linux-hardening - [PATCH v4 16/26] arm64: head: factor out TTBR1 assignment into a macro

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Date:   Mon, 13 Jun 2022 16:45:40 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-hardening@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Brown <broonie@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: [PATCH v4 16/26] arm64: head: factor out TTBR1 assignment into a macro

Create a macro load_ttbr1 to avoid having to repeat the same instruction
sequence 3 times in a subsequent patch. No functional change intended.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/arm64/include/asm/assembler.h | 17 +++++++++++++----
 arch/arm64/kernel/head.S           |  5 +----
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 9468f45c07a6..b2584709c332 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -479,6 +479,18 @@ alternative_endif
 	_cond_extable .Licache_op\@, \fixup
 	.endm
 
+/*
+ * load_ttbr1 - install @pgtbl as a TTBR1 page table
+ * pgtbl preserved
+ * tmp1/tmp2 clobbered, either may overlap with pgtbl
+ */
+	.macro		load_ttbr1, pgtbl, tmp1, tmp2
+	phys_to_ttbr	\tmp1, \pgtbl
+	offset_ttbr1 	\tmp1, \tmp2
+	msr		ttbr1_el1, \tmp1
+	isb
+	.endm
+
 /*
  * To prevent the possibility of old and new partial table walks being visible
  * in the tlb, switch the ttbr to a zero page when we invalidate the old
@@ -492,10 +504,7 @@ alternative_endif
 	isb
 	tlbi	vmalle1
 	dsb	nsh
-	phys_to_ttbr \tmp, \page_table
-	offset_ttbr1 \tmp, \tmp2
-	msr	ttbr1_el1, \tmp
-	isb
+	load_ttbr1 \page_table, \tmp, \tmp2
 	.endm
 
 /*
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 64ebff634b83..d704d0bd8ffc 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -722,12 +722,9 @@ SYM_FUNC_START(__enable_mmu)
 	cmp     x3, #ID_AA64MMFR0_TGRAN_SUPPORTED_MAX
 	b.gt    __no_granule_support
 	update_early_cpu_boot_status 0, x3, x4
-	phys_to_ttbr x1, x1
 	phys_to_ttbr x2, x2
 	msr	ttbr0_el1, x2			// load TTBR0
-	offset_ttbr1 x1, x3
-	msr	ttbr1_el1, x1			// load TTBR1
-	isb
+	load_ttbr1 x1, x1, x3
 
 	set_sctlr_el1	x0
 
-- 
2.30.2