2 * Copyright 2018 Google, Inc.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met: redistributions of source code must retain the above copyright
7 * notice, this list of conditions and the following disclaimer;
8 * redistributions in binary form must reproduce the above copyright
9 * notice, this list of conditions and the following disclaimer in the
10 * documentation and/or other materials provided with the distribution;
11 * neither the name of the copyright holders nor the names of its
12 * contributors may be used to endorse or promote products derived from
13 * this software without specific prior written permission.
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
18 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
19 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
21 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 #include "base/fiber.hh"
31 #include <valgrind/valgrind.h>
34 // Mac OS requires _DARWIN_C_SOURCE if _POSIX_C_SOURCE is defined,
35 // otherwise it will mask the definition of MAP_ANONYMOUS.
36 // _POSIX_C_SOURCE is already defined by including <ucontext.h> in
38 #if defined(__APPLE__) && defined(__MACH__)
39 #define _DARWIN_C_SOURCE
49 #include "base/logging.hh"
57 * The PrimaryFiber class is a special case that attaches to the currently
58 * executing context. That makes handling the "primary" fiber, aka the one
59 * which most of gem5 is running under, no different than other Fibers.
61 class PrimaryFiber
: public Fiber
64 PrimaryFiber() : Fiber(nullptr, 0) { setStarted(); }
65 void main() { panic("PrimaryFiber main executed.\n"); }
68 PrimaryFiber _primaryFiber
;
70 // A pointer to whatever the currently executing Fiber is.
71 Fiber
*_currentFiber
= &_primaryFiber
;
73 // A pointer to the Fiber which is currently being started/initialized.
74 Fiber
*startingFiber
= nullptr;
76 } // anonymous namespace
79 Fiber::entryTrampoline()
81 startingFiber
->start();
84 Fiber::Fiber(size_t stack_size
) : Fiber(primaryFiber(), stack_size
)
87 Fiber::Fiber(Fiber
*link
, size_t stack_size
) :
88 link(link
), stack(nullptr), stackSize(stack_size
), guardPage(nullptr),
89 guardPageSize(sysconf(_SC_PAGE_SIZE
)), _started(false), _finished(false)
92 guardPage
= mmap(nullptr, guardPageSize
+ stack_size
,
93 PROT_READ
| PROT_WRITE
,
94 MAP_ANONYMOUS
| MAP_PRIVATE
, -1, 0);
95 if (guardPage
== (void *)MAP_FAILED
) {
97 fatal("Could not mmap %d byte fiber stack.\n", stack_size
);
99 stack
= (void *)((uint8_t *)guardPage
+ guardPageSize
);
100 if (mprotect(guardPage
, guardPageSize
, PROT_NONE
)) {
102 fatal("Could not forbid access to fiber stack guard page.");
106 valgrindStackId
= VALGRIND_STACK_REGISTER(
107 stack
, (uint8_t *)stack
+ stack_size
);
113 panic_if(stack
&& _currentFiber
== this, "Fiber stack is in use.");
115 VALGRIND_STACK_DEREGISTER(valgrindStackId
);
118 munmap(guardPage
, guardPageSize
+ stackSize
);
122 Fiber::createContext()
124 // Set up a context for the new fiber, starting it in the trampoline.
126 ctx
.uc_stack
.ss_sp
= stack
;
127 ctx
.uc_stack
.ss_size
= stackSize
;
128 ctx
.uc_link
= nullptr;
129 makecontext(&ctx
, &entryTrampoline
, 0);
131 // Swap to the new context so it can enter its start() function. It
132 // will then swap itself back out and return here.
133 startingFiber
= this;
134 panic_if(!_currentFiber
, "No active Fiber object.");
135 swapcontext(&_currentFiber
->ctx
, &ctx
);
137 // The new context is now ready and about to call main().
143 // Avoid a dangling pointer.
144 startingFiber
= nullptr;
148 if (_setjmp(jmp
) == 0) {
149 // Swap back to the parent context which is still considered "current",
150 // now that we're ready to go.
151 int ret
= swapcontext(&ctx
, &_currentFiber
->ctx
);
152 panic_if(ret
== -1, strerror(errno
));
155 // Call main() when we're been reactivated for the first time.
158 // main has returned, so this Fiber has finished. Switch to the "link"
167 panic_if(_finished
, "Fiber has already run to completion.");
169 // If we're already running this fiber, we're done.
170 if (_currentFiber
== this)
176 // Switch out of the current Fiber's context and this one's in.
177 Fiber
*prev
= _currentFiber
;
179 _currentFiber
= next
;
180 if (_setjmp(prev
->jmp
) == 0)
181 _longjmp(next
->jmp
, 1);
184 Fiber
*Fiber::currentFiber() { return _currentFiber
; }
185 Fiber
*Fiber::primaryFiber() { return &_primaryFiber
; }