Commit 851140ab authored Oct 02, 2019 by Masahiro Yamada Committed by Russell King Oct 10, 2019

ARM: 8908/1: add __always_inline to functions called from __get_user_check()

KernelCI reports that bcm2835_defconfig is no longer booting since
commit ac7c3e4f ("compiler: enable CONFIG_OPTIMIZE_INLINING
forcibly") (https://lkml.org/lkml/2019/9/26/825).

I also received a regression report from Nicolas Saenz Julienne
(https://lkml.org/lkml/2019/9/27/263

).

This problem has cropped up on bcm2835_defconfig because it enables
CONFIG_CC_OPTIMIZE_FOR_SIZE. The compiler tends to prefer not inlining
functions with -Os. I was able to reproduce it with other boards and
defconfig files by manually enabling CONFIG_CC_OPTIMIZE_FOR_SIZE.

The __get_user_check() specifically uses r0, r1, r2 registers.
So, uaccess_save_and_enable() and uaccess_restore() must be inlined.
Otherwise, those register assignments would be entirely dropped,
according to my analysis of the disassembly.

Prior to commit 9012d011 ("compiler: allow all arches to enable
CONFIG_OPTIMIZE_INLINING"), the 'inline' marker was always enough for
inlining functions, except on x86.

Since that commit, all architectures can enable CONFIG_OPTIMIZE_INLINING.
So, __always_inline is now the only guaranteed way of forcible inlining.

I added __always_inline to 4 functions in the call-graph from the
__get_user_check() macro.

Fixes: 9012d011 ("compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Reported-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

parent 1bb9fb0a

arch/arm/include/asm/domain.h

+4 −4

Original line number	Diff line number	Diff line
		@@ -82,7 +82,7 @@
		#ifndef __ASSEMBLY__

		#ifdef CONFIG_CPU_CP15_MMU
		static inline unsigned int get_domain(void)
		static __always_inline unsigned int get_domain(void)
		{
		unsigned int domain;

		@@ -94,7 +94,7 @@ static inline unsigned int get_domain(void)
		return domain;
		}

		static inline void set_domain(unsigned val)
		static __always_inline void set_domain(unsigned int val)
		{
		asm volatile(
		"mcr p15, 0, %0, c3, c0 @ set domain"
		@@ -102,12 +102,12 @@ static inline void set_domain(unsigned val)
		isb();
		}
		#else
		static inline unsigned int get_domain(void)
		static __always_inline unsigned int get_domain(void)
		{
		return 0;
		}

		static inline void set_domain(unsigned val)
		static __always_inline void set_domain(unsigned int val)
		{
		}
		#endif

arch/arm/include/asm/uaccess.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -22,7 +22,7 @@
		* perform such accesses (eg, via list poison values) which could then
		* be exploited for priviledge escalation.
		*/
		static inline unsigned int uaccess_save_and_enable(void)
		static __always_inline unsigned int uaccess_save_and_enable(void)
		{
		#ifdef CONFIG_CPU_SW_DOMAIN_PAN
		unsigned int old_domain = get_domain();
		@@ -37,7 +37,7 @@ static inline unsigned int uaccess_save_and_enable(void)
		#endif
		}

		static inline void uaccess_restore(unsigned int flags)
		static __always_inline void uaccess_restore(unsigned int flags)
		{
		#ifdef CONFIG_CPU_SW_DOMAIN_PAN
		/* Restore the user access mask */

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