commit 2f4d7ae9cfc9d3076a428aa381c6b40bb10166cf Author: Jan de Mooij jdemooij@mozilla.com Date: Tue Mar 15 14:33:07 2016 +0100

Bug 1238694 - Limit the number of asm.js/wasm code allocations to avoid running into Linux kernel limits. r=luke --- js/src/asmjs/AsmJSModule.cpp | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/js/src/asmjs/AsmJSModule.cpp b/js/src/asmjs/AsmJSModule.cpp index 3508270..08ac9a7 100644 --- a/js/src/asmjs/AsmJSModule.cpp +++ b/js/src/asmjs/AsmJSModule.cpp @@ -18,6 +18,7 @@

#include "asmjs/AsmJSModule.h"

+#include "mozilla/Atomics.h" #include "mozilla/BinarySearch.h" #include "mozilla/Compression.h" #include "mozilla/EnumeratedRange.h" @@ -51,6 +52,7 @@ using namespace js; using namespace js::jit; using namespace js::wasm; using namespace js::frontend; +using mozilla::Atomic; using mozilla::BinarySearch; using mozilla::Compression::LZ4; using mozilla::MakeEnumeratedRange; @@ -61,17 +63,26 @@ using mozilla::PodZero; using mozilla::Swap; using JS::GenericNaN;

+// Limit the number of concurrent wasm code allocations per process. Note that +// on Linux, the real maximum is ~32k, as each module requires 2 maps (RW/RX), +// and the kernel's default max_map_count is ~65k. +static Atomic<uint32_t> wasmCodeAllocations(0); +static const uint32_t MaxWasmCodeAllocations = 16384; + static uint8_t* AllocateExecutableMemory(ExclusiveContext* cx, size_t bytes) { - // On most platforms, this will allocate RWX memory. On iOS, or when - // --non-writable-jitcode is used, this will allocate RW memory. In this - // case, DynamicallyLinkModule will reprotect the code as RX. + // Allocate RW memory. DynamicallyLinkModule will reprotect the code as RX. unsigned permissions = ExecutableAllocator::initialProtectionFlags(ExecutableAllocator::Writable); - void* p = AllocateExecutableMemory(nullptr, bytes, permissions, "asm-js-code", AsmJSPageSize); - if (!p) + void* p = nullptr; + if (wasmCodeAllocations++ < MaxWasmCodeAllocations) + p = AllocateExecutableMemory(nullptr, bytes, permissions, "asm-js-code", AsmJSPageSize); + if (!p) { + wasmCodeAllocations--; ReportOutOfMemory(cx); + } + return (uint8_t*)p; }

@@ -122,6 +133,8 @@ AsmJSModule::~AsmJSModule() exitDatum.baselineScript->removeDependentAsmJSModule(exit); }

+ MOZ_ASSERT(wasmCodeAllocations > 0); + wasmCodeAllocations--; DeallocateExecutableMemory(code_, pod.totalBytes_, AsmJSPageSize); }