From ea637639591def87a54cea811cbac796980cb30d Mon Sep 17 00:00:00 2001 From: Jie Zhang Date: Mon, 14 Dec 2009 18:00:02 -0800 Subject: nommu: fix malloc performance by adding uninitialized flag The NOMMU code currently clears all anonymous mmapped memory. While this is what we want in the default case, all memory allocation from userspace under NOMMU has to go through this interface, including malloc() which is allowed to return uninitialized memory. This can easily be a significant performance penalty. So for constrained embedded systems were security is irrelevant, allow people to avoid clearing memory unnecessarily. This also alters the ELF-FDPIC binfmt such that it obtains uninitialised memory for the brk and stack region. Signed-off-by: Jie Zhang Signed-off-by: Robin Getz Signed-off-by: Mike Frysinger Signed-off-by: David Howells Acked-by: Paul Mundt Acked-by: Greg Ungerer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/mman-common.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/asm-generic') diff --git a/include/asm-generic/mman-common.h b/include/asm-generic/mman-common.h index 5ee13b2fd22..20111265afd 100644 --- a/include/asm-generic/mman-common.h +++ b/include/asm-generic/mman-common.h @@ -19,6 +19,11 @@ #define MAP_TYPE 0x0f /* Mask for type of mapping */ #define MAP_FIXED 0x10 /* Interpret addr exactly */ #define MAP_ANONYMOUS 0x20 /* don't use a file */ +#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED +# define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be uninitialized */ +#else +# define MAP_UNINITIALIZED 0x0 /* Don't support this flag */ +#endif #define MS_ASYNC 1 /* sync memory asynchronously */ #define MS_INVALIDATE 2 /* invalidate the caches */ -- cgit v1.2.3