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From: Will Deacon <will@kernel.org>
To: torvalds@linux-foundation.org, yamada.masahiro@socionext.com
Cc: Arnd Bergmann <arnd@arndb.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Will Deacon <will@kernel.org>,
	Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Subject: [PATCH] Partially revert "compiler: enable CONFIG_OPTIMIZE_INLINING forcibly"
Date: Mon, 30 Sep 2019 12:45:40 +0100	[thread overview]
Message-ID: <20190930114540.27498-1-will@kernel.org> (raw)

This reverts commit ac7c3e4ff401b304489a031938dbeaab585bfe0a for ARM and
arm64.

Building an arm64 kernel with CONFIG_OPTIMIZE_INLINING=y has been shown
to violate fixed register allocations of local variables passed to
inline assembly with GCC prior to version 9 which can lead to subtle
failures at runtime:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91111

A very similar has been reported for 32-bit ARM as well:

  https://lkml.kernel.org/r/f5c221f5749e5768c9f0d909175a14910d349456.camel@suse.de

Although GCC 9.1 appears to work for the specific case in the bugzilla
above, the exact issue has not been root-caused so play safe and disable
the option for now on these architectures.

Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>,
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will@kernel.org>
---
 lib/Kconfig.debug | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 93d97f9b0157..c37c72adaeff 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -312,6 +312,7 @@ config HEADERS_CHECK
 
 config OPTIMIZE_INLINING
 	def_bool y
+	depends on !(ARM || ARM64) # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91111
 	help
 	  This option determines if the kernel forces gcc to inline the functions
 	  developers have marked 'inline'. Doing so takes away freedom from gcc to
-- 
2.23.0.444.g18eeb5a265-goog


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WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org>
To: torvalds@linux-foundation.org, yamada.masahiro@socionext.com
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
	Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH] Partially revert "compiler: enable CONFIG_OPTIMIZE_INLINING forcibly"
Date: Mon, 30 Sep 2019 12:45:40 +0100	[thread overview]
Message-ID: <20190930114540.27498-1-will@kernel.org> (raw)

This reverts commit ac7c3e4ff401b304489a031938dbeaab585bfe0a for ARM and
arm64.

Building an arm64 kernel with CONFIG_OPTIMIZE_INLINING=y has been shown
to violate fixed register allocations of local variables passed to
inline assembly with GCC prior to version 9 which can lead to subtle
failures at runtime:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91111

A very similar has been reported for 32-bit ARM as well:

  https://lkml.kernel.org/r/f5c221f5749e5768c9f0d909175a14910d349456.camel@suse.de

Although GCC 9.1 appears to work for the specific case in the bugzilla
above, the exact issue has not been root-caused so play safe and disable
the option for now on these architectures.

Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>,
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will@kernel.org>
---
 lib/Kconfig.debug | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 93d97f9b0157..c37c72adaeff 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -312,6 +312,7 @@ config HEADERS_CHECK
 
 config OPTIMIZE_INLINING
 	def_bool y
+	depends on !(ARM || ARM64) # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91111
 	help
 	  This option determines if the kernel forces gcc to inline the functions
 	  developers have marked 'inline'. Doing so takes away freedom from gcc to
-- 
2.23.0.444.g18eeb5a265-goog


             reply	other threads:[~2019-09-30 11:45 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-30 11:45 Will Deacon [this message]
2019-09-30 11:45 ` [PATCH] Partially revert "compiler: enable CONFIG_OPTIMIZE_INLINING forcibly" Will Deacon
2019-10-01  9:40 ` Masahiro Yamada
2019-10-01  9:40   ` Masahiro Yamada
2019-10-01 10:42   ` Will Deacon
2019-10-01 10:42     ` Will Deacon
2019-10-01 11:41     ` Andrew Murray
2019-10-01 11:41       ` Andrew Murray
2019-10-01 14:36       ` Russell King - ARM Linux admin
2019-10-01 14:36         ` Russell King - ARM Linux admin
2019-10-01 15:28         ` Andrew Murray
2019-10-01 15:28           ` Andrew Murray
2019-10-01 15:48           ` Russell King - ARM Linux admin
2019-10-01 15:48             ` Russell King - ARM Linux admin
2019-10-01 16:14             ` Andrew Murray
2019-10-01 16:14               ` Andrew Murray
2019-10-01 16:21     ` Nick Desaulniers
2019-10-01 16:21       ` Nick Desaulniers
2019-10-01 17:12       ` Will Deacon
2019-10-01 17:12         ` Will Deacon

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