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 <linux/capability.h>
11 #include <sys/syscall.h>
12 #include <unistd.h>
13
14 #define MAX_LINUX_CAPABILITY_U32S _LINUX_CAPABILITY_U32S_3
15
16 bool perf_cap__capable(int cap, bool *used_root)
17 {
18 struct __user_cap_header_struct header = {
19 .version = _LINUX_CAPABILITY_VERSION_3,
20 .pid = 0,
21 };
22 struct __user_cap_data_struct data[MAX_LINUX_CAPABILITY_U32S] = {};
23 __u32 cap_val;
24
25 *used_root = false;
26 while (syscall(SYS_capget, &header, &data[0]) == -1) {
27 /* Retry, first attempt has set the header.version correctly. */
28 if (errno == EINVAL && header.version != _LINUX_CAPABILITY_VERSION_3 &&
29 header.version == _LINUX_CAPABILITY_VERSION_1)
30 continue;
31
32 pr_debug2("capget syscall failed (%s - %d) fall back on root check\n",
33 strerror(errno), errno);
34 *used_root = true;
35 return geteuid() == 0;
36 }
37
38 /* Extract the relevant capability bit. */
39 if (cap >= 32) {
40 if (header.version == _LINUX_CAPABILITY_VERSION_3) {
41 cap_val = data[1].effective;
42 } else {
43 /* Capability beyond 32 is requested but only 32 are supported. */
44 return false;
45 }
46 } else {
47 cap_val = data[0].effective;
48 }
49 return (cap_val & (1 << (cap & 0x1f))) != 0;
50 }
51
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