src/lib/process-title.c

	process-title.c revision 29ca4c8015b4936378d49937f97049f33d3aaaf9
/* Copyright (c) 2002-2016 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "env-util.h"
#include "process-title.h"

#include <unistd.h> /* FreeBSD */

static char *process_name = NULL;

#ifdef HAVE_SETPROCTITLE
#  undef PROCTITLE_HACK
#endif

#ifdef PROCTITLE_HACK

#define PROCTITLE_CLEAR_CHAR 0xab

static char *process_title;
static size_t process_title_len, process_title_clean_pos;
static void *argv_memblock, *environ_memblock;

static void proctitle_hack_init(char *argv[], char *env[])
{
    char *last;
    unsigned int i;
    bool clear_env;

    i_assert(argv[0] != NULL);

    /* find the last argv or environment string. it should always be the
       last string in environ, but don't rely on it. this is what openssh
       does, so hopefully it's safe enough. */
    last = argv[0] + strlen(argv[0]) + 1;
    for (i = 1; argv[i] != NULL; i++) {
        if (argv[i] == last)
            last = argv[i] + strlen(argv[i]) + 1;
    }
    if (env[0] == NULL)
        clear_env = FALSE;
    else {
        clear_env = last == env[0];
        for (i = 0; env[i] != NULL; i++) {
            if (env[i] == last)
                last = env[i] + strlen(env[i]) + 1;
        }
    }

    process_title = argv[0];
    process_title_len = last - argv[0];

    /* if there are problems with this approach, try to make sure we
       notice it */
    if (clear_env) {
        memset(env[0], PROCTITLE_CLEAR_CHAR, last - env[0]);
        process_title_clean_pos = env[0] - process_title;
    } else {
        process_title_clean_pos = 0;
    }
}

static char **argv_dup(char *old_argv[], void **memblock_r)
{
    /* @UNSAFE */
    void *memblock, *memblock_end;
    char **new_argv;
    unsigned int i, count;
    size_t len, memblock_len = 0;

    for (count = 0; old_argv[count] != NULL; count++)
        memblock_len += strlen(old_argv[count]) + 1;
    memblock_len += sizeof(char *) * (count + 1);

    memblock = malloc(memblock_len);
    if (memblock == NULL)
        i_fatal_status(FATAL_OUTOFMEM, "malloc() failed: %m");
    *memblock_r = memblock;
    memblock_end = PTR_OFFSET(memblock, memblock_len);

    new_argv = memblock;
    memblock = PTR_OFFSET(memblock, sizeof(char *) * (count + 1));

    for (i = 0; i < count; i++) {
        new_argv[i] = memblock;
        len = strlen(old_argv[i]) + 1;
        memcpy(memblock, old_argv[i], len);
        memblock = PTR_OFFSET(memblock, len);
    }
    i_assert(memblock == memblock_end);
    new_argv[i] = NULL;
    return new_argv;
}

static void proctitle_hack_set(const char *title)
{
    size_t len = strlen(title);

    /* OS X wants two NULs */
    if (len >= process_title_len-1)
        len = process_title_len - 2;

    memcpy(process_title, title, len);
    process_title[len++] = '\0';
    process_title[len++] = '\0';

    if (len < process_title_clean_pos) {
        memset(process_title + len, PROCTITLE_CLEAR_CHAR,
               process_title_clean_pos - len);
        process_title_clean_pos = len;
    } else if (process_title_clean_pos != 0) {
        process_title_clean_pos = len;
    }
}

#endif

void process_title_init(char **argv[])
{
#ifdef PROCTITLE_HACK
    char ***environ_p = env_get_environ_p();
    char **orig_argv = *argv;
    char **orig_environ = *environ_p;

    *argv = argv_dup(orig_argv, &argv_memblock);
    *environ_p = argv_dup(orig_environ, &environ_memblock);
    proctitle_hack_init(orig_argv, orig_environ);
#endif
    process_name = (*argv)[0];
}

void process_title_set(const char *title ATTR_UNUSED)
{
    i_assert(process_name != NULL);

#ifdef HAVE_SETPROCTITLE
    if (title == NULL)
        setproctitle(NULL);
    else
        setproctitle("%s", title);
#elif defined(PROCTITLE_HACK)
    T_BEGIN {
        proctitle_hack_set(t_strconcat(process_name, " ", title, NULL));
    } T_END;
#endif
}

void process_title_deinit(void)
{
#ifdef PROCTITLE_HACK
    char ***environ_p = env_get_environ_p();

    free(argv_memblock);
    free(environ_memblock);

    /* Environment is no longer usable. Make sure we won't crash in case
       some library's deinit function still calls getenv(). This code was
       mainly added because of GNUTLS where we don't really care about the
       getenv() call.

       Alternatively we could remove the free() calls above, but that would
       annoy memory leak checking tools. Also we could attempt to restore
       the environ_p to its original state, but that's a bit complicated. */
    *environ_p = NULL;
#endif
}