From: Andrii Nakryiko andrii@kernel.org
mainline inclusion from mainline-5.13-rc1 commit d80b2fcbe0a023619e0fc73112f2a02c2662f6ab category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Add `bpftool gen object <output-file> <input_file>...` command to statically link multiple BPF ELF object files into a single output BPF ELF object file.
This patch also updates bash completions and man page. Man page gets a short section on `gen object` command, but also updates the skeleton example to show off workflow for BPF application with two .bpf.c files, compiled individually with Clang, then resulting object files are linked together with `gen object`, and then final object file is used to generate usable BPF skeleton. This should help new users understand realistic workflow w.r.t. compiling mutli-file BPF application.
Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Reviewed-by: Quentin Monnet quentin@isovalent.com Link: https://lore.kernel.org/bpf/20210318194036.3521577-10-andrii@kernel.org (cherry picked from commit d80b2fcbe0a023619e0fc73112f2a02c2662f6ab) Signed-off-by: Wang Yufen wangyufen@huawei.com --- .../bpf/bpftool/Documentation/bpftool-gen.rst | 65 +++++++++++++++---- tools/bpf/bpftool/bash-completion/bpftool | 6 +- tools/bpf/bpftool/gen.c | 45 ++++++++++++- 3 files changed, 100 insertions(+), 16 deletions(-)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-gen.rst b/tools/bpf/bpftool/Documentation/bpftool-gen.rst index d4e7338e22e7..7cd6681137f3 100644 --- a/tools/bpf/bpftool/Documentation/bpftool-gen.rst +++ b/tools/bpf/bpftool/Documentation/bpftool-gen.rst @@ -14,16 +14,37 @@ SYNOPSIS
*OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] }
- *COMMAND* := { **skeleton** | **help** } + *COMMAND* := { **object** | **skeleton** | **help** }
GEN COMMANDS =============
+| **bpftool** **gen object** *OUTPUT_FILE* *INPUT_FILE* [*INPUT_FILE*...] | **bpftool** **gen skeleton** *FILE* [**name** *OBJECT_NAME*] | **bpftool** **gen help**
DESCRIPTION =========== + **bpftool gen object** *OUTPUT_FILE* *INPUT_FILE* [*INPUT_FILE*...] + Statically link (combine) together one or more *INPUT_FILE*'s + into a single resulting *OUTPUT_FILE*. All the files involved + are BPF ELF object files. + + The rules of BPF static linking are mostly the same as for + user-space object files, but in addition to combining data + and instruction sections, .BTF and .BTF.ext (if present in + any of the input files) data are combined together. .BTF + data is deduplicated, so all the common types across + *INPUT_FILE*'s will only be represented once in the resulting + BTF information. + + BPF static linking allows to partition BPF source code into + individually compiled files that are then linked into + a single resulting BPF object file, which can be used to + generated BPF skeleton (with **gen skeleton** command) or + passed directly into **libbpf** (using **bpf_object__open()** + family of APIs). + **bpftool gen skeleton** *FILE* Generate BPF skeleton C header file for a given *FILE*.
@@ -133,26 +154,19 @@ OPTIONS
EXAMPLES ======== -**$ cat example.c** +**$ cat example1.bpf.c**
::
#include <stdbool.h> #include <linux/ptrace.h> #include <linux/bpf.h> - #include "bpf_helpers.h" + #include <bpf/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) { @@ -164,6 +178,21 @@ EXAMPLES return 0; }
+**$ cat example2.bpf.c** + +:: + + #include <linux/ptrace.h> + #include <linux/bpf.h> + #include <bpf/bpf_helpers.h> + + 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_exit") int handle_sys_exit(struct pt_regs *ctx) { @@ -173,9 +202,17 @@ EXAMPLES }
This is example BPF application with two BPF programs and a mix of BPF maps -and global variables. +and global variables. Source code is split across two source code files.
-**$ bpftool gen skeleton example.o** +**$ clang -target bpf -g example1.bpf.c -o example1.bpf.o** +**$ clang -target bpf -g example2.bpf.c -o example2.bpf.o** +**$ bpftool gen object example.bpf.o example1.bpf.o example2.bpf.o** + +This set of commands compiles *example1.bpf.c* and *example2.bpf.c* +individually and then statically links respective object files into the final +BPF ELF object file *example.bpf.o*. + +**$ bpftool gen skeleton example.bpf.o name example | tee example.skel.h**
::
@@ -230,7 +267,7 @@ and global variables.
#endif /* __EXAMPLE_SKEL_H__ */
-**$ cat example_user.c** +**$ cat example.c**
::
@@ -273,7 +310,7 @@ and global variables. return err; }
-**# ./example_user** +**# ./example**
::
diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool index 5590f6209e3d..888758ec5d27 100644 --- a/tools/bpf/bpftool/bash-completion/bpftool +++ b/tools/bpf/bpftool/bash-completion/bpftool @@ -981,6 +981,10 @@ _bpftool() ;; gen) case $command in + object) + _filedir + return 0 + ;; skeleton) case $prev in $command) @@ -995,7 +999,7 @@ _bpftool() ;; *) [[ $prev == $object ]] && \ - COMPREPLY=( $( compgen -W 'skeleton help' -- "$cur" ) ) + COMPREPLY=( $( compgen -W 'object skeleton help' -- "$cur" ) ) ;; esac ;; diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index 9bff89a66835..31ade77f5ef8 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -614,6 +614,47 @@ static int do_skeleton(int argc, char **argv) return err; }
+static int do_object(int argc, char **argv) +{ + struct bpf_linker *linker; + const char *output_file, *file; + int err = 0; + + if (!REQ_ARGS(2)) { + usage(); + return -1; + } + + output_file = GET_ARG(); + + linker = bpf_linker__new(output_file, NULL); + if (!linker) { + p_err("failed to create BPF linker instance"); + return -1; + } + + while (argc) { + file = GET_ARG(); + + err = bpf_linker__add_file(linker, file); + if (err) { + p_err("failed to link '%s': %s (%d)", file, strerror(err), err); + goto out; + } + } + + err = bpf_linker__finalize(linker); + if (err) { + p_err("failed to finalize ELF file: %s (%d)", strerror(err), err); + goto out; + } + + err = 0; +out: + bpf_linker__free(linker); + return err; +} + static int do_help(int argc, char **argv) { if (json_output) { @@ -622,7 +663,8 @@ static int do_help(int argc, char **argv) }
fprintf(stderr, - "Usage: %1$s %2$s skeleton FILE [name OBJECT_NAME]\n" + "Usage: %1$s %2$s object OUTPUT_FILE INPUT_FILE [INPUT_FILE...]\n" + " %1$s %2$s skeleton FILE [name OBJECT_NAME]\n" " %1$s %2$s help\n" "\n" " " HELP_SPEC_OPTIONS "\n" @@ -633,6 +675,7 @@ static int do_help(int argc, char **argv) }
static const struct cmd cmds[] = { + { "object", do_object }, { "skeleton", do_skeleton }, { "help", do_help }, { 0 }