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ps_status.c
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1 /*--------------------------------------------------------------------
2  * ps_status.c
3  *
4  * Routines to support changing the ps display of PostgreSQL backends
5  * to contain some useful information. Mechanism differs wildly across
6  * platforms.
7  *
8  * src/backend/utils/misc/ps_status.c
9  *
10  * Copyright (c) 2000-2014, PostgreSQL Global Development Group
11  * various details abducted from various places
12  *--------------------------------------------------------------------
13  */
14 
15 #include "postgres.h"
16 
17 #include <unistd.h>
18 #ifdef HAVE_SYS_PSTAT_H
19 #include <sys/pstat.h> /* for HP-UX */
20 #endif
21 #ifdef HAVE_PS_STRINGS
22 #include <machine/vmparam.h> /* for old BSD */
23 #include <sys/exec.h>
24 #endif
25 #if defined(__darwin__)
26 #include <crt_externs.h>
27 #endif
28 
29 #include "libpq/libpq.h"
30 #include "miscadmin.h"
31 #include "utils/ps_status.h"
32 
33 extern char **environ;
35 
36 
37 /*
38  * Alternative ways of updating ps display:
39  *
40  * PS_USE_SETPROCTITLE
41  * use the function setproctitle(const char *, ...)
42  * (newer BSD systems)
43  * PS_USE_PSTAT
44  * use the pstat(PSTAT_SETCMD, )
45  * (HPUX)
46  * PS_USE_PS_STRINGS
47  * assign PS_STRINGS->ps_argvstr = "string"
48  * (some BSD systems)
49  * PS_USE_CHANGE_ARGV
50  * assign argv[0] = "string"
51  * (some other BSD systems)
52  * PS_USE_CLOBBER_ARGV
53  * write over the argv and environment area
54  * (Linux and most SysV-like systems)
55  * PS_USE_WIN32
56  * push the string out as the name of a Windows event
57  * PS_USE_NONE
58  * don't update ps display
59  * (This is the default, as it is safest.)
60  */
61 #if defined(HAVE_SETPROCTITLE)
62 #define PS_USE_SETPROCTITLE
63 #elif defined(HAVE_PSTAT) && defined(PSTAT_SETCMD)
64 #define PS_USE_PSTAT
65 #elif defined(HAVE_PS_STRINGS)
66 #define PS_USE_PS_STRINGS
67 #elif (defined(BSD) || defined(__hurd__)) && !defined(__darwin__)
68 #define PS_USE_CHANGE_ARGV
69 #elif defined(__linux__) || defined(_AIX) || defined(__sgi) || (defined(sun) && !defined(BSD)) || defined(ultrix) || defined(__ksr__) || defined(__osf__) || defined(__svr5__) || defined(__darwin__)
70 #define PS_USE_CLOBBER_ARGV
71 #elif defined(WIN32)
72 #define PS_USE_WIN32
73 #else
74 #define PS_USE_NONE
75 #endif
76 
77 
78 /* Different systems want the buffer padded differently */
79 #if defined(_AIX) || defined(__linux__) || defined(__darwin__)
80 #define PS_PADDING '\0'
81 #else
82 #define PS_PADDING ' '
83 #endif
84 
85 
86 #ifndef PS_USE_CLOBBER_ARGV
87 /* all but one option need a buffer to write their ps line in */
88 #define PS_BUFFER_SIZE 256
90 static const size_t ps_buffer_size = PS_BUFFER_SIZE;
91 #else /* PS_USE_CLOBBER_ARGV */
92 static char *ps_buffer; /* will point to argv area */
93 static size_t ps_buffer_size; /* space determined at run time */
94 static size_t last_status_len; /* use to minimize length of clobber */
95 #endif /* PS_USE_CLOBBER_ARGV */
96 
97 static size_t ps_buffer_cur_len; /* nominal strlen(ps_buffer) */
98 
99 static size_t ps_buffer_fixed_size; /* size of the constant prefix */
100 
101 /* save the original argv[] location here */
102 static int save_argc;
103 static char **save_argv;
104 
105 
106 /*
107  * Call this early in startup to save the original argc/argv values.
108  * If needed, we make a copy of the original argv[] array to preserve it
109  * from being clobbered by subsequent ps_display actions.
110  *
111  * (The original argv[] will not be overwritten by this routine, but may be
112  * overwritten during init_ps_display. Also, the physical location of the
113  * environment strings may be moved, so this should be called before any code
114  * that might try to hang onto a getenv() result.)
115  */
116 char **
117 save_ps_display_args(int argc, char **argv)
118 {
119  save_argc = argc;
120  save_argv = argv;
121 
122 #if defined(PS_USE_CLOBBER_ARGV)
123 
124  /*
125  * If we're going to overwrite the argv area, count the available space.
126  * Also move the environment to make additional room.
127  */
128  {
129  char *end_of_area = NULL;
130  char **new_environ;
131  int i;
132 
133  /*
134  * check for contiguous argv strings
135  */
136  for (i = 0; i < argc; i++)
137  {
138  if (i == 0 || end_of_area + 1 == argv[i])
139  end_of_area = argv[i] + strlen(argv[i]);
140  }
141 
142  if (end_of_area == NULL) /* probably can't happen? */
143  {
144  ps_buffer = NULL;
145  ps_buffer_size = 0;
146  return argv;
147  }
148 
149  /*
150  * check for contiguous environ strings following argv
151  */
152  for (i = 0; environ[i] != NULL; i++)
153  {
154  if (end_of_area + 1 == environ[i])
155  end_of_area = environ[i] + strlen(environ[i]);
156  }
157 
158  ps_buffer = argv[0];
159  last_status_len = ps_buffer_size = end_of_area - argv[0];
160 
161  /*
162  * move the environment out of the way
163  */
164  new_environ = (char **) malloc((i + 1) * sizeof(char *));
165  for (i = 0; environ[i] != NULL; i++)
166  new_environ[i] = strdup(environ[i]);
167  new_environ[i] = NULL;
168  environ = new_environ;
169  }
170 #endif /* PS_USE_CLOBBER_ARGV */
171 
172 #if defined(PS_USE_CHANGE_ARGV) || defined(PS_USE_CLOBBER_ARGV)
173 
174  /*
175  * If we're going to change the original argv[] then make a copy for
176  * argument parsing purposes.
177  *
178  * (NB: do NOT think to remove the copying of argv[], even though
179  * postmaster.c finishes looking at argv[] long before we ever consider
180  * changing the ps display. On some platforms, getopt() keeps pointers
181  * into the argv array, and will get horribly confused when it is
182  * re-called to analyze a subprocess' argument string if the argv storage
183  * has been clobbered meanwhile. Other platforms have other dependencies
184  * on argv[].
185  */
186  {
187  char **new_argv;
188  int i;
189 
190  new_argv = (char **) malloc((argc + 1) * sizeof(char *));
191  for (i = 0; i < argc; i++)
192  new_argv[i] = strdup(argv[i]);
193  new_argv[argc] = NULL;
194 
195 #if defined(__darwin__)
196 
197  /*
198  * Darwin (and perhaps other NeXT-derived platforms?) has a static
199  * copy of the argv pointer, which we may fix like so:
200  */
201  *_NSGetArgv() = new_argv;
202 #endif
203 
204  argv = new_argv;
205  }
206 #endif /* PS_USE_CHANGE_ARGV or PS_USE_CLOBBER_ARGV */
207 
208  return argv;
209 }
210 
211 /*
212  * Call this once during subprocess startup to set the identification
213  * values. At this point, the original argv[] array may be overwritten.
214  */
215 void
216 init_ps_display(const char *username, const char *dbname,
217  const char *host_info, const char *initial_str)
218 {
219  Assert(username);
220  Assert(dbname);
221  Assert(host_info);
222 
223 #ifndef PS_USE_NONE
224  /* no ps display for stand-alone backend */
225  if (!IsUnderPostmaster)
226  return;
227 
228  /* no ps display if you didn't call save_ps_display_args() */
229  if (!save_argv)
230  return;
231 
232 #ifdef PS_USE_CLOBBER_ARGV
233  /* If ps_buffer is a pointer, it might still be null */
234  if (!ps_buffer)
235  return;
236 #endif
237 
238  /*
239  * Overwrite argv[] to point at appropriate space, if needed
240  */
241 
242 #ifdef PS_USE_CHANGE_ARGV
243  save_argv[0] = ps_buffer;
244  save_argv[1] = NULL;
245 #endif /* PS_USE_CHANGE_ARGV */
246 
247 #ifdef PS_USE_CLOBBER_ARGV
248  {
249  int i;
250 
251  /* make extra argv slots point at end_of_area (a NUL) */
252  for (i = 1; i < save_argc; i++)
254  }
255 #endif /* PS_USE_CLOBBER_ARGV */
256 
257  /*
258  * Make fixed prefix of ps display.
259  */
260 
261 #ifdef PS_USE_SETPROCTITLE
262 
263  /*
264  * apparently setproctitle() already adds a `progname:' prefix to the ps
265  * line
266  */
268  "%s %s %s ",
269  username, dbname, host_info);
270 #else
272  "postgres: %s %s %s ",
273  username, dbname, host_info);
274 #endif
275 
277 
278  set_ps_display(initial_str, true);
279 #endif /* not PS_USE_NONE */
280 }
281 
282 
283 
284 /*
285  * Call this to update the ps status display to a fixed prefix plus an
286  * indication of what you're currently doing passed in the argument.
287  */
288 void
289 set_ps_display(const char *activity, bool force)
290 {
291 #ifndef PS_USE_NONE
292  /* update_process_title=off disables updates, unless force = true */
293  if (!force && !update_process_title)
294  return;
295 
296  /* no ps display for stand-alone backend */
297  if (!IsUnderPostmaster)
298  return;
299 
300 #ifdef PS_USE_CLOBBER_ARGV
301  /* If ps_buffer is a pointer, it might still be null */
302  if (!ps_buffer)
303  return;
304 #endif
305 
306  /* Update ps_buffer to contain both fixed part and activity */
309  ps_buffer_cur_len = strlen(ps_buffer);
310 
311  /* Transmit new setting to kernel, if necessary */
312 
313 #ifdef PS_USE_SETPROCTITLE
314  setproctitle("%s", ps_buffer);
315 #endif
316 
317 #ifdef PS_USE_PSTAT
318  {
319  union pstun pst;
320 
321  pst.pst_command = ps_buffer;
322  pstat(PSTAT_SETCMD, pst, ps_buffer_cur_len, 0, 0);
323  }
324 #endif /* PS_USE_PSTAT */
325 
326 #ifdef PS_USE_PS_STRINGS
327  PS_STRINGS->ps_nargvstr = 1;
328  PS_STRINGS->ps_argvstr = ps_buffer;
329 #endif /* PS_USE_PS_STRINGS */
330 
331 #ifdef PS_USE_CLOBBER_ARGV
332  /* pad unused memory; need only clobber remainder of old status string */
333  if (last_status_len > ps_buffer_cur_len)
335  last_status_len - ps_buffer_cur_len);
336  last_status_len = ps_buffer_cur_len;
337 #endif /* PS_USE_CLOBBER_ARGV */
338 
339 #ifdef PS_USE_WIN32
340  {
341  /*
342  * Win32 does not support showing any changed arguments. To make it at
343  * all possible to track which backend is doing what, we create a
344  * named object that can be viewed with for example Process Explorer.
345  */
346  static HANDLE ident_handle = INVALID_HANDLE_VALUE;
347  char name[PS_BUFFER_SIZE + 32];
348 
349  if (ident_handle != INVALID_HANDLE_VALUE)
350  CloseHandle(ident_handle);
351 
352  sprintf(name, "pgident(%d): %s", MyProcPid, ps_buffer);
353 
354  ident_handle = CreateEvent(NULL, TRUE, FALSE, name);
355  }
356 #endif /* PS_USE_WIN32 */
357 #endif /* not PS_USE_NONE */
358 }
359 
360 
361 /*
362  * Returns what's currently in the ps display, in case someone needs
363  * it. Note that only the activity part is returned. On some platforms
364  * the string will not be null-terminated, so return the effective
365  * length into *displen.
366  */
367 const char *
368 get_ps_display(int *displen)
369 {
370 #ifdef PS_USE_CLOBBER_ARGV
371  /* If ps_buffer is a pointer, it might still be null */
372  if (!ps_buffer)
373  {
374  *displen = 0;
375  return "";
376  }
377 #endif
378 
379  *displen = (int) (ps_buffer_cur_len - ps_buffer_fixed_size);
380 
382 }