From 0f31ea4b42fd0a593d539e2278b1baa35a31a122 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Fri, 16 Feb 2018 13:20:48 -0800 Subject: [PATCH 41/93] nospec: Allow index argument to have const-qualified type commit b98c6a160a057d5686a8c54c79cc6c8c94a7d0c8 upstream. 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 Signed-off-by: Dan Williams Acked-by: Linus Torvalds Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Dave Hansen Cc: David Woodhouse Cc: Greg Kroah-Hartman Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Cc: linux-arch@vger.kernel.org Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/151881604837.17395.10812767547837568328.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- 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 fbc98e2..132e3f5 100644 --- a/include/linux/nospec.h +++ b/include/linux/nospec.h @@ -72,7 +72,6 @@ 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 */ -- 2.7.4