On 2021/7/14 2:35, Lorenzo Fontana wrote:
> bpftool can dump an xlated or jitted representation
> of the programs already loaded into the kernel.
> That capability is very useful for understanding what
> are the instructions the kernel will execute for that program.
>
> However, sometimes the verifier does not load the program and
> one cannot use this feature until changes are made to make the
> verifier happy again.
>
> This patch reuses the same dump function to dump the program
> from an ELF file directly instead of loading the instructions
> from a loaded file descriptor. In this way, the user
> can use all the bpftool features for "xlated" without loading.
>
> In particular, the "visual" command is very useful when combined
> to this because the dot graph makes easy to spot bad instruction
> sequences.
>
> Usage:
>
> bpftool prog dump xlated elf program.o
>
> It also works with the other commands like 'visual' to print
> an dot representation of the program.
>
> bpftool prog dump xlated elf program.o visual
>
> Signed-off-by: Lorenzo Fontana <fontanalorenz@xxxxxxxxx>
> ---
> tools/bpf/bpftool/common.c | 15 ++++++++++++---
> tools/bpf/bpftool/main.h | 2 +-
> tools/bpf/bpftool/prog.c | 26 +++++++++++++++++++++++---
> 3 files changed, 36 insertions(+), 7 deletions(-)
>
> diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
> index 1828bba19020..b28d15505705 100644
> --- a/tools/bpf/bpftool/common.c
> +++ b/tools/bpf/bpftool/common.c
> @@ -703,7 +703,7 @@ static int prog_fd_by_nametag(void *nametag, int **fds, bool tag)
> return -1;
> }
>
> -int prog_parse_fds(int *argc, char ***argv, int **fds)
> +int prog_parse_fds(int *argc, char ***argv, int **fds, char **elf_filepath)
> {
> if (is_prefix(**argv, "id")) {
> unsigned int id;
> @@ -763,9 +763,18 @@ int prog_parse_fds(int *argc, char ***argv, int **fds)
> if ((*fds)[0] < 0)
> return -1;
> return 1;
> + } else if (is_prefix(**argv, "elf")) {
> + NEXT_ARGP();
> + if (!argc) {
> + p_err("expected ELF file path");
> + return -1;
> + }
> + *elf_filepath = **argv;
> + NEXT_ARGP();
> + return 1;
> }
>
> - p_err("expected 'id', 'tag', 'name' or 'pinned', got: '%s'?", **argv);
> + p_err("expected 'id', 'tag', 'name', 'elf' or 'pinned', got: '%s'?", **argv);
Should we update the 'HELP_SPEC_PROGRAM' info as well?
Thanks,
Wei
> return -1;
> }
>
> @@ -779,7 +788,7 @@ int prog_parse_fd(int *argc, char ***argv)
> p_err("mem alloc failed");
> return -1;
> }
> - nb_fds = prog_parse_fds(argc, argv, &fds);
> + nb_fds = prog_parse_fds(argc, argv, &fds, NULL);
> if (nb_fds != 1) {
> if (nb_fds > 1) {
> p_err("several programs match this handle");
> diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
> index c1cf29798b99..f4e426d03b4a 100644
> --- a/tools/bpf/bpftool/main.h
> +++ b/tools/bpf/bpftool/main.h
> @@ -187,7 +187,7 @@ int do_iter(int argc, char **argv) __weak;
>
> int parse_u32_arg(int *argc, char ***argv, __u32 *val, const char *what);
> int prog_parse_fd(int *argc, char ***argv);
> -int prog_parse_fds(int *argc, char ***argv, int **fds);
> +int prog_parse_fds(int *argc, char ***argv, int **fds, char **elf_filepath);
> int map_parse_fd(int *argc, char ***argv);
> int map_parse_fds(int *argc, char ***argv, int **fds);
> int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len);
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index cc48726740ad..04fa9a83ef7e 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -537,7 +537,7 @@ static int do_show_subset(int argc, char **argv)
> p_err("mem alloc failed");
> return -1;
> }
> - nb_fds = prog_parse_fds(&argc, &argv, &fds);
> + nb_fds = prog_parse_fds(&argc, &argv, &fds, NULL);
> if (nb_fds < 1)
> goto exit_free;
>
> @@ -787,7 +787,10 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode,
> static int do_dump(int argc, char **argv)
> {
> struct bpf_prog_info_linear *info_linear;
> + struct bpf_object *obj;
> + struct bpf_program *prog;
> char *filepath = NULL;
> + char *elf_filepath = NULL;
> bool opcodes = false;
> bool visual = false;
> enum dump_mode mode;
> @@ -817,7 +820,8 @@ static int do_dump(int argc, char **argv)
> p_err("mem alloc failed");
> return -1;
> }
> - nb_fds = prog_parse_fds(&argc, &argv, &fds);
> + elf_filepath = malloc(sizeof(char) * PATH_MAX);
> + nb_fds = prog_parse_fds(&argc, &argv, &fds, &elf_filepath);
> if (nb_fds < 1)
> goto exit_free;
>
> @@ -849,7 +853,6 @@ static int do_dump(int argc, char **argv)
> linum = true;
> NEXT_ARG();
> }
> -
> if (argc) {
> usage();
> goto exit_close;
> @@ -866,9 +869,26 @@ static int do_dump(int argc, char **argv)
> arrays |= 1UL << BPF_PROG_INFO_LINE_INFO;
> arrays |= 1UL << BPF_PROG_INFO_JITED_LINE_INFO;
>
> + if (elf_filepath != NULL) {
> + obj = bpf_object__open(elf_filepath);
> + if (libbpf_get_error(obj)) {
> + p_err("ERROR: opening BPF object file failed");
> + return 0;
> + }
> +
> + bpf_object__for_each_program(prog, obj) {
> + struct bpf_prog_info pinfo;
> + pinfo.xlated_prog_insns = ptr_to_u64(bpf_program__insns(prog));
> + pinfo.xlated_prog_len = bpf_program__size(prog);
> + err = prog_dump(&pinfo, mode, filepath, opcodes, visual, linum);
> + }
> + return 0;
> + }
> +
> if (json_output && nb_fds > 1)
> jsonw_start_array(json_wtr); /* root array */
> for (i = 0; i < nb_fds; i++) {
> + printf("uno\n");
> info_linear = bpf_program__get_prog_info_linear(fds[i], arrays);
> if (IS_ERR_OR_NULL(info_linear)) {
> p_err("can't get prog info: %s", strerror(errno));
>
