Commit-ID: 04c17341b42699a5859a8afa05e64ba08a4e5235 Gitweb: http://git.kernel.org/tip/04c17341b42699a5859a8afa05e64ba08a4e5235 Author: Borislav Petkov <bp@xxxxxxxxx> AuthorDate: Fri, 19 Jun 2015 13:49:06 +0200 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Fri, 19 Jun 2015 16:03:26 +0200 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@xxxxxxx> Reported-and-tested-by: Enrico Mioso <mrkiko.rs@xxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/kernel/head_32.S | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 53eeb22..7e429c9 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 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
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