linux-kernel - [PATCH] um: Switch to large mcmodel on x86

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Message-Id: <1327432152-26992-1-git-send-email-richard@nod.at>
Date:	Tue, 24 Jan 2012 20:09:12 +0100
From:	Richard Weinberger <richard@....at>
To:	user-mode-linux-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org, Richard Weinberger <richard@....at>
Subject: [PATCH] um: Switch to large mcmodel on x86_64

x86_64 UML is unable to load modules if more than 504MiB
of memory are used.
This happens because on x86_64 the UML process has a quite high
start address (typically around 0x6000000).
If UML's memory is larger than 504MiB VMALLOC_START happens to be after
0x8000000. This is no problem unless one loads a module which was built
with R_X86_64_32S relocations.
Symbols with a location > 0x8000000 cannot be used with R_X86_64_32S

To deal with this x86_64 UML has to be compiled with -mcmodel=large
such that no R_X86_64_32S relocations are used.

Signed-off-by: Richard Weinberger <richard@....at>
Reported-by: 전하늘 <allskyee@...il.com>
---
 arch/um/Makefile |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/um/Makefile b/arch/um/Makefile
index 28688e6..123f073 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -28,6 +28,7 @@ ifeq ($(SUBARCH),i386)
 endif
 ifeq ($(SUBARCH),x86_64)
         HEADER_ARCH := x86
+	KBUILD_CFLAGS += -mcmodel=large
 endif

 HOST_DIR := arch/$(HEADER_ARCH)
-- 
1.7.8.3

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