From baa41469a7b992c1e3db2a39854219cc7442e48f Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Wed, 28 Jun 2017 10:11:07 -0500
Subject: objtool: Implement stack validation 2.0
This is a major rewrite of objtool. Instead of only tracking frame
pointer changes, it now tracks all stack-related operations, including
all register saves/restores.
In addition to making stack validation more robust, this also paves the
way for undwarf generation.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/678bd94c0566c6129bcc376cddb259c4c5633004.1498659915.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
tools/objtool/arch/x86/decode.c | 400 ++++++++++++++++++++++++++++++++++++----
1 file changed, 362 insertions(+), 38 deletions(-)
(limited to 'tools/objtool/arch/x86')
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 6ac99e3266eb..a36c2eba64e7 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -27,6 +27,17 @@
#include "../../arch.h"
#include "../../warn.h"
+static unsigned char op_to_cfi_reg[][2] = {
+ {CFI_AX, CFI_R8},
+ {CFI_CX, CFI_R9},
+ {CFI_DX, CFI_R10},
+ {CFI_BX, CFI_R11},
+ {CFI_SP, CFI_R12},
+ {CFI_BP, CFI_R13},
+ {CFI_SI, CFI_R14},
+ {CFI_DI, CFI_R15},
+};
+
static int is_x86_64(struct elf *elf)
{
switch (elf->ehdr.e_machine) {
@@ -40,24 +51,50 @@ static int is_x86_64(struct elf *elf)
}
}
+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;
+ }
+}
+
int arch_decode_instruction(struct elf *elf, struct section *sec,
unsigned long offset, unsigned int maxlen,
unsigned int *len, unsigned char *type,
- unsigned long *immediate)
+ unsigned long *immediate, struct stack_op *op)
{
struct insn insn;
- int x86_64;
- unsigned char op1, op2, ext;
+ int x86_64, sign;
+ unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0,
+ modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0,
+ sib = 0;
x86_64 = is_x86_64(elf);
if (x86_64 == -1)
return -1;
- insn_init(&insn, (void *)(sec->data + offset), maxlen, x86_64);
+ insn_init(&insn, sec->data->d_buf + offset, maxlen, x86_64);
insn_get_length(&insn);
- insn_get_opcode(&insn);
- insn_get_modrm(&insn);
- insn_get_immediate(&insn);
if (!insn_complete(&insn)) {
WARN_FUNC("can't decode instruction", sec, offset);
@@ -73,67 +110,323 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
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_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);
+ modrm_rm = X86_MODRM_RM(modrm);
+ }
+
+ if (insn.sib.nbytes)
+ sib = insn.sib.bytes[0];
+
switch (op1) {
- case 0x55:
- if (!insn.rex_prefix.nbytes)
- /* push rbp */
- *type = INSN_FP_SAVE;
+
+ case 0x1:
+ case 0x29:
+ if (rex_w && !rex_b && modrm_mod == 3 && modrm_rm == 4) {
+
+ /* add/sub reg, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_SRC_REG;
+ op->dest.reg = CFI_SP;
+ }
+ break;
+
+ case 0x50 ... 0x57:
+
+ /* push reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+ op->dest.type = OP_DEST_PUSH;
+
break;
- case 0x5d:
- if (!insn.rex_prefix.nbytes)
- /* pop rbp */
- *type = INSN_FP_RESTORE;
+ case 0x58 ... 0x5f:
+
+ /* pop reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+
+ break;
+
+ case 0x68:
+ case 0x6a:
+ /* push immediate */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
break;
case 0x70 ... 0x7f:
*type = INSN_JUMP_CONDITIONAL;
break;
+ case 0x81:
+ case 0x83:
+ if (rex != 0x48)
+ break;
+
+ if (modrm == 0xe4) {
+ /* and imm, %rsp */
+ *type = INSN_STACK;
+ 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;
+ }
+
+ if (modrm == 0xc4)
+ sign = 1;
+ else if (modrm == 0xec)
+ sign = -1;
+ else
+ break;
+
+ /* add/sub imm, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = insn.immediate.value * sign;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+
case 0x89:
- if (insn.rex_prefix.nbytes == 1 &&
- insn.rex_prefix.bytes[0] == 0x48 &&
- insn.modrm.nbytes && insn.modrm.bytes[0] == 0xe5)
- /* mov rsp, rbp */
- *type = INSN_FP_SETUP;
+ if (rex == 0x48 && modrm == 0xe5) {
+
+ /* mov %rsp, %rbp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = CFI_SP;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_BP;
+ break;
+ }
+ /* fallthrough */
+ case 0x88:
+ if (!rex_b &&
+ (modrm_mod == 1 || modrm_mod == 2) && modrm_rm == 5) {
+
+ /* mov reg, disp(%rbp) */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_DEST_REG_INDIRECT;
+ op->dest.reg = CFI_BP;
+ op->dest.offset = insn.displacement.value;
+
+ } else if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) {
+
+ /* mov reg, disp(%rsp) */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_DEST_REG_INDIRECT;
+ op->dest.reg = CFI_SP;
+ op->dest.offset = insn.displacement.value;
+ }
+
+ break;
+
+ case 0x8b:
+ if (rex_w && !rex_b && modrm_mod == 1 && modrm_rm == 5) {
+
+ /* mov disp(%rbp), reg */
+ *type = INSN_STACK;
+ 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 = op_to_cfi_reg[modrm_reg][rex_r];
+
+ } else if (rex_w && !rex_b && sib == 0x24 &&
+ modrm_mod != 3 && modrm_rm == 4) {
+
+ /* mov disp(%rsp), reg */
+ *type = INSN_STACK;
+ 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 = op_to_cfi_reg[modrm_reg][rex_r];
+ }
+
break;
case 0x8d:
- if (insn.rex_prefix.nbytes &&
- insn.rex_prefix.bytes[0] == 0x48 &&
- insn.modrm.nbytes && insn.modrm.bytes[0] == 0x2c &&
- insn.sib.nbytes && insn.sib.bytes[0] == 0x24)
- /* lea %(rsp), %rbp */
- *type = INSN_FP_SETUP;
+ if (rex == 0x48 && modrm == 0x65) {
+
+ /* lea -disp(%rbp), %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_BP;
+ op->src.offset = insn.displacement.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
+ insn.displacement.value == 8) {
+
+ /*
+ * lea 0x8(%rsp), %r10
+ *
+ * Here r10 is the "drap" pointer, used as a stack
+ * pointer helper when the stack gets realigned.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = 8;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_R10;
+ break;
+ }
+
+ if (rex == 0x4c && modrm == 0x6c && sib == 0x24 &&
+ insn.displacement.value == 16) {
+
+ /*
+ * lea 0x10(%rsp), %r13
+ *
+ * Here r13 is the "drap" pointer, used as a stack
+ * pointer helper when the stack gets realigned.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = 16;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_R13;
+ break;
+ }
+
+ if (rex == 0x49 && modrm == 0x62 &&
+ insn.displacement.value == -8) {
+
+ /*
+ * lea -0x8(%r10), %rsp
+ *
+ * Restoring rsp back to its original value after a
+ * stack realignment.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_R10;
+ op->src.offset = -8;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ if (rex == 0x49 && modrm == 0x65 &&
+ insn.displacement.value == -16) {
+
+ /*
+ * lea -0x10(%r13), %rsp
+ *
+ * Restoring rsp back to its original value after a
+ * stack realignment.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_R13;
+ op->src.offset = -16;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ break;
+
+ case 0x8f:
+ /* pop to mem */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
break;
case 0x90:
*type = INSN_NOP;
break;
+ case 0x9c:
+ /* pushf */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+ break;
+
+ case 0x9d:
+ /* popf */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
+ break;
+
case 0x0f:
+
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 == 0x0d || op2 == 0x1f)
+
/* nopl/nopw */
*type = INSN_NOP;
- else if (op2 == 0x01 && insn.modrm.nbytes &&
- (insn.modrm.bytes[0] == 0xc2 ||
- insn.modrm.bytes[0] == 0xd8))
- /* vmlaunch, vmrun */
- *type = INSN_CONTEXT_SWITCH;
+
+ else if (op2 == 0xa0 || op2 == 0xa8) {
+
+ /* push fs/gs */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+
+ } else if (op2 == 0xa1 || op2 == 0xa9) {
+
+ /* pop fs/gs */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
+ }
break;
- case 0xc9: /* leave */
- *type = INSN_FP_RESTORE;
+ case 0xc9:
+ /*
+ * leave
+ *
+ * equivalent to:
+ * mov bp, sp
+ * pop bp
+ */
+ *type = INSN_STACK;
+ op->dest.type = OP_DEST_LEAVE;
+
break;
- case 0xe3: /* jecxz/jrcxz */
+ case 0xe3:
+ /* jecxz/jrcxz */
*type = INSN_JUMP_CONDITIONAL;
break;
@@ -158,14 +451,27 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
break;
case 0xff:
- ext = X86_MODRM_REG(insn.modrm.bytes[0]);
- if (ext == 2 || ext == 3)
+ if (modrm_reg == 2 || modrm_reg == 3)
+
*type = INSN_CALL_DYNAMIC;
- else if (ext == 4)
+
+ else if (modrm_reg == 4)
+
*type = INSN_JUMP_DYNAMIC;
- else if (ext == 5) /*jmpf */
+
+ else if (modrm_reg == 5)
+
+ /* jmpf */
*type = INSN_CONTEXT_SWITCH;
+ else if (modrm_reg == 6) {
+
+ /* push from mem */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+ }
+
break;
default:
@@ -176,3 +482,21 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
return 0;
}
+
+void arch_initial_func_cfi_state(struct cfi_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[16].base = CFI_CFA;
+ state->regs[16].offset = -8;
+}
--
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