From d5ae04da34a213cc518558ecd25af0f609428560 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Wed, 18 Mar 2020 10:16:50 -0700 Subject: bpftool: Translate prog_id to its bpf prog_name The kernel struct_ops obj has kernel's func ptrs implemented by bpf_progs. The bpf prog_id is stored as the value of the func ptr for introspection purpose. In the latter patch, a struct_ops dump subcmd will be added to introspect these func ptrs. It is desired to print the actual bpf prog_name instead of only printing the prog_id. Since struct_ops is the only usecase storing prog_id in the func ptr, this patch adds a prog_id_as_func_ptr bool (default is false) to "struct btf_dumper" in order not to mis-interpret the ptr value for the other existing use-cases. While printing a func_ptr as a bpf prog_name, this patch also prefix the bpf prog_name with the ptr's func_proto. [ Note that it is the ptr's func_proto instead of the bpf prog's func_proto ] It reuses the current btf_dump_func() to obtain the ptr's func_proto string. Here is an example from the bpf_cubic.c: "void (struct sock *, u32, u32) bictcp_cong_avoid/prog_id:140" Signed-off-by: Martin KaFai Lau Signed-off-by: Daniel Borkmann Acked-by: Quentin Monnet Link: https://lore.kernel.org/bpf/20200318171650.129252-1-kafai@fb.com --- tools/bpf/bpftool/btf_dumper.c | 118 ++++++++++++++++++++++++++++++++++++----- tools/bpf/bpftool/main.h | 1 + 2 files changed, 107 insertions(+), 12 deletions(-) diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c index e0cff4de2101..497807bec675 100644 --- a/tools/bpf/bpftool/btf_dumper.c +++ b/tools/bpf/bpftool/btf_dumper.c @@ -4,11 +4,13 @@ #include #include /* for (FILE *) used by json_writer */ #include +#include #include #include #include #include #include +#include #include "json_writer.h" #include "main.h" @@ -22,13 +24,102 @@ static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id, __u8 bit_offset, const void *data); -static void btf_dumper_ptr(const void *data, json_writer_t *jw, - bool is_plain_text) +static int btf_dump_func(const struct btf *btf, char *func_sig, + const struct btf_type *func_proto, + const struct btf_type *func, int pos, int size); + +static int dump_prog_id_as_func_ptr(const struct btf_dumper *d, + const struct btf_type *func_proto, + __u32 prog_id) { - if (is_plain_text) - jsonw_printf(jw, "%p", *(void **)data); + struct bpf_prog_info_linear *prog_info = NULL; + const struct btf_type *func_type; + const char *prog_name = NULL; + struct bpf_func_info *finfo; + struct btf *prog_btf = NULL; + struct bpf_prog_info *info; + int prog_fd, func_sig_len; + char prog_str[1024]; + + /* Get the ptr's func_proto */ + func_sig_len = btf_dump_func(d->btf, prog_str, func_proto, NULL, 0, + sizeof(prog_str)); + if (func_sig_len == -1) + return -1; + + if (!prog_id) + goto print; + + /* Get the bpf_prog's name. Obtain from func_info. */ + prog_fd = bpf_prog_get_fd_by_id(prog_id); + if (prog_fd == -1) + goto print; + + prog_info = bpf_program__get_prog_info_linear(prog_fd, + 1UL << BPF_PROG_INFO_FUNC_INFO); + close(prog_fd); + if (IS_ERR(prog_info)) { + prog_info = NULL; + goto print; + } + info = &prog_info->info; + + if (!info->btf_id || !info->nr_func_info || + btf__get_from_id(info->btf_id, &prog_btf)) + goto print; + finfo = (struct bpf_func_info *)info->func_info; + func_type = btf__type_by_id(prog_btf, finfo->type_id); + if (!func_type || !btf_is_func(func_type)) + goto print; + + prog_name = btf__name_by_offset(prog_btf, func_type->name_off); + +print: + if (!prog_id) + snprintf(&prog_str[func_sig_len], + sizeof(prog_str) - func_sig_len, " 0"); + else if (prog_name) + snprintf(&prog_str[func_sig_len], + sizeof(prog_str) - func_sig_len, + " %s/prog_id:%u", prog_name, prog_id); else - jsonw_printf(jw, "%lu", *(unsigned long *)data); + snprintf(&prog_str[func_sig_len], + sizeof(prog_str) - func_sig_len, + " /prog_id:%u", prog_id); + + prog_str[sizeof(prog_str) - 1] = '\0'; + jsonw_string(d->jw, prog_str); + btf__free(prog_btf); + free(prog_info); + return 0; +} + +static void btf_dumper_ptr(const struct btf_dumper *d, + const struct btf_type *t, + const void *data) +{ + unsigned long value = *(unsigned long *)data; + const struct btf_type *ptr_type; + __s32 ptr_type_id; + + if (!d->prog_id_as_func_ptr || value > UINT32_MAX) + goto print_ptr_value; + + ptr_type_id = btf__resolve_type(d->btf, t->type); + if (ptr_type_id < 0) + goto print_ptr_value; + ptr_type = btf__type_by_id(d->btf, ptr_type_id); + if (!ptr_type || !btf_is_func_proto(ptr_type)) + goto print_ptr_value; + + if (!dump_prog_id_as_func_ptr(d, ptr_type, value)) + return; + +print_ptr_value: + if (d->is_plain_text) + jsonw_printf(d->jw, "%p", (void *)value); + else + jsonw_printf(d->jw, "%lu", value); } static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id, @@ -442,7 +533,7 @@ static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id, case BTF_KIND_ENUM: return btf_dumper_enum(d, t, data); case BTF_KIND_PTR: - btf_dumper_ptr(data, d->jw, d->is_plain_text); + btf_dumper_ptr(d, t, data); return 0; case BTF_KIND_UNKN: jsonw_printf(d->jw, "(unknown)"); @@ -487,10 +578,6 @@ int btf_dumper_type(const struct btf_dumper *d, __u32 type_id, return -1; \ } while (0) -static int btf_dump_func(const struct btf *btf, char *func_sig, - const struct btf_type *func_proto, - const struct btf_type *func, int pos, int size); - static int __btf_dumper_type_only(const struct btf *btf, __u32 type_id, char *func_sig, int pos, int size) { @@ -599,8 +686,15 @@ static int btf_dump_func(const struct btf *btf, char *func_sig, BTF_PRINT_ARG(", "); if (arg->type) { BTF_PRINT_TYPE(arg->type); - BTF_PRINT_ARG("%s", - btf__name_by_offset(btf, arg->name_off)); + if (arg->name_off) + BTF_PRINT_ARG("%s", + btf__name_by_offset(btf, arg->name_off)); + else if (pos && func_sig[pos - 1] == ' ') + /* Remove unnecessary space for + * FUNC_PROTO that does not have + * arg->name_off + */ + func_sig[--pos] = '\0'; } else { BTF_PRINT_ARG("..."); } diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h index 5f6dccd43622..6db2398ae7e9 100644 --- a/tools/bpf/bpftool/main.h +++ b/tools/bpf/bpftool/main.h @@ -205,6 +205,7 @@ struct btf_dumper { const struct btf *btf; json_writer_t *jw; bool is_plain_text; + bool prog_id_as_func_ptr; }; /* btf_dumper_type - print data along with type information -- cgit v1.2.3-58-ga151