objtool: Rework allocating stack_ops on decode

Wrap each stack_op in a macro that allocates and adds it to the list.
This simplifies trying to figure out what to do with the pre-allocated
stack_op at the end.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200428191659.736151601@infradead.org

tools/objtool/arch/x86/decode.c

@@ -77,6 +77,11 @@ 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)
+
 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,
@@ -88,7 +93,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 	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;
-	struct stack_op *op;
+	struct stack_op *op = NULL;
 
 	x86_64 = is_x86_64(elf);
 	if (x86_64 == -1)
@@ -129,10 +134,6 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 	if (insn.sib.nbytes)
 		sib = insn.sib.bytes[0];
 
-	op = calloc(1, sizeof(*op));
-	if (!op)
-		return -1;
-
 	switch (op1) {
 
 	case 0x1:
@@ -141,20 +142,24 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 			/* add/sub reg, %rsp */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				op->src.type = OP_SRC_ADD;
 				op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
 				op->dest.type = OP_DEST_REG;
 				op->dest.reg = CFI_SP;
 			}
+		}
 		break;
 
 	case 0x50 ... 0x57:
 
 		/* push reg */
 		*type = INSN_STACK;
+		ADD_OP(op) {
 			op->src.type = OP_SRC_REG;
 			op->src.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
 			op->dest.type = OP_DEST_PUSH;
+		}
 
 		break;
 
@@ -162,9 +167,11 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 		/* pop reg */
 		*type = INSN_STACK;
+		ADD_OP(op) {
 			op->src.type = OP_SRC_POP;
 			op->dest.type = OP_DEST_REG;
 			op->dest.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+		}
 
 		break;
 
@@ -172,8 +179,10 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 	case 0x6a:
 		/* push immediate */
 		*type = INSN_STACK;
+		ADD_OP(op) {
 			op->src.type = OP_SRC_CONST;
 			op->dest.type = OP_DEST_PUSH;
+		}
 		break;
 
 	case 0x70 ... 0x7f:
@@ -188,11 +197,13 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 		if (modrm == 0xe4) {
 			/* and imm, %rsp */
 			*type = INSN_STACK;
+			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;
 		}
 
@@ -205,11 +216,13 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 		/* add/sub imm, %rsp */
 		*type = INSN_STACK;
+		ADD_OP(op) {
 			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:
@@ -217,10 +230,12 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 			/* mov %rsp, reg */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				op->src.type = OP_SRC_REG;
 				op->src.reg = CFI_SP;
 				op->dest.type = OP_DEST_REG;
 				op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b];
+			}
 			break;
 		}
 
@@ -228,10 +243,12 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 			/* mov reg, %rsp */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				op->src.type = OP_SRC_REG;
 				op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
 				op->dest.type = OP_DEST_REG;
 				op->dest.reg = CFI_SP;
+			}
 			break;
 		}
 
@@ -242,22 +259,26 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 			/* mov reg, disp(%rbp) */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				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;
+			ADD_OP(op) {
 				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;
 
@@ -266,23 +287,27 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 			/* mov disp(%rbp), reg */
 			*type = INSN_STACK;
+			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 = 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;
+			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 = op_to_cfi_reg[modrm_reg][rex_r];
 			}
+		}
 
 		break;
 
@@ -290,6 +315,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 		if (sib == 0x24 && rex_w && !rex_b && !rex_x) {
 
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				if (!insn.displacement.value) {
 					/* lea (%rsp), reg */
 					op->src.type = OP_SRC_REG;
@@ -301,16 +327,19 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 				op->src.reg = CFI_SP;
 				op->dest.type = OP_DEST_REG;
 				op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
+			}
 
 		} else if (rex == 0x48 && modrm == 0x65) {
 
 			/* lea disp(%rbp), %rsp */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				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;
+			}
 
 		} else if (rex == 0x49 && modrm == 0x62 &&
 			   insn.displacement.value == -8) {
@@ -322,11 +351,13 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 			 * stack realignment.
 			 */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				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;
+			}
 
 		} else if (rex == 0x49 && modrm == 0x65 &&
 			   insn.displacement.value == -16) {
@@ -338,20 +369,24 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 			 * stack realignment.
 			 */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				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;
 
 	case 0x8f:
 		/* pop to mem */
 		*type = INSN_STACK;
+		ADD_OP(op) {
 			op->src.type = OP_SRC_POP;
 			op->dest.type = OP_DEST_MEM;
+		}
 		break;
 
 	case 0x90:
@@ -361,15 +396,19 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 	case 0x9c:
 		/* pushf */
 		*type = INSN_STACK;
+		ADD_OP(op) {
 			op->src.type = OP_SRC_CONST;
 			op->dest.type = OP_DEST_PUSHF;
+		}
 		break;
 
 	case 0x9d:
 		/* popf */
 		*type = INSN_STACK;
+		ADD_OP(op) {
 			op->src.type = OP_SRC_POPF;
 			op->dest.type = OP_DEST_MEM;
+		}
 		break;
 
 	case 0x0f:
@@ -405,16 +444,20 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 			/* push fs/gs */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				op->src.type = OP_SRC_CONST;
 				op->dest.type = OP_DEST_PUSH;
+			}
 
 		} else if (op2 == 0xa1 || op2 == 0xa9) {
 
 			/* pop fs/gs */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				op->src.type = OP_SRC_POP;
 				op->dest.type = OP_DEST_MEM;
 			}
+		}
 
 		break;
 
@@ -427,6 +470,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 		 * pop bp
 		 */
 		*type = INSN_STACK;
+		ADD_OP(op)
 			op->dest.type = OP_DEST_LEAVE;
 
 		break;
@@ -449,12 +493,14 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 	case 0xcf: /* iret */
 		*type = INSN_EXCEPTION_RETURN;
 
+		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;
 
 	case 0xca: /* retf */
@@ -492,9 +538,11 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 			/* push from mem */
 			*type = INSN_STACK;
+			ADD_OP(op) {
 				op->src.type = OP_SRC_CONST;
 				op->dest.type = OP_DEST_PUSH;
 			}
+		}
 
 		break;
 
@@ -504,11 +552,6 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
 	*immediate = insn.immediate.nbytes ? insn.immediate.value : 0;
 
-	if (*type == INSN_STACK || *type == INSN_EXCEPTION_RETURN)
-		list_add_tail(&op->list, ops_list);
-	else
-		free(op);
-
 	return 0;
 }