linux-kernel - [RFC][PATCH v2 4/7] objtool,x86: Rewrite LEAVE

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Date:   Thu, 11 Feb 2021 18:30:48 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org
Cc:     Miroslav Benes <mbenes@...e.cz>,
        Julien Thierry <jthierry@...hat.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [RFC][PATCH v2 4/7] objtool,x86: Rewrite LEAVE

Since we can now have multiple stack-ops per instruction, we don't
need to special case LEAVE and can simply emit the composite
operations.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/arch/x86/decode.c      |   14 +++++++++++---
 tools/objtool/check.c                |   24 ++----------------------
 tools/objtool/include/objtool/arch.h |    1 -
 3 files changed, 13 insertions(+), 26 deletions(-)

--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -441,9 +441,17 @@ int arch_decode_instruction(const struct
 		 * mov bp, sp
 		 * pop bp
 		 */
-		ADD_OP(op)
-			op->dest.type = OP_DEST_LEAVE;
-
+		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:
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1931,7 +1931,7 @@ static int update_cfi_state(struct instr
 			}
 
 			else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
-				 cfa->base == CFI_BP) {
+				 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
 
 				/*
 				 * mov %rbp, %rsp
@@ -2114,7 +2114,7 @@ static int update_cfi_state(struct instr
 				cfa->offset = 0;
 				cfi->drap_offset = -1;
 
-			} else if (regs[op->dest.reg].offset == -cfi->stack_size) {
+			} else if (cfi->stack_size == -regs[op->dest.reg].offset) {
 
 				/* pop %reg */
 				restore_reg(cfi, op->dest.reg);
@@ -2254,26 +2254,6 @@ static int update_cfi_state(struct instr
 		}
 
 		break;
-
-	case OP_DEST_LEAVE:
-		if ((!cfi->drap && cfa->base != CFI_BP) ||
-		    (cfi->drap && cfa->base != cfi->drap_reg)) {
-			WARN_FUNC("leave instruction with modified stack frame",
-				  insn->sec, insn->offset);
-			return -1;
-		}
-
-		/* leave (mov %rbp, %rsp; pop %rbp) */
-
-		cfi->stack_size = -cfi->regs[CFI_BP].offset - 8;
-		restore_reg(cfi, CFI_BP);
-
-		if (!cfi->drap) {
-			cfa->base = CFI_SP;
-			cfa->offset -= 8;
-		}
-
-		break;
 
 	case OP_DEST_MEM:
 		if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -35,7 +35,6 @@ enum op_dest_type {
 	OP_DEST_MEM,
 	OP_DEST_PUSH,
 	OP_DEST_PUSHF,
-	OP_DEST_LEAVE,
 };
 
 struct op_dest {