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7d485f64 AB |
1 | /* |
2 | * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License version 2 as | |
6 | * published by the Free Software Foundation. | |
7 | */ | |
8 | ||
9 | #include <linux/elf.h> | |
10 | #include <linux/kernel.h> | |
11 | #include <linux/module.h> | |
12 | ||
13 | #include <asm/cache.h> | |
14 | #include <asm/opcodes.h> | |
15 | ||
16 | #define PLT_ENT_STRIDE L1_CACHE_BYTES | |
17 | #define PLT_ENT_COUNT (PLT_ENT_STRIDE / sizeof(u32)) | |
18 | #define PLT_ENT_SIZE (sizeof(struct plt_entries) / PLT_ENT_COUNT) | |
19 | ||
20 | #ifdef CONFIG_THUMB2_KERNEL | |
21 | #define PLT_ENT_LDR __opcode_to_mem_thumb32(0xf8dff000 | \ | |
22 | (PLT_ENT_STRIDE - 4)) | |
23 | #else | |
24 | #define PLT_ENT_LDR __opcode_to_mem_arm(0xe59ff000 | \ | |
25 | (PLT_ENT_STRIDE - 8)) | |
26 | #endif | |
27 | ||
28 | struct plt_entries { | |
29 | u32 ldr[PLT_ENT_COUNT]; | |
30 | u32 lit[PLT_ENT_COUNT]; | |
31 | }; | |
32 | ||
33 | static bool in_init(const struct module *mod, u32 addr) | |
34 | { | |
35 | return addr - (u32)mod->module_init < mod->init_size; | |
36 | } | |
37 | ||
38 | u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val) | |
39 | { | |
40 | struct plt_entries *plt, *plt_end; | |
41 | int c, *count; | |
42 | ||
43 | if (in_init(mod, loc)) { | |
44 | plt = (void *)mod->arch.init_plt->sh_addr; | |
45 | plt_end = (void *)plt + mod->arch.init_plt->sh_size; | |
46 | count = &mod->arch.init_plt_count; | |
47 | } else { | |
48 | plt = (void *)mod->arch.core_plt->sh_addr; | |
49 | plt_end = (void *)plt + mod->arch.core_plt->sh_size; | |
50 | count = &mod->arch.core_plt_count; | |
51 | } | |
52 | ||
53 | /* Look for an existing entry pointing to 'val' */ | |
54 | for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) { | |
55 | int i; | |
56 | ||
57 | if (!c) { | |
58 | /* Populate a new set of entries */ | |
59 | *plt = (struct plt_entries){ | |
60 | { [0 ... PLT_ENT_COUNT - 1] = PLT_ENT_LDR, }, | |
61 | { val, } | |
62 | }; | |
63 | ++*count; | |
64 | return (u32)plt->ldr; | |
65 | } | |
66 | for (i = 0; i < PLT_ENT_COUNT; i++) { | |
67 | if (!plt->lit[i]) { | |
68 | plt->lit[i] = val; | |
69 | ++*count; | |
70 | } | |
71 | if (plt->lit[i] == val) | |
72 | return (u32)&plt->ldr[i]; | |
73 | } | |
74 | } | |
75 | BUG(); | |
76 | } | |
77 | ||
78 | static int duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num, | |
79 | u32 mask) | |
80 | { | |
81 | u32 *loc1, *loc2; | |
82 | int i; | |
83 | ||
84 | for (i = 0; i < num; i++) { | |
85 | if (rel[i].r_info != rel[num].r_info) | |
86 | continue; | |
87 | ||
88 | /* | |
89 | * Identical relocation types against identical symbols can | |
90 | * still result in different PLT entries if the addend in the | |
91 | * place is different. So resolve the target of the relocation | |
92 | * to compare the values. | |
93 | */ | |
94 | loc1 = (u32 *)(base + rel[i].r_offset); | |
95 | loc2 = (u32 *)(base + rel[num].r_offset); | |
96 | if (((*loc1 ^ *loc2) & mask) == 0) | |
97 | return 1; | |
98 | } | |
99 | return 0; | |
100 | } | |
101 | ||
102 | /* Count how many PLT entries we may need */ | |
103 | static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num) | |
104 | { | |
105 | unsigned int ret = 0; | |
106 | int i; | |
107 | ||
108 | /* | |
109 | * Sure, this is order(n^2), but it's usually short, and not | |
110 | * time critical | |
111 | */ | |
112 | for (i = 0; i < num; i++) | |
113 | switch (ELF32_R_TYPE(rel[i].r_info)) { | |
114 | case R_ARM_CALL: | |
115 | case R_ARM_PC24: | |
116 | case R_ARM_JUMP24: | |
117 | if (!duplicate_rel(base, rel, i, | |
118 | __opcode_to_mem_arm(0x00ffffff))) | |
119 | ret++; | |
120 | break; | |
121 | case R_ARM_THM_CALL: | |
122 | case R_ARM_THM_JUMP24: | |
123 | if (!duplicate_rel(base, rel, i, | |
124 | __opcode_to_mem_thumb32(0x07ff2fff))) | |
125 | ret++; | |
126 | } | |
127 | return ret; | |
128 | } | |
129 | ||
130 | int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, | |
131 | char *secstrings, struct module *mod) | |
132 | { | |
133 | unsigned long core_plts = 0, init_plts = 0; | |
134 | Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum; | |
135 | ||
136 | /* | |
137 | * To store the PLTs, we expand the .text section for core module code | |
138 | * and the .init.text section for initialization code. | |
139 | */ | |
140 | for (s = sechdrs; s < sechdrs_end; ++s) | |
141 | if (strcmp(".core.plt", secstrings + s->sh_name) == 0) | |
142 | mod->arch.core_plt = s; | |
143 | else if (strcmp(".init.plt", secstrings + s->sh_name) == 0) | |
144 | mod->arch.init_plt = s; | |
145 | ||
146 | if (!mod->arch.core_plt || !mod->arch.init_plt) { | |
147 | pr_err("%s: sections missing\n", mod->name); | |
148 | return -ENOEXEC; | |
149 | } | |
150 | ||
151 | for (s = sechdrs + 1; s < sechdrs_end; ++s) { | |
152 | const Elf32_Rel *rels = (void *)ehdr + s->sh_offset; | |
153 | int numrels = s->sh_size / sizeof(Elf32_Rel); | |
154 | Elf32_Shdr *dstsec = sechdrs + s->sh_info; | |
155 | ||
156 | if (s->sh_type != SHT_REL) | |
157 | continue; | |
158 | ||
159 | if (strstr(secstrings + s->sh_name, ".init")) | |
160 | init_plts += count_plts(dstsec->sh_addr, rels, numrels); | |
161 | else | |
162 | core_plts += count_plts(dstsec->sh_addr, rels, numrels); | |
163 | } | |
164 | ||
165 | mod->arch.core_plt->sh_type = SHT_NOBITS; | |
166 | mod->arch.core_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; | |
167 | mod->arch.core_plt->sh_addralign = L1_CACHE_BYTES; | |
168 | mod->arch.core_plt->sh_size = round_up(core_plts * PLT_ENT_SIZE, | |
169 | sizeof(struct plt_entries)); | |
170 | mod->arch.core_plt_count = 0; | |
171 | ||
172 | mod->arch.init_plt->sh_type = SHT_NOBITS; | |
173 | mod->arch.init_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; | |
174 | mod->arch.init_plt->sh_addralign = L1_CACHE_BYTES; | |
175 | mod->arch.init_plt->sh_size = round_up(init_plts * PLT_ENT_SIZE, | |
176 | sizeof(struct plt_entries)); | |
177 | mod->arch.init_plt_count = 0; | |
178 | pr_debug("%s: core.plt=%x, init.plt=%x\n", __func__, | |
179 | mod->arch.core_plt->sh_size, mod->arch.init_plt->sh_size); | |
180 | return 0; | |
181 | } |