linux-kernel - [018/127] um: remove PAGE_SIZE alignment in linker script causing kernel segfault.

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Date:	Tue, 07 Dec 2010 16:43:24 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Tim Abbott <tabbott@...lice.com>, Jeff Dike <jdike@...toit.com>
Subject: [018/127] um: remove PAGE_SIZE alignment in linker script causing kernel segfault.

2.6.32-stable review patch.  If anyone has any objections, please let us know.

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

From: Richard Weinberger <richard@....at>

commit 6915e04f8847bea16d0890f559694ad8eedd026c upstream.

The linker script cleanup that I did in commit 5d150a97f93 ("um: Clean up
linker script using standard macros.") (2.6.32) accidentally introduced an
ALIGN(PAGE_SIZE) when converting to use INIT_TEXT_SECTION; Richard
Weinberger reported that this causes the kernel to segfault with
CONFIG_STATIC_LINK=y.

I'm not certain why this extra alignment is a problem, but it seems likely
it is because previously

__init_begin = _stext = _text = _sinittext

and with the extra ALIGN(PAGE_SIZE), _sinittext becomes different from the
rest.  So there is likely a bug here where something is assuming that
_sinittext is the same as one of those other symbols.  But reverting the
accidental change fixes the regression, so it seems worth committing that
now.

Signed-off-by: Tim Abbott <tabbott@...lice.com>
Reported-by: Richard Weinberger <richard@....at>
Cc: Jeff Dike <jdike@...toit.com>
Tested by: Antoine Martin <antoine@...afix.co.uk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/um/kernel/uml.lds.S |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/um/kernel/uml.lds.S
+++ b/arch/um/kernel/uml.lds.S
@@ -22,7 +22,7 @@ SECTIONS
   _text = .;
   _stext = .;
   __init_begin = .;
-  INIT_TEXT_SECTION(PAGE_SIZE)
+  INIT_TEXT_SECTION(0)
   . = ALIGN(PAGE_SIZE);
 
   .text      :


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