/*--------------------------------------------------------------------

 * ps_status.c

 *

 * Routines to support changing the ps display of PostgreSQL backends

 * to contain some useful information. Mechanism differs wildly across

 * platforms.

 *

 * src/backend/utils/misc/ps_status.c

 *

 * Copyright (c) 2000-2026, PostgreSQL Global Development Group

 * various details abducted from various places

 *--------------------------------------------------------------------

 */

#include "postgres.h"

#include <unistd.h>

#if defined(__darwin__)

#include <crt_externs.h>

#endif

#include "miscadmin.h"

#include "utils/guc.h"

#include "utils/ps_status.h"

#if !defined(WIN32)

extern char **environ;

#endif

/* GUC variable */

bool    update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;

/*

 * Alternative ways of updating ps display:

 *

 * PS_USE_SETPROCTITLE_FAST

 *     use the function setproctitle_fast(const char *, ...)

 *     (FreeBSD)

 * PS_USE_SETPROCTITLE

 *     use the function setproctitle(const char *, ...)

 *     (other BSDs)

 * 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_FAST)

#define PS_USE_SETPROCTITLE_FAST

#elif defined(HAVE_SETPROCTITLE)

#define PS_USE_SETPROCTITLE

#elif defined(__linux__) || defined(_AIX) || defined(__sun) || defined(__darwin__) || defined(__GNU__)

#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(__darwin__) || defined(__GNU__)

#define PS_PADDING '\0'

#else

#define PS_PADDING ' '

#endif

#ifndef PS_USE_NONE

#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 */

/*

 * Length of ps_buffer before the suffix was appended to the end, or 0 if we

 * didn't set a suffix.

 */

static size_t ps_buffer_nosuffix_len;

static void flush_ps_display(void);

#endif              /* not PS_USE_NONE */

/* save the original argv[] location here */

static int  save_argc;

static char **save_argv;

/*

 * Valgrind seems not to consider the global "environ" variable as a valid

 * root pointer; so when we allocate a new environment array, it claims that

 * data is leaked.  To fix that, keep our own statically-allocated copy of the

 * pointer.  (Oddly, this doesn't seem to be a problem for "argv".)

 */

#if defined(PS_USE_CLOBBER_ARGV) && defined(USE_VALGRIND)

extern char **ps_status_new_environ;

char    **ps_status_new_environ;

#endif

/*

 * 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.  But see hack for musl

 * within.)

 *

 * Note that in case of failure this cannot call elog() as that is not

 * initialized yet.  We rely on write_stderr() instead.

 */

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 strings 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])

      {

        /*

         * The musl dynamic linker keeps a static pointer to the

         * initial value of LD_LIBRARY_PATH, if that is defined in the

         * process's environment. Therefore, we must not overwrite the

         * value of that setting and thus cannot advance end_of_area

         * beyond it.  Musl does not define any identifying compiler

         * symbol, so we have to do this unless we see a symbol

         * identifying a Linux libc we know is safe.

         */

#if defined(__linux__) && (!defined(__GLIBC__) && !defined(__UCLIBC__))

        if (strncmp(environ[i], "LD_LIBRARY_PATH=", 16) == 0)

        {

          /*

           * We can overwrite the name, but stop at the equals sign.

           * Future loop iterations will not find any more

           * contiguous space, but we don't break early because we

           * need to count the total number of environ[] entries.

           */

          end_of_area = environ[i] + 15;

        }

        else

#endif

        {

          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 *));

    if (!new_environ)

    {

      write_stderr("out of memory\n");

      exit(1);

    }

    for (i = 0; environ[i] != NULL; i++)

    {

      new_environ[i] = strdup(environ[i]);

      if (!new_environ[i])

      {

        write_stderr("out of memory\n");

        exit(1);

      }

    }

    new_environ[i] = NULL;

    environ = new_environ;

    /* See notes about Valgrind above. */

#ifdef USE_VALGRIND

    ps_status_new_environ = new_environ;

#endif

  }

  /*

   * 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[]. (We use custom pg_getopt_start/next() functions nowadays

   * that don't do that, but those other dependencies might still exist.)

   */

  {

    char    **new_argv;

    int     i;

    new_argv = (char **) malloc((argc + 1) * sizeof(char *));

    if (!new_argv)

    {

      write_stderr("out of memory\n");

      exit(1);

    }

    for (i = 0; i < argc; i++)

    {

      new_argv[i] = strdup(argv[i]);

      if (!new_argv[i])

      {

        write_stderr("out of memory\n");

        exit(1);

      }

    }

    new_argv[argc] = NULL;

#if defined(__darwin__)

    /*

     * macOS has a static copy of the argv pointer, which we may fix like

     * so:

     */

    *_NSGetArgv() = new_argv;

#endif

    argv = new_argv;

  }

#endif              /* PS_USE_CLOBBER_ARGV */

  return argv;

}

/*

 * Call this once during subprocess startup to set the identification

 * values.

 *

 * If fixed_part is NULL, a default will be obtained from MyBackendType.

 *

 * At this point, the original argv[] array may be overwritten.

 */

void

init_ps_display(const char *fixed_part)

{

#ifndef PS_USE_NONE

  bool    save_update_process_title;

#endif

  Assert(fixed_part || MyBackendType);

  if (!fixed_part)

    fixed_part = GetBackendTypeDesc(MyBackendType);

#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;

  /* make extra argv slots point at end_of_area (a NUL) */

  for (int 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.

   */

#if defined(PS_USE_SETPROCTITLE) || defined(PS_USE_SETPROCTITLE_FAST)

  /*

   * apparently setproctitle() already adds a `progname:' prefix to the ps

   * line

   */

#define PROGRAM_NAME_PREFIX ""

#else

#define PROGRAM_NAME_PREFIX "postgres: "

#endif

  if (*cluster_name == '\0')

  {

    snprintf(ps_buffer, ps_buffer_size,

         PROGRAM_NAME_PREFIX "%s ",

         fixed_part);

  }

  else

  {

    snprintf(ps_buffer, ps_buffer_size,

         PROGRAM_NAME_PREFIX "%s: %s ",

         cluster_name, fixed_part);

  }

  ps_buffer_cur_len = ps_buffer_fixed_size = strlen(ps_buffer);

  /*

   * On the first run, force the update.

   */

  save_update_process_title = update_process_title;

  update_process_title = true;

  set_ps_display("");

  update_process_title = save_update_process_title;

#endif              /* not PS_USE_NONE */

}

#ifndef PS_USE_NONE

/*

 * update_ps_display_precheck

 *    Helper function to determine if updating the process title is

 *    something that we need to do.

 */

static bool

update_ps_display_precheck(void)

{

  /* update_process_title=off disables updates */

  if (!update_process_title)

    return false;

  /* no ps display for stand-alone backend */

  if (!IsUnderPostmaster)

    return false;

#ifdef PS_USE_CLOBBER_ARGV

  /* If ps_buffer is a pointer, it might still be null */

  if (!ps_buffer)

    return false;

#endif

  return true;

}

#endif              /* not PS_USE_NONE */

/*

 * set_ps_display_suffix

 *    Adjust the process title to append 'suffix' onto the end with a space

 *    between it and the current process title.

 */

void

set_ps_display_suffix(const char *suffix)

{

#ifndef PS_USE_NONE

  size_t    len;

  /* first, check if we need to update the process title */

  if (!update_ps_display_precheck())

    return;

  /* if there's already a suffix, overwrite it */

  if (ps_buffer_nosuffix_len > 0)

    ps_buffer_cur_len = ps_buffer_nosuffix_len;

  else

    ps_buffer_nosuffix_len = ps_buffer_cur_len;

  len = strlen(suffix);

  /* check if we have enough space to append the suffix */

  if (ps_buffer_cur_len + len + 1 >= ps_buffer_size)

  {

    /* not enough space.  Check the buffer isn't full already */

    if (ps_buffer_cur_len < ps_buffer_size - 1)

    {

      /* append a space before the suffix */

      ps_buffer[ps_buffer_cur_len++] = ' ';

      /* just add what we can and fill the ps_buffer */

      memcpy(ps_buffer + ps_buffer_cur_len, suffix,

           ps_buffer_size - ps_buffer_cur_len - 1);

      ps_buffer[ps_buffer_size - 1] = '\0';

      ps_buffer_cur_len = ps_buffer_size - 1;

    }

  }

  else

  {

    ps_buffer[ps_buffer_cur_len++] = ' ';

    memcpy(ps_buffer + ps_buffer_cur_len, suffix, len + 1);

    ps_buffer_cur_len = ps_buffer_cur_len + len;

  }

  Assert(strlen(ps_buffer) == ps_buffer_cur_len);

  /* and set the new title */

  flush_ps_display();

#endif              /* not PS_USE_NONE */

}

/*

 * set_ps_display_remove_suffix

 *    Remove the process display suffix added by set_ps_display_suffix

 */

void

set_ps_display_remove_suffix(void)

{

#ifndef PS_USE_NONE

  /* first, check if we need to update the process title */

  if (!update_ps_display_precheck())

    return;

  /* check we added a suffix */

  if (ps_buffer_nosuffix_len == 0)

    return;         /* no suffix */

  /* remove the suffix from ps_buffer */

  ps_buffer[ps_buffer_nosuffix_len] = '\0';

  ps_buffer_cur_len = ps_buffer_nosuffix_len;

  ps_buffer_nosuffix_len = 0;

  Assert(ps_buffer_cur_len == strlen(ps_buffer));

  /* and set the new title */

  flush_ps_display();

#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.

 *

 * 'len' must be the same as strlen(activity)

 */

void

set_ps_display_with_len(const char *activity, size_t len)

{

  Assert(strlen(activity) == len);

#ifndef PS_USE_NONE

  /* first, check if we need to update the process title */

  if (!update_ps_display_precheck())

    return;

  /* wipe out any suffix when the title is completely changed */

  ps_buffer_nosuffix_len = 0;

  /* Update ps_buffer to contain both fixed part and activity */

  if (ps_buffer_fixed_size + len >= ps_buffer_size)

  {

    /* handle the case where ps_buffer doesn't have enough space */

    memcpy(ps_buffer + ps_buffer_fixed_size, activity,

         ps_buffer_size - ps_buffer_fixed_size - 1);

    ps_buffer[ps_buffer_size - 1] = '\0';

    ps_buffer_cur_len = ps_buffer_size - 1;

  }

  else

  {

    memcpy(ps_buffer + ps_buffer_fixed_size, activity, len + 1);

    ps_buffer_cur_len = ps_buffer_fixed_size + len;

  }

  Assert(strlen(ps_buffer) == ps_buffer_cur_len);

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

  flush_ps_display();

#endif              /* not PS_USE_NONE */

}

#ifndef PS_USE_NONE

static void

flush_ps_display(void)

{

#ifdef PS_USE_SETPROCTITLE

  setproctitle("%s", ps_buffer);

#elif defined(PS_USE_SETPROCTITLE_FAST)

  setproctitle_fast("%s", ps_buffer);

#endif

#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

#ifndef PS_USE_NONE

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

  return ps_buffer + ps_buffer_fixed_size;

#else

  *displen = 0;

  return "";

#endif

}