1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Copyright (c) 2024 Meta Platforms, Inc. and affiliates. 4 * Copyright (c) 2024 Tejun Heo <tj@kernel.org> 5 * Copyright (c) 2024 David Vernet <dvernet@meta.com> 6 */ 7 #ifndef __SCX_COMPAT_H 8 #define __SCX_COMPAT_H 9 10 #include <bpf/btf.h> 11 #include <fcntl.h> 12 #include <stdlib.h> 13 #include <unistd.h> 14 15 struct btf *__COMPAT_vmlinux_btf __attribute__((weak)); 16 17 static inline void __COMPAT_load_vmlinux_btf(void) 18 { 19 if (!__COMPAT_vmlinux_btf) { 20 __COMPAT_vmlinux_btf = btf__load_vmlinux_btf(); 21 SCX_BUG_ON(!__COMPAT_vmlinux_btf, "btf__load_vmlinux_btf()"); 22 } 23 } 24 25 static inline bool __COMPAT_read_enum(const char *type, const char *name, u64 *v) 26 { 27 const struct btf_type *t; 28 const char *n; 29 s32 tid; 30 int i; 31 32 __COMPAT_load_vmlinux_btf(); 33 34 tid = btf__find_by_name(__COMPAT_vmlinux_btf, type); 35 if (tid < 0) 36 return false; 37 38 t = btf__type_by_id(__COMPAT_vmlinux_btf, tid); 39 SCX_BUG_ON(!t, "btf__type_by_id(%d)", tid); 40 41 if (btf_is_enum(t)) { 42 struct btf_enum *e = btf_enum(t); 43 44 for (i = 0; i < BTF_INFO_VLEN(t->info); i++) { 45 n = btf__name_by_offset(__COMPAT_vmlinux_btf, e[i].name_off); 46 SCX_BUG_ON(!n, "btf__name_by_offset()"); 47 if (!strcmp(n, name)) { 48 *v = e[i].val; 49 return true; 50 } 51 } 52 } else if (btf_is_enum64(t)) { 53 struct btf_enum64 *e = btf_enum64(t); 54 55 for (i = 0; i < BTF_INFO_VLEN(t->info); i++) { 56 n = btf__name_by_offset(__COMPAT_vmlinux_btf, e[i].name_off); 57 SCX_BUG_ON(!n, "btf__name_by_offset()"); 58 if (!strcmp(n, name)) { 59 *v = btf_enum64_value(&e[i]); 60 return true; 61 } 62 } 63 } 64 65 return false; 66 } 67 68 #define __COMPAT_ENUM_OR_ZERO(__type, __ent) \ 69 ({ \ 70 u64 __val = 0; \ 71 __COMPAT_read_enum(__type, __ent, &__val); \ 72 __val; \ 73 }) 74 75 static inline bool __COMPAT_has_ksym(const char *ksym) 76 { 77 __COMPAT_load_vmlinux_btf(); 78 return btf__find_by_name(__COMPAT_vmlinux_btf, ksym) >= 0; 79 } 80 81 static inline bool __COMPAT_struct_has_field(const char *type, const char *field) 82 { 83 const struct btf_type *t; 84 const struct btf_member *m; 85 const char *n; 86 s32 tid; 87 int i; 88 89 __COMPAT_load_vmlinux_btf(); 90 tid = btf__find_by_name_kind(__COMPAT_vmlinux_btf, type, BTF_KIND_STRUCT); 91 if (tid < 0) 92 return false; 93 94 t = btf__type_by_id(__COMPAT_vmlinux_btf, tid); 95 SCX_BUG_ON(!t, "btf__type_by_id(%d)", tid); 96 97 m = btf_members(t); 98 99 for (i = 0; i < BTF_INFO_VLEN(t->info); i++) { 100 n = btf__name_by_offset(__COMPAT_vmlinux_btf, m[i].name_off); 101 SCX_BUG_ON(!n, "btf__name_by_offset()"); 102 if (!strcmp(n, field)) 103 return true; 104 } 105 106 return false; 107 } 108 109 #define SCX_OPS_SWITCH_PARTIAL \ 110 __COMPAT_ENUM_OR_ZERO("scx_ops_flags", "SCX_OPS_SWITCH_PARTIAL") 111 112 static inline long scx_hotplug_seq(void) 113 { 114 int fd; 115 char buf[32]; 116 ssize_t len; 117 long val; 118 119 fd = open("/sys/kernel/sched_ext/hotplug_seq", O_RDONLY); 120 if (fd < 0) 121 return -ENOENT; 122 123 len = read(fd, buf, sizeof(buf) - 1); 124 SCX_BUG_ON(len <= 0, "read failed (%ld)", len); 125 buf[len] = 0; 126 close(fd); 127 128 val = strtoul(buf, NULL, 10); 129 SCX_BUG_ON(val < 0, "invalid num hotplug events: %lu", val); 130 131 return val; 132 } 133 134 /* 135 * struct sched_ext_ops can change over time. If compat.bpf.h::SCX_OPS_DEFINE() 136 * is used to define ops and compat.h::SCX_OPS_LOAD/ATTACH() are used to load 137 * and attach it, backward compatibility is automatically maintained where 138 * reasonable. 139 * 140 * ec7e3b0463e1 ("implement-ops") in https://github.com/sched-ext/sched_ext is 141 * the current minimum required kernel version. 142 */ 143 #define SCX_OPS_OPEN(__ops_name, __scx_name) ({ \ 144 struct __scx_name *__skel; \ 145 \ 146 SCX_BUG_ON(!__COMPAT_struct_has_field("sched_ext_ops", "dump"), \ 147 "sched_ext_ops.dump() missing, kernel too old?"); \ 148 \ 149 __skel = __scx_name##__open(); \ 150 SCX_BUG_ON(!__skel, "Could not open " #__scx_name); \ 151 __skel->struct_ops.__ops_name->hotplug_seq = scx_hotplug_seq(); \ 152 __skel; \ 153 }) 154 155 #define SCX_OPS_LOAD(__skel, __ops_name, __scx_name, __uei_name) ({ \ 156 UEI_SET_SIZE(__skel, __ops_name, __uei_name); \ 157 SCX_BUG_ON(__scx_name##__load((__skel)), "Failed to load skel"); \ 158 }) 159 160 /* 161 * New versions of bpftool now emit additional link placeholders for BPF maps, 162 * and set up BPF skeleton in such a way that libbpf will auto-attach BPF maps 163 * automatically, assumming libbpf is recent enough (v1.5+). Old libbpf will do 164 * nothing with those links and won't attempt to auto-attach maps. 165 * 166 * To maintain compatibility with older libbpf while avoiding trying to attach 167 * twice, disable the autoattach feature on newer libbpf. 168 */ 169 #if LIBBPF_MAJOR_VERSION > 1 || \ 170 (LIBBPF_MAJOR_VERSION == 1 && LIBBPF_MINOR_VERSION >= 5) 171 #define __SCX_OPS_DISABLE_AUTOATTACH(__skel, __ops_name) \ 172 bpf_map__set_autoattach((__skel)->maps.__ops_name, false) 173 #else 174 #define __SCX_OPS_DISABLE_AUTOATTACH(__skel, __ops_name) do {} while (0) 175 #endif 176 177 #define SCX_OPS_ATTACH(__skel, __ops_name, __scx_name) ({ \ 178 struct bpf_link *__link; \ 179 __SCX_OPS_DISABLE_AUTOATTACH(__skel, __ops_name); \ 180 SCX_BUG_ON(__scx_name##__attach((__skel)), "Failed to attach skel"); \ 181 __link = bpf_map__attach_struct_ops((__skel)->maps.__ops_name); \ 182 SCX_BUG_ON(!__link, "Failed to attach struct_ops"); \ 183 __link; \ 184 }) 185 186 #endif /* __SCX_COMPAT_H */ 187