lldb/source/Utility/SelectHelper.cpp

   1 //===-- SelectHelper.cpp --------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #if defined(__APPLE__)
  10 // Enable this special support for Apple builds where we can have unlimited
  11 // select bounds. We tried switching to poll() and kqueue and we were panicing
  12 // the kernel, so we have to stick with select for now.
  13 #define _DARWIN_UNLIMITED_SELECT
  14 #endif
  15
  16 #include "lldb/Utility/SelectHelper.h"
  17 #include "lldb/Utility/LLDBAssert.h"
  18 #include "lldb/Utility/Status.h"
  19 #include "lldb/lldb-enumerations.h"
  20 #include "lldb/lldb-types.h"
  21
  22 #include "llvm/ADT/DenseMap.h"
  23
  24 #include <algorithm>
  25 #include <chrono>
  26 #include <optional>
  27
  28 #include <cerrno>
  29 #if defined(_WIN32)
  30 // Define NOMINMAX to avoid macros that conflict with std::min and std::max
  31 #define NOMINMAX
  32 #include <winsock2.h>
  33 #else
  34 #include <sys/time.h>
  35 #include <sys/select.h>
  36 #endif
  37
  38
  39 SelectHelper::SelectHelper()
  40     : m_fd_map(), m_end_time() // Infinite timeout unless
  41                                // SelectHelper::SetTimeout() gets called
  42 {}
  43
  44 void SelectHelper::SetTimeout(const std::chrono::microseconds &timeout) {
  45   using namespace std::chrono;
  46   m_end_time = steady_clock::time_point(steady_clock::now() + timeout);
  47 }
  48
  49 void SelectHelper::FDSetRead(lldb::socket_t fd) {
  50   m_fd_map[fd].read_set = true;
  51 }
  52
  53 void SelectHelper::FDSetWrite(lldb::socket_t fd) {
  54   m_fd_map[fd].write_set = true;
  55 }
  56
  57 void SelectHelper::FDSetError(lldb::socket_t fd) {
  58   m_fd_map[fd].error_set = true;
  59 }
  60
  61 bool SelectHelper::FDIsSetRead(lldb::socket_t fd) const {
  62   auto pos = m_fd_map.find(fd);
  63   if (pos != m_fd_map.end())
  64     return pos->second.read_is_set;
  65   else
  66     return false;
  67 }
  68
  69 bool SelectHelper::FDIsSetWrite(lldb::socket_t fd) const {
  70   auto pos = m_fd_map.find(fd);
  71   if (pos != m_fd_map.end())
  72     return pos->second.write_is_set;
  73   else
  74     return false;
  75 }
  76
  77 bool SelectHelper::FDIsSetError(lldb::socket_t fd) const {
  78   auto pos = m_fd_map.find(fd);
  79   if (pos != m_fd_map.end())
  80     return pos->second.error_is_set;
  81   else
  82     return false;
  83 }
  84
  85 static void updateMaxFd(std::optional<lldb::socket_t> &vold,
  86                         lldb::socket_t vnew) {
  87   if (!vold)
  88     vold = vnew;
  89   else
  90     vold = std::max(*vold, vnew);
  91 }
  92
  93 lldb_private::Status SelectHelper::Select() {
  94   lldb_private::Status error;
  95 #ifdef _WIN32
  96   // On windows FD_SETSIZE limits the number of file descriptors, not their
  97   // numeric value.
  98   lldbassert(m_fd_map.size() <= FD_SETSIZE);
  99   if (m_fd_map.size() > FD_SETSIZE)
 100     return lldb_private::Status::FromErrorString(
 101         "Too many file descriptors for select()");
 102 #endif
 103
 104   std::optional<lldb::socket_t> max_read_fd;
 105   std::optional<lldb::socket_t> max_write_fd;
 106   std::optional<lldb::socket_t> max_error_fd;
 107   std::optional<lldb::socket_t> max_fd;
 108   for (auto &pair : m_fd_map) {
 109     pair.second.PrepareForSelect();
 110     const lldb::socket_t fd = pair.first;
 111 #if !defined(__APPLE__) && !defined(_WIN32)
 112     lldbassert(fd < static_cast<int>(FD_SETSIZE));
 113     if (fd >= static_cast<int>(FD_SETSIZE)) {
 114       error = lldb_private::Status::FromErrorStringWithFormat(
 115           "%i is too large for select()", fd);
 116       return error;
 117     }
 118 #endif
 119     if (pair.second.read_set)
 120       updateMaxFd(max_read_fd, fd);
 121     if (pair.second.write_set)
 122       updateMaxFd(max_write_fd, fd);
 123     if (pair.second.error_set)
 124       updateMaxFd(max_error_fd, fd);
 125     updateMaxFd(max_fd, fd);
 126   }
 127
 128   if (!max_fd) {
 129     return lldb_private::Status::FromErrorString("no valid file descriptors");
 130   }
 131
 132   const unsigned nfds = static_cast<unsigned>(*max_fd) + 1;
 133   fd_set *read_fdset_ptr = nullptr;
 134   fd_set *write_fdset_ptr = nullptr;
 135   fd_set *error_fdset_ptr = nullptr;
 136 // Initialize and zero out the fdsets
 137 #if defined(__APPLE__)
 138   llvm::SmallVector<fd_set, 1> read_fdset;
 139   llvm::SmallVector<fd_set, 1> write_fdset;
 140   llvm::SmallVector<fd_set, 1> error_fdset;
 141
 142   if (max_read_fd.has_value()) {
 143     read_fdset.resize((nfds / FD_SETSIZE) + 1);
 144     read_fdset_ptr = read_fdset.data();
 145   }
 146   if (max_write_fd.has_value()) {
 147     write_fdset.resize((nfds / FD_SETSIZE) + 1);
 148     write_fdset_ptr = write_fdset.data();
 149   }
 150   if (max_error_fd.has_value()) {
 151     error_fdset.resize((nfds / FD_SETSIZE) + 1);
 152     error_fdset_ptr = error_fdset.data();
 153   }
 154   for (auto &fd_set : read_fdset)
 155     FD_ZERO(&fd_set);
 156   for (auto &fd_set : write_fdset)
 157     FD_ZERO(&fd_set);
 158   for (auto &fd_set : error_fdset)
 159     FD_ZERO(&fd_set);
 160 #else
 161   fd_set read_fdset;
 162   fd_set write_fdset;
 163   fd_set error_fdset;
 164
 165   if (max_read_fd) {
 166     FD_ZERO(&read_fdset);
 167     read_fdset_ptr = &read_fdset;
 168   }
 169   if (max_write_fd) {
 170     FD_ZERO(&write_fdset);
 171     write_fdset_ptr = &write_fdset;
 172   }
 173   if (max_error_fd) {
 174     FD_ZERO(&error_fdset);
 175     error_fdset_ptr = &error_fdset;
 176   }
 177 #endif
 178   // Set the FD bits in the fdsets for read/write/error
 179   for (auto &pair : m_fd_map) {
 180     const lldb::socket_t fd = pair.first;
 181
 182     if (pair.second.read_set)
 183       FD_SET(fd, read_fdset_ptr);
 184
 185     if (pair.second.write_set)
 186       FD_SET(fd, write_fdset_ptr);
 187
 188     if (pair.second.error_set)
 189       FD_SET(fd, error_fdset_ptr);
 190   }
 191
 192   // Setup our timeout time value if needed
 193   struct timeval *tv_ptr = nullptr;
 194   struct timeval tv = {0, 0};
 195
 196   while (true) {
 197     using namespace std::chrono;
 198     // Setup out relative timeout based on the end time if we have one
 199     if (m_end_time) {
 200       tv_ptr = &tv;
 201       const auto remaining_dur =
 202           duration_cast<microseconds>(*m_end_time - steady_clock::now());
 203       if (remaining_dur.count() > 0) {
 204         // Wait for a specific amount of time
 205         const auto dur_secs = duration_cast<seconds>(remaining_dur);
 206         const auto dur_usecs = remaining_dur % seconds(1);
 207         tv.tv_sec = dur_secs.count();
 208         tv.tv_usec = dur_usecs.count();
 209       } else {
 210         // Just poll once with no timeout
 211         tv.tv_sec = 0;
 212         tv.tv_usec = 0;
 213       }
 214     }
 215     const int num_set_fds = ::select(nfds, read_fdset_ptr, write_fdset_ptr,
 216                                      error_fdset_ptr, tv_ptr);
 217     if (num_set_fds < 0) {
 218       // We got an error
 219       error = lldb_private::Status::FromErrno();
 220       if (error.GetError() == EINTR) {
 221         error.Clear();
 222         continue; // Keep calling select if we get EINTR
 223       } else
 224         return error;
 225     } else if (num_set_fds == 0) {
 226       // Timeout
 227       return lldb_private::Status(ETIMEDOUT, lldb::eErrorTypePOSIX,
 228                                   "timed out");
 229     } else {
 230       // One or more descriptors were set, update the FDInfo::select_is_set
 231       // mask so users can ask the SelectHelper class so clients can call one
 232       // of:
 233
 234       for (auto &pair : m_fd_map) {
 235         const int fd = pair.first;
 236
 237         if (pair.second.read_set) {
 238           if (FD_ISSET(fd, read_fdset_ptr))
 239             pair.second.read_is_set = true;
 240         }
 241         if (pair.second.write_set) {
 242           if (FD_ISSET(fd, write_fdset_ptr))
 243             pair.second.write_is_set = true;
 244         }
 245         if (pair.second.error_set) {
 246           if (FD_ISSET(fd, error_fdset_ptr))
 247             pair.second.error_is_set = true;
 248         }
 249       }
 250       break;
 251     }
 252   }
 253   return error;
 254 }