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Commit 47eff617 authored by Stanislav Fomichev's avatar Stanislav Fomichev Committed by Daniel Borkmann
Browse files

bpf, libbpf: introduce bpf_object__probe_caps to test BPF capabilities 



It currently only checks whether kernel supports map/prog names.
This capability check will be used in the next two commits to
skip setting prog/map names.

Suggested-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 8c4905b9

tools/lib/bpf/libbpf.c

+58 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 
#include <linux/kernel.h>

#include <linux/bpf.h>

#include <linux/btf.h>

#include <linux/filter.h>

#include <linux/list.h>

#include <linux/limits.h>

#include <linux/perf_event.h>
@@ -114,6 +115,11 @@ void libbpf_set_print(libbpf_print_fn_t warn, 
# define LIBBPF_ELF_C_READ_MMAP ELF_C_READ

#endif



struct bpf_capabilities {

	/* v4.14: kernel support for program & map names. */

	__u32 name:1;

};



/*

 * bpf_prog should be a better name but it has been used in

 * linux/filter.h.
@@ -160,6 +166,8 @@ struct bpf_program { 
	void *func_info;

	__u32 func_info_rec_size;

	__u32 func_info_len;



	struct bpf_capabilities *caps;

};



struct bpf_map {
@@ -221,6 +229,8 @@ struct bpf_object { 
	void *priv;

	bpf_object_clear_priv_t clear_priv;



	struct bpf_capabilities caps;



	char path[];

};

#define obj_elf_valid(o)	((o)->efile.elf)
@@ -342,6 +352,7 @@ bpf_object__add_program(struct bpf_object *obj, void *data, size_t size, 
	if (err)

		return err;



	prog.caps = &obj->caps;

	progs = obj->programs;

	nr_progs = obj->nr_programs;
@@ -1135,6 +1146,52 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd) 
	return -errno;

}



static int

bpf_object__probe_name(struct bpf_object *obj)

{

	struct bpf_load_program_attr attr;

	char *cp, errmsg[STRERR_BUFSIZE];

	struct bpf_insn insns[] = {

		BPF_MOV64_IMM(BPF_REG_0, 0),

		BPF_EXIT_INSN(),

	};

	int ret;



	/* make sure basic loading works */



	memset(&attr, 0, sizeof(attr));

	attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;

	attr.insns = insns;

	attr.insns_cnt = ARRAY_SIZE(insns);

	attr.license = "GPL";



	ret = bpf_load_program_xattr(&attr, NULL, 0);

	if (ret < 0) {

		cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));

		pr_warning("Error in %s():%s(%d). Couldn't load basic 'r0 = 0' BPF program.\n",

			   __func__, cp, errno);

		return -errno;

	}

	close(ret);



	/* now try the same program, but with the name */



	attr.name = "test";

	ret = bpf_load_program_xattr(&attr, NULL, 0);

	if (ret >= 0) {

		obj->caps.name = 1;

		close(ret);

	}



	return 0;

}



static int

bpf_object__probe_caps(struct bpf_object *obj)

{

	return bpf_object__probe_name(obj);

}



static int

bpf_object__create_maps(struct bpf_object *obj)

{
@@ -1708,6 +1765,7 @@ int bpf_object__load(struct bpf_object *obj) 


	obj->loaded = true;



	CHECK_ERR(bpf_object__probe_caps(obj), err, out);

	CHECK_ERR(bpf_object__create_maps(obj), err, out);

	CHECK_ERR(bpf_object__relocate(obj), err, out);

	CHECK_ERR(bpf_object__load_progs(obj), err, out);