linux-kernel - [RFC PATCH v4 05/37] objtool: arm64: Decode add/sub instructions

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Date:   Fri, 29 Apr 2022 17:43:23 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arch@...r.kernel.org>
CC:     <jthierry@...hat.com>, <catalin.marinas@....com>,
        <will@...nel.org>, <masahiroy@...nel.org>, <jpoimboe@...hat.com>,
        <peterz@...radead.org>, <ycote@...hat.com>,
        <herbert@...dor.apana.org.au>, <mark.rutland@....com>,
        <davem@...emloft.net>, <ardb@...nel.org>, <maz@...nel.org>,
        <tglx@...utronix.de>, <luc.vanoostenryck@...il.com>,
        <chenzhongjin@...wei.com>
Subject: [RFC PATCH v4 05/37] objtool: arm64: Decode add/sub instructions

From: Julien Thierry <jthierry@...hat.com>

Decode aarch64 additions and substractions and create stack_ops for
instructions interacting with SP or FP.

Signed-off-by: Julien Thierry <jthierry@...hat.com>
Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
---
 tools/objtool/arch/arm64/decode.c | 91 +++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/tools/objtool/arch/arm64/decode.c b/tools/objtool/arch/arm64/decode.c
index 42a9ce4aab87..84daec62006a 100644
--- a/tools/objtool/arch/arm64/decode.c
+++ b/tools/objtool/arch/arm64/decode.c
@@ -13,6 +13,15 @@
 #include <objtool/builtin.h>
 #include <arch/cfi_regs.h>
 
+#include "../../../arch/arm64/lib/insn.c"
+
+static unsigned long sign_extend(unsigned long x, int nbits)
+{
+	unsigned long sign_bit = (x >> (nbits - 1)) & 1;
+
+	return ((~0UL + (sign_bit ^ 1)) << nbits) | x;
+}
+
 bool arch_callee_saved_reg(unsigned char reg)
 {
 	switch (reg) {
@@ -103,6 +112,59 @@ int arch_decode_hint_reg(u8 sp_reg, int *base)
 	return -1;
 }
 
+static struct stack_op *arm_make_add_op(enum aarch64_insn_register dest,
+					enum aarch64_insn_register src,
+					int val)
+{
+	struct stack_op *op;
+
+	op = calloc(1, sizeof(*op));
+	if (!op) {
+		WARN("calloc failed");
+		return NULL;
+	}
+	op->dest.type = OP_DEST_REG;
+	op->dest.reg = dest;
+	op->src.reg = src;
+	op->src.type = val != 0 ? OP_SRC_ADD : OP_SRC_REG;
+	op->src.offset = val;
+
+	return op;
+}
+
+static int arm_decode_add_sub_imm(u32 instr, bool set_flags,
+				  unsigned long *immediate,
+				  struct list_head *ops_list)
+{
+	u32 rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, instr);
+	u32 rn = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RN, instr);
+
+	*immediate = aarch64_insn_decode_immediate(AARCH64_INSN_IMM_12, instr);
+
+	if (instr & AARCH64_INSN_LSL_12)
+		*immediate <<= 12;
+
+	if ((!set_flags && rd == AARCH64_INSN_REG_SP) ||
+	    rd == AARCH64_INSN_REG_FP ||
+	    rn == AARCH64_INSN_REG_FP ||
+	    rn == AARCH64_INSN_REG_SP) {
+		struct stack_op *op;
+		int value;
+
+		if (aarch64_insn_is_subs_imm(instr) || aarch64_insn_is_sub_imm(instr))
+			value = -*immediate;
+		else
+			value = *immediate;
+
+		op = arm_make_add_op(rd, rn, value);
+		if (!op)
+			return -1;
+		list_add_tail(&op->list, ops_list);
+	}
+
+	return 0;
+}
+
 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,
@@ -128,6 +190,35 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
 	case AARCH64_INSN_CLS_UNKNOWN:
 		WARN("can't decode instruction at %s:0x%lx", sec->name, offset);
 		return -1;
+	case AARCH64_INSN_CLS_DP_IMM:
+		/* Mov register to and from SP are aliases of add_imm */
+		if (aarch64_insn_is_add_imm(insn) ||
+		    aarch64_insn_is_sub_imm(insn))
+			return arm_decode_add_sub_imm(insn, false, immediate,
+						      ops_list);
+		else if (aarch64_insn_is_adds_imm(insn) ||
+			     aarch64_insn_is_subs_imm(insn))
+			return arm_decode_add_sub_imm(insn, true, immediate,
+						      ops_list);
+		break;
+	case AARCH64_INSN_CLS_DP_REG:
+		if (aarch64_insn_is_mov_reg(insn)) {
+			enum aarch64_insn_register rd;
+			enum aarch64_insn_register rm;
+
+			rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, insn);
+			rm = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RM, insn);
+			if (rd == AARCH64_INSN_REG_FP || rm == AARCH64_INSN_REG_FP) {
+				struct stack_op *op;
+
+				op = arm_make_add_op(rd, rm, 0);
+				if (!op)
+					return -1;
+
+				list_add_tail(&op->list, ops_list);
+			}
+		}
+		break;
 	default:
 		break;
 	}
-- 
2.17.1