linux-kernel - [PATCH] ARM: mm: proc-macros: ensure *_tlb

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Date:   Wed, 29 Sep 2021 12:08:05 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Fangrui Song <maskray@...gle.com>,
        Peter Smith <peter.smith@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Richard Henderson <richard.henderson@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mike Rapoport <rppt@...nel.org>,
        YiFei Zhu <yifeifz2@...inois.edu>,
        "Uwe Kleine-König" 
        <u.kleine-koenig@...gutronix.de>,
        Dave Martin <dave.martin@...aro.org>,
        Nicolas Pitre <nico@...xnic.net>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: [PATCH] ARM: mm: proc-macros: ensure *_tlb_fns are 4B aligned

QEMU 6.1.0 is more correct about trapping on misaligned accesses. A
kernel built with CONFIG_THUMB2_KERNEL=y and using clang as the
assembler could generate non-naturally-aligned v7wbi_tlb_fns which
results in a boot failure. The original commit adding the macro missed
the .align directive on this data.

Fixes: 66a625a88174 ("ARM: mm: proc-macros: Add generic proc/cache/tlb struct definition macros")
Link: https://github.com/ClangBuiltLinux/linux/issues/1447
Link: https://lore.kernel.org/all/0699da7b-354f-aecc-a62f-e25693209af4@linaro.org/
Debugged-by: Ard Biesheuvel <ardb@...nel.org>
Debugged-by: Nathan Chancellor <nathan@...nel.org>
Debugged-by: Richard Henderson <richard.henderson@...aro.org>
Suggested-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 arch/arm/Kconfig          | 1 +
 arch/arm/mm/proc-macros.S | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index fc196421b2ce..b760dd45b734 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -92,6 +92,7 @@ config ARM
 	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
 	select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG
 	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
+	select HAVE_FUTEX_CMPXCHG if FUTEX
 	select HAVE_GCC_PLUGINS
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7)
 	select HAVE_IRQ_TIME_ACCOUNTING
diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index e2c743aa2eb2..d9f7dfe2a7ed 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -340,6 +340,7 @@ ENTRY(\name\()_cache_fns)
 
 .macro define_tlb_functions name:req, flags_up:req, flags_smp
 	.type	\name\()_tlb_fns, #object
+	.align 2
 ENTRY(\name\()_tlb_fns)
 	.long	\name\()_flush_user_tlb_range
 	.long	\name\()_flush_kern_tlb_range
-- 
2.33.0.685.g46640cef36-goog