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/*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2, or (at your option) any
* later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <sys/prctl.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <errno.h>
#include "c.h"
#include "caputils.h"
#include "pathnames.h"
#include "procfs.h"
static int test_cap(unsigned int cap)
{
/* prctl returns 0 or 1 for valid caps, -1 otherwise */
return prctl(PR_CAPBSET_READ, cap, 0, 0, 0) >= 0;
}
static int cap_last_by_bsearch(int *ret)
{
/* starting with cap=INT_MAX means we always know
* that cap1 is invalid after the first iteration */
int cap = INT_MAX;
unsigned int cap0 = 0, cap1 = INT_MAX;
while ((int)cap0 < cap) {
if (test_cap(cap))
cap0 = cap;
else
cap1 = cap;
cap = (cap0 + cap1) / 2U;
}
*ret = cap;
return 0;
}
static int cap_last_by_procfs(int *ret)
{
FILE *f = fopen(_PATH_PROC_CAPLASTCAP, "r");
int rc = -EINVAL;
*ret = 0;
if (f && fd_is_procfs(fileno(f))) {
int cap;
/* we check if the cap after this one really isn't valid */
if (fscanf(f, "%d", &cap) == 1 &&
cap < INT_MAX && !test_cap(cap + 1)) {
*ret = cap;
rc = 0;
}
}
if (f)
fclose(f);
return rc;
}
int cap_last_cap(void)
{
static int cap = -1;
if (cap != -1)
return cap;
if (cap_last_by_procfs(&cap) < 0)
cap_last_by_bsearch(&cap);
return cap;
}
#ifdef TEST_PROGRAM_CAPUTILS
int main(int argc, char *argv[])
{
int rc = 0, cap;
if (argc < 2) {
fprintf(stderr, "usage: %1$s --last-by-procfs\n"
" %1$s --last-by-bsearch\n"
" %1$s --last\n",
program_invocation_short_name);
return EXIT_FAILURE;
}
if (strcmp(argv[1], "--last-by-procfs") == 0) {
rc = cap_last_by_procfs(&cap);
if (rc == 0)
printf("last cap: %d\n", cap);
} else if (strcmp(argv[1], "--last-by-bsearch") == 0) {
rc = cap_last_by_bsearch(&cap);
if (rc == 0)
printf("last cap: %d\n", cap);
} else if (strcmp(argv[1], "--last") == 0)
printf("last cap: %d\n", cap_last_cap());
return rc == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
}
#endif
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