1 files changed, 372 insertions, 0 deletions
diff --git a/src/mds-server/reexec.c b/src/mds-server/reexec.c
new file mode 100644
index 0000000..0262288
--- /dev/null
+++ b/src/mds-server/reexec.c
@@ -0,0 +1,372 @@
+/**
+ * mds — A micro-display server
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "reexec.h"
+
+#include "globals.h"
+#include "client.h"
+#include "slavery.h"
+
+#include <libmdsserver/linked-list.h>
+#include <libmdsserver/hash-table.h>
+#include <libmdsserver/fd-table.h>
+#include <libmdsserver/macros.h>
+#include <libmdsserver/util.h>
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <pthread.h>
+#include <errno.h>
+#include <signal.h>
+#include <limits.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <string.h>
+
+
+/**
+ * Marshal the server's state into a file
+ * 
+ * @param   fd  The file descriptor
+ * @return      Negative on error
+ */
+int marshal_server(int fd)
+{
+  size_t list_size = linked_list_marshal_size(&client_list);
+  size_t map_size = fd_table_marshal_size(&client_map);
+  size_t list_elements = 0;
+  size_t state_n = 0;
+  char* state_buf = NULL;
+  char* state_buf_;
+  ssize_t node;
+  
+  
+  /* Calculate the grand size of all client information. */
+  for (node = client_list.edge;; list_elements++)
+    {
+      if ((node = client_list.next[node]) == client_list.edge)
+	break;
+      state_n += client_marshal_size((client_t*)(void*)(client_list.values[node]));
+    }
+  
+  /* Add the size of the rest of the program's state. */
+  state_n += sizeof(int) + sizeof(sig_atomic_t) + 2 * sizeof(uint64_t) + 2 * sizeof(size_t);
+  state_n += list_elements * sizeof(size_t) + list_size + map_size;
+  
+  /* Allocate a buffer for all data except the client list and the client map. */
+  state_buf = state_buf_ = malloc(state_n);
+  if (state_buf == NULL)
+    goto fail;
+  
+  
+  /* Tell the new version of the program what version of the program it is marshalling. */
+  buf_set_next(state_buf_, int, MDS_SERVER_VARS_VERSION);
+  
+  /* Marshal the miscellaneous state data. */
+  buf_set_next(state_buf_, sig_atomic_t, running);
+  buf_set_next(state_buf_, uint64_t, next_client_id);
+  buf_set_next(state_buf_, uint64_t, next_modify_id);
+  
+  /* Tell the program how large the marshalled client list is and how any clients are marshalled. */
+  buf_set_next(state_buf_, size_t, list_size);
+  buf_set_next(state_buf_, size_t, list_elements);
+  
+  /* Marshal the clients. */
+  foreach_linked_list_node (client_list, node)
+    {
+      /* Get the memory address of the client. */
+      size_t value_address = client_list.values[node];
+      /* Get the client's information. */
+      client_t* value = (client_t*)(void*)value_address;
+      
+      /* Marshal the address, it is used the the client list and the client map, that will be marshalled. */
+      buf_set_next(state_buf_, size_t, value_address);
+      /* Marshal the client informationation. */
+      state_buf_ += client_marshal(value, state_buf_) / sizeof(char);
+    }
+  
+  /* Marshal the client list. */
+  linked_list_marshal(&client_list, state_buf_);
+  state_buf_ += list_size / sizeof(char);
+  /* Marshal the client map. */
+  fd_table_marshal(&client_map, state_buf_);
+  
+  /* Send the marshalled data into the file. */
+  if (full_write(fd, state_buf, state_n) < 0)
+    goto fail;
+  free(state_buf);
+  
+  return 0;
+  
+ fail:
+  perror(*argv);
+  free(state_buf);
+  return -1;
+}
+
+
+/**
+ * Address translation table used by `unmarshal_server` and `remapper`
+ */
+static hash_table_t unmarshal_remap_map;
+
+/**
+ * Address translator for `unmarshal_server`
+ * 
+ * @param   old  The old address
+ * @return       The new address
+ */
+static size_t unmarshal_remapper(size_t old)
+{
+  return hash_table_get(&unmarshal_remap_map, old);
+}
+
+/**
+ * Unmarshal the server's state from a file
+ * 
+ * @param   fd  The file descriptor
+ * @return      Negative on error
+ */
+int unmarshal_server(int fd)
+{
+  int with_error = 0;
+  char* state_buf;
+  char* state_buf_;
+  size_t list_size;
+  size_t list_elements;
+  size_t i;
+  ssize_t node;
+  pthread_t slave_thread;
+  
+  
+  /* Read the file. */
+  if ((state_buf = state_buf_ = full_read(fd)) == NULL)
+    {
+      perror(*argv);
+      return -1;
+    }
+  
+  /* Create memory address remapping table. */
+  if (hash_table_create(&unmarshal_remap_map))
+    {
+      perror(*argv);
+      free(state_buf);
+      hash_table_destroy(&unmarshal_remap_map, NULL, NULL);
+      return -1;
+    }
+  
+  
+  /* Get the marshal protocal version. Not needed, there is only the one version right now. */
+  /* buf_get(state_buf_, int, 0, MDS_SERVER_VARS_VERSION); */
+  buf_next(state_buf_, int, 1);
+  
+  /* Unmarshal the miscellaneous state data. */
+  buf_get_next(state_buf_, sig_atomic_t, running);
+  buf_get_next(state_buf_, uint64_t, next_client_id);
+  buf_get_next(state_buf_, uint64_t, next_modify_id);
+  
+  /* Get the marshalled size of the client list and how any clients that are marshalled. */
+  buf_get_next(state_buf_, size_t, list_size);
+  buf_get_next(state_buf_, size_t, list_elements);
+  
+  /* Unmarshal the clients. */
+  for (i = 0; i < list_elements; i++)
+    {
+      size_t n;
+      size_t value_address;
+      client_t* value;
+      
+      /* Allocate the client's information. */
+      if (xmalloc(value, 1, client_t))
+	goto clients_fail;
+      
+      /* Unmarshal the address, it is used the the client list and the client map, that are also marshalled. */
+      buf_get_next(state_buf_, size_t, value_address);
+      /* Unmarshal the client information. */
+      n = client_unmarshal(value, state_buf_);
+      if (n == 0)
+	goto clients_fail;
+      
+      /* Populate the remapping table. */
+      if (hash_table_put(&unmarshal_remap_map, value_address, (size_t)(void*)value) == 0)
+	if (errno)
+	  goto clients_fail;
+      
+      /* Delayed seeking. */
+      state_buf_ += n / sizeof(char);
+      
+      
+      /* On error, seek past all clients. */
+      continue;
+    clients_fail:
+      perror(*argv);
+      with_error = 1;
+      if (value != NULL)
+	{
+	  buf_prev(state_buf_, size_t, 1);
+	  free(value);
+	}
+      for (; i < list_elements; i++)
+	/* There is not need to close the sockets, it is done by
+	   the caller because there are conditions where we cannot
+	   get here anyway. */
+	state_buf_ += client_unmarshal_skip(state_buf_) / sizeof(char);
+      break;
+    }
+  
+  /* Unmarshal the client list. */
+  if (linked_list_unmarshal(&client_list, state_buf_))
+    goto critical_fail;
+  state_buf_ += list_size / sizeof(char);
+  
+  /* Unmarshal the client map. */
+  if (fd_table_unmarshal(&client_map, state_buf_, unmarshal_remapper))
+    goto critical_fail;
+  
+  /* Release the raw data. */
+  free(state_buf);
+  
+  /* Remove non-found elements from the fd table. */
+#define __bit(I, _OP_)  client_map.used[I / 64] _OP_ ((uint64_t)1 << (I % 64))
+  if (with_error)
+    for (i = 0; i < client_map.capacity; i++)
+      if ((__bit(i, &)) && (client_map.values[i] == 0))
+	/* Lets not presume that fd-table actually initialise its allocations. */
+	__bit(i, &= ~);
+#undef __bit
+  
+  /* Remap the linked list and remove non-found elements, and start the clients. */
+  foreach_linked_list_node (client_list, node)
+    {
+      /* Remap the linked list and remove non-found elements. */
+      size_t new_address = unmarshal_remapper(client_list.values[node]);
+      client_list.values[node] = new_address;
+      if (new_address == 0) /* Returned if missing (or if the address is the invalid NULL.) */
+	linked_list_remove(&client_list, node);
+      else
+	{
+	  /* Start the clients. (Errors do not need to be reported.) */
+	  client_t* client = (client_t*)(void*)new_address;
+	  int socket_fd = client->socket_fd;
+	  
+	  /* Increase number of running slaves. */
+	  with_mutex (slave_mutex, running_slaves++;);
+	  
+	  /* Start slave thread. */
+	  create_slave(&slave_thread, socket_fd);
+	}
+    }
+  
+  /* Release the remapping table's resources. */
+  hash_table_destroy(&unmarshal_remap_map, NULL, NULL);
+  
+  return -with_error;
+
+ critical_fail:
+  perror(*argv);
+  abort();
+}
+
+
+/**
+ * Marshal and re-execute the server
+ * 
+ * @param  reexec  Whether the server was previously re-executed
+ */
+void perform_reexec(int reexec)
+{
+  pid_t pid = getpid();
+  int reexec_fd;
+  char shm_path[NAME_MAX + 1];
+  ssize_t node;
+    
+  /* Join with all slaves threads. */
+  with_mutex (slave_mutex,
+	      while (running_slaves > 0)
+		pthread_cond_wait(&slave_cond, &slave_mutex););
+    
+  /* Release resources. */
+  pthread_mutex_destroy(&slave_mutex);
+  pthread_cond_destroy(&slave_cond);
+  pthread_mutex_destroy(&modify_mutex);
+  pthread_cond_destroy(&modify_cond);
+  hash_table_destroy(&modify_map, NULL, NULL);
+    
+  /* Marshal the state of the server. */
+  xsnprintf(shm_path, SHM_PATH_PATTERN, (unsigned long int)pid);
+  reexec_fd = shm_open(shm_path, O_RDWR | O_CREAT | O_EXCL, S_IRWXU);
+  fail_if (reexec_fd < 0);
+  fail_if (marshal_server(reexec_fd) < 0);
+  close(reexec_fd);
+  reexec_fd = -1;
+  
+  /* Release resources. */
+  foreach_linked_list_node (client_list, node)
+    {
+      client_t* client = (client_t*)(void*)(client_list.values[node]);
+      client_destroy(client);
+    }
+  fd_table_destroy(&client_map, NULL, NULL);
+  linked_list_destroy(&client_list);
+  
+  /* Re-exec the server. */
+  reexec_server(argc, argv, reexec);
+  
+ pfail:
+  perror(*argv);
+  if (reexec_fd >= 0)
+    {
+      close(reexec_fd);
+      shm_unlink(shm_path);
+    }
+}
+
+
+/**
+ * Attempt to reload the server after a re-execution
+ * 
+ * @param  socket_fd  The file descriptor of the server socket
+ */
+void complete_reexec(int socket_fd)
+{
+  pid_t pid = getpid();
+  int reexec_fd, r;
+  char shm_path[NAME_MAX + 1];
+  
+  /* Acquire access to marshalled data. */
+  xsnprintf(shm_path, SHM_PATH_PATTERN, (unsigned long int)pid);
+  reexec_fd = shm_open(shm_path, O_RDONLY, S_IRWXU);
+  fail_if (reexec_fd < 0); /* Critical. */
+  /* Unmarshal state. */
+  r = unmarshal_server(reexec_fd);
+  close(reexec_fd);
+  shm_unlink(shm_path);
+  if (r < 0)
+    {
+      /* Close all files (hopefully sockets) we do not know what they are. */
+      close_files((fd > 2) && (fd != socket_fd) && (fd_table_contains_key(&client_map, fd) == 0));
+    }
+  
+  return;
+ pfail:
+  perror(*argv);
+  abort();
+}
+