1 /* Copyright (c) 2009-2020. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 /* \file UContext.cpp Context switching with ucontexts from System V */
8 #include "context_private.hpp"
11 #include "simgrid/Exception.hpp"
12 #include "src/kernel/actor/ActorImpl.hpp"
13 #include "src/mc/mc_ignore.hpp"
14 #include "src/simix/smx_private.hpp"
16 #include "ContextUnix.hpp"
18 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
20 /** Up to two integers may be needed to store a pointer on the system we target */
21 constexpr int CTX_ADDR_LEN = 2;
23 static_assert(sizeof(simgrid::kernel::context::UContext*) <= CTX_ADDR_LEN * sizeof(int),
24 "Ucontexts are not supported on this arch yet. Please increase CTX_ADDR_LEN.");
26 // This function is called by makecontext(3): use extern "C" to have C language linkage for its type
28 XBT_ATTRIB_NORETURN static void sysv_ctx_wrapper(int i1, int i2)
30 // Rebuild the Context* pointer from the integers:
31 int ctx_addr[CTX_ADDR_LEN] = {i1, i2};
32 simgrid::kernel::context::UContext* context;
33 memcpy(&context, ctx_addr, sizeof context);
34 smx_ctx_wrapper(context);
43 UContext* UContextFactory::create_context(std::function<void()>&& code, actor::ActorImpl* actor)
45 return new_context<UContext>(std::move(code), actor, this);
51 UContext::UContext(std::function<void()>&& code, actor::ActorImpl* actor, SwappedContextFactory* factory)
52 : SwappedContext(std::move(code), actor, factory)
54 /* if the user provided a function for the actor then use it. If not, nothing to do for maestro. */
56 getcontext(&this->uc_);
57 this->uc_.uc_link = nullptr;
58 this->uc_.uc_stack.ss_sp = sg_makecontext_stack_addr(get_stack());
59 this->uc_.uc_stack.ss_size = sg_makecontext_stack_size(smx_context_stack_size);
60 // Makecontext expects integer arguments; we want to pass a pointer.
61 // This context address is decomposed into a series of integers, which are passed as arguments to makecontext.
63 int ctx_addr[CTX_ADDR_LEN]{};
65 memcpy(ctx_addr, &arg, sizeof this);
66 makecontext(&this->uc_, (void (*)())sysv_ctx_wrapper, 2, ctx_addr[0], ctx_addr[1]);
70 MC_register_stack_area(get_stack(), &(this->uc_), smx_context_stack_size);
76 void UContext::swap_into(SwappedContext* to_)
78 const UContext* to = static_cast<UContext*>(to_);
79 ASAN_ONLY(void* fake_stack = nullptr);
80 ASAN_ONLY(to_->asan_ctx_ = this);
81 ASAN_START_SWITCH(this->asan_stop_ ? nullptr : &fake_stack, to_->asan_stack_, to_->asan_stack_size_);
82 swapcontext(&this->uc_, &to->uc_);
83 ASAN_FINISH_SWITCH(fake_stack, &this->asan_ctx_->asan_stack_, &this->asan_ctx_->asan_stack_size_);
87 XBT_PRIVATE ContextFactory* sysv_factory()
89 XBT_VERB("Activating SYSV context factory");
90 return new UContextFactory();
92 } // namespace context
94 } // namespace simgrid