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diff --git a/src/base/fiber.cc b/src/base/fiber.cc
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+/*
+ * Copyright 2018 Google, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Gabe Black
+ */
+
+#include "base/fiber.hh"
+
+#include <cerrno>
+#include <cstring>
+
+#include "base/logging.hh"
+
+using namespace std;
+
+namespace
+{
+
+/*
+ * The PrimaryFiber class is a special case that attaches to the currently
+ * executing context. That makes handling the "primary" fiber, aka the one
+ * which most of gem5 is running under, no different than other Fibers.
+ */
+class PrimaryFiber : public Fiber
+{
+  public:
+    PrimaryFiber() : Fiber(nullptr, 0) { setStarted(); }
+    void main() { panic("PrimaryFiber main executed.\n"); }
+};
+
+PrimaryFiber _primaryFiber;
+
+// A pointer to whatever the currently executing Fiber is.
+Fiber *_currentFiber = &_primaryFiber;
+
+// A pointer to the Fiber which is currently being started/initialized.
+Fiber *startingFiber = nullptr;
+
+} // anonymous namespace
+
+void
+Fiber::entryTrampoline()
+{
+    startingFiber->start();
+}
+
+Fiber::Fiber(size_t stack_size) :
+    link(primaryFiber()),
+    stack(stack_size ? new uint8_t[stack_size] : nullptr),
+    stackSize(stack_size), started(false), _finished(false)
+{}
+
+Fiber::Fiber(Fiber *link, size_t stack_size) :
+    link(link), stack(stack_size ? new uint8_t[stack_size] : nullptr),
+    stackSize(stack_size), started(false), _finished(false)
+{}
+
+Fiber::~Fiber()
+{
+    panic_if(stack && _currentFiber == this, "Fiber stack is in use.");
+    delete [] stack;
+}
+
+void
+Fiber::createContext()
+{
+    // Set up a context for the new fiber, starting it in the trampoline.
+    getcontext(&ctx);
+    ctx.uc_stack.ss_sp = stack;
+    ctx.uc_stack.ss_size = stackSize;
+    ctx.uc_link = nullptr;
+    makecontext(&ctx, &entryTrampoline, 0);
+
+    // Swap to the new context so it can enter its start() function. It
+    // will then swap itself back out and return here.
+    startingFiber = this;
+    panic_if(!_currentFiber, "No active Fiber object.");
+    swapcontext(&_currentFiber->ctx, &ctx);
+
+    // The new context is now ready and about to call main().
+}
+
+void
+Fiber::start()
+{
+    // Avoid a dangling pointer.
+    startingFiber = nullptr;
+
+    setStarted();
+
+    // Swap back to the parent context which is still considered "current",
+    // now that we're ready to go.
+    int ret M5_VAR_USED = swapcontext(&ctx, &_currentFiber->ctx);
+    panic_if(ret == -1, strerror(errno));
+
+    // Call main() when we're been reactivated for the first time.
+    main();
+
+    // main has returned, so this Fiber has finished. Switch to the "link"
+    // Fiber.
+    _finished = true;
+    link->run();
+}
+
+void
+Fiber::run()
+{
+    panic_if(_finished, "Fiber has already run to completion.");
+
+    // If we're already running this fiber, we're done.
+    if (_currentFiber == this)
+        return;
+
+    if (!started)
+        createContext();
+
+    // Switch out of the current Fiber's context and this one's in.
+    Fiber *prev = _currentFiber;
+    Fiber *next = this;
+    _currentFiber = next;
+    swapcontext(&prev->ctx, &next->ctx);
+}
+
+Fiber *Fiber::currentFiber() { return _currentFiber; }
+Fiber *Fiber::primaryFiber() { return &_primaryFiber; }