Commit f0fdfefb authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

bpf: Add BPF program and map iterators as built-in BPF programs. 



The program and map iterators work similar to seq_file-s.
Once the program is pinned in bpffs it can be read with "cat" tool
to print human readable output. In this case about BPF programs and maps.
For example:
$ cat /sys/fs/bpf/progs.debug
  id name            attached
   5 dump_bpf_map    bpf_iter_bpf_map
   6 dump_bpf_prog   bpf_iter_bpf_prog
$ cat /sys/fs/bpf/maps.debug
  id name            max_entries
   3 iterator.rodata     1

To avoid kernel build dependency on clang 10 separate bpf skeleton generation
into manual "make" step and instead check-in generated .skel.h into git.

Unlike 'bpftool prog show' in-kernel BTF name is used (when available)
to print full name of BPF program instead of 16-byte truncated name.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200819042759.51280-3-alexei.starovoitov@gmail.com
parent 005142b8

kernel/bpf/preload/iterators/.gitignore

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# SPDX-License-Identifier: GPL-2.0-only

/.output

kernel/bpf/preload/iterators/Makefile

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# SPDX-License-Identifier: GPL-2.0

OUTPUT := .output

CLANG ?= clang

LLC ?= llc

LLVM_STRIP ?= llvm-strip

DEFAULT_BPFTOOL := $(OUTPUT)/sbin/bpftool

BPFTOOL ?= $(DEFAULT_BPFTOOL)

LIBBPF_SRC := $(abspath ../../../../tools/lib/bpf)

BPFOBJ := $(OUTPUT)/libbpf.a

BPF_INCLUDE := $(OUTPUT)

INCLUDES := -I$(OUTPUT) -I$(BPF_INCLUDE) -I$(abspath ../../../../tools/lib)        \

       -I$(abspath ../../../../tools/include/uapi)

CFLAGS := -g -Wall



abs_out := $(abspath $(OUTPUT))

ifeq ($(V),1)

Q =

msg =

else

Q = @

msg = @printf '  %-8s %s%s\n' "$(1)" "$(notdir $(2))" "$(if $(3), $(3))";

MAKEFLAGS += --no-print-directory

submake_extras := feature_display=0

endif



.DELETE_ON_ERROR:



.PHONY: all clean



all: iterators.skel.h



clean:

	$(call msg,CLEAN)

	$(Q)rm -rf $(OUTPUT) iterators



iterators.skel.h: $(OUTPUT)/iterators.bpf.o | $(BPFTOOL)

	$(call msg,GEN-SKEL,$@)

	$(Q)$(BPFTOOL) gen skeleton $< > $@





$(OUTPUT)/iterators.bpf.o: iterators.bpf.c $(BPFOBJ) | $(OUTPUT)

	$(call msg,BPF,$@)

	$(Q)$(CLANG) -g -O2 -target bpf $(INCLUDES)			      \

		 -c $(filter %.c,$^) -o $@ &&				      \

	$(LLVM_STRIP) -g $@



$(OUTPUT):

	$(call msg,MKDIR,$@)

	$(Q)mkdir -p $(OUTPUT)



$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(OUTPUT)

	$(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC)			       \

		    OUTPUT=$(abspath $(dir $@))/ $(abspath $@)



$(DEFAULT_BPFTOOL):

	$(Q)$(MAKE) $(submake_extras) -C ../../../../tools/bpf/bpftool			      \

		    prefix= OUTPUT=$(abs_out)/ DESTDIR=$(abs_out) install

kernel/bpf/preload/iterators/README

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WARNING:

If you change "iterators.bpf.c" do "make -j" in this directory to rebuild "iterators.skel.h".

Make sure to have clang 10 installed.

See Documentation/bpf/bpf_devel_QA.rst

kernel/bpf/preload/iterators/iterators.bpf.c

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2020 Facebook */

#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_core_read.h>



#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)

struct seq_file;

struct bpf_iter_meta {

	struct seq_file *seq;

	__u64 session_id;

	__u64 seq_num;

};



struct bpf_map {

	__u32 id;

	char name[16];

	__u32 max_entries;

};



struct bpf_iter__bpf_map {

	struct bpf_iter_meta *meta;

	struct bpf_map *map;

};



struct btf_type {

	__u32 name_off;

};



struct btf_header {

	__u32   str_len;

};



struct btf {

	const char *strings;

	struct btf_type **types;

	struct btf_header hdr;

};



struct bpf_prog_aux {

	__u32 id;

	char name[16];

	const char *attach_func_name;

	struct bpf_prog *linked_prog;

	struct bpf_func_info *func_info;

	struct btf *btf;

};



struct bpf_prog {

	struct bpf_prog_aux *aux;

};



struct bpf_iter__bpf_prog {

	struct bpf_iter_meta *meta;

	struct bpf_prog *prog;

};

#pragma clang attribute pop



static const char *get_name(struct btf *btf, long btf_id, const char *fallback)

{

	struct btf_type **types, *t;

	unsigned int name_off;

	const char *str;



	if (!btf)

		return fallback;

	str = btf->strings;

	types = btf->types;

	bpf_probe_read_kernel(&t, sizeof(t), types + btf_id);

	name_off = BPF_CORE_READ(t, name_off);

	if (name_off >= btf->hdr.str_len)

		return fallback;

	return str + name_off;

}



SEC("iter/bpf_map")

int dump_bpf_map(struct bpf_iter__bpf_map *ctx)

{

	struct seq_file *seq = ctx->meta->seq;

	__u64 seq_num = ctx->meta->seq_num;

	struct bpf_map *map = ctx->map;



	if (!map)

		return 0;



	if (seq_num == 0)

		BPF_SEQ_PRINTF(seq, "  id name             max_entries\n");



	BPF_SEQ_PRINTF(seq, "%4u %-16s%6d\n", map->id, map->name, map->max_entries);

	return 0;

}



SEC("iter/bpf_prog")

int dump_bpf_prog(struct bpf_iter__bpf_prog *ctx)

{

	struct seq_file *seq = ctx->meta->seq;

	__u64 seq_num = ctx->meta->seq_num;

	struct bpf_prog *prog = ctx->prog;

	struct bpf_prog_aux *aux;



	if (!prog)

		return 0;



	aux = prog->aux;

	if (seq_num == 0)

		BPF_SEQ_PRINTF(seq, "  id name             attached\n");



	BPF_SEQ_PRINTF(seq, "%4u %-16s %s %s\n", aux->id,

		       get_name(aux->btf, aux->func_info[0].type_id, aux->name),

		       aux->attach_func_name, aux->linked_prog->aux->name);

	return 0;

}

char LICENSE[] SEC("license") = "GPL";

kernel/bpf/preload/iterators/iterators.skel.h

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