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Subject[RFC PATCH 08/17] objtool: arm64: Decode load/store instructions
Date
Decode load/store operations and create corresponding stack_ops for
operations targetting SP or FP.

Operations storing/loading multiple registers are split into separate
stack_ops storing single registers.

Operations modifying the base register get an additional stack_op
for the register update. Since the atomic register(s) load/store + base
register update gets split into multiple operations, to make sure
objtool always sees a valid stack, consider store instruction to perform
stack allocations (i.e. modifying the base pointer before the storing)
and loads de-allocations (i.e. modifying the base pointer after the
load).

Signed-off-by: Julien Thierry <jthierry@redhat.com>
---
tools/objtool/arch/arm64/decode.c | 127 ++++++++++++++++++++++++++++++
1 file changed, 127 insertions(+)

diff --git a/tools/objtool/arch/arm64/decode.c b/tools/objtool/arch/arm64/decode.c
index a4a587c400a1..1087ede67bcd 100644
--- a/tools/objtool/arch/arm64/decode.c
+++ b/tools/objtool/arch/arm64/decode.c
@@ -105,6 +105,40 @@ int arch_decode_hint_reg(struct instruction *insn, u8 sp_reg)
return -1;
}

+static struct stack_op *arm_make_store_op(enum aarch64_insn_register base,
+ enum aarch64_insn_register reg,
+ int offset)
+{
+ struct stack_op *op;
+
+ op = calloc(1, sizeof(*op));
+ op->dest.type = OP_DEST_REG_INDIRECT;
+ op->dest.reg = base;
+ op->dest.offset = offset;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = reg;
+ op->src.offset = 0;
+
+ return op;
+}
+
+static struct stack_op *arm_make_load_op(enum aarch64_insn_register base,
+ enum aarch64_insn_register reg,
+ int offset)
+{
+ struct stack_op *op;
+
+ op = calloc(1, sizeof(*op));
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = reg;
+ op->dest.offset = 0;
+ op->src.type = OP_SRC_REG_INDIRECT;
+ op->src.reg = base;
+ op->src.offset = offset;
+
+ return op;
+}
+
static struct stack_op *arm_make_add_op(enum aarch64_insn_register dest,
enum aarch64_insn_register src,
int val)
@@ -121,6 +155,94 @@ static struct stack_op *arm_make_add_op(enum aarch64_insn_register dest,
return op;
}

+static bool arm_decode_load_store(u32 insn, enum insn_type *type,
+ unsigned long *immediate,
+ struct list_head *ops_list)
+{
+ enum aarch64_insn_register base;
+ enum aarch64_insn_register rt;
+ struct stack_op *op;
+ int size;
+ int offset;
+
+ *type = INSN_OTHER;
+
+ if (aarch64_insn_is_store_single(insn) ||
+ aarch64_insn_is_load_single(insn))
+ size = 1 << ((insn & GENMASK(31, 30)) >> 30);
+ else
+ size = 4 << ((insn >> 31) & 1);
+
+ if (aarch64_insn_is_store_imm(insn) || aarch64_insn_is_load_imm(insn))
+ *immediate = size * aarch64_insn_decode_immediate(AARCH64_INSN_IMM_12,
+ insn);
+ else if (aarch64_insn_is_store_pre(insn) ||
+ aarch64_insn_is_load_pre(insn) ||
+ aarch64_insn_is_store_post(insn) ||
+ aarch64_insn_is_load_post(insn))
+ *immediate = sign_extend(aarch64_insn_decode_immediate(AARCH64_INSN_IMM_9,
+ insn),
+ 9);
+ else if (aarch64_insn_is_stp(insn) || aarch64_insn_is_ldp(insn) ||
+ aarch64_insn_is_stp_pre(insn) ||
+ aarch64_insn_is_ldp_pre(insn) ||
+ aarch64_insn_is_stp_post(insn) ||
+ aarch64_insn_is_ldp_post(insn))
+ *immediate = size * sign_extend(aarch64_insn_decode_immediate(AARCH64_INSN_IMM_7,
+ insn),
+ 7);
+ else
+ return false;
+
+ base = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RN, insn);
+ if (base != AARCH64_INSN_REG_FP && base != AARCH64_INSN_REG_SP)
+ return true;
+
+ offset = *immediate;
+
+ if (aarch64_insn_is_store_pre(insn) || aarch64_insn_is_stp_pre(insn) ||
+ aarch64_insn_is_store_post(insn) || aarch64_insn_is_stp_post(insn)) {
+ op = arm_make_add_op(base, base, *immediate);
+ list_add_tail(&op->list, ops_list);
+
+ if (aarch64_insn_is_store_post(insn) || aarch64_insn_is_stp_post(insn))
+ offset = -*immediate;
+ else
+ offset = 0;
+ } else if (aarch64_insn_is_load_post(insn) || aarch64_insn_is_ldp_post(insn)) {
+ offset = 0;
+ }
+
+ /* First register */
+ rt = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RT, insn);
+ if (aarch64_insn_is_store_single(insn) ||
+ aarch64_insn_is_store_pair(insn))
+ op = arm_make_store_op(base, rt, offset);
+ else
+ op = arm_make_load_op(base, rt, offset);
+ list_add_tail(&op->list, ops_list);
+
+ /* Second register (if present) */
+ if (aarch64_insn_is_store_pair(insn) ||
+ aarch64_insn_is_load_pair(insn)) {
+ rt = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RT2,
+ insn);
+ if (aarch64_insn_is_store_pair(insn))
+ op = arm_make_store_op(base, rt, offset + size);
+ else
+ op = arm_make_load_op(base, rt, offset + size);
+ list_add_tail(&op->list, ops_list);
+ }
+
+ if (aarch64_insn_is_load_pre(insn) || aarch64_insn_is_ldp_pre(insn) ||
+ aarch64_insn_is_load_post(insn) || aarch64_insn_is_ldp_post(insn)) {
+ op = arm_make_add_op(base, base, *immediate);
+ list_add_tail(&op->list, ops_list);
+ }
+
+ return true;
+}
+
static void arm_decode_add_sub_imm(u32 instr, bool set_flags,
enum insn_type *type,
unsigned long *immediate,
@@ -234,6 +356,11 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
*type = INSN_OTHER;
}
break;
+ case AARCH64_INSN_CLS_LDST:
+ if (arm_decode_load_store(insn, type, immediate, ops_list))
+ break;
+ *type = INSN_OTHER;
+ break;
default:
*type = INSN_OTHER;
break;
--
2.25.4
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