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Merge "Remove the KSM hack in mmap()." am: f2d59f93e6 am: 7fb7ec2d9f

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Original change: https://android-review.googlesource.com/c/platform/bionic/+/2100544

Change-Id: I7d7593a3167d2e85d1a588f15f703a96b6dda60e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
This commit is contained in:
Elliott Hughes 2022-05-19 00:54:51 +00:00 committed by Automerger Merge Worker
commit 6ea61e4990
1 changed files with 2 additions and 19 deletions
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21
libc/bionic/mmap.cpp
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@ -39,37 +39,20 @@ extern "C" void* __mmap2(void*, size_t, int, int, int, size_t);
#define MMAP2_SHIFT 12 // 2**12 == 4096
static bool kernel_has_MADV_MERGEABLE = true;
void* mmap64(void* addr, size_t size, int prot, int flags, int fd, off64_t offset) {
if (offset < 0 || (offset & ((1UL << MMAP2_SHIFT)-1)) != 0) {
errno = EINVAL;
return MAP_FAILED;
}
// prevent allocations large enough for `end - start` to overflow
// Prevent allocations large enough for `end - start` to overflow.
size_t rounded = __BIONIC_ALIGN(size, PAGE_SIZE);
if (rounded < size || rounded > PTRDIFF_MAX) {
errno = ENOMEM;
return MAP_FAILED;
}
bool is_private_anonymous =
(flags & (MAP_PRIVATE | MAP_ANONYMOUS)) == (MAP_PRIVATE | MAP_ANONYMOUS);
bool is_stack_or_grows_down = (flags & (MAP_STACK | MAP_GROWSDOWN)) != 0;
void* result = __mmap2(addr, size, prot, flags, fd, offset >> MMAP2_SHIFT);
if (result != MAP_FAILED && kernel_has_MADV_MERGEABLE &&
is_private_anonymous && !is_stack_or_grows_down) {
ErrnoRestorer errno_restorer;
int rc = madvise(result, size, MADV_MERGEABLE);
if (rc == -1 && errno == EINVAL) {
kernel_has_MADV_MERGEABLE = false;
}
}
return result;
return __mmap2(addr, size, prot, flags, fd, offset >> MMAP2_SHIFT);
}
void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {