diff options
| author | Borislav Petkov <bp@alien8.de> | 2015-06-19 13:49:06 +0200 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2015-07-13 08:50:08 -0400 |
| commit | 41a9cc4cdc9f75335731631575632a36c9c96d16 (patch) | |
| tree | 24dad94cba1b54a8efaa740901366896ecb12c2b /arch | |
| parent | 1bbf6a5be19ef725e3887a45ec86a133f13a4426 (diff) | |
x86/boot: Fix overflow warning with 32-bit binutils
[ Upstream commit 04c17341b42699a5859a8afa05e64ba08a4e5235 ]
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: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/head_32.S | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 30a2aa3782fa..e7be5290fe1f 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -61,9 +61,16 @@ #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 |