js/src/jit/Linker.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "jit/Linker.h"
   8
   9 #include "jit/JitZone.h"
  10 #include "util/Memory.h"
  11
  12 #include "gc/StoreBuffer-inl.h"
  13
  14 namespace js {
  15 namespace jit {
  16
  17 JitCode* Linker::newCode(JSContext* cx, CodeKind kind) {
  18   JS::AutoAssertNoGC nogc(cx);
  19   if (masm.oom()) {
  20     return fail(cx);
  21   }
  22
  23   static const size_t ExecutableAllocatorAlignment = sizeof(void*);
  24   static_assert(CodeAlignment >= ExecutableAllocatorAlignment,
  25                 "Unexpected alignment requirements");
  26
  27   // We require enough bytes for the code, header, and worst-case alignment
  28   // padding.
  29   size_t bytesNeeded = masm.bytesNeeded() + sizeof(JitCodeHeader) +
  30                        (CodeAlignment - ExecutableAllocatorAlignment);
  31   if (bytesNeeded >= MAX_BUFFER_SIZE) {
  32     return fail(cx);
  33   }
  34
  35   // ExecutableAllocator requires bytesNeeded to be aligned.
  36   bytesNeeded = AlignBytes(bytesNeeded, ExecutableAllocatorAlignment);
  37
  38   JitZone* jitZone = cx->zone()->getJitZone(cx);
  39   if (!jitZone) {
  40     // Note: don't call fail(cx) here, getJitZone reports OOM.
  41     return nullptr;
  42   }
  43
  44   ExecutablePool* pool;
  45   uint8_t* result =
  46       (uint8_t*)jitZone->execAlloc().alloc(cx, bytesNeeded, &pool, kind);
  47   if (!result) {
  48     return fail(cx);
  49   }
  50
  51   // The JitCodeHeader will be stored right before the code buffer.
  52   uint8_t* codeStart = result + sizeof(JitCodeHeader);
  53
  54   // Bump the code up to a nice alignment.
  55   codeStart = (uint8_t*)AlignBytes((uintptr_t)codeStart, CodeAlignment);
  56   MOZ_ASSERT(codeStart + masm.bytesNeeded() <= result + bytesNeeded);
  57   uint32_t headerSize = codeStart - result;
  58   JitCode* code =
  59       JitCode::New<NoGC>(cx, codeStart, bytesNeeded, headerSize, pool, kind);
  60   if (!code) {
  61     return fail(cx);
  62   }
  63   if (masm.oom()) {
  64     return fail(cx);
  65   }
  66   awjcf.emplace(result, bytesNeeded);
  67   if (!awjcf->makeWritable()) {
  68     return fail(cx);
  69   }
  70   code->copyFrom(masm);
  71   masm.link(code);
  72   if (masm.embedsNurseryPointers()) {
  73     cx->runtime()->gc.storeBuffer().putWholeCell(code);
  74   }
  75   return code;
  76 }
  77
  78 }  // namespace jit
  79 }  // namespace js