diff options
author | Andrii Nakryiko | 2021-08-15 00:05:57 -0700 |
---|---|---|
committer | Daniel Borkmann | 2021-08-17 00:45:07 +0200 |
commit | b89fbfbb854c9afc3047e8273cc3a694650b802e (patch) | |
tree | c7b3624e206ecc2f865cefb688bcdbf173c1beaa | |
parent | 652c1b17b85b9c195978c051aa283027529db1fe (diff) |
bpf: Implement minimal BPF perf link
Introduce a new type of BPF link - BPF perf link. This brings perf_event-based
BPF program attachments (perf_event, tracepoints, kprobes, and uprobes) into
the common BPF link infrastructure, allowing to list all active perf_event
based attachments, auto-detaching BPF program from perf_event when link's FD
is closed, get generic BPF link fdinfo/get_info functionality.
BPF_LINK_CREATE command expects perf_event's FD as target_fd. No extra flags
are currently supported.
Force-detaching and atomic BPF program updates are not yet implemented, but
with perf_event-based BPF links we now have common framework for this without
the need to extend ioctl()-based perf_event interface.
One interesting consideration is a new value for bpf_attach_type, which
BPF_LINK_CREATE command expects. Generally, it's either 1-to-1 mapping from
bpf_attach_type to bpf_prog_type, or many-to-1 mapping from a subset of
bpf_attach_types to one bpf_prog_type (e.g., see BPF_PROG_TYPE_SK_SKB or
BPF_PROG_TYPE_CGROUP_SOCK). In this case, though, we have three different
program types (KPROBE, TRACEPOINT, PERF_EVENT) using the same perf_event-based
mechanism, so it's many bpf_prog_types to one bpf_attach_type. I chose to
define a single BPF_PERF_EVENT attach type for all of them and adjust
link_create()'s logic for checking correspondence between attach type and
program type.
The alternative would be to define three new attach types (e.g., BPF_KPROBE,
BPF_TRACEPOINT, and BPF_PERF_EVENT), but that seemed like unnecessary overkill
and BPF_KPROBE will cause naming conflicts with BPF_KPROBE() macro, defined by
libbpf. I chose to not do this to avoid unnecessary proliferation of
bpf_attach_type enum values and not have to deal with naming conflicts.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210815070609.987780-5-andrii@kernel.org
-rw-r--r-- | include/linux/bpf_types.h | 3 | ||||
-rw-r--r-- | include/linux/trace_events.h | 3 | ||||
-rw-r--r-- | include/uapi/linux/bpf.h | 2 | ||||
-rw-r--r-- | kernel/bpf/syscall.c | 105 | ||||
-rw-r--r-- | kernel/events/core.c | 10 | ||||
-rw-r--r-- | tools/include/uapi/linux/bpf.h | 2 |
6 files changed, 112 insertions, 13 deletions
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h index ae3ac3a2018c..9c81724e4b98 100644 --- a/include/linux/bpf_types.h +++ b/include/linux/bpf_types.h @@ -136,3 +136,6 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter) BPF_LINK_TYPE(BPF_LINK_TYPE_NETNS, netns) BPF_LINK_TYPE(BPF_LINK_TYPE_XDP, xdp) #endif +#ifdef CONFIG_PERF_EVENTS +BPF_LINK_TYPE(BPF_LINK_TYPE_PERF_EVENT, perf) +#endif diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index ad413b382a3c..8ac92560d3a3 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -803,6 +803,9 @@ extern void ftrace_profile_free_filter(struct perf_event *event); void perf_trace_buf_update(void *record, u16 type); void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp); +int perf_event_set_bpf_prog(struct perf_event *event, struct bpf_prog *prog); +void perf_event_free_bpf_prog(struct perf_event *event); + void bpf_trace_run1(struct bpf_prog *prog, u64 arg1); void bpf_trace_run2(struct bpf_prog *prog, u64 arg1, u64 arg2); void bpf_trace_run3(struct bpf_prog *prog, u64 arg1, u64 arg2, diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 2db6925e04f4..94fe8329b28f 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -993,6 +993,7 @@ enum bpf_attach_type { BPF_SK_SKB_VERDICT, BPF_SK_REUSEPORT_SELECT, BPF_SK_REUSEPORT_SELECT_OR_MIGRATE, + BPF_PERF_EVENT, __MAX_BPF_ATTACH_TYPE }; @@ -1006,6 +1007,7 @@ enum bpf_link_type { BPF_LINK_TYPE_ITER = 4, BPF_LINK_TYPE_NETNS = 5, BPF_LINK_TYPE_XDP = 6, + BPF_LINK_TYPE_PERF_EVENT = 7, MAX_BPF_LINK_TYPE, }; diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 9a2068e39d23..80c03bedd6e6 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2906,6 +2906,79 @@ static const struct bpf_link_ops bpf_raw_tp_link_lops = { .fill_link_info = bpf_raw_tp_link_fill_link_info, }; +#ifdef CONFIG_PERF_EVENTS +struct bpf_perf_link { + struct bpf_link link; + struct file *perf_file; +}; + +static void bpf_perf_link_release(struct bpf_link *link) +{ + struct bpf_perf_link *perf_link = container_of(link, struct bpf_perf_link, link); + struct perf_event *event = perf_link->perf_file->private_data; + + perf_event_free_bpf_prog(event); + fput(perf_link->perf_file); +} + +static void bpf_perf_link_dealloc(struct bpf_link *link) +{ + struct bpf_perf_link *perf_link = container_of(link, struct bpf_perf_link, link); + + kfree(perf_link); +} + +static const struct bpf_link_ops bpf_perf_link_lops = { + .release = bpf_perf_link_release, + .dealloc = bpf_perf_link_dealloc, +}; + +static int bpf_perf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) +{ + struct bpf_link_primer link_primer; + struct bpf_perf_link *link; + struct perf_event *event; + struct file *perf_file; + int err; + + if (attr->link_create.flags) + return -EINVAL; + + perf_file = perf_event_get(attr->link_create.target_fd); + if (IS_ERR(perf_file)) + return PTR_ERR(perf_file); + + link = kzalloc(sizeof(*link), GFP_USER); + if (!link) { + err = -ENOMEM; + goto out_put_file; + } + bpf_link_init(&link->link, BPF_LINK_TYPE_PERF_EVENT, &bpf_perf_link_lops, prog); + link->perf_file = perf_file; + + err = bpf_link_prime(&link->link, &link_primer); + if (err) { + kfree(link); + goto out_put_file; + } + + event = perf_file->private_data; + err = perf_event_set_bpf_prog(event, prog); + if (err) { + bpf_link_cleanup(&link_primer); + goto out_put_file; + } + /* perf_event_set_bpf_prog() doesn't take its own refcnt on prog */ + bpf_prog_inc(prog); + + return bpf_link_settle(&link_primer); + +out_put_file: + fput(perf_file); + return err; +} +#endif /* CONFIG_PERF_EVENTS */ + #define BPF_RAW_TRACEPOINT_OPEN_LAST_FIELD raw_tracepoint.prog_fd static int bpf_raw_tracepoint_open(const union bpf_attr *attr) @@ -4147,15 +4220,26 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr) if (ret) goto out; - if (prog->type == BPF_PROG_TYPE_EXT) { + switch (prog->type) { + case BPF_PROG_TYPE_EXT: ret = tracing_bpf_link_attach(attr, uattr, prog); goto out; - } - - ptype = attach_type_to_prog_type(attr->link_create.attach_type); - if (ptype == BPF_PROG_TYPE_UNSPEC || ptype != prog->type) { - ret = -EINVAL; - goto out; + case BPF_PROG_TYPE_PERF_EVENT: + case BPF_PROG_TYPE_KPROBE: + case BPF_PROG_TYPE_TRACEPOINT: + if (attr->link_create.attach_type != BPF_PERF_EVENT) { + ret = -EINVAL; + goto out; + } + ptype = prog->type; + break; + default: + ptype = attach_type_to_prog_type(attr->link_create.attach_type); + if (ptype == BPF_PROG_TYPE_UNSPEC || ptype != prog->type) { + ret = -EINVAL; + goto out; + } + break; } switch (ptype) { @@ -4180,6 +4264,13 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr) ret = bpf_xdp_link_attach(attr, prog); break; #endif +#ifdef CONFIG_PERF_EVENTS + case BPF_PROG_TYPE_PERF_EVENT: + case BPF_PROG_TYPE_TRACEPOINT: + case BPF_PROG_TYPE_KPROBE: + ret = bpf_perf_link_attach(attr, prog); + break; +#endif default: ret = -EINVAL; } diff --git a/kernel/events/core.c b/kernel/events/core.c index 2f07718bd41c..9fd65667bcb2 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4697,7 +4697,6 @@ errout: } static void perf_event_free_filter(struct perf_event *event); -static void perf_event_free_bpf_prog(struct perf_event *event); static void free_event_rcu(struct rcu_head *head) { @@ -5574,7 +5573,6 @@ static inline int perf_fget_light(int fd, struct fd *p) static int perf_event_set_output(struct perf_event *event, struct perf_event *output_event); static int perf_event_set_filter(struct perf_event *event, void __user *arg); -static int perf_event_set_bpf_prog(struct perf_event *event, struct bpf_prog *prog); static int perf_copy_attr(struct perf_event_attr __user *uattr, struct perf_event_attr *attr); @@ -10013,7 +10011,7 @@ static inline bool perf_event_is_tracing(struct perf_event *event) return false; } -static int perf_event_set_bpf_prog(struct perf_event *event, struct bpf_prog *prog) +int perf_event_set_bpf_prog(struct perf_event *event, struct bpf_prog *prog) { bool is_kprobe, is_tracepoint, is_syscall_tp; @@ -10047,7 +10045,7 @@ static int perf_event_set_bpf_prog(struct perf_event *event, struct bpf_prog *pr return perf_event_attach_bpf_prog(event, prog); } -static void perf_event_free_bpf_prog(struct perf_event *event) +void perf_event_free_bpf_prog(struct perf_event *event) { if (!perf_event_is_tracing(event)) { perf_event_free_bpf_handler(event); @@ -10066,12 +10064,12 @@ static void perf_event_free_filter(struct perf_event *event) { } -static int perf_event_set_bpf_prog(struct perf_event *event, struct bpf_prog *prog) +int perf_event_set_bpf_prog(struct perf_event *event, struct bpf_prog *prog) { return -ENOENT; } -static void perf_event_free_bpf_prog(struct perf_event *event) +void perf_event_free_bpf_prog(struct perf_event *event) { } #endif /* CONFIG_EVENT_TRACING */ diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 2db6925e04f4..94fe8329b28f 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -993,6 +993,7 @@ enum bpf_attach_type { BPF_SK_SKB_VERDICT, BPF_SK_REUSEPORT_SELECT, BPF_SK_REUSEPORT_SELECT_OR_MIGRATE, + BPF_PERF_EVENT, __MAX_BPF_ATTACH_TYPE }; @@ -1006,6 +1007,7 @@ enum bpf_link_type { BPF_LINK_TYPE_ITER = 4, BPF_LINK_TYPE_NETNS = 5, BPF_LINK_TYPE_XDP = 6, + BPF_LINK_TYPE_PERF_EVENT = 7, MAX_BPF_LINK_TYPE, }; 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