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lslogins: consolidate and optimize utmp files use 

* the original read_utmp() code is from GPLv3+, but lslogins is GPLv2+
  (see a6bf40ee77 (commitcomment-53407151))

* remove redundant parse_btmp() and parse_wtmp() as it does not
  provide anything

* reduce realloc() calls, allocate all in one step

Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2021-07-15 12:24:07 +02:00
parent 22a2bce042
commit 650fca1a06
1 changed files with 39 additions and 42 deletions
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81
login-utils/lslogins.c
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@ -474,55 +474,52 @@ static struct utmpx *get_last_btmp(struct lslogins_control *ctl, const char *use
}
static int read_utmp(char const *file, size_t *nents, struct utmpx **res)
static int parse_utmpx(const char *path, size_t *nrecords, struct utmpx **records)
{
size_t n_read = 0, n_alloc = 0;
struct utmpx *utmp = NULL, *u;
size_t i, imax = 0;
struct utmpx *ary = NULL;
struct stat st;
if (utmpxname(file) < 0)
*nrecords = 0;
*records = NULL;
if (utmpxname(path) < 0)
return -errno;
setutxent();
errno = 0;
/* optimize allocation according to file size, the realloc() below is
* just fallback only */
if (stat(path, &st) == 0 && (size_t) st.st_size > sizeof(struct utmpx)) {
imax = st.st_size / sizeof(struct utmpx);
ary = xmalloc(imax * sizeof(struct utmpx));
}
while ((u = getutxent()) != NULL) {
if (n_read == n_alloc) {
n_alloc += 32;
utmp = xrealloc(utmp, n_alloc * sizeof (struct utmpx));
for (i = 0; ; i++) {
struct utmpx *u;
errno = 0;
u = getutxent();
if (!u) {
if (errno)
goto fail;
break;
}
utmp[n_read++] = *u;
if (i == imax)
ary = xrealloc(ary, (imax *= 2) * sizeof(struct utmpx));
ary[i] = *u;
}
if (!u && errno) {
free(utmp);
*nrecords = i;
*records = ary;
endutxent();
return 0;
fail:
endutxent();
free(ary);
if (errno) {
if (errno != EACCES)
err(EXIT_FAILURE, "%s", path);
return -errno;
}
endutxent();
*nents = n_read;
*res = utmp;
return 0;
}
static int parse_wtmp(struct lslogins_control *ctl, char *path)
{
int rc = 0;
rc = read_utmp(path, &ctl->wtmp_size, &ctl->wtmp);
if (rc < 0 && errno != EACCES)
err(EXIT_FAILURE, "%s", path);
return rc;
}
static int parse_btmp(struct lslogins_control *ctl, char *path)
{
int rc = 0;
rc = read_utmp(path, &ctl->btmp_size, &ctl->btmp);
if (rc < 0 && errno != EACCES)
err(EXIT_FAILURE, "%s", path);
return rc;
return -EINVAL;
}
static void get_lastlog(struct lslogins_control *ctl, uid_t uid, void *dst, int what)
@ -1647,11 +1644,11 @@ int main(int argc, char *argv[])
return EXIT_FAILURE;
if (require_wtmp()) {
parse_wtmp(ctl, path_wtmp);
parse_utmpx(path_wtmp, &ctl->wtmp_size, &ctl->wtmp);
ctl->lastlogin_fd = open(path_lastlog, O_RDONLY, 0);
}
if (require_btmp())
parse_btmp(ctl, path_btmp);
parse_utmpx(path_btmp, &ctl->btmp_size, &ctl->btmp);
if (logins || groups)
get_ulist(ctl, logins, groups);