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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) 2000-2024, PostgreSQL Global Development Group
11  * various details abducted from various places
12  *--------------------------------------------------------------------
13  */
14 
15 #include "postgres.h"
16 
17 #include <unistd.h>
18 #if defined(__darwin__)
19 #include <crt_externs.h>
20 #endif
21 
22 #include "miscadmin.h"
23 #include "utils/guc.h"
24 #include "utils/ps_status.h"
25 
26 extern char **environ;
27 
28 /* GUC variable */
30 
31 /*
32  * Alternative ways of updating ps display:
33  *
34  * PS_USE_SETPROCTITLE_FAST
35  * use the function setproctitle_fast(const char *, ...)
36  * (FreeBSD)
37  * PS_USE_SETPROCTITLE
38  * use the function setproctitle(const char *, ...)
39  * (other BSDs)
40  * PS_USE_CLOBBER_ARGV
41  * write over the argv and environment area
42  * (Linux and most SysV-like systems)
43  * PS_USE_WIN32
44  * push the string out as the name of a Windows event
45  * PS_USE_NONE
46  * don't update ps display
47  * (This is the default, as it is safest.)
48  */
49 #if defined(HAVE_SETPROCTITLE_FAST)
50 #define PS_USE_SETPROCTITLE_FAST
51 #elif defined(HAVE_SETPROCTITLE)
52 #define PS_USE_SETPROCTITLE
53 #elif defined(__linux__) || defined(__sun) || defined(__darwin__)
54 #define PS_USE_CLOBBER_ARGV
55 #elif defined(WIN32)
56 #define PS_USE_WIN32
57 #else
58 #define PS_USE_NONE
59 #endif
60 
61 
62 /* Different systems want the buffer padded differently */
63 #if defined(__linux__) || defined(__darwin__)
64 #define PS_PADDING '\0'
65 #else
66 #define PS_PADDING ' '
67 #endif
68 
69 
70 #ifndef PS_USE_NONE
71 
72 #ifndef PS_USE_CLOBBER_ARGV
73 /* all but one option need a buffer to write their ps line in */
74 #define PS_BUFFER_SIZE 256
75 static char ps_buffer[PS_BUFFER_SIZE];
76 static const size_t ps_buffer_size = PS_BUFFER_SIZE;
77 #else /* PS_USE_CLOBBER_ARGV */
78 static char *ps_buffer; /* will point to argv area */
79 static size_t ps_buffer_size; /* space determined at run time */
80 static size_t last_status_len; /* use to minimize length of clobber */
81 #endif /* PS_USE_CLOBBER_ARGV */
82 
83 static size_t ps_buffer_cur_len; /* nominal strlen(ps_buffer) */
84 
85 static size_t ps_buffer_fixed_size; /* size of the constant prefix */
86 
87 /*
88  * Length of ps_buffer before the suffix was appended to the end, or 0 if we
89  * didn't set a suffix.
90  */
91 static size_t ps_buffer_nosuffix_len;
92 
93 static void flush_ps_display(void);
94 
95 #endif /* not PS_USE_NONE */
96 
97 /* save the original argv[] location here */
98 static int save_argc;
99 static char **save_argv;
100 
101 
102 /*
103  * Call this early in startup to save the original argc/argv values.
104  * If needed, we make a copy of the original argv[] array to preserve it
105  * from being clobbered by subsequent ps_display actions.
106  *
107  * (The original argv[] will not be overwritten by this routine, but may be
108  * overwritten during init_ps_display. Also, the physical location of the
109  * environment strings may be moved, so this should be called before any code
110  * that might try to hang onto a getenv() result. But see hack for musl
111  * within.)
112  *
113  * Note that in case of failure this cannot call elog() as that is not
114  * initialized yet. We rely on write_stderr() instead.
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 strings 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  {
156  /*
157  * The musl dynamic linker keeps a static pointer to the
158  * initial value of LD_LIBRARY_PATH, if that is defined in the
159  * process's environment. Therefore, we must not overwrite the
160  * value of that setting and thus cannot advance end_of_area
161  * beyond it. Musl does not define any identifying compiler
162  * symbol, so we have to do this unless we see a symbol
163  * identifying a Linux libc we know is safe.
164  */
165 #if defined(__linux__) && (!defined(__GLIBC__) && !defined(__UCLIBC__))
166  if (strncmp(environ[i], "LD_LIBRARY_PATH=", 16) == 0)
167  {
168  /*
169  * We can overwrite the name, but stop at the equals sign.
170  * Future loop iterations will not find any more
171  * contiguous space, but we don't break early because we
172  * need to count the total number of environ[] entries.
173  */
174  end_of_area = environ[i] + 15;
175  }
176  else
177 #endif
178  {
179  end_of_area = environ[i] + strlen(environ[i]);
180  }
181  }
182  }
183 
184  ps_buffer = argv[0];
185  last_status_len = ps_buffer_size = end_of_area - argv[0];
186 
187  /*
188  * move the environment out of the way
189  */
190  new_environ = (char **) malloc((i + 1) * sizeof(char *));
191  if (!new_environ)
192  {
193  write_stderr("out of memory\n");
194  exit(1);
195  }
196  for (i = 0; environ[i] != NULL; i++)
197  {
198  new_environ[i] = strdup(environ[i]);
199  if (!new_environ[i])
200  {
201  write_stderr("out of memory\n");
202  exit(1);
203  }
204  }
205  new_environ[i] = NULL;
206  environ = new_environ;
207  }
208 
209  /*
210  * If we're going to change the original argv[] then make a copy for
211  * argument parsing purposes.
212  *
213  * NB: do NOT think to remove the copying of argv[], even though
214  * postmaster.c finishes looking at argv[] long before we ever consider
215  * changing the ps display. On some platforms, getopt() keeps pointers
216  * into the argv array, and will get horribly confused when it is
217  * re-called to analyze a subprocess' argument string if the argv storage
218  * has been clobbered meanwhile. Other platforms have other dependencies
219  * on argv[].
220  */
221  {
222  char **new_argv;
223  int i;
224 
225  new_argv = (char **) malloc((argc + 1) * sizeof(char *));
226  if (!new_argv)
227  {
228  write_stderr("out of memory\n");
229  exit(1);
230  }
231  for (i = 0; i < argc; i++)
232  {
233  new_argv[i] = strdup(argv[i]);
234  if (!new_argv[i])
235  {
236  write_stderr("out of memory\n");
237  exit(1);
238  }
239  }
240  new_argv[argc] = NULL;
241 
242 #if defined(__darwin__)
243 
244  /*
245  * macOS has a static copy of the argv pointer, which we may fix like
246  * so:
247  */
248  *_NSGetArgv() = new_argv;
249 #endif
250 
251  argv = new_argv;
252  }
253 #endif /* PS_USE_CLOBBER_ARGV */
254 
255  return argv;
256 }
257 
258 /*
259  * Call this once during subprocess startup to set the identification
260  * values.
261  *
262  * If fixed_part is NULL, a default will be obtained from MyBackendType.
263  *
264  * At this point, the original argv[] array may be overwritten.
265  */
266 void
267 init_ps_display(const char *fixed_part)
268 {
269 #ifndef PS_USE_NONE
270  bool save_update_process_title;
271 #endif
272 
273  Assert(fixed_part || MyBackendType);
274  if (!fixed_part)
275  fixed_part = GetBackendTypeDesc(MyBackendType);
276 
277 #ifndef PS_USE_NONE
278  /* no ps display for stand-alone backend */
279  if (!IsUnderPostmaster)
280  return;
281 
282  /* no ps display if you didn't call save_ps_display_args() */
283  if (!save_argv)
284  return;
285 
286 #ifdef PS_USE_CLOBBER_ARGV
287  /* If ps_buffer is a pointer, it might still be null */
288  if (!ps_buffer)
289  return;
290 
291  /* make extra argv slots point at end_of_area (a NUL) */
292  for (int i = 1; i < save_argc; i++)
293  save_argv[i] = ps_buffer + ps_buffer_size;
294 #endif /* PS_USE_CLOBBER_ARGV */
295 
296  /*
297  * Make fixed prefix of ps display.
298  */
299 
300 #if defined(PS_USE_SETPROCTITLE) || defined(PS_USE_SETPROCTITLE_FAST)
301 
302  /*
303  * apparently setproctitle() already adds a `progname:' prefix to the ps
304  * line
305  */
306 #define PROGRAM_NAME_PREFIX ""
307 #else
308 #define PROGRAM_NAME_PREFIX "postgres: "
309 #endif
310 
311  if (*cluster_name == '\0')
312  {
313  snprintf(ps_buffer, ps_buffer_size,
314  PROGRAM_NAME_PREFIX "%s ",
315  fixed_part);
316  }
317  else
318  {
319  snprintf(ps_buffer, ps_buffer_size,
320  PROGRAM_NAME_PREFIX "%s: %s ",
321  cluster_name, fixed_part);
322  }
323 
324  ps_buffer_cur_len = ps_buffer_fixed_size = strlen(ps_buffer);
325 
326  /*
327  * On the first run, force the update.
328  */
329  save_update_process_title = update_process_title;
330  update_process_title = true;
331  set_ps_display("");
332  update_process_title = save_update_process_title;
333 #endif /* not PS_USE_NONE */
334 }
335 
336 #ifndef PS_USE_NONE
337 /*
338  * update_ps_display_precheck
339  * Helper function to determine if updating the process title is
340  * something that we need to do.
341  */
342 static bool
343 update_ps_display_precheck(void)
344 {
345  /* update_process_title=off disables updates */
347  return false;
348 
349  /* no ps display for stand-alone backend */
350  if (!IsUnderPostmaster)
351  return false;
352 
353 #ifdef PS_USE_CLOBBER_ARGV
354  /* If ps_buffer is a pointer, it might still be null */
355  if (!ps_buffer)
356  return false;
357 #endif
358 
359  return true;
360 }
361 #endif /* not PS_USE_NONE */
362 
363 /*
364  * set_ps_display_suffix
365  * Adjust the process title to append 'suffix' onto the end with a space
366  * between it and the current process title.
367  */
368 void
369 set_ps_display_suffix(const char *suffix)
370 {
371 #ifndef PS_USE_NONE
372  size_t len;
373 
374  /* first, check if we need to update the process title */
375  if (!update_ps_display_precheck())
376  return;
377 
378  /* if there's already a suffix, overwrite it */
379  if (ps_buffer_nosuffix_len > 0)
380  ps_buffer_cur_len = ps_buffer_nosuffix_len;
381  else
382  ps_buffer_nosuffix_len = ps_buffer_cur_len;
383 
384  len = strlen(suffix);
385 
386  /* check if we have enough space to append the suffix */
387  if (ps_buffer_cur_len + len + 1 >= ps_buffer_size)
388  {
389  /* not enough space. Check the buffer isn't full already */
390  if (ps_buffer_cur_len < ps_buffer_size - 1)
391  {
392  /* append a space before the suffix */
393  ps_buffer[ps_buffer_cur_len++] = ' ';
394 
395  /* just add what we can and fill the ps_buffer */
396  memcpy(ps_buffer + ps_buffer_cur_len, suffix,
397  ps_buffer_size - ps_buffer_cur_len - 1);
398  ps_buffer[ps_buffer_size - 1] = '\0';
399  ps_buffer_cur_len = ps_buffer_size - 1;
400  }
401  }
402  else
403  {
404  ps_buffer[ps_buffer_cur_len++] = ' ';
405  memcpy(ps_buffer + ps_buffer_cur_len, suffix, len + 1);
406  ps_buffer_cur_len = ps_buffer_cur_len + len;
407  }
408 
409  Assert(strlen(ps_buffer) == ps_buffer_cur_len);
410 
411  /* and set the new title */
412  flush_ps_display();
413 #endif /* not PS_USE_NONE */
414 }
415 
416 /*
417  * set_ps_display_remove_suffix
418  * Remove the process display suffix added by set_ps_display_suffix
419  */
420 void
422 {
423 #ifndef PS_USE_NONE
424  /* first, check if we need to update the process title */
425  if (!update_ps_display_precheck())
426  return;
427 
428  /* check we added a suffix */
429  if (ps_buffer_nosuffix_len == 0)
430  return; /* no suffix */
431 
432  /* remove the suffix from ps_buffer */
433  ps_buffer[ps_buffer_nosuffix_len] = '\0';
434  ps_buffer_cur_len = ps_buffer_nosuffix_len;
435  ps_buffer_nosuffix_len = 0;
436 
437  Assert(ps_buffer_cur_len == strlen(ps_buffer));
438 
439  /* and set the new title */
440  flush_ps_display();
441 #endif /* not PS_USE_NONE */
442 }
443 
444 /*
445  * Call this to update the ps status display to a fixed prefix plus an
446  * indication of what you're currently doing passed in the argument.
447  *
448  * 'len' must be the same as strlen(activity)
449  */
450 void
451 set_ps_display_with_len(const char *activity, size_t len)
452 {
453  Assert(strlen(activity) == len);
454 
455 #ifndef PS_USE_NONE
456  /* first, check if we need to update the process title */
457  if (!update_ps_display_precheck())
458  return;
459 
460  /* wipe out any suffix when the title is completely changed */
461  ps_buffer_nosuffix_len = 0;
462 
463  /* Update ps_buffer to contain both fixed part and activity */
464  if (ps_buffer_fixed_size + len >= ps_buffer_size)
465  {
466  /* handle the case where ps_buffer doesn't have enough space */
467  memcpy(ps_buffer + ps_buffer_fixed_size, activity,
468  ps_buffer_size - ps_buffer_fixed_size - 1);
469  ps_buffer[ps_buffer_size - 1] = '\0';
470  ps_buffer_cur_len = ps_buffer_size - 1;
471  }
472  else
473  {
474  memcpy(ps_buffer + ps_buffer_fixed_size, activity, len + 1);
475  ps_buffer_cur_len = ps_buffer_fixed_size + len;
476  }
477  Assert(strlen(ps_buffer) == ps_buffer_cur_len);
478 
479  /* Transmit new setting to kernel, if necessary */
480  flush_ps_display();
481 #endif /* not PS_USE_NONE */
482 }
483 
484 #ifndef PS_USE_NONE
485 static void
486 flush_ps_display(void)
487 {
488 #ifdef PS_USE_SETPROCTITLE
489  setproctitle("%s", ps_buffer);
490 #elif defined(PS_USE_SETPROCTITLE_FAST)
491  setproctitle_fast("%s", ps_buffer);
492 #endif
493 
494 #ifdef PS_USE_CLOBBER_ARGV
495  /* pad unused memory; need only clobber remainder of old status string */
496  if (last_status_len > ps_buffer_cur_len)
497  MemSet(ps_buffer + ps_buffer_cur_len, PS_PADDING,
498  last_status_len - ps_buffer_cur_len);
499  last_status_len = ps_buffer_cur_len;
500 #endif /* PS_USE_CLOBBER_ARGV */
501 
502 #ifdef PS_USE_WIN32
503  {
504  /*
505  * Win32 does not support showing any changed arguments. To make it at
506  * all possible to track which backend is doing what, we create a
507  * named object that can be viewed with for example Process Explorer.
508  */
509  static HANDLE ident_handle = INVALID_HANDLE_VALUE;
510  char name[PS_BUFFER_SIZE + 32];
511 
512  if (ident_handle != INVALID_HANDLE_VALUE)
513  CloseHandle(ident_handle);
514 
515  sprintf(name, "pgident(%d): %s", MyProcPid, ps_buffer);
516 
517  ident_handle = CreateEvent(NULL, TRUE, FALSE, name);
518  }
519 #endif /* PS_USE_WIN32 */
520 }
521 #endif /* not PS_USE_NONE */
522 
523 /*
524  * Returns what's currently in the ps display, in case someone needs
525  * it. Note that only the activity part is returned. On some platforms
526  * the string will not be null-terminated, so return the effective
527  * length into *displen.
528  */
529 const char *
530 get_ps_display(int *displen)
531 {
532 #ifdef PS_USE_CLOBBER_ARGV
533  /* If ps_buffer is a pointer, it might still be null */
534  if (!ps_buffer)
535  {
536  *displen = 0;
537  return "";
538  }
539 #endif
540 
541 #ifndef PS_USE_NONE
542  *displen = (int) (ps_buffer_cur_len - ps_buffer_fixed_size);
543 
544  return ps_buffer + ps_buffer_fixed_size;
545 #else
546  *displen = 0;
547  return "";
548 #endif
549 }
#define write_stderr(str)
Definition: parallel.c:186
#define Assert(condition)
Definition: c.h:812
#define MemSet(start, val, len)
Definition: c.h:974
int MyProcPid
Definition: globals.c:46
bool IsUnderPostmaster
Definition: globals.c:119
char * cluster_name
Definition: guc_tables.c:537
#define malloc(a)
Definition: header.h:50
int i
Definition: isn.c:72
exit(1)
const char * GetBackendTypeDesc(BackendType backendType)
Definition: miscinit.c:270
BackendType MyBackendType
Definition: miscinit.c:64
const void size_t len
#define sprintf
Definition: port.h:240
#define snprintf
Definition: port.h:238
#define PS_PADDING
Definition: ps_status.c:66
const char * get_ps_display(int *displen)
Definition: ps_status.c:530
static int save_argc
Definition: ps_status.c:98
void set_ps_display_remove_suffix(void)
Definition: ps_status.c:421
void set_ps_display_with_len(const char *activity, size_t len)
Definition: ps_status.c:451
void init_ps_display(const char *fixed_part)
Definition: ps_status.c:267
void set_ps_display_suffix(const char *suffix)
Definition: ps_status.c:369
char ** environ
bool update_process_title
Definition: ps_status.c:29
char ** save_ps_display_args(int argc, char **argv)
Definition: ps_status.c:117
static char ** save_argv
Definition: ps_status.c:99
static void set_ps_display(const char *activity)
Definition: ps_status.h:40
#define DEFAULT_UPDATE_PROCESS_TITLE
Definition: ps_status.h:19
const char * name