From 647cafa22349026a8435030e9157074ab7fe5710 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Tue, 12 Jul 2022 13:31:44 +0100 Subject: bpf: add a ksym BPF iterator add a "ksym" iterator which provides access to a "struct kallsym_iter" for each symbol. Intent is to support more flexible symbol parsing as discussed in [1]. [1] https://lore.kernel.org/all/YjRPZj6Z8vuLeEZo@krava/ Suggested-by: Alexei Starovoitov Signed-off-by: Alan Maguire Acked-by: Yonghong Song Link: https://lore.kernel.org/r/1657629105-7812-2-git-send-email-alan.maguire@oracle.com Signed-off-by: Alexei Starovoitov --- kernel/kallsyms.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index fbdf8d3279ac..79a85834ce9d 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -30,6 +30,7 @@ #include #include #include +#include /* * These will be re-linked against their real values @@ -799,6 +800,96 @@ static const struct seq_operations kallsyms_op = { .show = s_show }; +#ifdef CONFIG_BPF_SYSCALL + +struct bpf_iter__ksym { + __bpf_md_ptr(struct bpf_iter_meta *, meta); + __bpf_md_ptr(struct kallsym_iter *, ksym); +}; + +static int ksym_prog_seq_show(struct seq_file *m, bool in_stop) +{ + struct bpf_iter__ksym ctx; + struct bpf_iter_meta meta; + struct bpf_prog *prog; + + meta.seq = m; + prog = bpf_iter_get_info(&meta, in_stop); + if (!prog) + return 0; + + ctx.meta = &meta; + ctx.ksym = m ? m->private : NULL; + return bpf_iter_run_prog(prog, &ctx); +} + +static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p) +{ + return ksym_prog_seq_show(m, false); +} + +static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p) +{ + if (!p) + (void) ksym_prog_seq_show(m, true); + else + s_stop(m, p); +} + +static const struct seq_operations bpf_iter_ksym_ops = { + .start = s_start, + .next = s_next, + .stop = bpf_iter_ksym_seq_stop, + .show = bpf_iter_ksym_seq_show, +}; + +static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux) +{ + struct kallsym_iter *iter = priv_data; + + reset_iter(iter, 0); + + /* cache here as in kallsyms_open() case; use current process + * credentials to tell BPF iterators if values should be shown. + */ + iter->show_value = kallsyms_show_value(current_cred()); + + return 0; +} + +DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym) + +static const struct bpf_iter_seq_info ksym_iter_seq_info = { + .seq_ops = &bpf_iter_ksym_ops, + .init_seq_private = bpf_iter_ksym_init, + .fini_seq_private = NULL, + .seq_priv_size = sizeof(struct kallsym_iter), +}; + +static struct bpf_iter_reg ksym_iter_reg_info = { + .target = "ksym", + .feature = BPF_ITER_RESCHED, + .ctx_arg_info_size = 1, + .ctx_arg_info = { + { offsetof(struct bpf_iter__ksym, ksym), + PTR_TO_BTF_ID_OR_NULL }, + }, + .seq_info = &ksym_iter_seq_info, +}; + +BTF_ID_LIST(btf_ksym_iter_id) +BTF_ID(struct, kallsym_iter) + +static int __init bpf_ksym_iter_register(void) +{ + ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id; + return bpf_iter_reg_target(&ksym_iter_reg_info); +} + +late_initcall(bpf_ksym_iter_register); + +#endif /* CONFIG_BPF_SYSCALL */ + static inline int kallsyms_for_perf(void) { #ifdef CONFIG_PERF_EVENTS -- cgit From a9d2fae89fa8eb638203d8a4da435c647c12dfa3 Mon Sep 17 00:00:00 2001 From: Alan Maguire Date: Tue, 12 Jul 2022 13:31:45 +0100 Subject: selftests/bpf: add a ksym iter subtest add subtest verifying BPF ksym iter behaviour. The BPF ksym iter program shows an example of dumping a format different to /proc/kallsyms. It adds KIND and MAX_SIZE fields which represent the kind of symbol (core kernel, module, ftrace, bpf, or kprobe) and the maximum size the symbol can be. The latter is calculated from the difference between current symbol value and the next symbol value. The key benefit for this iterator will likely be supporting in-kernel data-gathering rather than dumping symbol details to userspace and parsing the results. Signed-off-by: Alan Maguire Acked-by: Yonghong Song Link: https://lore.kernel.org/r/1657629105-7812-3-git-send-email-alan.maguire@oracle.com Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/prog_tests/bpf_iter.c | 16 +++++ tools/testing/selftests/bpf/progs/bpf_iter.h | 7 +++ tools/testing/selftests/bpf/progs/bpf_iter_ksym.c | 74 +++++++++++++++++++++++ 3 files changed, 97 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_ksym.c diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c index 7ff5fa93d056..a33874b081b6 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c @@ -27,6 +27,7 @@ #include "bpf_iter_test_kern5.skel.h" #include "bpf_iter_test_kern6.skel.h" #include "bpf_iter_bpf_link.skel.h" +#include "bpf_iter_ksym.skel.h" static int duration; @@ -1120,6 +1121,19 @@ static void test_link_iter(void) bpf_iter_bpf_link__destroy(skel); } +static void test_ksym_iter(void) +{ + struct bpf_iter_ksym *skel; + + skel = bpf_iter_ksym__open_and_load(); + if (!ASSERT_OK_PTR(skel, "bpf_iter_ksym__open_and_load")) + return; + + do_dummy_read(skel->progs.dump_ksym); + + bpf_iter_ksym__destroy(skel); +} + #define CMP_BUFFER_SIZE 1024 static char task_vma_output[CMP_BUFFER_SIZE]; static char proc_maps_output[CMP_BUFFER_SIZE]; @@ -1267,4 +1281,6 @@ void test_bpf_iter(void) test_buf_neg_offset(); if (test__start_subtest("link-iter")) test_link_iter(); + if (test__start_subtest("ksym")) + test_ksym_iter(); } diff --git a/tools/testing/selftests/bpf/progs/bpf_iter.h b/tools/testing/selftests/bpf/progs/bpf_iter.h index 97ec8bc76ae6..e9846606690d 100644 --- a/tools/testing/selftests/bpf/progs/bpf_iter.h +++ b/tools/testing/selftests/bpf/progs/bpf_iter.h @@ -22,6 +22,7 @@ #define BTF_F_NONAME BTF_F_NONAME___not_used #define BTF_F_PTR_RAW BTF_F_PTR_RAW___not_used #define BTF_F_ZERO BTF_F_ZERO___not_used +#define bpf_iter__ksym bpf_iter__ksym___not_used #include "vmlinux.h" #undef bpf_iter_meta #undef bpf_iter__bpf_map @@ -44,6 +45,7 @@ #undef BTF_F_NONAME #undef BTF_F_PTR_RAW #undef BTF_F_ZERO +#undef bpf_iter__ksym struct bpf_iter_meta { struct seq_file *seq; @@ -151,3 +153,8 @@ enum { BTF_F_PTR_RAW = (1ULL << 2), BTF_F_ZERO = (1ULL << 3), }; + +struct bpf_iter__ksym { + struct bpf_iter_meta *meta; + struct kallsym_iter *ksym; +}; diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c b/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c new file mode 100644 index 000000000000..285c008cbf9c --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_iter_ksym.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2022, Oracle and/or its affiliates. */ +#include "bpf_iter.h" +#include + +char _license[] SEC("license") = "GPL"; + +unsigned long last_sym_value = 0; + +static inline char tolower(char c) +{ + if (c >= 'A' && c <= 'Z') + c += ('a' - 'A'); + return c; +} + +static inline char toupper(char c) +{ + if (c >= 'a' && c <= 'z') + c -= ('a' - 'A'); + return c; +} + +/* Dump symbols with max size; the latter is calculated by caching symbol N value + * and when iterating on symbol N+1, we can print max size of symbol N via + * address of N+1 - address of N. + */ +SEC("iter/ksym") +int dump_ksym(struct bpf_iter__ksym *ctx) +{ + struct seq_file *seq = ctx->meta->seq; + struct kallsym_iter *iter = ctx->ksym; + __u32 seq_num = ctx->meta->seq_num; + unsigned long value; + char type; + int ret; + + if (!iter) + return 0; + + if (seq_num == 0) { + BPF_SEQ_PRINTF(seq, "ADDR TYPE NAME MODULE_NAME KIND MAX_SIZE\n"); + return 0; + } + if (last_sym_value) + BPF_SEQ_PRINTF(seq, "0x%x\n", iter->value - last_sym_value); + else + BPF_SEQ_PRINTF(seq, "\n"); + + value = iter->show_value ? iter->value : 0; + + last_sym_value = value; + + type = iter->type; + + if (iter->module_name[0]) { + type = iter->exported ? toupper(type) : tolower(type); + BPF_SEQ_PRINTF(seq, "0x%llx %c %s [ %s ] ", + value, type, iter->name, iter->module_name); + } else { + BPF_SEQ_PRINTF(seq, "0x%llx %c %s ", value, type, iter->name); + } + if (!iter->pos_arch_end || iter->pos_arch_end > iter->pos) + BPF_SEQ_PRINTF(seq, "CORE "); + else if (!iter->pos_mod_end || iter->pos_mod_end > iter->pos) + BPF_SEQ_PRINTF(seq, "MOD "); + else if (!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > iter->pos) + BPF_SEQ_PRINTF(seq, "FTRACE_MOD "); + else if (!iter->pos_bpf_end || iter->pos_bpf_end > iter->pos) + BPF_SEQ_PRINTF(seq, "BPF "); + else + BPF_SEQ_PRINTF(seq, "KPROBE "); + return 0; +} -- cgit