* [PATCH bpf-next 1/3] bpftool, selftests/bpf: embed object file inside skeleton
2019-12-17 5:36 [PATCH bpf-next 0/3] Skeleton improvements and documnetation Andrii Nakryiko
@ 2019-12-17 5:36 ` Andrii Nakryiko
2019-12-17 21:23 ` Yonghong Song
2019-12-17 5:36 ` [PATCH bpf-next 2/3] libbpf: remove BPF_EMBED_OBJ macro from libbpf.h Andrii Nakryiko
2019-12-17 5:36 ` [PATCH bpf-next 3/3] bpftool: add gen subcommand manpage Andrii Nakryiko
2 siblings, 1 reply; 8+ messages in thread
From: Andrii Nakryiko @ 2019-12-17 5:36 UTC (permalink / raw)
To: bpf, netdev, ast, daniel; +Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Embed contents of BPF object file used for BPF skeleton generation inside
skeleton itself. This allows to keep BPF object file and its skeleton in sync
at all times, and simpifies skeleton instantiation.
Also switch existing selftests to not require BPF_EMBED_OBJ anymore.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
tools/bpf/bpftool/gen.c | 226 +++++++++++-------
.../selftests/bpf/prog_tests/attach_probe.c | 4 +-
.../selftests/bpf/prog_tests/core_extern.c | 4 +-
.../selftests/bpf/prog_tests/fentry_fexit.c | 10 +-
.../selftests/bpf/prog_tests/fentry_test.c | 7 +-
tools/testing/selftests/bpf/prog_tests/mmap.c | 4 +-
.../selftests/bpf/prog_tests/skeleton.c | 4 +-
.../bpf/prog_tests/stacktrace_build_id.c | 4 +-
.../bpf/prog_tests/stacktrace_build_id_nmi.c | 4 +-
9 files changed, 152 insertions(+), 115 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index f70088b4c19b..27dfbd363430 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -16,6 +16,7 @@
#include <libbpf.h>
#include <sys/types.h>
#include <sys/stat.h>
+#include <sys/mman.h>
#include <unistd.h>
#include "btf.h"
@@ -261,14 +262,16 @@ static int codegen(const char *template, ...)
static int do_skeleton(int argc, char **argv)
{
char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SKEL_H__")];
- size_t i, map_cnt = 0, prog_cnt = 0;
- char obj_name[MAX_OBJ_NAME_LEN];
+ size_t i, map_cnt = 0, prog_cnt = 0, file_sz, mmap_sz;
+ DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts);
+ char obj_name[MAX_OBJ_NAME_LEN], *obj_data;
+ struct bpf_object *obj = NULL;
const char *file, *ident;
struct bpf_program *prog;
- struct bpf_object *obj;
+ int fd, len, err = -1;
struct bpf_map *map;
struct btf *btf;
- int err = -1;
+ struct stat st;
if (!REQ_ARGS(1)) {
usage();
@@ -281,14 +284,31 @@ static int do_skeleton(int argc, char **argv)
return -1;
}
- obj = bpf_object__open_file(file, NULL);
- if (IS_ERR(obj)) {
- p_err("failed to open BPF object file: %ld", PTR_ERR(obj));
+ if (stat(file, &st)) {
+ p_err("failed to stat() %s: %s", file, strerror(errno));
return -1;
}
-
+ file_sz = st.st_size;
+ mmap_sz = roundup(file_sz, sysconf(_SC_PAGE_SIZE));
+ fd = open(file, O_RDONLY);
+ if (fd < 0) {
+ p_err("failed to open() %s: %s", file, strerror(errno));
+ return -1;
+ }
+ obj_data = mmap(NULL, mmap_sz, PROT_READ, MAP_PRIVATE, fd, 0);
+ if (obj_data == MAP_FAILED) {
+ obj_data = NULL;
+ p_err("failed to mmap() %s: %s", file, strerror(errno));
+ goto out;
+ }
get_obj_name(obj_name, file);
- get_header_guard(header_guard, obj_name);
+ opts.object_name = obj_name;
+ obj = bpf_object__open_mem(obj_data, file_sz, &opts);
+ if (IS_ERR(obj)) {
+ obj = NULL;
+ p_err("failed to open BPF object file: %ld", PTR_ERR(obj));
+ goto out;
+ }
bpf_object__for_each_map(map, obj) {
ident = get_map_ident(map);
@@ -303,8 +323,11 @@ static int do_skeleton(int argc, char **argv)
prog_cnt++;
}
+ get_header_guard(header_guard, obj_name);
codegen("\
\n\
+ /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ \n\
+ \n\
/* THIS FILE IS AUTOGENERATED! */ \n\
#ifndef %2$s \n\
#define %2$s \n\
@@ -356,8 +379,88 @@ static int do_skeleton(int argc, char **argv)
\n\
}; \n\
\n\
+ static void \n\
+ %1$s__destroy(struct %1$s *obj) \n\
+ { \n\
+ if (!obj) \n\
+ return; \n\
+ if (obj->skeleton) \n\
+ bpf_object__destroy_skeleton(obj->skeleton);\n\
+ free(obj); \n\
+ } \n\
+ \n\
static inline struct bpf_object_skeleton * \n\
- %1$s__create_skeleton(struct %1$s *obj, struct bpf_embed_data *embed)\n\
+ %1$s__create_skeleton(struct %1$s *obj); \n\
+ \n\
+ static inline struct %1$s * \n\
+ %1$s__open_opts(const struct bpf_object_open_opts *opts) \n\
+ { \n\
+ struct %1$s *obj; \n\
+ \n\
+ obj = calloc(1, sizeof(*obj)); \n\
+ if (!obj) \n\
+ return NULL; \n\
+ \n\
+ obj->skeleton = %1$s__create_skeleton(obj); \n\
+ if (!obj->skeleton) \n\
+ goto err; \n\
+ \n\
+ if (bpf_object__open_skeleton(obj->skeleton, opts)) \n\
+ goto err; \n\
+ \n\
+ return obj; \n\
+ err: \n\
+ %1$s__destroy(obj); \n\
+ return NULL; \n\
+ } \n\
+ \n\
+ static inline struct %1$s * \n\
+ %1$s__open() \n\
+ { \n\
+ return %1$s__open_opts(NULL); \n\
+ } \n\
+ \n\
+ static inline int \n\
+ %1$s__load(struct %1$s *obj) \n\
+ { \n\
+ return bpf_object__load_skeleton(obj->skeleton); \n\
+ } \n\
+ \n\
+ static inline struct %1$s * \n\
+ %1$s__open_and_load() \n\
+ { \n\
+ struct %1$s *obj; \n\
+ \n\
+ obj = %1$s__open(); \n\
+ if (!obj) \n\
+ return NULL; \n\
+ if (%1$s__load(obj)) { \n\
+ %1$s__destroy(obj); \n\
+ return NULL; \n\
+ } \n\
+ return obj; \n\
+ } \n\
+ \n\
+ static inline int \n\
+ %1$s__attach(struct %1$s *obj) \n\
+ { \n\
+ return bpf_object__attach_skeleton(obj->skeleton); \n\
+ } \n\
+ \n\
+ static inline void \n\
+ %1$s__detach(struct %1$s *obj) \n\
+ { \n\
+ return bpf_object__detach_skeleton(obj->skeleton); \n\
+ } \n\
+ ",
+ obj_name
+ );
+
+ codegen("\
+ \n\
+ \n\
+ static inline struct bpf_object_skeleton * \n\
+ %1$s__create_skeleton(struct %1$s *obj) \n\
{ \n\
struct bpf_object_skeleton *s; \n\
\n\
@@ -367,8 +470,6 @@ static int do_skeleton(int argc, char **argv)
\n\
s->sz = sizeof(*s); \n\
s->name = \"%1$s\"; \n\
- s->data = embed->data; \n\
- s->data_sz = embed->size; \n\
s->obj = &obj->obj; \n\
",
obj_name
@@ -438,90 +539,45 @@ static int do_skeleton(int argc, char **argv)
codegen("\
\n\
\n\
+ s->data_sz = %d; \n\
+ s->data = \"\\ \n\
+ ",
+ file_sz);
+
+ /* embed contents of BPF object file */
+ for (i = 0, len = 0; i < file_sz; i++) {
+ int w = obj_data[i] ? 4 : 2;
+
+ len += w;
+ if (len > 78) {
+ printf("\\\n");
+ len = w;
+ }
+ if (!obj_data[i])
+ printf("\\0");
+ else
+ printf("\\x%02x", (unsigned char)obj_data[i]);
+ }
+
+ codegen("\
+ \n\
+ \"; \n\
+ \n\
return s; \n\
err: \n\
bpf_object__destroy_skeleton(s); \n\
return NULL; \n\
} \n\
\n\
- static void \n\
- %1$s__destroy(struct %1$s *obj) \n\
- { \n\
- if (!obj) \n\
- return; \n\
- if (obj->skeleton) \n\
- bpf_object__destroy_skeleton(obj->skeleton);\n\
- free(obj); \n\
- } \n\
- \n\
- static inline struct %1$s * \n\
- %1$s__open_opts(struct bpf_embed_data *embed, const struct bpf_object_open_opts *opts)\n\
- { \n\
- struct %1$s *obj; \n\
- \n\
- obj = calloc(1, sizeof(*obj)); \n\
- if (!obj) \n\
- return NULL; \n\
- \n\
- obj->skeleton = %1$s__create_skeleton(obj, embed); \n\
- if (!obj->skeleton) \n\
- goto err; \n\
- \n\
- if (bpf_object__open_skeleton(obj->skeleton, opts)) \n\
- goto err; \n\
- \n\
- return obj; \n\
- err: \n\
- %1$s__destroy(obj); \n\
- return NULL; \n\
- } \n\
- \n\
- static inline struct %1$s * \n\
- %1$s__open(struct bpf_embed_data *embed) \n\
- { \n\
- return %1$s__open_opts(embed, NULL); \n\
- } \n\
- \n\
- static inline int \n\
- %1$s__load(struct %1$s *obj) \n\
- { \n\
- return bpf_object__load_skeleton(obj->skeleton); \n\
- } \n\
- \n\
- static inline struct %1$s * \n\
- %1$s__open_and_load(struct bpf_embed_data *embed) \n\
- { \n\
- struct %1$s *obj; \n\
- \n\
- obj = %1$s__open(embed); \n\
- if (!obj) \n\
- return NULL; \n\
- if (%1$s__load(obj)) { \n\
- %1$s__destroy(obj); \n\
- return NULL; \n\
- } \n\
- return obj; \n\
- } \n\
- \n\
- static inline int \n\
- %1$s__attach(struct %1$s *obj) \n\
- { \n\
- return bpf_object__attach_skeleton(obj->skeleton); \n\
- } \n\
- \n\
- static inline void \n\
- %1$s__detach(struct %1$s *obj) \n\
- { \n\
- return bpf_object__detach_skeleton(obj->skeleton); \n\
- } \n\
- \n\
#endif /* %2$s */ \n\
",
- obj_name, header_guard
- );
+ obj_name, header_guard);
err = 0;
out:
bpf_object__close(obj);
+ if (obj_data)
+ munmap(obj_data, mmap_sz);
+ close(fd);
return err;
}
diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index 60da1d08daa0..5ed90ede2f1d 100644
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
@@ -22,8 +22,6 @@ ssize_t get_base_addr() {
return -EINVAL;
}
-BPF_EMBED_OBJ(probe, "test_attach_probe.o");
-
void test_attach_probe(void)
{
int duration = 0;
@@ -39,7 +37,7 @@ void test_attach_probe(void)
return;
uprobe_offset = (size_t)&get_base_addr - base_addr;
- skel = test_attach_probe__open_and_load(&probe_embed);
+ skel = test_attach_probe__open_and_load();
if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
return;
if (CHECK(!skel->bss, "check_bss", ".bss wasn't mmap()-ed\n"))
diff --git a/tools/testing/selftests/bpf/prog_tests/core_extern.c b/tools/testing/selftests/bpf/prog_tests/core_extern.c
index 30a7972e9012..5f03dc1de29e 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_extern.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_extern.c
@@ -124,8 +124,6 @@ static struct test_case {
{ .name = "u64 (max+1)", .fails = 1, .cfg = CFG"CONFIG_ULONG=0x10000000000000000" },
};
-BPF_EMBED_OBJ(core_extern, "test_core_extern.o");
-
void test_core_extern(void)
{
const uint32_t kern_ver = get_kernel_version();
@@ -159,7 +157,7 @@ void test_core_extern(void)
opts.kconfig_path = tmp_cfg_path;
}
- skel = test_core_extern__open_opts(&core_extern_embed, &opts);
+ skel = test_core_extern__open_opts(&opts);
if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
goto cleanup;
err = test_core_extern__load(skel);
diff --git a/tools/testing/selftests/bpf/prog_tests/fentry_fexit.c b/tools/testing/selftests/bpf/prog_tests/fentry_fexit.c
index 110fcf053fd0..235ac4f67f5b 100644
--- a/tools/testing/selftests/bpf/prog_tests/fentry_fexit.c
+++ b/tools/testing/selftests/bpf/prog_tests/fentry_fexit.c
@@ -5,10 +5,6 @@
#include "fentry_test.skel.h"
#include "fexit_test.skel.h"
-BPF_EMBED_OBJ(pkt_access, "test_pkt_access.o");
-BPF_EMBED_OBJ(fentry, "fentry_test.o");
-BPF_EMBED_OBJ(fexit, "fexit_test.o");
-
void test_fentry_fexit(void)
{
struct test_pkt_access *pkt_skel = NULL;
@@ -18,13 +14,13 @@ void test_fentry_fexit(void)
__u32 duration = 0, retval;
int err, pkt_fd, i;
- pkt_skel = test_pkt_access__open_and_load(&pkt_access_embed);
+ pkt_skel = test_pkt_access__open_and_load();
if (CHECK(!pkt_skel, "pkt_skel_load", "pkt_access skeleton failed\n"))
return;
- fentry_skel = fentry_test__open_and_load(&fentry_embed);
+ fentry_skel = fentry_test__open_and_load();
if (CHECK(!fentry_skel, "fentry_skel_load", "fentry skeleton failed\n"))
goto close_prog;
- fexit_skel = fexit_test__open_and_load(&fexit_embed);
+ fexit_skel = fexit_test__open_and_load();
if (CHECK(!fexit_skel, "fexit_skel_load", "fexit skeleton failed\n"))
goto close_prog;
diff --git a/tools/testing/selftests/bpf/prog_tests/fentry_test.c b/tools/testing/selftests/bpf/prog_tests/fentry_test.c
index 46a4afdf507a..e1a379f5f7d2 100644
--- a/tools/testing/selftests/bpf/prog_tests/fentry_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/fentry_test.c
@@ -4,9 +4,6 @@
#include "test_pkt_access.skel.h"
#include "fentry_test.skel.h"
-BPF_EMBED_OBJ_DECLARE(pkt_access);
-BPF_EMBED_OBJ_DECLARE(fentry);
-
void test_fentry_test(void)
{
struct test_pkt_access *pkt_skel = NULL;
@@ -15,10 +12,10 @@ void test_fentry_test(void)
__u32 duration, retval;
__u64 *result;
- pkt_skel = test_pkt_access__open_and_load(&pkt_access_embed);
+ pkt_skel = test_pkt_access__open_and_load();
if (CHECK(!pkt_skel, "pkt_skel_load", "pkt_access skeleton failed\n"))
return;
- fentry_skel = fentry_test__open_and_load(&fentry_embed);
+ fentry_skel = fentry_test__open_and_load();
if (CHECK(!fentry_skel, "fentry_skel_load", "fentry skeleton failed\n"))
goto cleanup;
diff --git a/tools/testing/selftests/bpf/prog_tests/mmap.c b/tools/testing/selftests/bpf/prog_tests/mmap.c
index 95a44d37ccea..16a814eb4d64 100644
--- a/tools/testing/selftests/bpf/prog_tests/mmap.c
+++ b/tools/testing/selftests/bpf/prog_tests/mmap.c
@@ -13,8 +13,6 @@ static size_t roundup_page(size_t sz)
return (sz + page_size - 1) / page_size * page_size;
}
-BPF_EMBED_OBJ(test_mmap, "test_mmap.o");
-
void test_mmap(void)
{
const size_t bss_sz = roundup_page(sizeof(struct test_mmap__bss));
@@ -30,7 +28,7 @@ void test_mmap(void)
__u64 val = 0;
- skel = test_mmap__open_and_load(&test_mmap_embed);
+ skel = test_mmap__open_and_load();
if (CHECK(!skel, "skel_open_and_load", "skeleton open/load failed\n"))
return;
diff --git a/tools/testing/selftests/bpf/prog_tests/skeleton.c b/tools/testing/selftests/bpf/prog_tests/skeleton.c
index 151cdad3ad0d..ec6f2aec3853 100644
--- a/tools/testing/selftests/bpf/prog_tests/skeleton.c
+++ b/tools/testing/selftests/bpf/prog_tests/skeleton.c
@@ -10,8 +10,6 @@ struct s {
#include "test_skeleton.skel.h"
-BPF_EMBED_OBJ(skeleton, "test_skeleton.o");
-
void test_skeleton(void)
{
int duration = 0, err;
@@ -19,7 +17,7 @@ void test_skeleton(void)
struct test_skeleton__bss *bss;
struct test_skeleton__externs *exts;
- skel = test_skeleton__open(&skeleton_embed);
+ skel = test_skeleton__open();
if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
return;
diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
index 4af8b8253f25..e8399ae50e77 100644
--- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
+++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
@@ -2,8 +2,6 @@
#include <test_progs.h>
#include "test_stacktrace_build_id.skel.h"
-BPF_EMBED_OBJ(stacktrace_build_id, "test_stacktrace_build_id.o");
-
void test_stacktrace_build_id(void)
{
@@ -18,7 +16,7 @@ void test_stacktrace_build_id(void)
int retry = 1;
retry:
- skel = test_stacktrace_build_id__open_and_load(&stacktrace_build_id_embed);
+ skel = test_stacktrace_build_id__open_and_load();
if (CHECK(!skel, "skel_open_and_load", "skeleton open/load failed\n"))
return;
diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
index 32fb03881a7b..8974450a4bdb 100644
--- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
+++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
@@ -15,8 +15,6 @@ static __u64 read_perf_max_sample_freq(void)
return sample_freq;
}
-BPF_EMBED_OBJ_DECLARE(stacktrace_build_id);
-
void test_stacktrace_build_id_nmi(void)
{
int control_map_fd, stackid_hmap_fd, stackmap_fd;
@@ -37,7 +35,7 @@ void test_stacktrace_build_id_nmi(void)
attr.sample_freq = read_perf_max_sample_freq();
retry:
- skel = test_stacktrace_build_id__open(&stacktrace_build_id_embed);
+ skel = test_stacktrace_build_id__open();
if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
return;
--
2.17.1
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH bpf-next 3/3] bpftool: add gen subcommand manpage
2019-12-17 5:36 [PATCH bpf-next 0/3] Skeleton improvements and documnetation Andrii Nakryiko
2019-12-17 5:36 ` [PATCH bpf-next 1/3] bpftool, selftests/bpf: embed object file inside skeleton Andrii Nakryiko
2019-12-17 5:36 ` [PATCH bpf-next 2/3] libbpf: remove BPF_EMBED_OBJ macro from libbpf.h Andrii Nakryiko
@ 2019-12-17 5:36 ` Andrii Nakryiko
2019-12-17 21:27 ` Yonghong Song
2 siblings, 1 reply; 8+ messages in thread
From: Andrii Nakryiko @ 2019-12-17 5:36 UTC (permalink / raw)
To: bpf, netdev, ast, daniel; +Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Add bpftool-gen.rst describing skeleton on the high level. Also include
a small, but complete, example BPF app (BPF side, userspace side, generated
skeleton) in example section to demonstrate skeleton API and its usage.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
.../bpf/bpftool/Documentation/bpftool-gen.rst | 302 ++++++++++++++++++
tools/bpf/bpftool/Documentation/bpftool.rst | 3 +-
2 files changed, 304 insertions(+), 1 deletion(-)
create mode 100644 tools/bpf/bpftool/Documentation/bpftool-gen.rst
diff --git a/tools/bpf/bpftool/Documentation/bpftool-gen.rst b/tools/bpf/bpftool/Documentation/bpftool-gen.rst
new file mode 100644
index 000000000000..855d03b88590
--- /dev/null
+++ b/tools/bpf/bpftool/Documentation/bpftool-gen.rst
@@ -0,0 +1,302 @@
+================
+bpftool-gen
+================
+-------------------------------------------------------------------------------
+tool for BPF code-generation
+-------------------------------------------------------------------------------
+
+:Manual section: 8
+
+SYNOPSIS
+========
+
+ **bpftool** [*OPTIONS*] **gen** *COMMAND*
+
+ *OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] }
+
+ *COMMAND* := { **skeleton | **help** }
+
+GEN COMMANDS
+=============
+
+| **bpftool** **gen skeleton** *FILE*
+| **bpftool** **gen help**
+
+DESCRIPTION
+===========
+ **bpftool gen skeleton** *FILE*
+ Generate BPF skeleton C header file for a given *FILE*.
+
+ BPF skeleton is an alternative interface to existing libbpf
+ APIs for working with BPF objects. Skeleton code is intended
+ to significantly shorten and simplify code to load and work
+ with BPF programs from userspace side. Generated code is
+ tailored to specific input BPF object *FILE*, reflecting its
+ structure by listing out available maps, program, variables,
+ etc. Skeleton eliminates the need to lookup mentioned
+ components by name. Instead, if skeleton instantiation
+ succeeds, they are populated in skeleton structure as valid
+ libbpf types (e.g., struct bpf_map pointer) and can be
+ passed to existing generic libbpf APIs.
+
+ In addition to simple and reliable access to maps and
+ programs, skeleton provides a storage for BPF links (struct
+ bpf_link) for each BPF program within BPF object. When
+ requested, supported BPF programs will be automatically
+ attached and resulting BPF links stored for further use by
+ user in pre-allocated fields in skeleton struct. For BPF
+ programs that can't be automatically attached by libbpf,
+ user can attach them manually, but store resulting BPF link
+ in per-program link field. All such set up links will be
+ automatically destroyed on BPF skeleton destruction. This
+ eliminates the need for users to manage links manually and
+ rely on libbpf support to detach programs and free up
+ resources.
+
+ Another facility provided by BPF skeleton is an interface to
+ global variables of all supported kinds: mutable, read-only,
+ as well as extern ones. This interface allows to pre-setup
+ initial values of variables before BPF object is loaded and
+ verified by kernel. For non-read-only variables, the same
+ interface can be used to fetch values of global variables on
+ userspace side, even if they are modified by BPF code.
+
+ During skeleton generation, contents of source BPF object
+ *FILE* is embedded within generated code and is thus not
+ necessary to keep around. This ensures skeleton and BPF
+ object file are matching 1-to-1 and always stay in sync.
+ Generated code is dual-licensed under LGPL-2.1 and
+ BSD-2-Clause licenses.
+
+ It is a design goal and guarantee that skeleton interfaces
+ are interoperable with generic libbpf APIs. User should
+ always be able to use skeleton API to create and load BPF
+ object, and later use libbpf APIs to keep working with
+ specific maps, programs, etc.
+
+ As part of skeleton, few custom functions are generated.
+ Each of them is prefixed with object name, derived from
+ object file name. I.e., if BPF object file name is
+ **example.o**, BPF object name will be **example**. The
+ following custom functions are provided in such case:
+
+ - **example__open** and **example__open_opts**.
+ These functions are used to instantiate skeleton. It
+ corresponds to libbpf's **bpf_object__open()** API.
+ **_opts** variants accepts extra **bpf_object_open_opts**
+ options.
+
+ - **example__load**.
+ This functions creates maps, loads and verifies BPF
+ programs, initializes global data maps. It corresponds to
+ libppf's **bpf_object__load** API.
+
+ - **example__open_and_load** combines **example__open** and
+ **example__load** invocations in one commonly used
+ operation.
+
+ - **example__attach** and **example__detach**
+ This pair of functions allow to attach and detach,
+ correspondingly, already loaded BPF object. Only BPF
+ programs of types supported by libbpf for auto-attachment
+ will be auto-attached and their corresponding BPF links
+ instantiated. For other BPF programs, user can manually
+ create a BPF link and assign it to corresponding fields in
+ skeleton struct. **example__detach** will detach both
+ links created automatically, as well as those populated by
+ user manually.
+
+ - **example__destroy**
+ Detach and unload BPF programs, free up all the resources
+ used by skeleton and BPF object.
+
+ If BPF object has global variables, corresponding structs
+ with memory layout corresponding to global data datasection
+ layout will be created. Currently supported ones are: .data,
+ .bss, .rodata, and .extern structs/datasections. These
+ datasections/structs can be used to set up initial values of
+ variables, if set before **example__load**. Afterwards, if
+ target kernel supports memory-mapped BPF arrays, same
+ structs can be used to fetch and update (non-read-only)
+ data from userspace, with same simplicity as for BPF side.
+
+ **bpftool gen help**
+ Print short help message.
+
+OPTIONS
+=======
+ -h, --help
+ Print short generic help message (similar to **bpftool help**).
+
+ -V, --version
+ Print version number (similar to **bpftool version**).
+
+ -j, --json
+ Generate JSON output. For commands that cannot produce JSON,
+ this option has no effect.
+
+ -p, --pretty
+ Generate human-readable JSON output. Implies **-j**.
+
+ -d, --debug
+ Print all logs available from libbpf, including debug-level
+ information.
+
+EXAMPLES
+========
+**$ cat example.c**
+::
+
+ #include <stdbool.h>
+ #include <linux/ptrace.h>
+ #include <linux/bpf.h>
+ #include "bpf_helpers.h"
+
+ const volatile int param1 = 42;
+ bool global_flag = true;
+ struct { int x; } data = {};
+
+ struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(max_entries, 128);
+ __type(key, int);
+ __type(value, long);
+ } my_map SEC(".maps");
+
+ SEC("raw_tp/sys_enter")
+ int handle_sys_enter(struct pt_regs *ctx)
+ {
+ static long my_static_var;
+ if (global_flag)
+ my_static_var++;
+ else
+ data.x += param1;
+ return 0;
+ }
+
+ SEC("raw_tp/sys_exit")
+ int handle_sys_exit(struct pt_regs *ctx)
+ {
+ int zero = 0;
+ bpf_map_lookup_elem(&my_map, &zero);
+ return 0;
+ }
+
+This is example BPF application with two BPF programs and a mix of BPF maps
+and global variables.
+
+**$ bpftool gen skeleton example.o**
+::
+
+ /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+
+ /* THIS FILE IS AUTOGENERATED! */
+ #ifndef __EXAMPLE_SKEL_H__
+ #define __EXAMPLE_SKEL_H__
+
+ #include <stdlib.h>
+ #include <libbpf.h>
+
+ struct example {
+ struct bpf_object_skeleton *skeleton;
+ struct bpf_object *obj;
+ struct {
+ struct bpf_map *rodata;
+ struct bpf_map *data;
+ struct bpf_map *bss;
+ struct bpf_map *my_map;
+ } maps;
+ struct {
+ struct bpf_program *handle_sys_enter;
+ struct bpf_program *handle_sys_exit;
+ } progs;
+ struct {
+ struct bpf_link *handle_sys_enter;
+ struct bpf_link *handle_sys_exit;
+ } links;
+ struct example__bss {
+ struct {
+ int x;
+ } data;
+ } *bss;
+ struct example__data {
+ _Bool global_flag;
+ long int handle_sys_enter_my_static_var;
+ } *data;
+ struct example__rodata {
+ int param1;
+ } *rodata;
+ };
+
+ static void example__destroy(struct example *obj);
+ static inline struct example *example__open_opts(
+ const struct bpf_object_open_opts *opts);
+ static inline struct example *example__open();
+ static inline int example__load(struct example *obj);
+ static inline struct example *example__open_and_load();
+ static inline int example__attach(struct example *obj);
+ static inline void example__detach(struct example *obj);
+
+ #endif /* __EXAMPLE_SKEL_H__ */
+
+**$ cat example_user.c**
+::
+ #include "example.skel.h"
+
+ int main()
+ {
+ struct example *skel;
+ int err = 0;
+
+ skel = example__open();
+ if (!skel)
+ goto cleanup;
+
+ skel->rodata->param1 = 128;
+
+ err = example__load(skel);
+ if (err)
+ goto cleanup;
+
+ err = example__attach(skel);
+ if (err)
+ goto cleanup;
+
+ /* all libbpf APIs are usable */
+ printf("my_map name: %s\n", bpf_map__name(skel->maps.my_map));
+ printf("sys_enter prog FD: %d\n",
+ bpf_program__fd(skel->progs.handle_sys_enter));
+
+ /* detach and re-attach sys_exit program */
+ bpf_link__destroy(skel->links.handle_sys_exit);
+ skel->links.handle_sys_exit =
+ bpf_program__attach(skel->progs.handle_sys_exit);
+
+ printf("my_static_var: %ld\n",
+ skel->bss->handle_sys_enter_my_static_var);
+
+ cleanup:
+ example__destroy(skel);
+ return err;
+ }
+
+**# ./example_user**
+::
+ my_map name: my_map
+ sys_enter prog FD: 8
+ my_static_var: 7
+
+This is a stripped-out version of skeleton generated for above example code.
+
+SEE ALSO
+========
+ **bpf**\ (2),
+ **bpf-helpers**\ (7),
+ **bpftool**\ (8),
+ **bpftool-map**\ (8),
+ **bpftool-prog**\ (8),
+ **bpftool-cgroup**\ (8),
+ **bpftool-feature**\ (8),
+ **bpftool-net**\ (8),
+ **bpftool-perf**\ (8),
+ **bpftool-btf**\ (8)
diff --git a/tools/bpf/bpftool/Documentation/bpftool.rst b/tools/bpf/bpftool/Documentation/bpftool.rst
index 6a9c52ef84a9..34239fda69ed 100644
--- a/tools/bpf/bpftool/Documentation/bpftool.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool.rst
@@ -81,4 +81,5 @@ SEE ALSO
**bpftool-feature**\ (8),
**bpftool-net**\ (8),
**bpftool-perf**\ (8),
- **bpftool-btf**\ (8)
+ **bpftool-btf**\ (8),
+ **bpftool-gen**\ (8),
--
2.17.1
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