Commit-ID: b98c6a160a057d5686a8c54c79cc6c8c94a7d0c8 Gitweb: https://git.kernel.org/tip/b98c6a160a057d5686a8c54c79cc6c8c94a7d0c8 Author: Rasmus Villemoes <[email protected]> AuthorDate: Fri, 16 Feb 2018 13:20:48 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Sat, 17 Feb 2018 08:40:59 +0100
nospec: Allow index argument to have const-qualified type The last expression in a statement expression need not be a bare variable, quoting gcc docs The last thing in the compound statement should be an expression followed by a semicolon; the value of this subexpression serves as the value of the entire construct. and we already use that in e.g. the min/max macros which end with a ternary expression. This way, we can allow index to have const-qualified type, which will in some cases avoid the need for introducing a local copy of index of non-const qualified type. That, in turn, can prevent readers not familiar with the internals of array_index_nospec from wondering about the seemingly redundant extra variable, and I think that's worthwhile considering how confusing the whole _nospec business is. The expression _i&_mask has type unsigned long (since that is the type of _mask, and the BUILD_BUG_ONs guarantee that _i will get promoted to that), so in order not to change the type of the whole expression, add a cast back to typeof(_i). Signed-off-by: Rasmus Villemoes <[email protected]> Signed-off-by: Dan Williams <[email protected]> Acked-by: Linus Torvalds <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Arjan van de Ven <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Hansen <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Will Deacon <[email protected]> Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/151881604837.17395.10812767547837568328.st...@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar <[email protected]> --- include/linux/nospec.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/include/linux/nospec.h b/include/linux/nospec.h index d6701e3..172a19d 100644 --- a/include/linux/nospec.h +++ b/include/linux/nospec.h @@ -52,7 +52,6 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \ BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \ \ - _i &= _mask; \ - _i; \ + (typeof(_i)) (_i & _mask); \ }) #endif /* _LINUX_NOSPEC_H */
