From 2541517c32be2531e0da59dfd7efc1ce844644f5 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Wed, 25 Mar 2015 12:49:20 -0700 Subject: tracing, perf: Implement BPF programs attached to kprobes BPF programs, attached to kprobes, provide a safe way to execute user-defined BPF byte-code programs without being able to crash or hang the kernel in any way. The BPF engine makes sure that such programs have a finite execution time and that they cannot break out of their sandbox. The user interface is to attach to a kprobe via the perf syscall: struct perf_event_attr attr = { .type = PERF_TYPE_TRACEPOINT, .config = event_id, ... }; event_fd = perf_event_open(&attr,...); ioctl(event_fd, PERF_EVENT_IOC_SET_BPF, prog_fd); 'prog_fd' is a file descriptor associated with BPF program previously loaded. 'event_id' is an ID of the kprobe created. Closing 'event_fd': close(event_fd); ... automatically detaches BPF program from it. BPF programs can call in-kernel helper functions to: - lookup/update/delete elements in maps - probe_read - wraper of probe_kernel_read() used to access any kernel data structures BPF programs receive 'struct pt_regs *' as an input ('struct pt_regs' is architecture dependent) and return 0 to ignore the event and 1 to store kprobe event into the ring buffer. Note, kprobes are a fundamentally _not_ a stable kernel ABI, so BPF programs attached to kprobes must be recompiled for every kernel version and user must supply correct LINUX_VERSION_CODE in attr.kern_version during bpf_prog_load() call. Signed-off-by: Alexei Starovoitov Reviewed-by: Steven Rostedt Reviewed-by: Masami Hiramatsu Cc: Andrew Morton Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Daniel Borkmann Cc: David S. Miller Cc: Jiri Olsa Cc: Linus Torvalds Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1427312966-8434-4-git-send-email-ast@plumgrid.com Signed-off-by: Ingo Molnar --- include/uapi/linux/bpf.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/uapi/linux/bpf.h') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 45da7ec7d274..b2948feeb70b 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -118,6 +118,7 @@ enum bpf_map_type { enum bpf_prog_type { BPF_PROG_TYPE_UNSPEC, BPF_PROG_TYPE_SOCKET_FILTER, + BPF_PROG_TYPE_KPROBE, }; /* flags for BPF_MAP_UPDATE_ELEM command */ @@ -151,6 +152,7 @@ union bpf_attr { __u32 log_level; /* verbosity level of verifier */ __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied buffer */ + __u32 kern_version; /* checked when prog_type=kprobe */ }; } __attribute__((aligned(8))); @@ -162,6 +164,7 @@ enum bpf_func_id { BPF_FUNC_map_lookup_elem, /* void *map_lookup_elem(&map, &key) */ BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */ BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */ + BPF_FUNC_probe_read, /* int bpf_probe_read(void *dst, int size, void *src) */ __BPF_FUNC_MAX_ID, }; -- cgit v1.2.3-55-g7522