arch/riscv/kernel/module-sections.c

   1 /* SPDX-License-Identifier: GPL-2.0
   2  *
   3  * Copyright (C) 2014-2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
   4  *
   5  * Copyright (C) 2018 Andes Technology Corporation <zong@andestech.com>
   6  */
   7
   8 #include <linux/elf.h>
   9 #include <linux/kernel.h>
  10 #include <linux/module.h>
  11 #include <linux/moduleloader.h>
  12
  13 unsigned long module_emit_got_entry(struct module *mod, unsigned long 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, got_sec);
  18
  19         if (got)
  20                 return (unsigned long)got;
  21
  22         /* There is no duplicate entry, create a new one */
  23         got = (struct got_entry *)got_sec->shdr->sh_addr;
  24         got[i] = emit_got_entry(val);
  25
  26         got_sec->num_entries++;
  27         BUG_ON(got_sec->num_entries > got_sec->max_entries);
  28
  29         return (unsigned long)&got[i];
  30 }
  31
  32 unsigned long module_emit_plt_entry(struct module *mod, unsigned long val)
  33 {
  34         struct mod_section *got_plt_sec = &mod->arch.got_plt;
  35         struct got_entry *got_plt;
  36         struct mod_section *plt_sec = &mod->arch.plt;
  37         struct plt_entry *plt = get_plt_entry(val, plt_sec, got_plt_sec);
  38         int i = plt_sec->num_entries;
  39
  40         if (plt)
  41                 return (unsigned long)plt;
  42
  43         /* There is no duplicate entry, create a new one */
  44         got_plt = (struct got_entry *)got_plt_sec->shdr->sh_addr;
  45         got_plt[i] = emit_got_entry(val);
  46         plt = (struct plt_entry *)plt_sec->shdr->sh_addr;
  47         plt[i] = emit_plt_entry(val,
  48                                 (unsigned long)&plt[i],
  49                                 (unsigned long)&got_plt[i]);
  50
  51         plt_sec->num_entries++;
  52         got_plt_sec->num_entries++;
  53         BUG_ON(plt_sec->num_entries > plt_sec->max_entries);
  54
  55         return (unsigned long)&plt[i];
  56 }
  57
  58 static int is_rela_equal(const Elf_Rela *x, const Elf_Rela *y)
  59 {
  60         return x->r_info == y->r_info && x->r_addend == y->r_addend;
  61 }
  62
  63 static bool duplicate_rela(const Elf_Rela *rela, int idx)
  64 {
  65         int i;
  66         for (i = 0; i < idx; i++) {
  67                 if (is_rela_equal(&rela[i], &rela[idx]))
  68                         return true;
  69         }
  70         return false;
  71 }
  72
  73 static void count_max_entries(Elf_Rela *relas, int num,
  74                               unsigned int *plts, unsigned int *gots)
  75 {
  76         unsigned int type, i;
  77
  78         for (i = 0; i < num; i++) {
  79                 type = ELF_RISCV_R_TYPE(relas[i].r_info);
  80                 if (type == R_RISCV_CALL_PLT) {
  81                         if (!duplicate_rela(relas, i))
  82                                 (*plts)++;
  83                 } else if (type == R_RISCV_GOT_HI20) {
  84                         if (!duplicate_rela(relas, i))
  85                                 (*gots)++;
  86                 }
  87         }
  88 }
  89
  90 int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
  91                               char *secstrings, struct module *mod)
  92 {
  93         unsigned int num_plts = 0;
  94         unsigned int num_gots = 0;
  95         int i;
  96
  97         /*
  98          * Find the empty .got and .plt sections.
  99          */
 100         for (i = 0; i < ehdr->e_shnum; i++) {
 101                 if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
 102                         mod->arch.plt.shdr = sechdrs + i;
 103                 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got"))
 104                         mod->arch.got.shdr = sechdrs + i;
 105                 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got.plt"))
 106                         mod->arch.got_plt.shdr = sechdrs + i;
 107         }
 108
 109         if (!mod->arch.plt.shdr) {
 110                 pr_err("%s: module PLT section(s) missing\n", mod->name);
 111                 return -ENOEXEC;
 112         }
 113         if (!mod->arch.got.shdr) {
 114                 pr_err("%s: module GOT section(s) missing\n", mod->name);
 115                 return -ENOEXEC;
 116         }
 117         if (!mod->arch.got_plt.shdr) {
 118                 pr_err("%s: module GOT.PLT section(s) missing\n", mod->name);
 119                 return -ENOEXEC;
 120         }
 121
 122         /* Calculate the maxinum number of entries */
 123         for (i = 0; i < ehdr->e_shnum; i++) {
 124                 Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset;
 125                 int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela);
 126                 Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info;
 127
 128                 if (sechdrs[i].sh_type != SHT_RELA)
 129                         continue;
 130
 131                 /* ignore relocations that operate on non-exec sections */
 132                 if (!(dst_sec->sh_flags & SHF_EXECINSTR))
 133                         continue;
 134
 135                 count_max_entries(relas, num_rela, &num_plts, &num_gots);
 136         }
 137
 138         mod->arch.plt.shdr->sh_type = SHT_NOBITS;
 139         mod->arch.plt.shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
 140         mod->arch.plt.shdr->sh_addralign = L1_CACHE_BYTES;
 141         mod->arch.plt.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_entry);
 142         mod->arch.plt.num_entries = 0;
 143         mod->arch.plt.max_entries = num_plts;
 144
 145         mod->arch.got.shdr->sh_type = SHT_NOBITS;
 146         mod->arch.got.shdr->sh_flags = SHF_ALLOC;
 147         mod->arch.got.shdr->sh_addralign = L1_CACHE_BYTES;
 148         mod->arch.got.shdr->sh_size = (num_gots + 1) * sizeof(struct got_entry);
 149         mod->arch.got.num_entries = 0;
 150         mod->arch.got.max_entries = num_gots;
 151
 152         mod->arch.got_plt.shdr->sh_type = SHT_NOBITS;
 153         mod->arch.got_plt.shdr->sh_flags = SHF_ALLOC;
 154         mod->arch.got_plt.shdr->sh_addralign = L1_CACHE_BYTES;
 155         mod->arch.got_plt.shdr->sh_size = (num_plts + 1) * sizeof(struct got_entry);
 156         mod->arch.got_plt.num_entries = 0;
 157         mod->arch.got_plt.max_entries = num_plts;
 158         return 0;
 159 }