From f8b299bc6a0f8695d4005ecff29773c79a1d29af Mon Sep 17 00:00:00 2001 From: Menglong Dong Date: Mon, 6 Mar 2023 14:48:31 +0800 Subject: libbpf: Add support to set kprobe/uprobe attach mode By default, libbpf will attach the kprobe/uprobe BPF program in the latest mode that supported by kernel. In this patch, we add the support to let users manually attach kprobe/uprobe in legacy or perf mode. There are 3 mode that supported by the kernel to attach kprobe/uprobe: LEGACY: create perf event in legacy way and don't use bpf_link PERF: create perf event with perf_event_open() and don't use bpf_link Signed-off-by: Menglong Dong Signed-off-by: Andrii Nakryiko Reviewed-by: Biao Jiang Link: create perf event with perf_event_open() and use bpf_link Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/ Link: https://lore.kernel.org/bpf/20230306064833.7932-2-imagedong@tencent.com Users now can manually choose the mode with bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts(). --- tools/lib/bpf/libbpf.h | 50 +++++++++++++++++++++++++++++++++++++------------- 1 file changed, 37 insertions(+), 13 deletions(-) (limited to 'tools/lib/bpf/libbpf.h') diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 2efd80f6f7b9..db4992a036f8 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -447,12 +447,15 @@ LIBBPF_API struct bpf_link * bpf_program__attach(const struct bpf_program *prog); struct bpf_perf_event_opts { - /* size of this struct, for forward/backward compatiblity */ + /* size of this struct, for forward/backward compatibility */ size_t sz; /* custom user-provided value fetchable through bpf_get_attach_cookie() */ __u64 bpf_cookie; + /* don't use BPF link when attach BPF program */ + bool force_ioctl_attach; + size_t :0; }; -#define bpf_perf_event_opts__last_field bpf_cookie +#define bpf_perf_event_opts__last_field force_ioctl_attach LIBBPF_API struct bpf_link * bpf_program__attach_perf_event(const struct bpf_program *prog, int pfd); @@ -461,8 +464,25 @@ LIBBPF_API struct bpf_link * bpf_program__attach_perf_event_opts(const struct bpf_program *prog, int pfd, const struct bpf_perf_event_opts *opts); +/** + * enum probe_attach_mode - the mode to attach kprobe/uprobe + * + * force libbpf to attach kprobe/uprobe in specific mode, -ENOTSUP will + * be returned if it is not supported by the kernel. + */ +enum probe_attach_mode { + /* attach probe in latest supported mode by kernel */ + PROBE_ATTACH_MODE_DEFAULT = 0, + /* attach probe in legacy mode, using debugfs/tracefs */ + PROBE_ATTACH_MODE_LEGACY, + /* create perf event with perf_event_open() syscall */ + PROBE_ATTACH_MODE_PERF, + /* attach probe with BPF link */ + PROBE_ATTACH_MODE_LINK, +}; + struct bpf_kprobe_opts { - /* size of this struct, for forward/backward compatiblity */ + /* size of this struct, for forward/backward compatibility */ size_t sz; /* custom user-provided value fetchable through bpf_get_attach_cookie() */ __u64 bpf_cookie; @@ -470,9 +490,11 @@ struct bpf_kprobe_opts { size_t offset; /* kprobe is return probe */ bool retprobe; + /* kprobe attach mode */ + enum probe_attach_mode attach_mode; size_t :0; }; -#define bpf_kprobe_opts__last_field retprobe +#define bpf_kprobe_opts__last_field attach_mode LIBBPF_API struct bpf_link * bpf_program__attach_kprobe(const struct bpf_program *prog, bool retprobe, @@ -506,7 +528,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, const struct bpf_kprobe_multi_opts *opts); struct bpf_ksyscall_opts { - /* size of this struct, for forward/backward compatiblity */ + /* size of this struct, for forward/backward compatibility */ size_t sz; /* custom user-provided value fetchable through bpf_get_attach_cookie() */ __u64 bpf_cookie; @@ -552,7 +574,7 @@ bpf_program__attach_ksyscall(const struct bpf_program *prog, const struct bpf_ksyscall_opts *opts); struct bpf_uprobe_opts { - /* size of this struct, for forward/backward compatiblity */ + /* size of this struct, for forward/backward compatibility */ size_t sz; /* offset of kernel reference counted USDT semaphore, added in * a6ca88b241d5 ("trace_uprobe: support reference counter in fd-based uprobe") @@ -570,9 +592,11 @@ struct bpf_uprobe_opts { * binary_path. */ const char *func_name; + /* uprobe attach mode */ + enum probe_attach_mode attach_mode; size_t :0; }; -#define bpf_uprobe_opts__last_field func_name +#define bpf_uprobe_opts__last_field attach_mode /** * @brief **bpf_program__attach_uprobe()** attaches a BPF program @@ -646,7 +670,7 @@ bpf_program__attach_usdt(const struct bpf_program *prog, const struct bpf_usdt_opts *opts); struct bpf_tracepoint_opts { - /* size of this struct, for forward/backward compatiblity */ + /* size of this struct, for forward/backward compatibility */ size_t sz; /* custom user-provided value fetchable through bpf_get_attach_cookie() */ __u64 bpf_cookie; @@ -1110,7 +1134,7 @@ struct user_ring_buffer; typedef int (*ring_buffer_sample_fn)(void *ctx, void *data, size_t size); struct ring_buffer_opts { - size_t sz; /* size of this struct, for forward/backward compatiblity */ + size_t sz; /* size of this struct, for forward/backward compatibility */ }; #define ring_buffer_opts__last_field sz @@ -1475,7 +1499,7 @@ LIBBPF_API void bpf_object__destroy_subskeleton(struct bpf_object_subskeleton *s); struct gen_loader_opts { - size_t sz; /* size of this struct, for forward/backward compatiblity */ + size_t sz; /* size of this struct, for forward/backward compatibility */ const char *data; const char *insns; __u32 data_sz; @@ -1493,13 +1517,13 @@ enum libbpf_tristate { }; struct bpf_linker_opts { - /* size of this struct, for forward/backward compatiblity */ + /* size of this struct, for forward/backward compatibility */ size_t sz; }; #define bpf_linker_opts__last_field sz struct bpf_linker_file_opts { - /* size of this struct, for forward/backward compatiblity */ + /* size of this struct, for forward/backward compatibility */ size_t sz; }; #define bpf_linker_file_opts__last_field sz @@ -1542,7 +1566,7 @@ typedef int (*libbpf_prog_attach_fn_t)(const struct bpf_program *prog, long cook struct bpf_link **link); struct libbpf_prog_handler_opts { - /* size of this struct, for forward/backward compatiblity */ + /* size of this struct, for forward/backward compatibility */ size_t sz; /* User-provided value that is passed to prog_setup_fn, * prog_prepare_load_fn, and prog_attach_fn callbacks. Allows user to -- cgit From 912dd4b0c2a50a839301520badb241f36664ae07 Mon Sep 17 00:00:00 2001 From: Kui-Feng Lee Date: Wed, 22 Mar 2023 20:24:03 -0700 Subject: libbpf: Update a bpf_link with another struct_ops. Introduce bpf_link__update_map(), which allows to atomically update underlying struct_ops implementation for given struct_ops BPF link. Also add old_map_fd to struct bpf_link_update_opts to handle BPF_F_REPLACE feature. Signed-off-by: Kui-Feng Lee Link: https://lore.kernel.org/r/20230323032405.3735486-7-kuifeng@meta.com Signed-off-by: Martin KaFai Lau --- tools/lib/bpf/bpf.c | 8 +++++++- tools/lib/bpf/bpf.h | 3 ++- tools/lib/bpf/libbpf.c | 35 +++++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.h | 1 + tools/lib/bpf/libbpf.map | 1 + 5 files changed, 46 insertions(+), 2 deletions(-) (limited to 'tools/lib/bpf/libbpf.h') diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index e750b6f5fcc3..767035900354 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -794,11 +794,17 @@ int bpf_link_update(int link_fd, int new_prog_fd, if (!OPTS_VALID(opts, bpf_link_update_opts)) return libbpf_err(-EINVAL); + if (OPTS_GET(opts, old_prog_fd, 0) && OPTS_GET(opts, old_map_fd, 0)) + return libbpf_err(-EINVAL); + memset(&attr, 0, attr_sz); attr.link_update.link_fd = link_fd; attr.link_update.new_prog_fd = new_prog_fd; attr.link_update.flags = OPTS_GET(opts, flags, 0); - attr.link_update.old_prog_fd = OPTS_GET(opts, old_prog_fd, 0); + if (OPTS_GET(opts, old_prog_fd, 0)) + attr.link_update.old_prog_fd = OPTS_GET(opts, old_prog_fd, 0); + else if (OPTS_GET(opts, old_map_fd, 0)) + attr.link_update.old_map_fd = OPTS_GET(opts, old_map_fd, 0); ret = sys_bpf(BPF_LINK_UPDATE, &attr, attr_sz); return libbpf_err_errno(ret); diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index f0f786373238..b073e73439ef 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -336,8 +336,9 @@ struct bpf_link_update_opts { size_t sz; /* size of this struct for forward/backward compatibility */ __u32 flags; /* extra flags */ __u32 old_prog_fd; /* expected old program FD */ + __u32 old_map_fd; /* expected old map FD */ }; -#define bpf_link_update_opts__last_field old_prog_fd +#define bpf_link_update_opts__last_field old_map_fd LIBBPF_API int bpf_link_update(int link_fd, int new_prog_fd, const struct bpf_link_update_opts *opts); diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 4ff82baba0ea..2b5ea2500b80 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11677,6 +11677,41 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map) return &link->link; } +/* + * Swap the back struct_ops of a link with a new struct_ops map. + */ +int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map) +{ + struct bpf_link_struct_ops *st_ops_link; + __u32 zero = 0; + int err; + + if (!bpf_map__is_struct_ops(map) || map->fd < 0) + return -EINVAL; + + st_ops_link = container_of(link, struct bpf_link_struct_ops, link); + /* Ensure the type of a link is correct */ + if (st_ops_link->map_fd < 0) + return -EINVAL; + + err = bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0); + /* It can be EBUSY if the map has been used to create or + * update a link before. We don't allow updating the value of + * a struct_ops once it is set. That ensures that the value + * never changed. So, it is safe to skip EBUSY. + */ + if (err && err != -EBUSY) + return err; + + err = bpf_link_update(link->fd, map->fd, NULL); + if (err < 0) + return err; + + st_ops_link->map_fd = map->fd; + + return 0; +} + typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct perf_event_header *hdr, void *private_data); diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index db4992a036f8..1615e55e2e79 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -719,6 +719,7 @@ bpf_program__attach_freplace(const struct bpf_program *prog, struct bpf_map; LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map); +LIBBPF_API int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map); struct bpf_iter_attach_opts { size_t sz; /* size of this struct for forward/backward compatibility */ diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 50dde1f6521e..a5aa3a383d69 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -386,6 +386,7 @@ LIBBPF_1.1.0 { LIBBPF_1.2.0 { global: bpf_btf_get_info_by_fd; + bpf_link__update_map; bpf_link_get_info_by_fd; bpf_map_get_info_by_fd; bpf_prog_get_info_by_fd; -- cgit From f1cb927cdb6280e0ce283174cc1bf395dffc43d4 Mon Sep 17 00:00:00 2001 From: JP Kobryn Date: Fri, 24 Mar 2023 18:08:45 -0700 Subject: libbpf: Ensure print callback usage is thread-safe This patch prevents races on the print function pointer, allowing the libbpf_set_print() function to become thread-safe. Signed-off-by: JP Kobryn Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20230325010845.46000-1-inwardvessel@gmail.com --- tools/lib/bpf/libbpf.c | 9 ++++++--- tools/lib/bpf/libbpf.h | 2 ++ 2 files changed, 8 insertions(+), 3 deletions(-) (limited to 'tools/lib/bpf/libbpf.h') diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index f6a071db5c6e..15737d7b5a28 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -216,9 +216,10 @@ static libbpf_print_fn_t __libbpf_pr = __base_pr; libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn) { - libbpf_print_fn_t old_print_fn = __libbpf_pr; + libbpf_print_fn_t old_print_fn; + + old_print_fn = __atomic_exchange_n(&__libbpf_pr, fn, __ATOMIC_RELAXED); - __libbpf_pr = fn; return old_print_fn; } @@ -227,8 +228,10 @@ void libbpf_print(enum libbpf_print_level level, const char *format, ...) { va_list args; int old_errno; + libbpf_print_fn_t print_fn; - if (!__libbpf_pr) + print_fn = __atomic_load_n(&__libbpf_pr, __ATOMIC_RELAXED); + if (!print_fn) return; old_errno = errno; diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 1615e55e2e79..0b7362397ea3 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -101,6 +101,8 @@ typedef int (*libbpf_print_fn_t)(enum libbpf_print_level level, * be used for libbpf warnings and informational messages. * @param fn The log print function. If NULL, libbpf won't print anything. * @return Pointer to old print function. + * + * This function is thread-safe. */ LIBBPF_API libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn); -- cgit