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tools lib bpf: Introduce bpf_program__get_prog_info_linear()

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Currently, bpf_prog_info includes 9 arrays. The user has the option to
fetch any combination of these arrays. However, this requires a lot of
handling.

This work becomes more tricky when we need to store bpf_prog_info to a
file, because these arrays are allocated independently.

This patch introduces 'struct bpf_prog_info_linear', which stores arrays
of bpf_prog_info in continuous memory.

Helper functions are introduced to unify the work to get different sets
of bpf_prog_info.  Specifically, bpf_program__get_prog_info_linear()
allows the user to select which arrays to fetch, and handles details for
the user.

Please see the comments right before 'enum bpf_prog_info_array' for more
details and examples.

Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lkml.kernel.org/r/ce92c091-e80d-a0c1-4aa0-987706c42b20@iogearbox.net
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: kernel-team@fb.com
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislav Fomichev <sdf@google.com>
Link: http://lkml.kernel.org/r/20190312053051.2690567-3-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Song Liu
2019-03-11 22:30:38 -07:00
committed by Andrii Nakryiko
parent 556285a37a
commit 413703c8cb
3 changed files with 317 additions and 0 deletions
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63
src/libbpf.h
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@@ -378,6 +378,69 @@ LIBBPF_API bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex);
LIBBPF_API bool bpf_probe_helper(enum bpf_func_id id,
enum bpf_prog_type prog_type, __u32 ifindex);
/*
* Get bpf_prog_info in continuous memory
*
* struct bpf_prog_info has multiple arrays. The user has option to choose
* arrays to fetch from kernel. The following APIs provide an uniform way to
* fetch these data. All arrays in bpf_prog_info are stored in a single
* continuous memory region. This makes it easy to store the info in a
* file.
*
* Before writing bpf_prog_info_linear to files, it is necessary to
* translate pointers in bpf_prog_info to offsets. Helper functions
* bpf_program__bpil_addr_to_offs() and bpf_program__bpil_offs_to_addr()
* are introduced to switch between pointers and offsets.
*
* Examples:
* # To fetch map_ids and prog_tags:
* __u64 arrays = (1UL << BPF_PROG_INFO_MAP_IDS) |
* (1UL << BPF_PROG_INFO_PROG_TAGS);
* struct bpf_prog_info_linear *info_linear =
* bpf_program__get_prog_info_linear(fd, arrays);
*
* # To save data in file
* bpf_program__bpil_addr_to_offs(info_linear);
* write(f, info_linear, sizeof(*info_linear) + info_linear->data_len);
*
* # To read data from file
* read(f, info_linear, <proper_size>);
* bpf_program__bpil_offs_to_addr(info_linear);
*/
enum bpf_prog_info_array {
BPF_PROG_INFO_FIRST_ARRAY = 0,
BPF_PROG_INFO_JITED_INSNS = 0,
BPF_PROG_INFO_XLATED_INSNS,
BPF_PROG_INFO_MAP_IDS,
BPF_PROG_INFO_JITED_KSYMS,
BPF_PROG_INFO_JITED_FUNC_LENS,
BPF_PROG_INFO_FUNC_INFO,
BPF_PROG_INFO_LINE_INFO,
BPF_PROG_INFO_JITED_LINE_INFO,
BPF_PROG_INFO_PROG_TAGS,
BPF_PROG_INFO_LAST_ARRAY,
};
struct bpf_prog_info_linear {
/* size of struct bpf_prog_info, when the tool is compiled */
__u32 info_len;
/* total bytes allocated for data, round up to 8 bytes */
__u32 data_len;
/* which arrays are included in data */
__u64 arrays;
struct bpf_prog_info info;
__u8 data[];
};
LIBBPF_API struct bpf_prog_info_linear *
bpf_program__get_prog_info_linear(int fd, __u64 arrays);
LIBBPF_API void
bpf_program__bpil_addr_to_offs(struct bpf_prog_info_linear *info_linear);
LIBBPF_API void
bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear);
#ifdef __cplusplus
} /* extern "C" */
#endif