From 166750bc1dd256b2184b22588fb9fe6d3fbb93ae Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Fri, 13 Dec 2019 17:47:08 -0800 Subject: libbpf: Support libbpf-provided extern variables Add support for extern variables, provided to BPF program by libbpf. Currently the following extern variables are supported: - LINUX_KERNEL_VERSION; version of a kernel in which BPF program is executing, follows KERNEL_VERSION() macro convention, can be 4- and 8-byte long; - CONFIG_xxx values; a set of values of actual kernel config. Tristate, boolean, strings, and integer values are supported. Set of possible values is determined by declared type of extern variable. Supported types of variables are: - Tristate values. Are represented as `enum libbpf_tristate`. Accepted values are **strictly** 'y', 'n', or 'm', which are represented as TRI_YES, TRI_NO, or TRI_MODULE, respectively. - Boolean values. Are represented as bool (_Bool) types. Accepted values are 'y' and 'n' only, turning into true/false values, respectively. - Single-character values. Can be used both as a substritute for bool/tristate, or as a small-range integer: - 'y'/'n'/'m' are represented as is, as characters 'y', 'n', or 'm'; - integers in a range [-128, 127] or [0, 255] (depending on signedness of char in target architecture) are recognized and represented with respective values of char type. - Strings. String values are declared as fixed-length char arrays. String of up to that length will be accepted and put in first N bytes of char array, with the rest of bytes zeroed out. If config string value is longer than space alloted, it will be truncated and warning message emitted. Char array is always zero terminated. String literals in config have to be enclosed in double quotes, just like C-style string literals. - Integers. 8-, 16-, 32-, and 64-bit integers are supported, both signed and unsigned variants. Libbpf enforces parsed config value to be in the supported range of corresponding integer type. Integers values in config can be: - decimal integers, with optional + and - signs; - hexadecimal integers, prefixed with 0x or 0X; - octal integers, starting with 0. Config file itself is searched in /boot/config-$(uname -r) location with fallback to /proc/config.gz, unless config path is specified explicitly through bpf_object_open_opts' kernel_config_path option. Both gzipped and plain text formats are supported. Libbpf adds explicit dependency on zlib because of this, but this shouldn't be a problem, given libelf already depends on zlib. All detected extern variables, are put into a separate .extern internal map. It, similarly to .rodata map, is marked as read-only from BPF program side, as well as is frozen on load. This allows BPF verifier to track extern values as constants and perform enhanced branch prediction and dead code elimination. This can be relied upon for doing kernel version/feature detection and using potentially unsupported field relocations or BPF helpers in a CO-RE-based BPF program, while still having a single version of BPF program running on old and new kernels. Selftests are validating this explicitly for unexisting BPF helper. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20191214014710.3449601-3-andriin@fb.com --- tools/lib/bpf/bpf_helpers.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'tools/lib/bpf/bpf_helpers.h') diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index 0c7d28292898..aa46700075e1 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -25,6 +25,9 @@ #ifndef __always_inline #define __always_inline __attribute__((always_inline)) #endif +#ifndef __weak +#define __weak __attribute__((weak)) +#endif /* * Helper structure used by eBPF C program @@ -44,4 +47,10 @@ enum libbpf_pin_type { LIBBPF_PIN_BY_NAME, }; +enum libbpf_tristate { + TRI_NO = 0, + TRI_YES = 1, + TRI_MODULE = 2, +}; + #endif -- cgit v1.2.3 From 81bfdd087bf31a87c5ff25cc7004d5308954a35c Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 18 Dec 2019 16:28:34 -0800 Subject: libbpf: Put Kconfig externs into .kconfig section Move Kconfig-provided externs into custom .kconfig section. Add __kconfig into bpf_helpers.h for user convenience. Update selftests accordingly. Suggested-by: Daniel Borkmann Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20191219002837.3074619-2-andriin@fb.com --- tools/bpf/bpftool/gen.c | 8 +-- tools/lib/bpf/bpf_helpers.h | 2 + tools/lib/bpf/libbpf.c | 58 +++++++++++++--------- tools/testing/selftests/bpf/prog_tests/skeleton.c | 16 +++--- .../testing/selftests/bpf/progs/test_core_extern.c | 20 ++++---- tools/testing/selftests/bpf/progs/test_skeleton.c | 4 +- 6 files changed, 60 insertions(+), 48 deletions(-) (limited to 'tools/lib/bpf/bpf_helpers.h') diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index 851c465f99dc..a14d8bc5d31d 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -83,8 +83,8 @@ static const char *get_map_ident(const struct bpf_map *map) return "rodata"; else if (str_has_suffix(name, ".bss")) return "bss"; - else if (str_has_suffix(name, ".extern")) - return "externs"; /* extern is a C keyword */ + else if (str_has_suffix(name, ".kconfig")) + return "kconfig"; else return NULL; } @@ -112,8 +112,8 @@ static int codegen_datasec_def(struct bpf_object *obj, sec_ident = "bss"; else if (strcmp(sec_name, ".rodata") == 0) sec_ident = "rodata"; - else if (strcmp(sec_name, ".extern") == 0) - sec_ident = "externs"; /* extern is a C keyword */ + else if (strcmp(sec_name, ".kconfig") == 0) + sec_ident = "kconfig"; else return 0; diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index aa46700075e1..f69cc208778a 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -53,4 +53,6 @@ enum libbpf_tristate { TRI_MODULE = 2, }; +#define __kconfig __attribute__((section(".kconfig"))) + #endif diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 2a341a5b9f63..0772eb3254e2 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -231,21 +231,21 @@ struct bpf_program { #define DATA_SEC ".data" #define BSS_SEC ".bss" #define RODATA_SEC ".rodata" -#define EXTERN_SEC ".extern" +#define KCONFIG_SEC ".kconfig" enum libbpf_map_type { LIBBPF_MAP_UNSPEC, LIBBPF_MAP_DATA, LIBBPF_MAP_BSS, LIBBPF_MAP_RODATA, - LIBBPF_MAP_EXTERN, + LIBBPF_MAP_KCONFIG, }; static const char * const libbpf_type_to_btf_name[] = { [LIBBPF_MAP_DATA] = DATA_SEC, [LIBBPF_MAP_BSS] = BSS_SEC, [LIBBPF_MAP_RODATA] = RODATA_SEC, - [LIBBPF_MAP_EXTERN] = EXTERN_SEC, + [LIBBPF_MAP_KCONFIG] = KCONFIG_SEC, }; struct bpf_map { @@ -305,7 +305,7 @@ struct bpf_object { char *kconfig_path; struct extern_desc *externs; int nr_extern; - int extern_map_idx; + int kconfig_map_idx; bool loaded; bool has_pseudo_calls; @@ -606,7 +606,7 @@ static struct bpf_object *bpf_object__new(const char *path, obj->efile.data_shndx = -1; obj->efile.rodata_shndx = -1; obj->efile.bss_shndx = -1; - obj->extern_map_idx = -1; + obj->kconfig_map_idx = -1; obj->kern_version = get_kernel_version(); obj->loaded = false; @@ -902,11 +902,25 @@ static size_t bpf_map_mmap_sz(const struct bpf_map *map) return map_sz; } +static char *internal_map_name(struct bpf_object *obj, + enum libbpf_map_type type) +{ + char map_name[BPF_OBJ_NAME_LEN]; + const char *sfx = libbpf_type_to_btf_name[type]; + int sfx_len = max((size_t)7, strlen(sfx)); + int pfx_len = min((size_t)BPF_OBJ_NAME_LEN - sfx_len - 1, + strlen(obj->name)); + + snprintf(map_name, sizeof(map_name), "%.*s%.*s", pfx_len, obj->name, + sfx_len, libbpf_type_to_btf_name[type]); + + return strdup(map_name); +} + static int bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, int sec_idx, void *data, size_t data_sz) { - char map_name[BPF_OBJ_NAME_LEN]; struct bpf_map_def *def; struct bpf_map *map; int err; @@ -918,9 +932,7 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, map->libbpf_type = type; map->sec_idx = sec_idx; map->sec_offset = 0; - snprintf(map_name, sizeof(map_name), "%.8s%.7s", obj->name, - libbpf_type_to_btf_name[type]); - map->name = strdup(map_name); + map->name = internal_map_name(obj, type); if (!map->name) { pr_warn("failed to alloc map name\n"); return -ENOMEM; @@ -931,12 +943,12 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, def->key_size = sizeof(int); def->value_size = data_sz; def->max_entries = 1; - def->map_flags = type == LIBBPF_MAP_RODATA || type == LIBBPF_MAP_EXTERN + def->map_flags = type == LIBBPF_MAP_RODATA || type == LIBBPF_MAP_KCONFIG ? BPF_F_RDONLY_PROG : 0; def->map_flags |= BPF_F_MMAPABLE; pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %x.\n", - map_name, map->sec_idx, map->sec_offset, def->map_flags); + map->name, map->sec_idx, map->sec_offset, def->map_flags); map->mmaped = mmap(NULL, bpf_map_mmap_sz(map), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); @@ -1232,7 +1244,7 @@ out: return err; } -static int bpf_object__init_extern_map(struct bpf_object *obj) +static int bpf_object__init_kconfig_map(struct bpf_object *obj) { struct extern_desc *last_ext; size_t map_sz; @@ -1244,13 +1256,13 @@ static int bpf_object__init_extern_map(struct bpf_object *obj) last_ext = &obj->externs[obj->nr_extern - 1]; map_sz = last_ext->data_off + last_ext->sz; - err = bpf_object__init_internal_map(obj, LIBBPF_MAP_EXTERN, + err = bpf_object__init_internal_map(obj, LIBBPF_MAP_KCONFIG, obj->efile.symbols_shndx, NULL, map_sz); if (err) return err; - obj->extern_map_idx = obj->nr_maps - 1; + obj->kconfig_map_idx = obj->nr_maps - 1; return 0; } @@ -1742,7 +1754,7 @@ static int bpf_object__init_maps(struct bpf_object *obj, err = bpf_object__init_user_maps(obj, strict); err = err ?: bpf_object__init_user_btf_maps(obj, strict, pin_root_path); err = err ?: bpf_object__init_global_data_maps(obj); - err = err ?: bpf_object__init_extern_map(obj); + err = err ?: bpf_object__init_kconfig_map(obj); if (err) return err; @@ -2269,9 +2281,9 @@ static int bpf_object__collect_externs(struct bpf_object *obj) i, ext->sym_idx, ext->data_off, ext->name); } - btf_id = btf__find_by_name(obj->btf, EXTERN_SEC); + btf_id = btf__find_by_name(obj->btf, KCONFIG_SEC); if (btf_id <= 0) { - pr_warn("no BTF info found for '%s' datasec\n", EXTERN_SEC); + pr_warn("no BTF info found for '%s' datasec\n", KCONFIG_SEC); return -ESRCH; } @@ -2361,7 +2373,7 @@ bpf_object__section_to_libbpf_map_type(const struct bpf_object *obj, int shndx) else if (shndx == obj->efile.rodata_shndx) return LIBBPF_MAP_RODATA; else if (shndx == obj->efile.symbols_shndx) - return LIBBPF_MAP_EXTERN; + return LIBBPF_MAP_KCONFIG; else return LIBBPF_MAP_UNSPEC; } @@ -2908,8 +2920,8 @@ bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map) return err; } - /* Freeze .rodata and .extern map as read-only from syscall side. */ - if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_EXTERN) { + /* Freeze .rodata and .kconfig map as read-only from syscall side. */ + if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG) { err = bpf_map_freeze(map->fd); if (err) { err = -errno; @@ -4264,7 +4276,7 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj) break; case RELO_EXTERN: insn[0].src_reg = BPF_PSEUDO_MAP_VALUE; - insn[0].imm = obj->maps[obj->extern_map_idx].fd; + insn[0].imm = obj->maps[obj->kconfig_map_idx].fd; insn[1].imm = relo->sym_off; break; case RELO_CALL: @@ -4743,7 +4755,7 @@ static int bpf_object__resolve_externs(struct bpf_object *obj, if (obj->nr_extern == 0) return 0; - data = obj->maps[obj->extern_map_idx].mmaped; + data = obj->maps[obj->kconfig_map_idx].mmaped; for (i = 0; i < obj->nr_extern; i++) { ext = &obj->externs[i]; @@ -7546,7 +7558,7 @@ int bpf_object__open_skeleton(struct bpf_object_skeleton *s, } /* externs shouldn't be pre-setup from user code */ - if (mmaped && (*map)->libbpf_type != LIBBPF_MAP_EXTERN) + if (mmaped && (*map)->libbpf_type != LIBBPF_MAP_KCONFIG) *mmaped = (*map)->mmaped; } diff --git a/tools/testing/selftests/bpf/prog_tests/skeleton.c b/tools/testing/selftests/bpf/prog_tests/skeleton.c index ec6f2aec3853..9264a2736018 100644 --- a/tools/testing/selftests/bpf/prog_tests/skeleton.c +++ b/tools/testing/selftests/bpf/prog_tests/skeleton.c @@ -15,20 +15,18 @@ void test_skeleton(void) int duration = 0, err; struct test_skeleton* skel; struct test_skeleton__bss *bss; - struct test_skeleton__externs *exts; + struct test_skeleton__kconfig *kcfg; skel = test_skeleton__open(); if (CHECK(!skel, "skel_open", "failed to open skeleton\n")) return; - printf("EXTERNS BEFORE: %p\n", skel->externs); - if (CHECK(skel->externs, "skel_externs", "externs are mmaped()!\n")) + if (CHECK(skel->kconfig, "skel_kconfig", "kconfig is mmaped()!\n")) goto cleanup; err = test_skeleton__load(skel); if (CHECK(err, "skel_load", "failed to load skeleton: %d\n", err)) goto cleanup; - printf("EXTERNS AFTER: %p\n", skel->externs); bss = skel->bss; bss->in1 = 1; @@ -37,7 +35,7 @@ void test_skeleton(void) bss->in4 = 4; bss->in5.a = 5; bss->in5.b = 6; - exts = skel->externs; + kcfg = skel->kconfig; err = test_skeleton__attach(skel); if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err)) @@ -55,10 +53,10 @@ void test_skeleton(void) CHECK(bss->handler_out5.b != 6, "res6", "got %lld != exp %d\n", bss->handler_out5.b, 6); - CHECK(bss->bpf_syscall != exts->CONFIG_BPF_SYSCALL, "ext1", - "got %d != exp %d\n", bss->bpf_syscall, exts->CONFIG_BPF_SYSCALL); - CHECK(bss->kern_ver != exts->LINUX_KERNEL_VERSION, "ext2", - "got %d != exp %d\n", bss->kern_ver, exts->LINUX_KERNEL_VERSION); + CHECK(bss->bpf_syscall != kcfg->CONFIG_BPF_SYSCALL, "ext1", + "got %d != exp %d\n", bss->bpf_syscall, kcfg->CONFIG_BPF_SYSCALL); + CHECK(bss->kern_ver != kcfg->LINUX_KERNEL_VERSION, "ext2", + "got %d != exp %d\n", bss->kern_ver, kcfg->LINUX_KERNEL_VERSION); cleanup: test_skeleton__destroy(skel); diff --git a/tools/testing/selftests/bpf/progs/test_core_extern.c b/tools/testing/selftests/bpf/progs/test_core_extern.c index e12f09f9e881..9bfc91d9d004 100644 --- a/tools/testing/selftests/bpf/progs/test_core_extern.c +++ b/tools/testing/selftests/bpf/progs/test_core_extern.c @@ -10,16 +10,16 @@ /* non-existing BPF helper, to test dead code elimination */ static int (*bpf_missing_helper)(const void *arg1, int arg2) = (void *) 999; -extern int LINUX_KERNEL_VERSION; -extern bool CONFIG_BPF_SYSCALL; /* strong */ -extern enum libbpf_tristate CONFIG_TRISTATE __weak; -extern bool CONFIG_BOOL __weak; -extern char CONFIG_CHAR __weak; -extern uint16_t CONFIG_USHORT __weak; -extern int CONFIG_INT __weak; -extern uint64_t CONFIG_ULONG __weak; -extern const char CONFIG_STR[8] __weak; -extern uint64_t CONFIG_MISSING __weak; +extern int LINUX_KERNEL_VERSION __kconfig; +extern bool CONFIG_BPF_SYSCALL __kconfig; /* strong */ +extern enum libbpf_tristate CONFIG_TRISTATE __kconfig __weak; +extern bool CONFIG_BOOL __kconfig __weak; +extern char CONFIG_CHAR __kconfig __weak; +extern uint16_t CONFIG_USHORT __kconfig __weak; +extern int CONFIG_INT __kconfig __weak; +extern uint64_t CONFIG_ULONG __kconfig __weak; +extern const char CONFIG_STR[8] __kconfig __weak; +extern uint64_t CONFIG_MISSING __kconfig __weak; uint64_t kern_ver = -1; uint64_t bpf_syscall = -1; diff --git a/tools/testing/selftests/bpf/progs/test_skeleton.c b/tools/testing/selftests/bpf/progs/test_skeleton.c index 9caa44758ea2..4f69aac5635f 100644 --- a/tools/testing/selftests/bpf/progs/test_skeleton.c +++ b/tools/testing/selftests/bpf/progs/test_skeleton.c @@ -21,8 +21,8 @@ char out3 = 0; long long out4 = 0; int out1 = 0; -extern bool CONFIG_BPF_SYSCALL; -extern int LINUX_KERNEL_VERSION; +extern bool CONFIG_BPF_SYSCALL __kconfig; +extern int LINUX_KERNEL_VERSION __kconfig; bool bpf_syscall = 0; int kern_ver = 0; -- cgit v1.2.3