Bug 1238694 - Limit the number of asm.js/wasm code allocations to avoid...

#include "asmjs/AsmJSModule.h"

#include "mozilla/Atomics.h"

#include "mozilla/BinarySearch.h"

#include "mozilla/Compression.h"

#include "mozilla/EnumeratedRange.h"

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;

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;

}

            exitDatum.baselineScript->removeDependentAsmJSModule(exit);

        }

        MOZ_ASSERT(wasmCodeAllocations > 0);

        wasmCodeAllocations--;

        DeallocateExecutableMemory(code_, pod.totalBytes_, AsmJSPageSize);

    }