From ef91cb9ed071a03594933eafff759649f92b874c Mon Sep 17 00:00:00 2001 From: Zheng Xu Date: Fri, 2 Sep 2016 15:03:30 +0800 Subject: [PATCH] Bug 1143022 - Manually mmap on arm64 to ensure high 17 bits are clear. r=ehoogeveen There might be 48-bit VA on arm64 depending on kernel configuration. Manually mmap heap memory to align with the assumption made by JS engine. Change-Id: Ic5d2b2fe4b758b3c87cc0688348af7e71a991146 --- js/src/gc/Memory.cpp | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/js/src/gc/Memory.cpp b/js/src/gc/Memory.cpp index 153ccb4..42aee6c 100644 --- a/js/src/gc/Memory.cpp +++ b/js/src/gc/Memory.cpp @@ -339,6 +339,41 @@ MapMemory(size_t length, int prot, int flags, int fd, off_t offset) return MAP_FAILED; } return region; +#elif defined(__aarch64__) + /* + * There might be similar virtual address issue on arm64 which depends on + * hardware and kernel configurations. But the work around is slightly + * different due to the different mmap behavior. + * + * TODO: Merge with the above code block if this implementation works for + * ia64 and sparc64. + */ + const uintptr_t start = (uintptr_t)0x0000070000000000; + const uintptr_t end = (uintptr_t)0x0000800000000000; + const uintptr_t step = ChunkSize; + /* + * Optimization options if there are too many retries in practice: + * 1. Examine /proc/self/maps to find an available address. This file is + * not always available, however. In addition, even if we examine + * /proc/self/maps, we may still need to retry several times due to + * racing with other threads. + * 2. Use a global/static variable with lock to track the addresses we have + * allocated or tried. + */ + uintptr_t hint; + void* region = MAP_FAILED; + for (hint = start; region == MAP_FAILED && hint + length <= end; hint += step) { + region = mmap((void*)hint, length, prot, flags, fd, offset); + if (region != MAP_FAILED) { + if ((uintptr_t(region) + (length - 1)) & 0xffff800000000000) { + if (munmap(region, length)) { + MOZ_ASSERT(errno == ENOMEM); + } + region = MAP_FAILED; + } + } + } + return region == MAP_FAILED ? nullptr : region; #else return mmap(NULL, length, prot, flags, fd, offset); #endif -- 1.9.1