projects/linux·blob master · refs

46 lines · 1.1 KiB

1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Capability utilities
4 */
5
6#include "cap.h"
7#include "debug.h"
8#include <errno.h>
9#include <string.h>
10#include <sys/syscall.h>
11#include <unistd.h>
12
13#define MAX_LINUX_CAPABILITY_U32S _LINUX_CAPABILITY_U32S_3
14
15bool perf_cap__capable(int cap)
16{
17 struct __user_cap_header_struct header = {
18 .version = _LINUX_CAPABILITY_VERSION_3,
19 .pid = 0,
20 };
21 struct __user_cap_data_struct data[MAX_LINUX_CAPABILITY_U32S] = {};
22 __u32 cap_val;
23
24 while (syscall(SYS_capget, &header, &data[0]) == -1) {
25 /* Retry, first attempt has set the header.version correctly. */
26 if (errno == EINVAL && header.version != _LINUX_CAPABILITY_VERSION_3 &&
27 header.version == _LINUX_CAPABILITY_VERSION_1)
28 continue;
29
30 pr_debug2("capget syscall failed (%m) fall back on root check\n");
31 return geteuid() == 0;
32 }
33
34 /* Extract the relevant capability bit. */
35 if (cap >= 32) {
36 if (header.version == _LINUX_CAPABILITY_VERSION_3) {
37 cap_val = data[1].effective;
38 } else {
39 /* Capability beyond 32 is requested but only 32 are supported. */
40 return false;
41 }
42 } else {
43 cap_val = data[0].effective;
44 }
45 return (cap_val & (1 << (cap & 0x1f))) != 0;
46}