linux-kernel - [PATCH 4.4 36/43] x86/build/64: Force the linker to use 2MB page size

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Message-Id: <20180327162718.436018102@linuxfoundation.org>
Date:   Tue, 27 Mar 2018 18:27:40 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "H.J. Lu" <hjl.tools@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>, Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.4 36/43] x86/build/64: Force the linker to use 2MB page size

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: H.J. Lu <hjl.tools@...il.com>

commit e3d03598e8ae7d195af5d3d049596dec336f569f upstream.

Binutils 2.31 will enable -z separate-code by default for x86 to avoid
mixing code pages with data to improve cache performance as well as
security.  To reduce x86-64 executable and shared object sizes, the
maximum page size is reduced from 2MB to 4KB.  But x86-64 kernel must
be aligned to 2MB.  Pass -z max-page-size=0x200000 to linker to force
2MB page size regardless of the default page size used by linker.

Tested with Linux kernel 4.15.6 on x86-64.

Signed-off-by: H.J. Lu <hjl.tools@...il.com>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Eric Biederman <ebiederm@...ssion.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/CAMe9rOp4_%3D_8twdpTyAP2DhONOCeaTOsniJLoppzhoNptL8xzA@mail.gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/Makefile |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -179,6 +179,15 @@ KBUILD_CFLAGS += $(cfi) $(cfi-sigframe)

 LDFLAGS := -m elf_$(UTS_MACHINE)

+#
+# The 64-bit kernel must be aligned to 2MB.  Pass -z max-page-size=0x200000 to
+# the linker to force 2MB page size regardless of the default page size used
+# by the linker.
+#
+ifdef CONFIG_X86_64
+LDFLAGS += $(call ld-option, -z max-page-size=0x200000)
+endif
+
 # Speed up the build
 KBUILD_CFLAGS += -pipe
 # Workaround for a gcc prelease that unfortunately was shipped in a suse release