blob: bc821056aba902e5630076f61273fdc5fb1c83cb [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
*/
#include <stdio.h>
#include <stdlib.h>
#define unlikely(cond) (cond)
#include <asm/insn.h>
#include "../../../arch/x86/lib/inat.c"
#include "../../../arch/x86/lib/insn.c"
#define CONFIG_64BIT 1
#include <asm/nops.h>
#include <asm/orc_types.h>
#include <objtool/check.h>
#include <objtool/elf.h>
#include <objtool/arch.h>
#include <objtool/warn.h>
#include <objtool/endianness.h>
#include <arch/elf.h>
static int is_x86_64(const struct elf *elf)
{
switch (elf->ehdr.e_machine) {
case EM_X86_64:
return 1;
case EM_386:
return 0;
default:
WARN("unexpected ELF machine type %d", elf->ehdr.e_machine);
return -1;
}
}
bool arch_callee_saved_reg(unsigned char reg)
{
switch (reg) {
case CFI_BP:
case CFI_BX:
case CFI_R12:
case CFI_R13:
case CFI_R14:
case CFI_R15:
return true;
case CFI_AX:
case CFI_CX:
case CFI_DX:
case CFI_SI:
case CFI_DI:
case CFI_SP:
case CFI_R8:
case CFI_R9:
case CFI_R10:
case CFI_R11:
case CFI_RA:
default:
return false;
}
}
unsigned long arch_dest_reloc_offset(int addend)
{
return addend + 4;
}
unsigned long arch_jump_destination(struct instruction *insn)
{
return insn->offset + insn->len + insn->immediate;
}
#define ADD_OP(op) \
if (!(op = calloc(1, sizeof(*op)))) \
return -1; \
else for (list_add_tail(&op->list, ops_list); op; op = NULL)
/*
* Helpers to decode ModRM/SIB:
*
* r/m| AX CX DX BX | SP | BP | SI DI |
* | R8 R9 R10 R11 | R12 | R13 | R14 R15 |
* Mod+----------------+-----+-----+---------+
* 00 | [r/m] |[SIB]|[IP+]| [r/m] |
* 01 | [r/m + d8] |[S+d]| [r/m + d8] |
* 10 | [r/m + d32] |[S+D]| [r/m + d32] |
* 11 | r/ m |
*/
#define mod_is_mem() (modrm_mod != 3)
#define mod_is_reg() (modrm_mod == 3)
#define is_RIP() ((modrm_rm & 7) == CFI_BP && modrm_mod == 0)
#define have_SIB() ((modrm_rm & 7) == CFI_SP && mod_is_mem())
#define rm_is(reg) (have_SIB() ? \
sib_base == (reg) && sib_index == CFI_SP : \
modrm_rm == (reg))
#define rm_is_mem(reg) (mod_is_mem() && !is_RIP() && rm_is(reg))
#define rm_is_reg(reg) (mod_is_reg() && modrm_rm == (reg))
int arch_decode_instruction(const struct elf *elf, const struct section *sec,
unsigned long offset, unsigned int maxlen,
unsigned int *len, enum insn_type *type,
unsigned long *immediate,
struct list_head *ops_list)
{
struct insn insn;
int x86_64, ret;
unsigned char op1, op2,
rex = 0, rex_b = 0, rex_r = 0, rex_w = 0, rex_x = 0,
modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0,
sib = 0, /* sib_scale = 0, */ sib_index = 0, sib_base = 0;
struct stack_op *op = NULL;
struct symbol *sym;
u64 imm;
x86_64 = is_x86_64(elf);
if (x86_64 == -1)
return -1;
ret = insn_decode(&insn, sec->data->d_buf + offset, maxlen,
x86_64 ? INSN_MODE_64 : INSN_MODE_32);
if (ret < 0) {
WARN("can't decode instruction at %s:0x%lx", sec->name, offset);
return -1;
}
*len = insn.length;
*type = INSN_OTHER;
if (insn.vex_prefix.nbytes)
return 0;
op1 = insn.opcode.bytes[0];
op2 = insn.opcode.bytes[1];
if (insn.rex_prefix.nbytes) {
rex = insn.rex_prefix.bytes[0];
rex_w = X86_REX_W(rex) >> 3;
rex_r = X86_REX_R(rex) >> 2;
rex_x = X86_REX_X(rex) >> 1;
rex_b = X86_REX_B(rex);
}
if (insn.modrm.nbytes) {
modrm = insn.modrm.bytes[0];
modrm_mod = X86_MODRM_MOD(modrm);
modrm_reg = X86_MODRM_REG(modrm) + 8*rex_r;
modrm_rm = X86_MODRM_RM(modrm) + 8*rex_b;
}
if (insn.sib.nbytes) {
sib = insn.sib.bytes[0];
/* sib_scale = X86_SIB_SCALE(sib); */
sib_index = X86_SIB_INDEX(sib) + 8*rex_x;
sib_base = X86_SIB_BASE(sib) + 8*rex_b;
}
switch (op1) {
case 0x1:
case 0x29:
if (rex_w && rm_is_reg(CFI_SP)) {
/* add/sub reg, %rsp */
ADD_OP(op) {
op->src.type = OP_SRC_ADD;
op->src.reg = modrm_reg;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
}
break;
case 0x50 ... 0x57:
/* push reg */
ADD_OP(op) {
op->src.type = OP_SRC_REG;
op->src.reg = (op1 & 0x7) + 8*rex_b;
op->dest.type = OP_DEST_PUSH;
}
break;
case 0x58 ... 0x5f:
/* pop reg */
ADD_OP(op) {
op->src.type = OP_SRC_POP;
op->dest.type = OP_DEST_REG;
op->dest.reg = (op1 & 0x7) + 8*rex_b;
}
break;
case 0x68:
case 0x6a:
/* push immediate */
ADD_OP(op) {
op->src.type = OP_SRC_CONST;
op->dest.type = OP_DEST_PUSH;
}
break;
case 0x70 ... 0x7f:
*type = INSN_JUMP_CONDITIONAL;
break;
case 0x80 ... 0x83:
/*
* 1000 00sw : mod OP r/m : immediate
*
* s - sign extend immediate
* w - imm8 / imm32
*
* OP: 000 ADD 100 AND
* 001 OR 101 SUB
* 010 ADC 110 XOR
* 011 SBB 111 CMP
*/
/* 64bit only */
if (!rex_w)
break;
/* %rsp target only */
if (!rm_is_reg(CFI_SP))
break;
imm = insn.immediate.value;
if (op1 & 2) { /* sign extend */
if (op1 & 1) { /* imm32 */
imm <<= 32;
imm = (s64)imm >> 32;
} else { /* imm8 */
imm <<= 56;
imm = (s64)imm >> 56;
}
}
switch (modrm_reg & 7) {
case 5:
imm = -imm;
/* fallthrough */
case 0:
/* add/sub imm, %rsp */
ADD_OP(op) {
op->src.type = OP_SRC_ADD;
op->src.reg = CFI_SP;
op->src.offset = imm;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
break;
case 4:
/* and imm, %rsp */
ADD_OP(op) {
op->src.type = OP_SRC_AND;
op->src.reg = CFI_SP;
op->src.offset = insn.immediate.value;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
break;
default:
/* WARN ? */
break;
}
break;
case 0x89:
if (!rex_w)
break;
if (modrm_reg == CFI_SP) {
if (mod_is_reg()) {
/* mov %rsp, reg */
ADD_OP(op) {
op->src.type = OP_SRC_REG;
op->src.reg = CFI_SP;
op->dest.type = OP_DEST_REG;
op->dest.reg = modrm_rm;
}
break;
} else {
/* skip RIP relative displacement */
if (is_RIP())
break;
/* skip nontrivial SIB */
if (have_SIB()) {
modrm_rm = sib_base;
if (sib_index != CFI_SP)
break;
}
/* mov %rsp, disp(%reg) */
ADD_OP(op) {
op->src.type = OP_SRC_REG;
op->src.reg = CFI_SP;
op->dest.type = OP_DEST_REG_INDIRECT;
op->dest.reg = modrm_rm;
op->dest.offset = insn.displacement.value;
}
break;
}
break;
}
if (rm_is_reg(CFI_SP)) {
/* mov reg, %rsp */
ADD_OP(op) {
op->src.type = OP_SRC_REG;
op->src.reg = modrm_reg;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
break;
}
/* fallthrough */
case 0x88:
if (!rex_w)
break;
if (rm_is_mem(CFI_BP)) {
/* mov reg, disp(%rbp) */
ADD_OP(op) {
op->src.type = OP_SRC_REG;
op->src.reg = modrm_reg;
op->dest.type = OP_DEST_REG_INDIRECT;
op->dest.reg = CFI_BP;
op->dest.offset = insn.displacement.value;
}
break;
}
if (rm_is_mem(CFI_SP)) {
/* mov reg, disp(%rsp) */
ADD_OP(op) {
op->src.type = OP_SRC_REG;
op->src.reg = modrm_reg;
op->dest.type = OP_DEST_REG_INDIRECT;
op->dest.reg = CFI_SP;
op->dest.offset = insn.displacement.value;
}
break;
}
break;
case 0x8b:
if (!rex_w)
break;
if (rm_is_mem(CFI_BP)) {
/* mov disp(%rbp), reg */
ADD_OP(op) {
op->src.type = OP_SRC_REG_INDIRECT;
op->src.reg = CFI_BP;
op->src.offset = insn.displacement.value;
op->dest.type = OP_DEST_REG;
op->dest.reg = modrm_reg;
}
break;
}
if (rm_is_mem(CFI_SP)) {
/* mov disp(%rsp), reg */
ADD_OP(op) {
op->src.type = OP_SRC_REG_INDIRECT;
op->src.reg = CFI_SP;
op->src.offset = insn.displacement.value;
op->dest.type = OP_DEST_REG;
op->dest.reg = modrm_reg;
}
break;
}
break;
case 0x8d:
if (mod_is_reg()) {
WARN("invalid LEA encoding at %s:0x%lx", sec->name, offset);
break;
}
/* skip non 64bit ops */
if (!rex_w)
break;
/* skip RIP relative displacement */
if (is_RIP())
break;
/* skip nontrivial SIB */
if (have_SIB()) {
modrm_rm = sib_base;
if (sib_index != CFI_SP)
break;
}
/* lea disp(%src), %dst */
ADD_OP(op) {
op->src.offset = insn.displacement.value;
if (!op->src.offset) {
/* lea (%src), %dst */
op->src.type = OP_SRC_REG;
} else {
/* lea disp(%src), %dst */
op->src.type = OP_SRC_ADD;
}
op->src.reg = modrm_rm;
op->dest.type = OP_DEST_REG;
op->dest.reg = modrm_reg;
}
break;
case 0x8f:
/* pop to mem */
ADD_OP(op) {
op->src.type = OP_SRC_POP;
op->dest.type = OP_DEST_MEM;
}
break;
case 0x90:
*type = INSN_NOP;
break;
case 0x9c:
/* pushf */
ADD_OP(op) {
op->src.type = OP_SRC_CONST;
op->dest.type = OP_DEST_PUSHF;
}
break;
case 0x9d:
/* popf */
ADD_OP(op) {
op->src.type = OP_SRC_POPF;
op->dest.type = OP_DEST_MEM;
}
break;
case 0x0f:
if (op2 == 0x01) {
if (modrm == 0xca)
*type = INSN_CLAC;
else if (modrm == 0xcb)
*type = INSN_STAC;
} else if (op2 >= 0x80 && op2 <= 0x8f) {
*type = INSN_JUMP_CONDITIONAL;
} else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
op2 == 0x35) {
/* sysenter, sysret */
*type = INSN_CONTEXT_SWITCH;
} else if (op2 == 0x0b || op2 == 0xb9) {
/* ud2 */
*type = INSN_BUG;
} else if (op2 == 0x0d || op2 == 0x1f) {
/* nopl/nopw */
*type = INSN_NOP;
} else if (op2 == 0xa0 || op2 == 0xa8) {
/* push fs/gs */
ADD_OP(op) {
op->src.type = OP_SRC_CONST;
op->dest.type = OP_DEST_PUSH;
}
} else if (op2 == 0xa1 || op2 == 0xa9) {
/* pop fs/gs */
ADD_OP(op) {
op->src.type = OP_SRC_POP;
op->dest.type = OP_DEST_MEM;
}
}
break;
case 0xc9:
/*
* leave
*
* equivalent to:
* mov bp, sp
* pop bp
*/
ADD_OP(op) {
op->src.type = OP_SRC_REG;
op->src.reg = CFI_BP;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
ADD_OP(op) {
op->src.type = OP_SRC_POP;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_BP;
}
break;
case 0xe3:
/* jecxz/jrcxz */
*type = INSN_JUMP_CONDITIONAL;
break;
case 0xe9:
case 0xeb:
*type = INSN_JUMP_UNCONDITIONAL;
break;
case 0xc2:
case 0xc3:
*type = INSN_RETURN;
break;
case 0xcf: /* iret */
/*
* Handle sync_core(), which has an IRET to self.
* All other IRET are in STT_NONE entry code.
*/
sym = find_symbol_containing(sec, offset);
if (sym && sym->type == STT_FUNC) {
ADD_OP(op) {
/* add $40, %rsp */
op->src.type = OP_SRC_ADD;
op->src.reg = CFI_SP;
op->src.offset = 5*8;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
}
break;
}
/* fallthrough */
case 0xca: /* retf */
case 0xcb: /* retf */
*type = INSN_CONTEXT_SWITCH;
break;
case 0xe8:
*type = INSN_CALL;
/*
* For the impact on the stack, a CALL behaves like
* a PUSH of an immediate value (the return address).
*/
ADD_OP(op) {
op->src.type = OP_SRC_CONST;
op->dest.type = OP_DEST_PUSH;
}
break;
case 0xfc:
*type = INSN_CLD;
break;
case 0xfd:
*type = INSN_STD;
break;
case 0xff:
if (modrm_reg == 2 || modrm_reg == 3)
*type = INSN_CALL_DYNAMIC;
else if (modrm_reg == 4)
*type = INSN_JUMP_DYNAMIC;
else if (modrm_reg == 5)
/* jmpf */
*type = INSN_CONTEXT_SWITCH;
else if (modrm_reg == 6) {
/* push from mem */
ADD_OP(op) {
op->src.type = OP_SRC_CONST;
op->dest.type = OP_DEST_PUSH;
}
}
break;
default:
break;
}
*immediate = insn.immediate.nbytes ? insn.immediate.value : 0;
return 0;
}
void arch_initial_func_cfi_state(struct cfi_init_state *state)
{
int i;
for (i = 0; i < CFI_NUM_REGS; i++) {
state->regs[i].base = CFI_UNDEFINED;
state->regs[i].offset = 0;
}
/* initial CFA (call frame address) */
state->cfa.base = CFI_SP;
state->cfa.offset = 8;
/* initial RA (return address) */
state->regs[CFI_RA].base = CFI_CFA;
state->regs[CFI_RA].offset = -8;
}
const char *arch_nop_insn(int len)
{
static const char nops[5][5] = {
{ BYTES_NOP1 },
{ BYTES_NOP2 },
{ BYTES_NOP3 },
{ BYTES_NOP4 },
{ BYTES_NOP5 },
};
if (len < 1 || len > 5) {
WARN("invalid NOP size: %d\n", len);
return NULL;
}
return nops[len-1];
}
/* asm/alternative.h ? */
#define ALTINSTR_FLAG_INV (1 << 15)
#define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV)
struct alt_instr {
s32 instr_offset; /* original instruction */
s32 repl_offset; /* offset to replacement instruction */
u16 cpuid; /* cpuid bit set for replacement */
u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction */
} __packed;
static int elf_add_alternative(struct elf *elf,
struct instruction *orig, struct symbol *sym,
int cpuid, u8 orig_len, u8 repl_len)
{
const int size = sizeof(struct alt_instr);
struct alt_instr *alt;
struct section *sec;
Elf_Scn *s;
sec = find_section_by_name(elf, ".altinstructions");
if (!sec) {
sec = elf_create_section(elf, ".altinstructions",
SHF_ALLOC, size, 0);
if (!sec) {
WARN_ELF("elf_create_section");
return -1;
}
}
s = elf_getscn(elf->elf, sec->idx);
if (!s) {
WARN_ELF("elf_getscn");
return -1;
}
sec->data = elf_newdata(s);
if (!sec->data) {
WARN_ELF("elf_newdata");
return -1;
}
sec->data->d_size = size;
sec->data->d_align = 1;
alt = sec->data->d_buf = malloc(size);
if (!sec->data->d_buf) {
perror("malloc");
return -1;
}
memset(sec->data->d_buf, 0, size);
if (elf_add_reloc_to_insn(elf, sec, sec->sh.sh_size,
R_X86_64_PC32, orig->sec, orig->offset)) {
WARN("elf_create_reloc: alt_instr::instr_offset");
return -1;
}
if (elf_add_reloc(elf, sec, sec->sh.sh_size + 4,
R_X86_64_PC32, sym, 0)) {
WARN("elf_create_reloc: alt_instr::repl_offset");
return -1;
}
alt->cpuid = bswap_if_needed(cpuid);
alt->instrlen = orig_len;
alt->replacementlen = repl_len;
sec->sh.sh_size += size;
sec->changed = true;
return 0;
}
#define X86_FEATURE_RETPOLINE ( 7*32+12)
int arch_rewrite_retpolines(struct objtool_file *file)
{
struct instruction *insn;
struct reloc *reloc;
struct symbol *sym;
char name[32] = "";
list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
if (insn->type != INSN_JUMP_DYNAMIC &&
insn->type != INSN_CALL_DYNAMIC)
continue;
if (!strcmp(insn->sec->name, ".text.__x86.indirect_thunk"))
continue;
reloc = insn->reloc;
sprintf(name, "__x86_indirect_alt_%s_%s",
insn->type == INSN_JUMP_DYNAMIC ? "jmp" : "call",
reloc->sym->name + 21);
sym = find_symbol_by_name(file->elf, name);
if (!sym) {
sym = elf_create_undef_symbol(file->elf, name);
if (!sym) {
WARN("elf_create_undef_symbol");
return -1;
}
}
if (elf_add_alternative(file->elf, insn, sym,
ALT_NOT(X86_FEATURE_RETPOLINE), 5, 5)) {
WARN("elf_add_alternative");
return -1;
}
}
return 0;
}
int arch_decode_hint_reg(struct instruction *insn, u8 sp_reg)
{
struct cfi_reg *cfa = &insn->cfi.cfa;
switch (sp_reg) {
case ORC_REG_UNDEFINED:
cfa->base = CFI_UNDEFINED;
break;
case ORC_REG_SP:
cfa->base = CFI_SP;
break;
case ORC_REG_BP:
cfa->base = CFI_BP;
break;
case ORC_REG_SP_INDIRECT:
cfa->base = CFI_SP_INDIRECT;
break;
case ORC_REG_R10:
cfa->base = CFI_R10;
break;
case ORC_REG_R13:
cfa->base = CFI_R13;
break;
case ORC_REG_DI:
cfa->base = CFI_DI;
break;
case ORC_REG_DX:
cfa->base = CFI_DX;
break;
default:
return -1;
}
return 0;
}
bool arch_is_retpoline(struct symbol *sym)
{
return !strncmp(sym->name, "__x86_indirect_", 15);
}