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Subject[PATCH 4.15 089/105] x86/build/64: Force the linker to use 2MB page size
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

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

From: H.J. Lu <hjl.tools@gmail.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@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/CAMe9rOp4_%3D_8twdpTyAP2DhONOCeaTOsniJLoppzhoNptL8xzA@mail.gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -223,6 +223,15 @@ 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

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