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