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lib/caputils: split to multiple functions, add test

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Let's split the code to make it possible to test separately bsearch as
well as procfs based cap_last_cap().

 $ ./test_caputils --last-by-bsearch
 last cap: 39
 $ ./test_caputils --last-by-procfs
 last cap: 39
 $ ./test_caputils --last
 last cap: 39

Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2020-11-20 11:21:41 +01:00
parent 1b54a74e86
commit 966420219c
2 changed files with 82 additions and 31 deletions
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106
lib/caputils.c
View file

@ -16,8 +16,11 @@
#include <sys/prctl.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <errno.h>
#include "c.h"
#include "caputils.h"
#include "procutils.h"
#include "pathnames.h"
@ -28,45 +31,88 @@ static int test_cap(unsigned int cap)
return prctl(PR_CAPBSET_READ, cap, 0, 0, 0) >= 0;
}
int cap_last_cap(void)
static int cap_last_by_bsearch(int *ret)
{
static int cap = -1;
FILE *f;
if (cap != -1)
return cap;
/* try to read value from kernel, check that the path is
* indeed in a procfs mount */
f = fopen(_PATH_PROC_CAPLASTCAP, "r");
if (f) {
int matched = 0;
if (proc_is_procfs(fileno(f))) {
matched = fscanf(f, "%d", &cap);
}
fclose(f);
/* we check if the cap after this one really isn't valid */
if (matched == 1 && cap < INT_MAX && !test_cap(cap + 1))
return cap;
}
/* if it wasn't possible to read the file in /proc,
* fall back to binary search over capabilities */
/* 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;
cap = INT_MAX;
while ((int)cap0 < cap) {
if (test_cap(cap)) {
if (test_cap(cap))
cap0 = cap;
} else {
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 && proc_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