1 /* Copyright (c) 2015-2019. 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. */
16 #include <sys/types.h>
23 #include "src/internal_config.h"
24 #include "src/xbt/memory_map.hpp"
26 #include "private.hpp"
27 #include "src/smpi/include/smpi_actor.hpp"
29 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(smpi_memory, smpi, "Memory layout support for SMPI");
31 int smpi_loaded_page = -1;
32 char* smpi_data_exe_start = nullptr;
33 int smpi_data_exe_size = 0;
34 SmpiPrivStrategies smpi_privatize_global_variables;
35 static void* smpi_data_exe_copy;
37 // Initialized by smpi_prepare_global_memory_segment().
38 static std::vector<simgrid::xbt::VmMap> initial_vm_map;
40 // We keep a copy of all the privatization regions: We can then delete everything easily by iterating over this
41 // collection and nothing can be leaked. We could also iterate over all actors but we would have to be diligent when two
42 // actors use the same privatization region (so, smart pointers would have to be used etc.)
43 // Use a std::deque so that pointers remain valid after push_back().
44 static std::deque<s_smpi_privatization_region_t> smpi_privatization_regions;
46 static constexpr int PROT_RWX = PROT_READ | PROT_WRITE | PROT_EXEC;
47 static constexpr int PROT_RW = PROT_READ | PROT_WRITE;
49 /** Take a snapshot of the process' memory map.
51 void smpi_prepare_global_memory_segment()
53 initial_vm_map = simgrid::xbt::get_memory_map(getpid());
56 static void smpi_get_executable_global_size()
58 char buffer[PATH_MAX];
59 char* full_name = realpath(xbt_binary_name, buffer);
60 xbt_assert(full_name != nullptr, "Could not resolve real path of binary file '%s'", xbt_binary_name);
62 std::vector<simgrid::xbt::VmMap> map = simgrid::xbt::get_memory_map(getpid());
63 for (auto i = map.begin(); i != map.end() ; ++i) {
64 // TODO, In practice, this implementation would not detect a completely
65 // anonymous data segment. This does not happen in practice, however.
67 // File backed RW entry:
68 if (i->pathname == full_name && (i->prot & PROT_RWX) == PROT_RW) {
69 smpi_data_exe_start = (char*)i->start_addr;
70 smpi_data_exe_size = i->end_addr - i->start_addr;
71 /* Here we are making the assumption that a suitable empty region
72 following the rw- area is the end of the data segment. It would
73 be better to check with the size of the data segment. */
75 if (i != map.end() && i->pathname.empty() && (i->prot & PROT_RWX) == PROT_RW &&
76 (char*)i->start_addr == smpi_data_exe_start + smpi_data_exe_size) {
77 // Only count the portion of this region not present in the initial map.
78 auto found = std::find_if(initial_vm_map.begin(), initial_vm_map.end(), [&i](const simgrid::xbt::VmMap& m) {
79 return i->start_addr <= m.start_addr && m.start_addr < i->end_addr;
81 auto end_addr = (found == initial_vm_map.end() ? i->end_addr : found->start_addr);
82 smpi_data_exe_size = (char*)end_addr - smpi_data_exe_start;
87 xbt_die("Did not find my data segment.");
91 #if HAVE_SANITIZER_ADDRESS
92 #include <sanitizer/asan_interface.h>
93 static void* asan_safe_memcpy(void* dest, void* src, size_t n)
95 char* psrc = static_cast<char*>(src);
96 char* pdest = static_cast<char*>(dest);
97 for (size_t i = 0; i < n;) {
98 while (i < n && __asan_address_is_poisoned(psrc + i))
101 char* p = static_cast<char*>(__asan_region_is_poisoned(psrc + i, n - i));
102 size_t j = p ? (p - psrc) : n;
103 memcpy(pdest + i, psrc + i, j - i);
110 #define asan_safe_memcpy(dest, src, n) memcpy((dest), (src), (n))
113 /** Map a given SMPI privatization segment (make a SMPI process active)
115 * When doing a state restoration, the state of the restored variables might not be consistent with the state of the
116 * virtual memory. In this case, we to change the data segment.
118 void smpi_switch_data_segment(simgrid::s4u::ActorPtr actor)
120 if (smpi_loaded_page == actor->get_pid()) // no need to switch, we've already loaded the one we want
123 if (smpi_data_exe_size == 0) // no need to switch
126 #if HAVE_PRIVATIZATION
127 // FIXME, cross-process support (mmap across process when necessary)
128 XBT_DEBUG("Switching data frame to the one of process %ld", actor->get_pid());
129 simgrid::smpi::ActorExt* process = smpi_process_remote(actor);
130 int current = process->privatized_region()->file_descriptor;
131 void* tmp = mmap(TOPAGE(smpi_data_exe_start), smpi_data_exe_size, PROT_RW, MAP_FIXED | MAP_SHARED, current, 0);
132 if (tmp != TOPAGE(smpi_data_exe_start))
133 xbt_die("Couldn't map the new region (errno %d): %s", errno, strerror(errno));
134 smpi_loaded_page = actor->get_pid();
139 * @brief Makes a backup of the segment in memory that stores the global variables of a process.
140 * This backup is then used to initialize the global variables for every single
141 * process that is added, regardless of the progress of the simulation.
143 void smpi_backup_global_memory_segment()
145 #if HAVE_PRIVATIZATION
146 smpi_get_executable_global_size();
147 initial_vm_map.clear();
148 initial_vm_map.shrink_to_fit();
150 XBT_DEBUG("bss+data segment found : size %d starting at %p", smpi_data_exe_size, smpi_data_exe_start);
152 if (smpi_data_exe_size == 0) { // no need to do anything as global variables don't exist
153 smpi_privatize_global_variables = SmpiPrivStrategies::NONE;
157 smpi_data_exe_copy = ::operator new(smpi_data_exe_size);
158 // Make a copy of the data segment. This clean copy is retained over the whole runtime
159 // of the simulation and can be used to initialize a dynamically added, new process.
160 asan_safe_memcpy(smpi_data_exe_copy, TOPAGE(smpi_data_exe_start), smpi_data_exe_size);
161 #else /* ! HAVE_PRIVATIZATION */
162 xbt_die("You are trying to use privatization on a system that does not support it. Don't.");
166 // Initializes the memory mapping for a single process and returns the privatization region
167 smpi_privatization_region_t smpi_init_global_memory_segment_process()
170 void* address = nullptr;
174 constexpr unsigned VAL_MASK = 0xffffffU;
175 static unsigned prev_val = VAL_MASK;
176 for (unsigned i = (prev_val + 1) & VAL_MASK; i != prev_val; i = (i + 1) & VAL_MASK) {
177 snprintf(path, sizeof(path), "/smpi-buffer-%06x", i);
178 file_descriptor = shm_open(path, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
179 if (file_descriptor != -1 || errno != EEXIST) {
184 if (file_descriptor < 0) {
185 if (errno == EMFILE) {
186 xbt_die("Impossible to create temporary file for memory mapping: %s\n\
187 The open() system call failed with the EMFILE error code (too many files). \n\n\
188 This means that you reached the system limits concerning the amount of files per process. \
189 This is not a surprise if you are trying to virtualize many processes on top of SMPI. \
190 Don't panic -- you should simply increase your system limits and try again. \n\n\
191 First, check what your limits are:\n\
192 cat /proc/sys/fs/file-max # Gives you the system-wide limit\n\
193 ulimit -Hn # Gives you the per process hard limit\n\
194 ulimit -Sn # Gives you the per process soft limit\n\
195 cat /proc/self/limits # Displays any per-process limitation (including the one given above)\n\n\
196 If one of these values is less than the amount of MPI processes that you try to run, then you got the explanation of this error. \
197 Ask the Internet about tutorials on how to increase the files limit such as: https://rtcamp.com/tutorials/linux/increase-open-files-limit/",
200 xbt_die("Impossible to create temporary file for memory mapping: %s", strerror(errno));
203 status = ftruncate(file_descriptor, smpi_data_exe_size);
205 xbt_die("Impossible to set the size of the temporary file for memory mapping");
207 /* Ask for a free region */
208 address = mmap(nullptr, smpi_data_exe_size, PROT_RW, MAP_SHARED, file_descriptor, 0);
209 if (address == MAP_FAILED)
210 xbt_die("Couldn't find a free region for memory mapping");
212 status = shm_unlink(path);
214 xbt_die("Impossible to unlink temporary file for memory mapping");
216 // initialize the values
217 asan_safe_memcpy(address, smpi_data_exe_copy, smpi_data_exe_size);
219 // store the address of the mapping for further switches
220 smpi_privatization_regions.emplace_back(s_smpi_privatization_region_t{address, file_descriptor});
222 return &smpi_privatization_regions.back();
225 void smpi_destroy_global_memory_segments(){
226 if (smpi_data_exe_size == 0) // no need to switch
228 #if HAVE_PRIVATIZATION
229 for (auto const& region : smpi_privatization_regions) {
230 if (munmap(region.address, smpi_data_exe_size) < 0)
231 XBT_WARN("Unmapping of fd %d failed: %s", region.file_descriptor, strerror(errno));
232 close(region.file_descriptor);
234 smpi_privatization_regions.clear();
235 ::operator delete(smpi_data_exe_copy);
239 static std::vector<unsigned char> sendbuffer;
240 static std::vector<unsigned char> recvbuffer;
242 //allocate a single buffer for all sends, growing it if needed
243 unsigned char* smpi_get_tmp_sendbuffer(size_t size)
245 if (not smpi_process()->replaying())
246 return new unsigned char[size];
247 // FIXME: a resize() may invalidate a previous pointer. Maybe we need to handle a queue of buffers with a reference
248 // counter. The same holds for smpi_get_tmp_recvbuffer.
249 if (sendbuffer.size() < size)
250 sendbuffer.resize(size);
251 return sendbuffer.data();
254 //allocate a single buffer for all recv
255 unsigned char* smpi_get_tmp_recvbuffer(size_t size)
257 if (not smpi_process()->replaying())
258 return new unsigned char[size];
259 if (recvbuffer.size() < size)
260 recvbuffer.resize(size);
261 return recvbuffer.data();
264 void smpi_free_tmp_buffer(const unsigned char* buf)
266 if (not smpi_process()->replaying())
270 void smpi_free_replay_tmp_buffers()
272 std::vector<unsigned char>().swap(sendbuffer);
273 std::vector<unsigned char>().swap(recvbuffer);