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-rw-r--r--tools/objtool/arch/x86/decode.c806
1 files changed, 806 insertions, 0 deletions
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
new file mode 100644
index 000000000..1ed49ab4e
--- /dev/null
+++ b/tools/objtool/arch/x86/decode.c
@@ -0,0 +1,806 @@
+// 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 <objtool/builtin.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))
+
+static bool has_notrack_prefix(struct insn *insn)
+{
+ int i;
+
+ for (i = 0; i < insn->prefixes.nbytes; i++) {
+ if (insn->prefixes.bytes[i] == 0x3e)
+ return true;
+ }
+
+ return false;
+}
+
+int arch_decode_instruction(struct objtool_file *file, 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)
+{
+ const struct elf *elf = file->elf;
+ struct insn insn;
+ int x86_64, ret;
+ unsigned char op1, op2, op3, prefix,
+ 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;
+
+ prefix = insn.prefixes.bytes[0];
+
+ op1 = insn.opcode.bytes[0];
+ op2 = insn.opcode.bytes[1];
+ op3 = insn.opcode.bytes[2];
+
+ 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 == 0x1e) {
+
+ if (prefix == 0xf3 && (modrm == 0xfa || modrm == 0xfb))
+ *type = INSN_ENDBR;
+
+
+ } else if (op2 == 0x38 && op3 == 0xf8) {
+ if (insn.prefixes.nbytes == 1 &&
+ insn.prefixes.bytes[0] == 0xf2) {
+ /* ENQCMD cannot be used in the kernel. */
+ WARN("ENQCMD instruction at %s:%lx", sec->name,
+ offset);
+ }
+
+ } 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 0xcc:
+ /* int3 */
+ *type = INSN_TRAP;
+ 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 0xc7: /* mov imm, r/m */
+ if (!opts.noinstr)
+ break;
+
+ if (insn.length == 3+4+4 && !strncmp(sec->name, ".init.text", 10)) {
+ struct reloc *immr, *disp;
+ struct symbol *func;
+ int idx;
+
+ immr = find_reloc_by_dest(elf, (void *)sec, offset+3);
+ disp = find_reloc_by_dest(elf, (void *)sec, offset+7);
+
+ if (!immr || strcmp(immr->sym->name, "pv_ops"))
+ break;
+
+ idx = (immr->addend + 8) / sizeof(void *);
+
+ func = disp->sym;
+ if (disp->sym->type == STT_SECTION)
+ func = find_symbol_by_offset(disp->sym->sec, disp->addend);
+ if (!func) {
+ WARN("no func for pv_ops[]");
+ return -1;
+ }
+
+ objtool_pv_add(file, idx, func);
+ }
+
+ 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 0xe0: /* loopne */
+ case 0xe1: /* loope */
+ case 0xe2: /* loop */
+ *type = INSN_JUMP_CONDITIONAL;
+ 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;
+ if (has_notrack_prefix(&insn))
+ WARN("notrack prefix found at %s:0x%lx", sec->name, offset);
+
+ } else if (modrm_reg == 4) {
+
+ *type = INSN_JUMP_DYNAMIC;
+ if (has_notrack_prefix(&insn))
+ WARN("notrack prefix found at %s:0x%lx", sec->name, offset);
+
+ } 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];
+}
+
+#define BYTE_RET 0xC3
+
+const char *arch_ret_insn(int len)
+{
+ static const char ret[5][5] = {
+ { BYTE_RET },
+ { BYTE_RET, 0xcc },
+ { BYTE_RET, 0xcc, BYTES_NOP1 },
+ { BYTE_RET, 0xcc, BYTES_NOP2 },
+ { BYTE_RET, 0xcc, BYTES_NOP3 },
+ };
+
+ if (len < 1 || len > 5) {
+ WARN("invalid RET size: %d\n", len);
+ return NULL;
+ }
+
+ return ret[len-1];
+}
+
+int arch_decode_hint_reg(u8 sp_reg, int *base)
+{
+ switch (sp_reg) {
+ case ORC_REG_UNDEFINED:
+ *base = CFI_UNDEFINED;
+ break;
+ case ORC_REG_SP:
+ *base = CFI_SP;
+ break;
+ case ORC_REG_BP:
+ *base = CFI_BP;
+ break;
+ case ORC_REG_SP_INDIRECT:
+ *base = CFI_SP_INDIRECT;
+ break;
+ case ORC_REG_R10:
+ *base = CFI_R10;
+ break;
+ case ORC_REG_R13:
+ *base = CFI_R13;
+ break;
+ case ORC_REG_DI:
+ *base = CFI_DI;
+ break;
+ case ORC_REG_DX:
+ *base = CFI_DX;
+ break;
+ default:
+ return -1;
+ }
+
+ return 0;
+}
+
+bool arch_is_retpoline(struct symbol *sym)
+{
+ return !strncmp(sym->name, "__x86_indirect_", 15);
+}
+
+bool arch_is_rethunk(struct symbol *sym)
+{
+ return !strcmp(sym->name, "__x86_return_thunk");
+}
+
+bool arch_is_embedded_insn(struct symbol *sym)
+{
+ return !strcmp(sym->name, "retbleed_return_thunk") ||
+ !strcmp(sym->name, "srso_safe_ret");
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-06 10:54:08 +0000