Re: [PATCH bpf-next 2/4] bpftool: use bpf_obj_get_info_by_fd directly
From: Dave Marchevsky <hidden>
Date: 2021-10-11 03:44:38
Also in:
bpf
On 10/10/21 10:27 PM, Dave Marchevsky wrote:
To prepare for impending deprecation of libbpf's bpf_program__get_prog_info_linear, migrate uses of this function to use bpf_obj_get_info_by_fd. Since the profile_target_name and dump_prog_id_as_func_ptr helpers were only looking at the first func_info, avoid grabbing the rest to save a malloc. For do_dump, add a more full-featured helper, but avoid free/realloc of buffer when possible for multi-prog dumps. Signed-off-by: Dave Marchevsky <redacted> --- tools/bpf/bpftool/btf_dumper.c | 40 +++++---- tools/bpf/bpftool/prog.c | 153 +++++++++++++++++++++++++-------- 2 files changed, 143 insertions(+), 50 deletions(-)
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diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c index a24ea7e26aa4..a7507cc165eb 100644 --- a/tools/bpf/bpftool/prog.c +++ b/tools/bpf/bpftool/prog.c@@ -98,6 +98,72 @@ static enum bpf_attach_type parse_attach_type(const char *str) return __MAX_BPF_ATTACH_TYPE; } +#define holder_prep_needed_rec_sz(nr, rec_size)\ +({ \ + holder.nr = info->nr; \ + needed += holder.nr * rec_size; \ +}) + +#define holder_prep_needed(nr, rec_size) \ +({ \ + holder.nr = info->nr; \ + holder.rec_size = info->rec_size; \ + needed += holder.nr * holder.rec_size; \ +}) + +#define holder_set_ptr(field, nr, rec_size) \ +({ \ + holder.field = ptr_to_u64(ptr); \ + ptr += nr * rec_size; \ +}) + +static int prep_prog_info(struct bpf_prog_info *const info, enum dump_mode mode, + void *info_data, size_t *const info_data_sz) +{ + struct bpf_prog_info holder = {}; + size_t needed = 0; + void *ptr; + + if (mode == DUMP_JITED) + holder_prep_needed_rec_sz(jited_prog_len, 1); + else + holder_prep_needed_rec_sz(xlated_prog_len, 1); + + holder_prep_needed_rec_sz(nr_jited_ksyms, sizeof(__u64)); + holder_prep_needed_rec_sz(nr_jited_func_lens, sizeof(__u32)); + holder_prep_needed(nr_func_info, func_info_rec_size); + holder_prep_needed(nr_line_info, line_info_rec_size); + holder_prep_needed(nr_jited_line_info, jited_line_info_rec_size); + + if (needed > *info_data_sz) { + info_data = realloc(info_data, needed);
This breaks 'bpftool prog dump' for multiple progs, need to pass info_data as a void ** so that the original ptr is updated on realloc. Will send v2 shortly.
+ if (!info_data) + return -1; + *info_data_sz = needed; + }
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@@ -791,16 +857,18 @@ 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_prog_info info = {}; + __u32 info_len = sizeof(info); + size_t info_data_sz = 0; + void *info_data = NULL; char *filepath = NULL; bool opcodes = false; bool visual = false; enum dump_mode mode; bool linum = false; - int *fds = NULL; int nb_fds, i = 0; + int *fds = NULL; int err = -1; - __u64 arrays; if (is_prefix(*argv, "jited")) { if (disasm_init())@@ -860,43 +928,42 @@ static int do_dump(int argc, char **argv) goto exit_close; } - if (mode == DUMP_JITED) - arrays = 1UL << BPF_PROG_INFO_JITED_INSNS; - else - arrays = 1UL << BPF_PROG_INFO_XLATED_INSNS; - - arrays |= 1UL << BPF_PROG_INFO_JITED_KSYMS; - arrays |= 1UL << BPF_PROG_INFO_JITED_FUNC_LENS; - arrays |= 1UL << BPF_PROG_INFO_FUNC_INFO; - arrays |= 1UL << BPF_PROG_INFO_LINE_INFO; - arrays |= 1UL << BPF_PROG_INFO_JITED_LINE_INFO; - if (json_output && nb_fds > 1) jsonw_start_array(json_wtr); /* root array */ for (i = 0; i < nb_fds; i++) { - info_linear = bpf_program__get_prog_info_linear(fds[i], arrays); - if (IS_ERR_OR_NULL(info_linear)) { + err = bpf_obj_get_info_by_fd(fds[i], &info, &info_len); + if (err) { + p_err("can't get prog info: %s", strerror(errno)); + break; + } + + err = prep_prog_info(&info, mode, info_data, &info_data_sz); + if (err) { + p_err("can't grow prog info_data"); + break; + } + + err = bpf_obj_get_info_by_fd(fds[i], &info, &info_len); + if (err) { p_err("can't get prog info: %s", strerror(errno)); break; }
There should be a memset(&info, 0, sizeof(info)) at the end of this loop. In current state, when dumping multiple progs, previous iteration's populated info will be passed to first bpf_obj_get_info_by_fd call in next iteration, resulting in unnecessary data copying.
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if (json_output && nb_fds > 1) { jsonw_start_object(json_wtr); /* prog object */ - print_prog_header_json(&info_linear->info); + print_prog_header_json(&info); jsonw_name(json_wtr, "insns"); } else if (nb_fds > 1) { - print_prog_header_plain(&info_linear->info); + print_prog_header_plain(&info); } - err = prog_dump(&info_linear->info, mode, filepath, opcodes, - visual, linum); + err = prog_dump(&info, mode, filepath, opcodes, visual, linum); if (json_output && nb_fds > 1) jsonw_end_object(json_wtr); /* prog object */ else if (i != nb_fds - 1 && nb_fds > 1) printf("\n"); - free(info_linear); if (err) break; close(fds[i]);@@ -908,6 +975,7 @@ static int do_dump(int argc, char **argv) for (; i < nb_fds; i++) close(fds[i]); exit_free: + free(info_data); free(fds); return err; }