cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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module-sections.c (3256B)

      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
     10Elf_Addr module_emit_plt_entry(struct module *mod, unsigned long val)
     11{
     12	int nr;
     13	struct mod_section *plt_sec = &mod->arch.plt;
     14	struct mod_section *plt_idx_sec = &mod->arch.plt_idx;
     15	struct plt_entry *plt = get_plt_entry(val, plt_sec, plt_idx_sec);
     16	struct plt_idx_entry *plt_idx;
     17
     18	if (plt)
     19		return (Elf_Addr)plt;
     20
     21	nr = plt_sec->num_entries;
     22
     23	/* There is no duplicate entry, create a new one */
     24	plt = (struct plt_entry *)plt_sec->shdr->sh_addr;
     25	plt[nr] = emit_plt_entry(val);
     26	plt_idx = (struct plt_idx_entry *)plt_idx_sec->shdr->sh_addr;
     27	plt_idx[nr] = emit_plt_idx_entry(val);
     28
     29	plt_sec->num_entries++;
     30	plt_idx_sec->num_entries++;
     31	BUG_ON(plt_sec->num_entries > plt_sec->max_entries);
     32
     33	return (Elf_Addr)&plt[nr];
     34}
     35
     36static int is_rela_equal(const Elf_Rela *x, const Elf_Rela *y)
     37{
     38	return x->r_info == y->r_info && x->r_addend == y->r_addend;
     39}
     40
     41static bool duplicate_rela(const Elf_Rela *rela, int idx)
     42{
     43	int i;
     44
     45	for (i = 0; i < idx; i++) {
     46		if (is_rela_equal(&rela[i], &rela[idx]))
     47			return true;
     48	}
     49
     50	return false;
     51}
     52
     53static void count_max_entries(Elf_Rela *relas, int num, unsigned int *plts)
     54{
     55	unsigned int i, type;
     56
     57	for (i = 0; i < num; i++) {
     58		type = ELF_R_TYPE(relas[i].r_info);
     59		if (type == R_LARCH_SOP_PUSH_PLT_PCREL) {
     60			if (!duplicate_rela(relas, i))
     61				(*plts)++;
     62		}
     63	}
     64}
     65
     66int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
     67			      char *secstrings, struct module *mod)
     68{
     69	unsigned int i, num_plts = 0;
     70
     71	/*
     72	 * Find the empty .plt sections.
     73	 */
     74	for (i = 0; i < ehdr->e_shnum; i++) {
     75		if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
     76			mod->arch.plt.shdr = sechdrs + i;
     77		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx"))
     78			mod->arch.plt_idx.shdr = sechdrs + i;
     79	}
     80
     81	if (!mod->arch.plt.shdr) {
     82		pr_err("%s: module PLT section(s) missing\n", mod->name);
     83		return -ENOEXEC;
     84	}
     85	if (!mod->arch.plt_idx.shdr) {
     86		pr_err("%s: module PLT.IDX section(s) missing\n", mod->name);
     87		return -ENOEXEC;
     88	}
     89
     90	/* Calculate the maxinum number of entries */
     91	for (i = 0; i < ehdr->e_shnum; i++) {
     92		int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela);
     93		Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset;
     94		Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info;
     95
     96		if (sechdrs[i].sh_type != SHT_RELA)
     97			continue;
     98
     99		/* ignore relocations that operate on non-exec sections */
    100		if (!(dst_sec->sh_flags & SHF_EXECINSTR))
    101			continue;
    102
    103		count_max_entries(relas, num_rela, &num_plts);
    104	}
    105
    106	mod->arch.plt.shdr->sh_type = SHT_NOBITS;
    107	mod->arch.plt.shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
    108	mod->arch.plt.shdr->sh_addralign = L1_CACHE_BYTES;
    109	mod->arch.plt.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_entry);
    110	mod->arch.plt.num_entries = 0;
    111	mod->arch.plt.max_entries = num_plts;
    112
    113	mod->arch.plt_idx.shdr->sh_type = SHT_NOBITS;
    114	mod->arch.plt_idx.shdr->sh_flags = SHF_ALLOC;
    115	mod->arch.plt_idx.shdr->sh_addralign = L1_CACHE_BYTES;
    116	mod->arch.plt_idx.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry);
    117	mod->arch.plt_idx.num_entries = 0;
    118	mod->arch.plt_idx.max_entries = num_plts;
    119
    120	return 0;
    121}