Patch "x86/boot: Fix overflow warning with 32-bit binutils" has been added to the 4.1-stable tree

Patch "x86/boot: Fix overflow warning with 32-bit binutils" has been added to the 4.1-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    x86/boot: Fix overflow warning with 32-bit binutils

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-boot-fix-overflow-warning-with-32-bit-binutils.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 04c17341b42699a5859a8afa05e64ba08a4e5235 Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@alien8.de>
Date: Fri, 19 Jun 2015 13:49:06 +0200
Subject: x86/boot: Fix overflow warning with 32-bit binutils

From: Borislav Petkov <bp@alien8.de>

commit 04c17341b42699a5859a8afa05e64ba08a4e5235 upstream.

When building the kernel with 32-bit binutils built with support
only for the i386 target, we get the following warning:

  arch/x86/kernel/head_32.S:66: Warning: shift count out of range (32 is not between 0 and 31)

The problem is that in that case, binutils' internal type
representation is 32-bit wide and the shift range overflows.

In order to fix this, manipulate the shift expression which
creates the 4GiB constant to not overflow the shift count.

Suggested-by: Michael Matz <matz@suse.de>
Reported-and-tested-by: Enrico Mioso <mrkiko.rs@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kernel/head_32.S |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -62,9 +62,16 @@
 #define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
 #endif
 
-/* Number of possible pages in the lowmem region */
-LOWMEM_PAGES = (((1<<32) - __PAGE_OFFSET) >> PAGE_SHIFT)
-	
+/*
+ * Number of possible pages in the lowmem region.
+ *
+ * We shift 2 by 31 instead of 1 by 32 to the left in order to avoid a
+ * gas warning about overflowing shift count when gas has been compiled
+ * with only a host target support using a 32-bit type for internal
+ * representation.
+ */
+LOWMEM_PAGES = (((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT)
+
 /* Enough space to fit pagetables for the low memory linear map */
 MAPPING_BEYOND_END = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT
 


Patches currently in stable-queue which might be from bp@alien8.de are

queue-4.1/x86-boot-fix-overflow-warning-with-32-bit-binutils.patch