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) 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 } 47