int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela); |
140 | Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset; |
141 | Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info; |
142 | |
143 | if (sechdrs[i].sh_type != SHT_RELA) |
144 | continue; |
145 | |
146 | /* ignore relocations that operate on non-exec sections */ |
147 | if (!(dst_sec->sh_flags & SHF_EXECINSTR)) |
148 | continue; |
149 | |
150 | count_max_entries(relas, num: num_rela, plts: &num_plts, gots: &num_gots); |
151 | } |
152 | |
153 | got_sec = sechdrs + mod->arch.got.shndx; |
154 | got_sec->sh_type = SHT_NOBITS; |
155 | got_sec->sh_flags = SHF_ALLOC; |
156 | got_sec->sh_addralign = L1_CACHE_BYTES; |
157 | got_sec->sh_size = (num_gots + 1) * sizeof(struct got_entry); |
158 | mod->arch.got.num_entries = 0; |
159 | mod->arch.got.max_entries = num_gots; |
160 | |
161 | plt_sec = sechdrs + mod->arch.plt.shndx; |
162 | plt_sec->sh_type = SHT_NOBITS; |
163 | plt_sec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; |
164 | plt_sec->sh_addralign = L1_CACHE_BYTES; |
165 | plt_sec->sh_size = (num_plts + 1) * sizeof(struct plt_entry); |
166 | mod->arch.plt.num_entries = 0; |
167 | mod->arch.plt.max_entries = num_plts; |
168 | |
169 | plt_idx_sec = sechdrs + mod->arch.plt_idx.shndx; |
170 | plt_idx_sec->sh_type = SHT_NOBITS; |
171 | plt_idx_sec->sh_flags = SHF_ALLOC; |
172 | plt_idx_sec->sh_addralign = L1_CACHE_BYTES; |
173 | plt_idx_sec->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry); |
174 | mod->arch.plt_idx.num_entries = 0; |
175 | mod->arch.plt_idx.max_entries = num_plts; |
176 | |
177 | if (tramp) { |
178 | tramp->sh_type = SHT_NOBITS; |
179 | tramp->sh_flags = SHF_EXECINSTR | SHF_ALLOC; |
180 | tramp->sh_addralign = __alignof__(struct plt_entry); |
181 | tramp->sh_size = NR_FTRACE_PLTS * sizeof(struct plt_entry); |
182 | } |
183 | |
184 | return 0; |
185 | } |
186 | |