From f214aa5dbe2c4aa3e543aecc2b6ad96d7786862e Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@gmail.com>
Date: Thu, 30 Aug 2018 12:26:26 +0200
Subject: Revert "Bug 1444668 - Avoid allocating large AssemblerBuffers.
 r=luke, r=bbouvier, a=RyanVM"

This reverts commit 9472136272f01b858412f2d9d7854d2daa82496f.
---
 js/src/jit/MacroAssembler.cpp                      |  6 ----
 js/src/jit/ProcessExecutableMemory.cpp             |  8 ++++++
 js/src/jit/ProcessExecutableMemory.h               |  8 ------
 js/src/jit/shared/IonAssemblerBuffer.h             |  4 ---
 js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h | 32 +---------------------
 5 files changed, 9 insertions(+), 49 deletions(-)

diff --git a/js/src/jit/MacroAssembler.cpp b/js/src/jit/MacroAssembler.cpp
index 9dbbe7624..f633b9b7b 100644
--- a/js/src/jit/MacroAssembler.cpp
+++ b/js/src/jit/MacroAssembler.cpp
@@ -2214,12 +2214,6 @@ MacroAssembler::finish()
     }
 
     MacroAssemblerSpecific::finish();
-
-    MOZ_RELEASE_ASSERT(size() <= MaxCodeBytesPerProcess,
-                       "AssemblerBuffer should ensure we don't exceed MaxCodeBytesPerProcess");
-
-    if (bytesNeeded() > MaxCodeBytesPerProcess)
-        setOOM();
 }
 
 void
diff --git a/js/src/jit/ProcessExecutableMemory.cpp b/js/src/jit/ProcessExecutableMemory.cpp
index 301541541..71c2ab0dc 100644
--- a/js/src/jit/ProcessExecutableMemory.cpp
+++ b/js/src/jit/ProcessExecutableMemory.cpp
@@ -385,6 +385,14 @@ class PageBitSet
 #endif
 };
 
+// Limit on the number of bytes of executable memory to prevent JIT spraying
+// attacks.
+#if JS_BITS_PER_WORD == 32
+static const size_t MaxCodeBytesPerProcess = 128 * 1024 * 1024;
+#else
+static const size_t MaxCodeBytesPerProcess = 1 * 1024 * 1024 * 1024;
+#endif
+
 // Per-process executable memory allocator. It reserves a block of memory of
 // MaxCodeBytesPerProcess bytes, then allocates/deallocates pages from that.
 //
diff --git a/js/src/jit/ProcessExecutableMemory.h b/js/src/jit/ProcessExecutableMemory.h
index a0e2fab98..078ce7cb7 100644
--- a/js/src/jit/ProcessExecutableMemory.h
+++ b/js/src/jit/ProcessExecutableMemory.h
@@ -17,14 +17,6 @@ namespace jit {
 // alignment though.
 static const size_t ExecutableCodePageSize = 64 * 1024;
 
-// Limit on the number of bytes of executable memory to prevent JIT spraying
-// attacks.
-#if JS_BITS_PER_WORD == 32
-static const size_t MaxCodeBytesPerProcess = 128 * 1024 * 1024;
-#else
-static const size_t MaxCodeBytesPerProcess = 1 * 1024 * 1024 * 1024;
-#endif
-
 enum class ProtectionSetting {
     Protected, // Not readable, writable, or executable.
     Writable,
diff --git a/js/src/jit/shared/IonAssemblerBuffer.h b/js/src/jit/shared/IonAssemblerBuffer.h
index 3a6552696..cc20e26d2 100644
--- a/js/src/jit/shared/IonAssemblerBuffer.h
+++ b/js/src/jit/shared/IonAssemblerBuffer.h
@@ -181,10 +181,6 @@ class AssemblerBuffer
 
   protected:
     virtual Slice* newSlice(LifoAlloc& a) {
-        if (size() > MaxCodeBytesPerProcess - sizeof(Slice)) {
-            fail_oom();
-            return nullptr;
-        }
         Slice* tmp = static_cast<Slice*>(a.alloc(sizeof(Slice)));
         if (!tmp) {
             fail_oom();
diff --git a/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h b/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h
index fe678fc7d..8cb557784 100644
--- a/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h
+++ b/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h
@@ -68,33 +68,6 @@ namespace js {
 
 namespace jit {
 
-    // AllocPolicy for AssemblerBuffer. OOMs when trying to allocate more than
-    // MaxCodeBytesPerProcess bytes. Use private inheritance to make sure we
-    // explicitly have to expose SystemAllocPolicy methods.
-    class AssemblerBufferAllocPolicy : private SystemAllocPolicy
-    {
-      public:
-        using SystemAllocPolicy::checkSimulatedOOM;
-        using SystemAllocPolicy::reportAllocOverflow;
-        using SystemAllocPolicy::free_;
-
-        template <typename T> T* pod_realloc(T* p, size_t oldSize, size_t newSize) {
-            static_assert(sizeof(T) == 1,
-                          "AssemblerBufferAllocPolicy should only be used with byte vectors");
-            MOZ_ASSERT(oldSize <= MaxCodeBytesPerProcess);
-            if (MOZ_UNLIKELY(newSize > MaxCodeBytesPerProcess))
-                return nullptr;
-            return SystemAllocPolicy::pod_realloc<T>(p, oldSize, newSize);
-        }
-        template <typename T> T* pod_malloc(size_t numElems) {
-            static_assert(sizeof(T) == 1,
-                          "AssemblerBufferAllocPolicy should only be used with byte vectors");
-            if (MOZ_UNLIKELY(numElems > MaxCodeBytesPerProcess))
-                return nullptr;
-            return SystemAllocPolicy::pod_malloc<T>(numElems);
-        }
-    };
-
     class AssemblerBuffer
     {
         template<size_t size, typename T>
@@ -120,9 +93,6 @@ namespace jit {
 
         void ensureSpace(size_t space)
         {
-            // This should only be called with small |space| values to ensure
-            // we don't overflow below.
-            MOZ_ASSERT(space <= 16);
             if (MOZ_UNLIKELY(!m_buffer.reserve(m_buffer.length() + space)))
                 oomDetected();
         }
@@ -198,7 +168,7 @@ namespace jit {
             m_buffer.clear();
         }
 
-        PageProtectingVector<unsigned char, 256, AssemblerBufferAllocPolicy> m_buffer;
+        PageProtectingVector<unsigned char, 256, SystemAllocPolicy> m_buffer;
         bool m_oom;
     };
 
-- 
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