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Bug 910845 - Add a wrapper for mmap() in order to keep the high 17-bits of JS pointers cleared on IA64. r=billm

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This commit is contained in:
Stephan Schreiber 2013-09-09 08:57:37 -04:00
parent 2e005c04f6
commit 072d82c472
1 changed files with 40 additions and 3 deletions
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43
js/src/gc/Memory.cpp
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@ -143,7 +143,7 @@ gc::UnmapPages(JSRuntime *rt, void *addr, size_t size)
}
static void *
gc::MapAlignedPagesRecursively(JSRuntime *rt, size_t size, size_t alignment, int& recursions)
MapAlignedPagesRecursively(JSRuntime *rt, size_t size, size_t alignment, int& recursions)
{
if (++recursions >= OS2_MAX_RECURSIONS)
return NULL;
@ -309,6 +309,40 @@ gc::InitMemorySubsystem(JSRuntime *rt)
rt->gcSystemPageSize = rt->gcSystemAllocGranularity = size_t(sysconf(_SC_PAGESIZE));
}
static inline void *
MapMemory(size_t length, int prot, int flags, int fd, off_t offset)
{
#if defined(__ia64__)
/*
* The JS engine assumes that all allocated pointers have their high 17 bits clear,
* which ia64's mmap doesn't support directly. However, we can emulate it by passing
* mmap an "addr" parameter with those bits clear. The mmap will return that address,
* or the nearest available memory above that address, providing a near-guarantee
* that those bits are clear. If they are not, we return NULL below to indicate
* out-of-memory.
*
* The addr is chosen as 0x0000070000000000, which still allows about 120TB of virtual
* address space.
*
* See Bug 589735 for more information.
*/
void *region = mmap((void*)0x0000070000000000, length, prot, flags, fd, offset);
if (region == MAP_FAILED)
return MAP_FAILED;
/*
* If the allocated memory doesn't have its upper 17 bits clear, consider it
* as out of memory.
*/
if ((uintptr_t(region) + (length - 1)) & 0xffff800000000000) {
JS_ALWAYS_TRUE(0 == munmap(region, length));
return MAP_FAILED;
}
return region;
#else
return mmap(NULL, length, prot, flags, fd, offset);
#endif
}
void *
gc::MapAlignedPages(JSRuntime *rt, size_t size, size_t alignment)
{
@ -322,12 +356,15 @@ gc::MapAlignedPages(JSRuntime *rt, size_t size, size_t alignment)
/* Special case: If we want page alignment, no further work is needed. */
if (alignment == rt->gcSystemAllocGranularity) {
return mmap(NULL, size, prot, flags, -1, 0);
void *region = MapMemory(size, prot, flags, -1, 0);
if (region == MAP_FAILED)
return NULL;
return region;
}
/* Overallocate and unmap the region's edges. */
size_t reqSize = Min(size + 2 * alignment, 2 * size);
void *region = mmap(NULL, reqSize, prot, flags, -1, 0);
void *region = MapMemory(reqSize, prot, flags, -1, 0);
if (region == MAP_FAILED)
return NULL;