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mm: fix the MAP_UNINITIALIZED flag

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We can't expose UAPI symbols differently based on CONFIG_ symbols, as
userspace won't have them available.  Instead always define the flag,
but only respect it based on the config option.

Link: http://lkml.kernel.org/r/20190703122359.18200-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Hellwig 2019-07-16 16:26:27 -07:00 committed by Linus Torvalds
parent c633324e31
commit 0bf5f94923
3 changed files with 7 additions and 11 deletions
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6
arch/xtensa/include/uapi/asm/mman.h
View File

@ -56,12 +56,8 @@
#define MAP_STACK 0x40000 /* give out an address that is best suited for process/thread stacks */
#define MAP_HUGETLB 0x80000 /* create a huge page mapping */
#define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */
#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED
# define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be
#define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be
* uninitialized */
#else
# define MAP_UNINITIALIZED 0x0 /* Don't support this flag */
#endif
/*
* Flags for msync

8
include/uapi/asm-generic/mman-common.h
View File

@ -19,15 +19,13 @@
#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
/* 0x0100 - 0x80000 flags are defined in asm-generic/mman.h */
#define MAP_FIXED_NOREPLACE 0x100000 /* MAP_FIXED which doesn't unmap underlying mapping */
#define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be
* uninitialized */
/*
* Flags for mlock
*/

4
mm/nommu.c
View File

@ -1261,7 +1261,9 @@ unsigned long do_mmap(struct file *file,
add_nommu_region(region);
/* clear anonymous mappings that don't ask for uninitialized data */
if (!vma->vm_file && !(flags & MAP_UNINITIALIZED))
if (!vma->vm_file &&
(!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
!(flags & MAP_UNINITIALIZED)))
memset((void *)region->vm_start, 0,
region->vm_end - region->vm_start);