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>

1 files changed, 362 insertions, 38 deletions

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;
+}