106 lines
4 KiB
Diff
106 lines
4 KiB
Diff
From a0c0f32299419359b44ac0f880c1ea9073ae51e1 Mon Sep 17 00:00:00 2001
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From: Zheng Xu <zheng.xu@linaro.org>
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Date: Fri, 02 Sep 2016 17:40:05 +0800
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Subject: [PATCH] Bug 1143022 - Manually mmap on arm64 to ensure high 17 bits are clear. r=ehoogeveen
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There might be 48-bit VA on arm64 depending on kernel configuration.
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Manually mmap heap memory to align with the assumption made by JS engine.
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Change-Id: Ic5d2b2fe4b758b3c87cc0688348af7e71a991146
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---
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diff --git a/js/src/gc/Memory.cpp b/js/src/gc/Memory.cpp
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index 5b386a2..38101cf 100644
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--- a/js/src/gc/Memory.cpp
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+++ b/js/src/gc/Memory.cpp
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@@ -309,6 +309,75 @@
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#endif
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}
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+static inline void *
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+MapMemory(size_t length, int prot, int flags, int fd, off_t offset)
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+{
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+#if defined(__ia64__)
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+ /*
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+ * The JS engine assumes that all allocated pointers have their high 17 bits clear,
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+ * which ia64's mmap doesn't support directly. However, we can emulate it by passing
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+ * mmap an "addr" parameter with those bits clear. The mmap will return that address,
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+ * or the nearest available memory above that address, providing a near-guarantee
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+ * that those bits are clear. If they are not, we return NULL below to indicate
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+ * out-of-memory.
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+ *
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+ * The addr is chosen as 0x0000070000000000, which still allows about 120TB of virtual
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+ * address space.
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+ *
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+ * See Bug 589735 for more information.
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+ */
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+ void *region = mmap((void*)0x0000070000000000, length, prot, flags, fd, offset);
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+ if (region == MAP_FAILED)
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+ return MAP_FAILED;
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+ /*
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+ * If the allocated memory doesn't have its upper 17 bits clear, consider it
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+ * as out of memory.
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+ */
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+ if ((uintptr_t(region) + (length - 1)) & 0xffff800000000000) {
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+ JS_ALWAYS_TRUE(0 == munmap(region, length));
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+ return MAP_FAILED;
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+ }
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+ return region;
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+#elif defined(__aarch64__)
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+ /*
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+ * There might be similar virtual address issue on arm64 which depends on
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+ * hardware and kernel configurations. But the work around is slightly
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+ * different due to the different mmap behavior.
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+ *
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+ * TODO: Merge with the above code block if this implementation works for
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+ * ia64 and sparc64.
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+ */
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+ const uintptr_t start = (uintptr_t)(0x0000070000000000UL);
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+ const uintptr_t end = (uintptr_t)(0x0000800000000000UL);
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+ const uintptr_t step = ChunkSize;
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+ /*
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+ * Optimization options if there are too many retries in practice:
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+ * 1. Examine /proc/self/maps to find an available address. This file is
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+ * not always available, however. In addition, even if we examine
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+ * /proc/self/maps, we may still need to retry several times due to
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+ * racing with other threads.
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+ * 2. Use a global/static variable with lock to track the addresses we have
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+ * allocated or tried.
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+ */
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+ uintptr_t hint;
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+ void* region = MAP_FAILED;
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+ for (hint = start; region == MAP_FAILED && hint + length <= end; hint += step) {
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+ region = mmap((void*)hint, length, prot, flags, fd, offset);
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+ if (region != MAP_FAILED) {
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+ if ((uintptr_t(region) + (length - 1)) & 0xffff800000000000) {
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+ if (munmap(region, length)) {
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+ MOZ_ASSERT(errno == ENOMEM);
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+ }
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+ region = MAP_FAILED;
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+ }
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+ }
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+ }
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+ return region == MAP_FAILED ? NULL : region;
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+#else
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+ return mmap(NULL, length, prot, flags, fd, offset);
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+#endif
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+}
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+
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void *
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MapAlignedPages(size_t size, size_t alignment)
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{
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@@ -322,12 +391,12 @@
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/* Special case: If we want page alignment, no further work is needed. */
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if (alignment == PageSize) {
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- return mmap(NULL, size, prot, flags, -1, 0);
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+ return MapMemory(size, prot, flags, -1, 0);
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}
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/* Overallocate and unmap the region's edges. */
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size_t reqSize = Min(size + 2 * alignment, 2 * size);
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- void *region = mmap(NULL, reqSize, prot, flags, -1, 0);
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+ void *region = MapMemory(reqSize, prot, flags, -1, 0);
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if (region == MAP_FAILED)
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return NULL;
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