linux-hardening - [PATCH v5 14/32] ARM: use TLS register for 'current' on !SMP as well

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Date:   Mon, 24 Jan 2022 18:47:26 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux@...linux.org.uk, linux-arm-kernel@...ts.infradead.org
Cc:     linux-hardening@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Nicolas Pitre <nico@...xnic.net>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Keith Packard <keithpac@...zon.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tony Lindgren <tony@...mide.com>,
        Marc Zyngier <maz@...nel.org>,
        Vladimir Murzin <vladimir.murzin@....com>,
        Jesse Taube <mr.bossman075@...il.com>
Subject: [PATCH v5 14/32] ARM: use TLS register for 'current' on !SMP as well

Enable the use of the TLS register to hold the 'current' pointer also on
non-SMP configurations that target v6k or later CPUs. This will permit
the use of THREAD_INFO_IN_TASK as well as IRQ stacks and vmap'ed stacks
for such configurations.

Acked-by: Linus Walleij <linus.walleij@...aro.org>
Acked-by: Nicolas Pitre <nico@...xnic.net>
Acked-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Tested-by: Marc Zyngier <maz@...nel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@....com> # ARMv7M
---
 arch/arm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 9586636289d2..0e1b93de10b4 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1163,7 +1163,7 @@ config SMP_ON_UP
 
 config CURRENT_POINTER_IN_TPIDRURO
 	def_bool y
-	depends on SMP && CPU_32v6K && !CPU_V6
+	depends on CPU_32v6K && !CPU_V6
 
 config ARM_CPU_TOPOLOGY
 	bool "Support cpu topology definition"
-- 
2.30.2