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 <unistd.h> 11 #include <linux/capability.h> 12 #include <sys/syscall.h> 13 14 #ifndef SYS_capget 15 #define SYS_capget 90 16 #endif 17 18 #define MAX_LINUX_CAPABILITY_U32S _LINUX_CAPABILITY_U32S_3 19 20 bool perf_cap__capable(int cap, bool *used_root) 21 { 22 struct __user_cap_header_struct header = { 23 .version = _LINUX_CAPABILITY_VERSION_3, 24 .pid = getpid(), 25 }; 26 struct __user_cap_data_struct data[MAX_LINUX_CAPABILITY_U32S]; 27 __u32 cap_val; 28 29 *used_root = false; 30 while (syscall(SYS_capget, &header, &data[0]) == -1) { 31 /* Retry, first attempt has set the header.version correctly. */ 32 if (errno == EINVAL && header.version != _LINUX_CAPABILITY_VERSION_3 && 33 header.version == _LINUX_CAPABILITY_VERSION_1) 34 continue; 35 36 pr_debug2("capget syscall failed (%s - %d) fall back on root check\n", 37 strerror(errno), errno); 38 *used_root = true; 39 return geteuid() == 0; 40 } 41 42 /* Extract the relevant capability bit. */ 43 if (cap >= 32) { 44 if (header.version == _LINUX_CAPABILITY_VERSION_3) { 45 cap_val = data[1].effective; 46 } else { 47 /* Capability beyond 32 is requested but only 32 are supported. */ 48 return false; 49 } 50 } else { 51 cap_val = data[0].effective; 52 } 53 return (cap_val & (1 << (cap & 0x1f))) != 0; 54 } 55