linux-kernel - [RFC PATCH 10/16] arm64/insn: always inline aarch64_insn_gen_branch

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Message-ID: <20250923174903.76283-11-ada.coupriediaz@arm.com>
Date: Tue, 23 Sep 2025 18:48:57 +0100
From: Ada Couprie Diaz <ada.coupriediaz@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Ard Biesheuvel <ardb@...nel.org>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev,
	kasan-dev@...glegroups.com,
	Mark Rutland <mark.rutland@....com>,
	Ada Couprie Diaz <ada.coupriediaz@....com>
Subject: [RFC PATCH 10/16] arm64/insn: always inline aarch64_insn_gen_branch_reg()

As it is always called with an explicit instruction branch type, we can
check for its validity at compile time and remove the runtime error print.

This makes `aarch64_insn_gen_branch_reg()` safe for inlining
and usage from patching callbacks, as `aarch64_insn_encode_register()`
has been made safe in a previous commit.

Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@....com>
---
 arch/arm64/include/asm/insn.h | 28 ++++++++++++++++++++++++++--
 arch/arm64/lib/insn.c         | 23 -----------------------
 2 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index a7caafd6f02b..6e6a53d4d750 100644
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -760,8 +760,32 @@ static __always_inline bool aarch64_insn_is_nop(u32 insn)
 	return insn == aarch64_insn_gen_nop();
 }
 
-u32 aarch64_insn_gen_branch_reg(enum aarch64_insn_register reg,
-				enum aarch64_insn_branch_type type);
+static __always_inline u32 aarch64_insn_gen_branch_reg(
+			 enum aarch64_insn_register reg,
+			 enum aarch64_insn_branch_type type)
+{
+	compiletime_assert(type >= AARCH64_INSN_BRANCH_NOLINK &&
+		type <= AARCH64_INSN_BRANCH_RETURN,
+		"unknown branch encoding");
+	u32 insn;
+
+	switch (type) {
+	case AARCH64_INSN_BRANCH_NOLINK:
+		insn = aarch64_insn_get_br_value();
+		break;
+	case AARCH64_INSN_BRANCH_LINK:
+		insn = aarch64_insn_get_blr_value();
+		break;
+	case AARCH64_INSN_BRANCH_RETURN:
+		insn = aarch64_insn_get_ret_value();
+		break;
+	default:
+		return AARCH64_BREAK_FAULT;
+	}
+
+	return aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RN, insn, reg);
+}
+
 u32 aarch64_insn_gen_load_store_reg(enum aarch64_insn_register reg,
 				    enum aarch64_insn_register base,
 				    enum aarch64_insn_register offset,
diff --git a/arch/arm64/lib/insn.c b/arch/arm64/lib/insn.c
index 34b6f1c692b4..8d38bf4bf203 100644
--- a/arch/arm64/lib/insn.c
+++ b/arch/arm64/lib/insn.c
@@ -178,29 +178,6 @@ u32 aarch64_insn_gen_cond_branch_imm(unsigned long pc, unsigned long addr,
 					     offset >> 2);
 }
 
-u32 aarch64_insn_gen_branch_reg(enum aarch64_insn_register reg,
-				enum aarch64_insn_branch_type type)
-{
-	u32 insn;
-
-	switch (type) {
-	case AARCH64_INSN_BRANCH_NOLINK:
-		insn = aarch64_insn_get_br_value();
-		break;
-	case AARCH64_INSN_BRANCH_LINK:
-		insn = aarch64_insn_get_blr_value();
-		break;
-	case AARCH64_INSN_BRANCH_RETURN:
-		insn = aarch64_insn_get_ret_value();
-		break;
-	default:
-		pr_err("%s: unknown branch encoding %d\n", __func__, type);
-		return AARCH64_BREAK_FAULT;
-	}
-
-	return aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RN, insn, reg);
-}
-
 u32 aarch64_insn_gen_load_store_reg(enum aarch64_insn_register reg,
 				    enum aarch64_insn_register base,
 				    enum aarch64_insn_register offset,
-- 
2.43.0