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Bug 828894 - Fix possible off-by-one-page in custom linker. r=nfroyd

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--HG--
extra : rebase_source : 7bdafcec8108b001bf2b817bd2c4b293a0dbee2e
This commit is contained in:
Mike Hommey 2013-01-11 12:24:31 +01:00
parent 3fd6510a59
commit 002fb23a0e
1 changed files with 6 additions and 5 deletions
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11
mozglue/linker/Mappable.cpp
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@ -197,12 +197,13 @@ public:
/* The Gecko crash reporter is confused by adjacent memory mappings of
* the same file. On Android, subsequent mappings are growing in memory
* address, and chances are we're going to map from the same file
* descriptor right away. Allocate one page more than requested so that
* there is a gap between this mapping and the subsequent one. */
* descriptor right away. To avoid problems with the crash reporter,
* create an empty anonymous page after the ashmem mapping. To do so,
* allocate one page more than requested, then replace the last page with
* an anonymous mapping. */
void *buf = ::mmap(NULL, length + PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (buf != MAP_FAILED) {
/* Actually create the gap with anonymous memory */
::mmap(reinterpret_cast<char *>(buf) + ((length + PAGE_SIZE) & PAGE_MASK),
::mmap(reinterpret_cast<char *>(buf) + ((length + PAGE_SIZE - 1) & PAGE_MASK),
PAGE_SIZE, PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
-1, 0);
debug("Decompression buffer of size %d in ashmem \"%s\", mapped @%p",
@ -248,7 +249,7 @@ public:
#ifdef ANDROID
~_MappableBuffer() {
/* Free the additional page we allocated. See _MappableBuffer::Create */
::munmap(*this + ((GetLength() + PAGE_SIZE) & ~(PAGE_SIZE - 1)), PAGE_SIZE);
::munmap(*this + ((GetLength() + PAGE_SIZE - 1) & PAGE_MASK), PAGE_SIZE);
}
#endif