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 15 bool perf_cap__capable(int cap, bool *used_root) 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 *used_root = false; 25 while (syscall(SYS_capget, &header, &data[0]) == -1) { 26 /* Retry, first attempt has set the header.version correctly. */ 27 if (errno == EINVAL && header.version != _LINUX_CAPABILITY_VERSION_3 && 28 header.version == _LINUX_CAPABILITY_VERSION_1) 29 continue; 30 31 pr_debug2("capget syscall failed (%m) fall back on root check\n"); 32 *used_root = true; 33 return geteuid() == 0; 34 } 35 36 /* Extract the relevant capability bit. */ 37 if (cap >= 32) { 38 if (header.version == _LINUX_CAPABILITY_VERSION_3) { 39 cap_val = data[1].effective; 40 } else { 41 /* Capability beyond 32 is requested but only 32 are supported. */ 42 return false; 43 } 44 } else { 45 cap_val = data[0].effective; 46 } 47 return (cap_val & (1 << (cap & 0x1f))) != 0; 48 } 49