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 perf_cap__capable(int cap,bool * used_root)15bool 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 (%s - %d) fall back on root check\n", 32 strerror(errno), errno); 33 *used_root = true; 34 return geteuid() == 0; 35 } 36 37 /* Extract the relevant capability bit. */ 38 if (cap >= 32) { 39 if (header.version == _LINUX_CAPABILITY_VERSION_3) { 40 cap_val = data[1].effective; 41 } else { 42 /* Capability beyond 32 is requested but only 32 are supported. */ 43 return false; 44 } 45 } else { 46 cap_val = data[0].effective; 47 } 48 return (cap_val & (1 << (cap & 0x1f))) != 0; 49 } 50