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ps_status.c

/*--------------------------------------------------------------------
 * ps_status.c
 *
 * Routines to support changing the ps display of PostgreSQL backends
 * to contain some useful information. Mechanism differs wildly across
 * platforms.
 *
 * $PostgreSQL: pgsql/src/backend/utils/misc/ps_status.c,v 1.39.2.1 2010/05/27 19:19:44 tgl Exp $
 *
 * Copyright (c) 2000-2009, PostgreSQL Global Development Group
 * various details abducted from various places
 *--------------------------------------------------------------------
 */

#include "postgres.h"

#include <unistd.h>
#ifdef HAVE_SYS_PSTAT_H
#include <sys/pstat.h>              /* for HP-UX */
#endif
#ifdef HAVE_PS_STRINGS
#include <machine/vmparam.h>  /* for old BSD */
#include <sys/exec.h>
#endif
#if defined(__darwin__)
#include <crt_externs.h>
#endif

#include "libpq/libpq.h"
#include "miscadmin.h"
#include "utils/ps_status.h"

extern char **environ;
bool        update_process_title = true;


/*
 * Alternative ways of updating ps display:
 *
 * PS_USE_SETPROCTITLE
 *       use the function setproctitle(const char *, ...)
 *       (newer BSD systems)
 * PS_USE_PSTAT
 *       use the pstat(PSTAT_SETCMD, )
 *       (HPUX)
 * PS_USE_PS_STRINGS
 *       assign PS_STRINGS->ps_argvstr = "string"
 *       (some BSD systems)
 * PS_USE_CHANGE_ARGV
 *       assign argv[0] = "string"
 *       (some other BSD systems)
 * PS_USE_CLOBBER_ARGV
 *       write over the argv and environment area
 *       (Linux and most SysV-like systems)
 * PS_USE_WIN32
 *       push the string out as the name of a Windows event
 * PS_USE_NONE
 *       don't update ps display
 *       (This is the default, as it is safest.)
 */
#if defined(HAVE_SETPROCTITLE)
#define PS_USE_SETPROCTITLE
#elif defined(HAVE_PSTAT) && defined(PSTAT_SETCMD)
#define PS_USE_PSTAT
#elif defined(HAVE_PS_STRINGS)
#define PS_USE_PS_STRINGS
#elif (defined(BSD) || defined(__bsdi__) || defined(__hurd__)) && !defined(__darwin__)
#define PS_USE_CHANGE_ARGV
#elif defined(__linux__) || defined(_AIX) || defined(__sgi) || (defined(sun) && !defined(BSD)) || defined(ultrix) || defined(__ksr__) || defined(__osf__) || defined(__svr4__) || defined(__svr5__) || defined(__darwin__)
#define PS_USE_CLOBBER_ARGV
#elif defined(WIN32)
#define PS_USE_WIN32
#else
#define PS_USE_NONE
#endif


/* Different systems want the buffer padded differently */
#if defined(_AIX) || defined(__linux__) || defined(__svr4__)
#define PS_PADDING '\0'
#else
#define PS_PADDING ' '
#endif


#ifndef PS_USE_CLOBBER_ARGV
/* all but one option need a buffer to write their ps line in */
#define PS_BUFFER_SIZE 256
static char ps_buffer[PS_BUFFER_SIZE];
static const size_t ps_buffer_size = PS_BUFFER_SIZE;
#else                                     /* PS_USE_CLOBBER_ARGV */
static char *ps_buffer;             /* will point to argv area */
static size_t ps_buffer_size; /* space determined at run time */
static size_t last_status_len;      /* use to minimize length of clobber */
#endif   /* PS_USE_CLOBBER_ARGV */

static size_t ps_buffer_cur_len;          /* nominal strlen(ps_buffer) */

static size_t ps_buffer_fixed_size;       /* size of the constant prefix */

/* save the original argv[] location here */
static int  save_argc;
static char **save_argv;


/*
 * Call this early in startup to save the original argc/argv values.
 * If needed, we make a copy of the original argv[] array to preserve it
 * from being clobbered by subsequent ps_display actions.
 *
 * (The original argv[] will not be overwritten by this routine, but may be
 * overwritten during init_ps_display.    Also, the physical location of the
 * environment strings may be moved, so this should be called before any code
 * that might try to hang onto a getenv() result.)
 */
char    **
save_ps_display_args(int argc, char **argv)
{
      save_argc = argc;
      save_argv = argv;

#if defined(PS_USE_CLOBBER_ARGV)

      /*
       * If we're going to overwrite the argv area, count the available space.
       * Also move the environment to make additional room.
       */
      {
            char     *end_of_area = NULL;
            char    **new_environ;
            int               i;

            /*
             * check for contiguous argv strings
             */
            for (i = 0; i < argc; i++)
            {
                  if (i == 0 || end_of_area + 1 == argv[i])
                        end_of_area = argv[i] + strlen(argv[i]);
            }

            if (end_of_area == NULL)      /* probably can't happen? */
            {
                  ps_buffer = NULL;
                  ps_buffer_size = 0;
                  return argv;
            }

            /*
             * check for contiguous environ strings following argv
             */
            for (i = 0; environ[i] != NULL; i++)
            {
                  if (end_of_area + 1 == environ[i])
                        end_of_area = environ[i] + strlen(environ[i]);
            }

            ps_buffer = argv[0];
            last_status_len = ps_buffer_size = end_of_area - argv[0];

            /*
             * move the environment out of the way
             */
            new_environ = (char **) malloc((i + 1) * sizeof(char *));
            for (i = 0; environ[i] != NULL; i++)
                  new_environ[i] = strdup(environ[i]);
            new_environ[i] = NULL;
            environ = new_environ;
      }
#endif   /* PS_USE_CLOBBER_ARGV */

#if defined(PS_USE_CHANGE_ARGV) || defined(PS_USE_CLOBBER_ARGV)

      /*
       * If we're going to change the original argv[] then make a copy for
       * argument parsing purposes.
       *
       * (NB: do NOT think to remove the copying of argv[], even though
       * postmaster.c finishes looking at argv[] long before we ever consider
       * changing the ps display.  On some platforms, getopt() keeps pointers
       * into the argv array, and will get horribly confused when it is
       * re-called to analyze a subprocess' argument string if the argv storage
       * has been clobbered meanwhile.  Other platforms have other dependencies
       * on argv[].
       */
      {
            char    **new_argv;
            int               i;

            new_argv = (char **) malloc((argc + 1) * sizeof(char *));
            for (i = 0; i < argc; i++)
                  new_argv[i] = strdup(argv[i]);
            new_argv[argc] = NULL;

#if defined(__darwin__)

            /*
             * Darwin (and perhaps other NeXT-derived platforms?) has a static
             * copy of the argv pointer, which we may fix like so:
             */
            *_NSGetArgv() = new_argv;
#endif

            argv = new_argv;
      }
#endif   /* PS_USE_CHANGE_ARGV or PS_USE_CLOBBER_ARGV */

      return argv;
}

/*
 * Call this once during subprocess startup to set the identification
 * values.  At this point, the original argv[] array may be overwritten.
 */
void
init_ps_display(const char *username, const char *dbname,
                        const char *host_info, const char *initial_str)
{
      Assert(username);
      Assert(dbname);
      Assert(host_info);

#ifndef PS_USE_NONE
      /* no ps display for stand-alone backend */
      if (!IsUnderPostmaster)
            return;

      /* no ps display if you didn't call save_ps_display_args() */
      if (!save_argv)
            return;

#ifdef PS_USE_CLOBBER_ARGV
      /* If ps_buffer is a pointer, it might still be null */
      if (!ps_buffer)
            return;
#endif

      /*
       * Overwrite argv[] to point at appropriate space, if needed
       */

#ifdef PS_USE_CHANGE_ARGV
      save_argv[0] = ps_buffer;
      save_argv[1] = NULL;
#endif   /* PS_USE_CHANGE_ARGV */

#ifdef PS_USE_CLOBBER_ARGV
      {
            int               i;

            /* make extra argv slots point at end_of_area (a NUL) */
            for (i = 1; i < save_argc; i++)
                  save_argv[i] = ps_buffer + ps_buffer_size;
      }
#endif   /* PS_USE_CLOBBER_ARGV */

      /*
       * Make fixed prefix of ps display.
       */

#ifdef PS_USE_SETPROCTITLE

      /*
       * apparently setproctitle() already adds a `progname:' prefix to the ps
       * line
       */
      snprintf(ps_buffer, ps_buffer_size,
                   "%s %s %s ",
                   username, dbname, host_info);
#else
      snprintf(ps_buffer, ps_buffer_size,
                   "postgres: %s %s %s ",
                   username, dbname, host_info);
#endif

      ps_buffer_cur_len = ps_buffer_fixed_size = strlen(ps_buffer);

      set_ps_display(initial_str, true);
#endif   /* not PS_USE_NONE */
}



/*
 * Call this to update the ps status display to a fixed prefix plus an
 * indication of what you're currently doing passed in the argument.
 */
void
set_ps_display(const char *activity, bool force)
{
#ifndef PS_USE_NONE
      /* update_process_title=off disables updates, unless force = true */
      if (!force && !update_process_title)
            return;

      /* no ps display for stand-alone backend */
      if (!IsUnderPostmaster)
            return;

#ifdef PS_USE_CLOBBER_ARGV
      /* If ps_buffer is a pointer, it might still be null */
      if (!ps_buffer)
            return;
#endif

      /* Update ps_buffer to contain both fixed part and activity */
      strlcpy(ps_buffer + ps_buffer_fixed_size, activity,
                  ps_buffer_size - ps_buffer_fixed_size);
      ps_buffer_cur_len = strlen(ps_buffer);

      /* Transmit new setting to kernel, if necessary */

#ifdef PS_USE_SETPROCTITLE
      setproctitle("%s", ps_buffer);
#endif

#ifdef PS_USE_PSTAT
      {
            union pstun pst;

            pst.pst_command = ps_buffer;
            pstat(PSTAT_SETCMD, pst, ps_buffer_cur_len, 0, 0);
      }
#endif   /* PS_USE_PSTAT */

#ifdef PS_USE_PS_STRINGS
      PS_STRINGS->ps_nargvstr = 1;
      PS_STRINGS->ps_argvstr = ps_buffer;
#endif   /* PS_USE_PS_STRINGS */

#ifdef PS_USE_CLOBBER_ARGV
      /* pad unused memory; need only clobber remainder of old status string */
      if (last_status_len > ps_buffer_cur_len)
            MemSet(ps_buffer + ps_buffer_cur_len, PS_PADDING,
                     last_status_len - ps_buffer_cur_len);
      last_status_len = ps_buffer_cur_len;
#endif   /* PS_USE_CLOBBER_ARGV */

#ifdef PS_USE_WIN32
      {
            /*
             * Win32 does not support showing any changed arguments. To make it at
             * all possible to track which backend is doing what, we create a
             * named object that can be viewed with for example Process Explorer.
             */
            static HANDLE ident_handle = INVALID_HANDLE_VALUE;
            char        name[PS_BUFFER_SIZE + 32];

            if (ident_handle != INVALID_HANDLE_VALUE)
                  CloseHandle(ident_handle);

            sprintf(name, "pgident(%d): %s", MyProcPid, ps_buffer);

            ident_handle = CreateEvent(NULL, TRUE, FALSE, name);
      }
#endif   /* PS_USE_WIN32 */
#endif   /* not PS_USE_NONE */
}


/*
 * Returns what's currently in the ps display, in case someone needs
 * it.      Note that only the activity part is returned.  On some platforms
 * the string will not be null-terminated, so return the effective
 * length into *displen.
 */
const char *
get_ps_display(int *displen)
{
#ifdef PS_USE_CLOBBER_ARGV
      /* If ps_buffer is a pointer, it might still be null */
      if (!ps_buffer)
      {
            *displen = 0;
            return "";
      }
#endif

      *displen = (int) (ps_buffer_cur_len - ps_buffer_fixed_size);

      return ps_buffer + ps_buffer_fixed_size;
}

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