arm64: Add helper to decode register from instruction

Add a helper to extract the register field from a given
instruction.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index bc85366..aecc07e 100644 (file)
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -332,6 +332,8 @@ bool aarch64_insn_is_branch(u32 insn);
 u64 aarch64_insn_decode_immediate(enum aarch64_insn_imm_type type, u32 insn);
 u32 aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
                                  u32 insn, u64 imm);
+u32 aarch64_insn_decode_register(enum aarch64_insn_register_type type,
+                                        u32 insn);
 u32 aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr,
                                enum aarch64_insn_branch_type type);
 u32 aarch64_insn_gen_comp_branch_imm(unsigned long pc, unsigned long addr,

diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 94b62c1..1f44cf8 100644 (file)
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -417,6 +417,35 @@ u32 __kprobes aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
        return insn;
 }
 
+u32 aarch64_insn_decode_register(enum aarch64_insn_register_type type,
+                                       u32 insn)
+{
+       int shift;
+
+       switch (type) {
+       case AARCH64_INSN_REGTYPE_RT:
+       case AARCH64_INSN_REGTYPE_RD:
+               shift = 0;
+               break;
+       case AARCH64_INSN_REGTYPE_RN:
+               shift = 5;
+               break;
+       case AARCH64_INSN_REGTYPE_RT2:
+       case AARCH64_INSN_REGTYPE_RA:
+               shift = 10;
+               break;
+       case AARCH64_INSN_REGTYPE_RM:
+               shift = 16;
+               break;
+       default:
+               pr_err("%s: unknown register type encoding %d\n", __func__,
+                      type);
+               return 0;
+       }
+
+       return (insn >> shift) & GENMASK(4, 0);
+}
+
 static u32 aarch64_insn_encode_register(enum aarch64_insn_register_type type,
                                        u32 insn,
                                        enum aarch64_insn_register reg)