arm64: introduce aarch64_insn_gen_comp_branch_imm()

Introduce function to generate compare & branch (immediate)
instructions.

Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 83 insertions, 5 deletions

diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 92f36835486b..d9f7827c5058 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -2,6 +2,8 @@
  * Copyright (C) 2013 Huawei Ltd.
  * Author: Jiang Liu <liuj97@gmail.com>
  *
+ * Copyright (C) 2014 Zi Shen Lim <zlim.lnx@gmail.com>
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
@@ -23,6 +25,8 @@
 #include <asm/cacheflush.h>
 #include <asm/insn.h>
 
+#define AARCH64_INSN_SF_BIT	BIT(31)
+
 static int aarch64_insn_encoding_class[] = {
 	AARCH64_INSN_CLS_UNKNOWN,
 	AARCH64_INSN_CLS_UNKNOWN,
@@ -264,10 +268,36 @@ u32 __kprobes aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type,
 	return insn;
 }
 
-u32 __kprobes aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr,
-					  enum aarch64_insn_branch_type type)
+static u32 aarch64_insn_encode_register(enum aarch64_insn_register_type type,
+					u32 insn,
+					enum aarch64_insn_register reg)
+{
+	int shift;
+
+	if (reg < AARCH64_INSN_REG_0 || reg > AARCH64_INSN_REG_SP) {
+		pr_err("%s: unknown register encoding %d\n", __func__, reg);
+		return 0;
+	}
+
+	switch (type) {
+	case AARCH64_INSN_REGTYPE_RT:
+		shift = 0;
+		break;
+	default:
+		pr_err("%s: unknown register type encoding %d\n", __func__,
+		       type);
+		return 0;
+	}
+
+	insn &= ~(GENMASK(4, 0) << shift);
+	insn |= reg << shift;
+
+	return insn;
+}
+
+static inline long branch_imm_common(unsigned long pc, unsigned long addr,
+				     long range)
 {
-	u32 insn;
 	long offset;
 
 	/*
@@ -276,13 +306,24 @@ u32 __kprobes aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr,
 	 */
 	BUG_ON((pc & 0x3) || (addr & 0x3));
 
+	offset = ((long)addr - (long)pc);
+	BUG_ON(offset < -range || offset >= range);
+
+	return offset;
+}
+
+u32 __kprobes aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr,
+					  enum aarch64_insn_branch_type type)
+{
+	u32 insn;
+	long offset;
+
 	/*
 	 * B/BL support [-128M, 128M) offset
 	 * ARM64 virtual address arrangement guarantees all kernel and module
 	 * texts are within +/-128M.
 	 */
-	offset = ((long)addr - (long)pc);
-	BUG_ON(offset < -SZ_128M || offset >= SZ_128M);
+	offset = branch_imm_common(pc, addr, SZ_128M);
 
 	if (type == AARCH64_INSN_BRANCH_LINK)
 		insn = aarch64_insn_get_bl_value();
@@ -293,6 +334,43 @@ u32 __kprobes aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr,
 					     offset >> 2);
 }
 
+u32 aarch64_insn_gen_comp_branch_imm(unsigned long pc, unsigned long addr,
+				     enum aarch64_insn_register reg,
+				     enum aarch64_insn_variant variant,
+				     enum aarch64_insn_branch_type type)
+{
+	u32 insn;
+	long offset;
+
+	offset = branch_imm_common(pc, addr, SZ_1M);
+
+	switch (type) {
+	case AARCH64_INSN_BRANCH_COMP_ZERO:
+		insn = aarch64_insn_get_cbz_value();
+		break;
+	case AARCH64_INSN_BRANCH_COMP_NONZERO:
+		insn = aarch64_insn_get_cbnz_value();
+		break;
+	default:
+		BUG_ON(1);
+	}
+
+	switch (variant) {
+	case AARCH64_INSN_VARIANT_32BIT:
+		break;
+	case AARCH64_INSN_VARIANT_64BIT:
+		insn |= AARCH64_INSN_SF_BIT;
+		break;
+	default:
+		BUG_ON(1);
+	}
+
+	insn = aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RT, insn, reg);
+
+	return aarch64_insn_encode_immediate(AARCH64_INSN_IMM_19, insn,
+					     offset >> 2);
+}
+
 u32 __kprobes aarch64_insn_gen_hint(enum aarch64_insn_hint_op op)
 {
 	return aarch64_insn_get_hint_value() | op;