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| author | Borislav Petkov <bp@alien8.de> | 2015-06-19 14:49:06 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-06-19 17:03:26 +0300 |
| commit | 04c17341b42699a5859a8afa05e64ba08a4e5235 (patch) | |
| tree | 1ff96306cb7c57b1658f02b68bbcfd80142036c4 | |
| parent | 0f57d86787d8b1076ea8f9cbdddda2a46d534a27 (diff) | |
| download | linux-04c17341b42699a5859a8afa05e64ba08a4e5235.tar.xz | |
x86/boot: Fix overflow warning with 32-bit binutils
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>
| -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 53eeb226657c..7e429c99c728 100644 --- 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 |