2 * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
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.
10 #include <linux/kernel.h>
11 #include <linux/module.h>
13 #include <asm/cache.h>
14 #include <asm/opcodes.h>
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)
20 #ifdef CONFIG_THUMB2_KERNEL
21 #define PLT_ENT_LDR __opcode_to_mem_thumb32(0xf8dff000 | \
24 #define PLT_ENT_LDR __opcode_to_mem_arm(0xe59ff000 | \
29 u32 ldr[PLT_ENT_COUNT];
30 u32 lit[PLT_ENT_COUNT];
33 static bool in_init(const struct module *mod, u32 addr)
35 return addr - (u32)mod->init_layout.base < mod->init_layout.size;
38 u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
40 struct plt_entries *plt, *plt_end;
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;
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;
53 /* Look for an existing entry pointing to 'val' */
54 for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) {
58 /* Populate a new set of entries */
59 *plt = (struct plt_entries){
60 { [0 ... PLT_ENT_COUNT - 1] = PLT_ENT_LDR, },
66 for (i = 0; i < PLT_ENT_COUNT; i++) {
71 if (plt->lit[i] == val)
72 return (u32)&plt->ldr[i];
78 static int duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num,
84 for (i = 0; i < num; i++) {
85 if (rel[i].r_info != rel[num].r_info)
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.
94 loc1 = (u32 *)(base + rel[i].r_offset);
95 loc2 = (u32 *)(base + rel[num].r_offset);
96 if (((*loc1 ^ *loc2) & mask) == 0)
102 /* Count how many PLT entries we may need */
103 static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num)
105 unsigned int ret = 0;
109 * Sure, this is order(n^2), but it's usually short, and not
112 for (i = 0; i < num; i++)
113 switch (ELF32_R_TYPE(rel[i].r_info)) {
117 if (!duplicate_rel(base, rel, i,
118 __opcode_to_mem_arm(0x00ffffff)))
121 #ifdef CONFIG_THUMB2_KERNEL
123 case R_ARM_THM_JUMP24:
124 if (!duplicate_rel(base, rel, i,
125 __opcode_to_mem_thumb32(0x07ff2fff)))
132 int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
133 char *secstrings, struct module *mod)
135 unsigned long core_plts = 0, init_plts = 0;
136 Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum;
139 * To store the PLTs, we expand the .text section for core module code
140 * and the .init.text section for initialization code.
142 for (s = sechdrs; s < sechdrs_end; ++s)
143 if (strcmp(".core.plt", secstrings + s->sh_name) == 0)
144 mod->arch.core_plt = s;
145 else if (strcmp(".init.plt", secstrings + s->sh_name) == 0)
146 mod->arch.init_plt = s;
148 if (!mod->arch.core_plt || !mod->arch.init_plt) {
149 pr_err("%s: sections missing\n", mod->name);
153 for (s = sechdrs + 1; s < sechdrs_end; ++s) {
154 const Elf32_Rel *rels = (void *)ehdr + s->sh_offset;
155 int numrels = s->sh_size / sizeof(Elf32_Rel);
156 Elf32_Shdr *dstsec = sechdrs + s->sh_info;
158 if (s->sh_type != SHT_REL)
161 if (strstr(secstrings + s->sh_name, ".init"))
162 init_plts += count_plts(dstsec->sh_addr, rels, numrels);
164 core_plts += count_plts(dstsec->sh_addr, rels, numrels);
167 mod->arch.core_plt->sh_type = SHT_NOBITS;
168 mod->arch.core_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
169 mod->arch.core_plt->sh_addralign = L1_CACHE_BYTES;
170 mod->arch.core_plt->sh_size = round_up(core_plts * PLT_ENT_SIZE,
171 sizeof(struct plt_entries));
172 mod->arch.core_plt_count = 0;
174 mod->arch.init_plt->sh_type = SHT_NOBITS;
175 mod->arch.init_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
176 mod->arch.init_plt->sh_addralign = L1_CACHE_BYTES;
177 mod->arch.init_plt->sh_size = round_up(init_plts * PLT_ENT_SIZE,
178 sizeof(struct plt_entries));
179 mod->arch.init_plt_count = 0;
180 pr_debug("%s: core.plt=%x, init.plt=%x\n", __func__,
181 mod->arch.core_plt->sh_size, mod->arch.init_plt->sh_size);