mirror of https://gitee.com/openkylin/linux.git
220 lines
6.8 KiB
C
220 lines
6.8 KiB
C
/*
|
|
* Copyright (C) 2014-2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
|
|
#include <linux/elf.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/module.h>
|
|
#include <linux/sort.h>
|
|
|
|
struct plt_entry {
|
|
/*
|
|
* A program that conforms to the AArch64 Procedure Call Standard
|
|
* (AAPCS64) must assume that a veneer that alters IP0 (x16) and/or
|
|
* IP1 (x17) may be inserted at any branch instruction that is
|
|
* exposed to a relocation that supports long branches. Since that
|
|
* is exactly what we are dealing with here, we are free to use x16
|
|
* as a scratch register in the PLT veneers.
|
|
*/
|
|
__le32 mov0; /* movn x16, #0x.... */
|
|
__le32 mov1; /* movk x16, #0x...., lsl #16 */
|
|
__le32 mov2; /* movk x16, #0x...., lsl #32 */
|
|
__le32 br; /* br x16 */
|
|
};
|
|
|
|
static bool in_init(const struct module *mod, void *loc)
|
|
{
|
|
return (u64)loc - (u64)mod->init_layout.base < mod->init_layout.size;
|
|
}
|
|
|
|
u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela *rela,
|
|
Elf64_Sym *sym)
|
|
{
|
|
struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core :
|
|
&mod->arch.init;
|
|
struct plt_entry *plt = (struct plt_entry *)pltsec->plt->sh_addr;
|
|
int i = pltsec->plt_num_entries;
|
|
u64 val = sym->st_value + rela->r_addend;
|
|
|
|
/*
|
|
* MOVK/MOVN/MOVZ opcode:
|
|
* +--------+------------+--------+-----------+-------------+---------+
|
|
* | sf[31] | opc[30:29] | 100101 | hw[22:21] | imm16[20:5] | Rd[4:0] |
|
|
* +--------+------------+--------+-----------+-------------+---------+
|
|
*
|
|
* Rd := 0x10 (x16)
|
|
* hw := 0b00 (no shift), 0b01 (lsl #16), 0b10 (lsl #32)
|
|
* opc := 0b11 (MOVK), 0b00 (MOVN), 0b10 (MOVZ)
|
|
* sf := 1 (64-bit variant)
|
|
*/
|
|
plt[i] = (struct plt_entry){
|
|
cpu_to_le32(0x92800010 | (((~val ) & 0xffff)) << 5),
|
|
cpu_to_le32(0xf2a00010 | ((( val >> 16) & 0xffff)) << 5),
|
|
cpu_to_le32(0xf2c00010 | ((( val >> 32) & 0xffff)) << 5),
|
|
cpu_to_le32(0xd61f0200)
|
|
};
|
|
|
|
/*
|
|
* Check if the entry we just created is a duplicate. Given that the
|
|
* relocations are sorted, this will be the last entry we allocated.
|
|
* (if one exists).
|
|
*/
|
|
if (i > 0 &&
|
|
plt[i].mov0 == plt[i - 1].mov0 &&
|
|
plt[i].mov1 == plt[i - 1].mov1 &&
|
|
plt[i].mov2 == plt[i - 1].mov2)
|
|
return (u64)&plt[i - 1];
|
|
|
|
pltsec->plt_num_entries++;
|
|
BUG_ON(pltsec->plt_num_entries > pltsec->plt_max_entries);
|
|
|
|
return (u64)&plt[i];
|
|
}
|
|
|
|
#define cmp_3way(a,b) ((a) < (b) ? -1 : (a) > (b))
|
|
|
|
static int cmp_rela(const void *a, const void *b)
|
|
{
|
|
const Elf64_Rela *x = a, *y = b;
|
|
int i;
|
|
|
|
/* sort by type, symbol index and addend */
|
|
i = cmp_3way(ELF64_R_TYPE(x->r_info), ELF64_R_TYPE(y->r_info));
|
|
if (i == 0)
|
|
i = cmp_3way(ELF64_R_SYM(x->r_info), ELF64_R_SYM(y->r_info));
|
|
if (i == 0)
|
|
i = cmp_3way(x->r_addend, y->r_addend);
|
|
return i;
|
|
}
|
|
|
|
static bool duplicate_rel(const Elf64_Rela *rela, int num)
|
|
{
|
|
/*
|
|
* Entries are sorted by type, symbol index and addend. That means
|
|
* that, if a duplicate entry exists, it must be in the preceding
|
|
* slot.
|
|
*/
|
|
return num > 0 && cmp_rela(rela + num, rela + num - 1) == 0;
|
|
}
|
|
|
|
static unsigned int count_plts(Elf64_Sym *syms, Elf64_Rela *rela, int num,
|
|
Elf64_Word dstidx)
|
|
{
|
|
unsigned int ret = 0;
|
|
Elf64_Sym *s;
|
|
int i;
|
|
|
|
for (i = 0; i < num; i++) {
|
|
switch (ELF64_R_TYPE(rela[i].r_info)) {
|
|
case R_AARCH64_JUMP26:
|
|
case R_AARCH64_CALL26:
|
|
/*
|
|
* We only have to consider branch targets that resolve
|
|
* to symbols that are defined in a different section.
|
|
* This is not simply a heuristic, it is a fundamental
|
|
* limitation, since there is no guaranteed way to emit
|
|
* PLT entries sufficiently close to the branch if the
|
|
* section size exceeds the range of a branch
|
|
* instruction. So ignore relocations against defined
|
|
* symbols if they live in the same section as the
|
|
* relocation target.
|
|
*/
|
|
s = syms + ELF64_R_SYM(rela[i].r_info);
|
|
if (s->st_shndx == dstidx)
|
|
break;
|
|
|
|
/*
|
|
* Jump relocations with non-zero addends against
|
|
* undefined symbols are supported by the ELF spec, but
|
|
* do not occur in practice (e.g., 'jump n bytes past
|
|
* the entry point of undefined function symbol f').
|
|
* So we need to support them, but there is no need to
|
|
* take them into consideration when trying to optimize
|
|
* this code. So let's only check for duplicates when
|
|
* the addend is zero: this allows us to record the PLT
|
|
* entry address in the symbol table itself, rather than
|
|
* having to search the list for duplicates each time we
|
|
* emit one.
|
|
*/
|
|
if (rela[i].r_addend != 0 || !duplicate_rel(rela, i))
|
|
ret++;
|
|
break;
|
|
}
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
|
|
char *secstrings, struct module *mod)
|
|
{
|
|
unsigned long core_plts = 0;
|
|
unsigned long init_plts = 0;
|
|
Elf64_Sym *syms = NULL;
|
|
int i;
|
|
|
|
/*
|
|
* Find the empty .plt section so we can expand it to store the PLT
|
|
* entries. Record the symtab address as well.
|
|
*/
|
|
for (i = 0; i < ehdr->e_shnum; i++) {
|
|
if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
|
|
mod->arch.core.plt = sechdrs + i;
|
|
else if (!strcmp(secstrings + sechdrs[i].sh_name, ".init.plt"))
|
|
mod->arch.init.plt = sechdrs + i;
|
|
else if (sechdrs[i].sh_type == SHT_SYMTAB)
|
|
syms = (Elf64_Sym *)sechdrs[i].sh_addr;
|
|
}
|
|
|
|
if (!mod->arch.core.plt || !mod->arch.init.plt) {
|
|
pr_err("%s: module PLT section(s) missing\n", mod->name);
|
|
return -ENOEXEC;
|
|
}
|
|
if (!syms) {
|
|
pr_err("%s: module symtab section missing\n", mod->name);
|
|
return -ENOEXEC;
|
|
}
|
|
|
|
for (i = 0; i < ehdr->e_shnum; i++) {
|
|
Elf64_Rela *rels = (void *)ehdr + sechdrs[i].sh_offset;
|
|
int numrels = sechdrs[i].sh_size / sizeof(Elf64_Rela);
|
|
Elf64_Shdr *dstsec = sechdrs + sechdrs[i].sh_info;
|
|
|
|
if (sechdrs[i].sh_type != SHT_RELA)
|
|
continue;
|
|
|
|
/* ignore relocations that operate on non-exec sections */
|
|
if (!(dstsec->sh_flags & SHF_EXECINSTR))
|
|
continue;
|
|
|
|
/* sort by type, symbol index and addend */
|
|
sort(rels, numrels, sizeof(Elf64_Rela), cmp_rela, NULL);
|
|
|
|
if (strncmp(secstrings + dstsec->sh_name, ".init", 5) != 0)
|
|
core_plts += count_plts(syms, rels, numrels,
|
|
sechdrs[i].sh_info);
|
|
else
|
|
init_plts += count_plts(syms, rels, numrels,
|
|
sechdrs[i].sh_info);
|
|
}
|
|
|
|
mod->arch.core.plt->sh_type = SHT_NOBITS;
|
|
mod->arch.core.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
|
|
mod->arch.core.plt->sh_addralign = L1_CACHE_BYTES;
|
|
mod->arch.core.plt->sh_size = (core_plts + 1) * sizeof(struct plt_entry);
|
|
mod->arch.core.plt_num_entries = 0;
|
|
mod->arch.core.plt_max_entries = core_plts;
|
|
|
|
mod->arch.init.plt->sh_type = SHT_NOBITS;
|
|
mod->arch.init.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
|
|
mod->arch.init.plt->sh_addralign = L1_CACHE_BYTES;
|
|
mod->arch.init.plt->sh_size = (init_plts + 1) * sizeof(struct plt_entry);
|
|
mod->arch.init.plt_num_entries = 0;
|
|
mod->arch.init.plt_max_entries = init_plts;
|
|
|
|
return 0;
|
|
}
|