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/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Copyright (C) 2017 Zihao Yu
*/
#include <linux/elf.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/moduleloader.h>
static int apply_r_riscv_64_rela(struct module *me, u32 *location, Elf_Addr v)
{
*(u64 *)location = v;
return 0;
}
static int apply_r_riscv_branch_rela(struct module *me, u32 *location,
Elf_Addr v)
{
s64 offset = (void *)v - (void *)location;
u32 imm12 = (offset & 0x1000) << (31 - 12);
u32 imm11 = (offset & 0x800) >> (11 - 7);
u32 imm10_5 = (offset & 0x7e0) << (30 - 10);
u32 imm4_1 = (offset & 0x1e) << (11 - 4);
*location = (*location & 0x1fff07f) | imm12 | imm11 | imm10_5 | imm4_1;
return 0;
}
static int apply_r_riscv_jal_rela(struct module *me, u32 *location,
Elf_Addr v)
{
s64 offset = (void *)v - (void *)location;
u32 imm20 = (offset & 0x100000) << (31 - 20);
u32 imm19_12 = (offset & 0xff000);
u32 imm11 = (offset & 0x800) << (20 - 11);
u32 imm10_1 = (offset & 0x7fe) << (30 - 10);
*location = (*location & 0xfff) | imm20 | imm19_12 | imm11 | imm10_1;
return 0;
}
static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location,
Elf_Addr v)
{
s64 offset = (void *)v - (void *)location;
s32 hi20;
if (offset != (s32)offset) {
pr_err(
"%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
me->name, v, location);
return -EINVAL;
}
hi20 = (offset + 0x800) & 0xfffff000;
*location = (*location & 0xfff) | hi20;
return 0;
}
static int apply_r_riscv_pcrel_lo12_i_rela(struct module *me, u32 *location,
Elf_Addr v)
{
/*
* v is the lo12 value to fill. It is calculated before calling this
* handler.
*/
*location = (*location & 0xfffff) | ((v & 0xfff) << 20);
return 0;
}
static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, u32 *location,
Elf_Addr v)
{
/*
* v is the lo12 value to fill. It is calculated before calling this
* handler.
*/
u32 imm11_5 = (v & 0xfe0) << (31 - 11);
u32 imm4_0 = (v & 0x1f) << (11 - 4);
*location = (*location & 0x1fff07f) | imm11_5 | imm4_0;
return 0;
}
static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
Elf_Addr v)
{
s64 offset = (void *)v - (void *)location;
s32 fill_v = offset;
u32 hi20, lo12;
if (offset != fill_v) {
pr_err(
"%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
me->name, v, location);
return -EINVAL;
}
hi20 = (offset + 0x800) & 0xfffff000;
lo12 = (offset - hi20) & 0xfff;
*location = (*location & 0xfff) | hi20;
*(location + 1) = (*(location + 1) & 0xfffff) | (lo12 << 20);
return 0;
}
static int apply_r_riscv_relax_rela(struct module *me, u32 *location,
Elf_Addr v)
{
return 0;
}
static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
Elf_Addr v) = {
[R_RISCV_64] = apply_r_riscv_64_rela,
[R_RISCV_BRANCH] = apply_r_riscv_branch_rela,
[R_RISCV_JAL] = apply_r_riscv_jal_rela,
[R_RISCV_PCREL_HI20] = apply_r_riscv_pcrel_hi20_rela,
[R_RISCV_PCREL_LO12_I] = apply_r_riscv_pcrel_lo12_i_rela,
[R_RISCV_PCREL_LO12_S] = apply_r_riscv_pcrel_lo12_s_rela,
[R_RISCV_CALL_PLT] = apply_r_riscv_call_plt_rela,
[R_RISCV_RELAX] = apply_r_riscv_relax_rela,
};
int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
unsigned int symindex, unsigned int relsec,
struct module *me)
{
Elf_Rela *rel = (void *) sechdrs[relsec].sh_addr;
int (*handler)(struct module *me, u32 *location, Elf_Addr v);
Elf_Sym *sym;
u32 *location;
unsigned int i, type;
Elf_Addr v;
int res;
pr_debug("Applying relocate section %u to %u\n", relsec,
sechdrs[relsec].sh_info);
for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
/* This is where to make the change */
location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
+ rel[i].r_offset;
/* This is the symbol it is referring to */
sym = (Elf_Sym *)sechdrs[symindex].sh_addr
+ ELF_RISCV_R_SYM(rel[i].r_info);
if (IS_ERR_VALUE(sym->st_value)) {
/* Ignore unresolved weak symbol */
if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
continue;
pr_warning("%s: Unknown symbol %s\n",
me->name, strtab + sym->st_name);
return -ENOENT;
}
type = ELF_RISCV_R_TYPE(rel[i].r_info);
if (type < ARRAY_SIZE(reloc_handlers_rela))
handler = reloc_handlers_rela[type];
else
handler = NULL;
if (!handler) {
pr_err("%s: Unknown relocation type %u\n",
me->name, type);
return -EINVAL;
}
v = sym->st_value + rel[i].r_addend;
if (type == R_RISCV_PCREL_LO12_I || type == R_RISCV_PCREL_LO12_S) {
unsigned int j;
for (j = 0; j < sechdrs[relsec].sh_size / sizeof(*rel); j++) {
u64 hi20_loc =
sechdrs[sechdrs[relsec].sh_info].sh_addr
+ rel[j].r_offset;
/* Find the corresponding HI20 PC-relative relocation entry */
if (hi20_loc == sym->st_value) {
Elf_Sym *hi20_sym =
(Elf_Sym *)sechdrs[symindex].sh_addr
+ ELF_RISCV_R_SYM(rel[j].r_info);
u64 hi20_sym_val =
hi20_sym->st_value
+ rel[j].r_addend;
/* Calculate lo12 */
s64 offset = hi20_sym_val - hi20_loc;
s32 hi20 = (offset + 0x800) & 0xfffff000;
s32 lo12 = offset - hi20;
v = lo12;
break;
}
}
if (j == sechdrs[relsec].sh_size / sizeof(*rel)) {
pr_err(
"%s: Can not find HI20 PC-relative relocation information\n",
me->name);
return -EINVAL;
}
}
res = handler(me, location, v);
if (res)
return res;
}
return 0;
}
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