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bpf, libbpf: introduce bpf_object__probe_caps to test BPF capabilities

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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: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Stanislav Fomichev 2018-11-20 17:11:19 -08:00 committed by Daniel Borkmann
parent 8c4905b995
commit 47eff61777
1 changed files with 58 additions and 0 deletions
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58
tools/lib/bpf/libbpf.c
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@ -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 @@ err_free_new_name:
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);