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From: Andrii Nakryiko <andriin@fb.com>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
	<daniel@iogearbox.net>
Cc: <andrii.nakryiko@gmail.com>, <kernel-team@fb.com>,
	Andrii Nakryiko <andriin@fb.com>
Subject: [RFC PATCH bpf-next 01/16] libbpf: don't require root for bpf_object__open()
Date: Tue, 3 Dec 2019 23:00:00 -0800	[thread overview]
Message-ID: <20191204070015.3523523-2-andriin@fb.com> (raw)
In-Reply-To: <20191204070015.3523523-1-andriin@fb.com>

Reorganize bpf_object__open and bpf_object__load steps such that
bpf_object__open doesn't need root access. This was previously done for
feature probing and BTF sanitization. This doesn't have to happen on open,
though, so move all those steps into the load phase.

This is important, because it makes it possible for tools like bpftool, to
just open BPF object file and inspect their contents: programs, maps, BTF,
etc. For such operations it is prohibitive to require root access. On the
other hand, there is a lot of custom libbpf logic in those steps, so its best
avoided for tools to reimplement all that on their own.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/libbpf.c | 83 +++++++++++++++++++++---------------------
 1 file changed, 41 insertions(+), 42 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3f09772192f1..1e29a47da4f5 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -101,13 +101,6 @@ void libbpf_print(enum libbpf_print_level level, const char *format, ...)
 
 #define STRERR_BUFSIZE  128
 
-#define CHECK_ERR(action, err, out) do {	\
-	err = action;			\
-	if (err)			\
-		goto out;		\
-} while (0)
-
-
 /* Copied from tools/perf/util/util.h */
 #ifndef zfree
 # define zfree(ptr) ({ free(*ptr); *ptr = NULL; })
@@ -864,8 +857,7 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
 	def->value_size = data->d_size;
 	def->max_entries = 1;
 	def->map_flags = type == LIBBPF_MAP_RODATA ? BPF_F_RDONLY_PROG : 0;
-	if (obj->caps.array_mmap)
-		def->map_flags |= BPF_F_MMAPABLE;
+	def->map_flags |= BPF_F_MMAPABLE;
 
 	pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %x.\n",
 		 map_name, map->sec_idx, map->sec_offset, def->map_flags);
@@ -888,8 +880,6 @@ static int bpf_object__init_global_data_maps(struct bpf_object *obj)
 {
 	int err;
 
-	if (!obj->caps.global_data)
-		return 0;
 	/*
 	 * Populate obj->maps with libbpf internal maps.
 	 */
@@ -1393,10 +1383,11 @@ static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
 	return 0;
 }
 
-static int bpf_object__init_maps(struct bpf_object *obj, bool relaxed_maps,
-				 const char *pin_root_path)
+static int bpf_object__init_maps(struct bpf_object *obj,
+				 struct bpf_object_open_opts *opts)
 {
-	bool strict = !relaxed_maps;
+	const char *pin_root_path = OPTS_GET(opts, pin_root_path, NULL);
+	bool strict = !OPTS_GET(opts, relaxed_maps, false);
 	int err;
 
 	err = bpf_object__init_user_maps(obj, strict);
@@ -1592,8 +1583,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 	return 0;
 }
 
-static int bpf_object__elf_collect(struct bpf_object *obj, bool relaxed_maps,
-				   const char *pin_root_path)
+static int bpf_object__elf_collect(struct bpf_object *obj)
 {
 	Elf *elf = obj->efile.elf;
 	GElf_Ehdr *ep = &obj->efile.ehdr;
@@ -1728,14 +1718,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, bool relaxed_maps,
 		pr_warn("Corrupted ELF file: index of strtab invalid\n");
 		return -LIBBPF_ERRNO__FORMAT;
 	}
-	err = bpf_object__init_btf(obj, btf_data, btf_ext_data);
-	if (!err)
-		err = bpf_object__init_maps(obj, relaxed_maps, pin_root_path);
-	if (!err)
-		err = bpf_object__sanitize_and_load_btf(obj);
-	if (!err)
-		err = bpf_object__init_prog_names(obj);
-	return err;
+	return bpf_object__init_btf(obj, btf_data, btf_ext_data);
 }
 
 static struct bpf_program *
@@ -1875,11 +1858,6 @@ static int bpf_program__record_reloc(struct bpf_program *prog,
 		pr_warn("bad data relo against section %u\n", shdr_idx);
 		return -LIBBPF_ERRNO__RELOC;
 	}
-	if (!obj->caps.global_data) {
-		pr_warn("relocation: kernel does not support global \'%s\' variable access in insns[%d]\n",
-			name, insn_idx);
-		return -LIBBPF_ERRNO__RELOC;
-	}
 	for (map_idx = 0; map_idx < nr_maps; map_idx++) {
 		map = &obj->maps[map_idx];
 		if (map->libbpf_type != type)
@@ -3917,12 +3895,10 @@ static struct bpf_object *
 __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
 		   struct bpf_object_open_opts *opts)
 {
-	const char *pin_root_path;
 	struct bpf_program *prog;
 	struct bpf_object *obj;
 	const char *obj_name;
 	char tmp_name[64];
-	bool relaxed_maps;
 	__u32 attach_prog_fd;
 	int err;
 
@@ -3952,16 +3928,16 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
 		return obj;
 
 	obj->relaxed_core_relocs = OPTS_GET(opts, relaxed_core_relocs, false);
-	relaxed_maps = OPTS_GET(opts, relaxed_maps, false);
-	pin_root_path = OPTS_GET(opts, pin_root_path, NULL);
 	attach_prog_fd = OPTS_GET(opts, attach_prog_fd, 0);
 
-	CHECK_ERR(bpf_object__elf_init(obj), err, out);
-	CHECK_ERR(bpf_object__check_endianness(obj), err, out);
-	CHECK_ERR(bpf_object__probe_caps(obj), err, out);
-	CHECK_ERR(bpf_object__elf_collect(obj, relaxed_maps, pin_root_path),
-		  err, out);
-	CHECK_ERR(bpf_object__collect_reloc(obj), err, out);
+	err = bpf_object__elf_init(obj);
+	err = err ? : bpf_object__check_endianness(obj);
+	err = err ? : bpf_object__elf_collect(obj);
+	err = err ? : bpf_object__init_maps(obj, opts);
+	err = err ? : bpf_object__init_prog_names(obj);
+	err = err ? : bpf_object__collect_reloc(obj);
+	if (err)
+		goto out;
 	bpf_object__elf_finish(obj);
 
 	bpf_object__for_each_program(prog, obj) {
@@ -4079,6 +4055,24 @@ int bpf_object__unload(struct bpf_object *obj)
 	return 0;
 }
 
+static int bpf_object__sanitize_maps(struct bpf_object *obj)
+{
+	struct bpf_map *m;
+
+	bpf_object__for_each_map(m, obj) {
+		if (!bpf_map__is_internal(m))
+			continue;
+		if (!obj->caps.global_data) {
+			pr_warn("kernel doesn't support global data\n");
+			return -ENOTSUP;
+		}
+		if (!obj->caps.array_mmap)
+			m->def.map_flags ^= BPF_F_MMAPABLE;
+	}
+
+	return 0;
+}
+
 int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
 {
 	struct bpf_object *obj;
@@ -4097,9 +4091,14 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
 
 	obj->loaded = true;
 
-	CHECK_ERR(bpf_object__create_maps(obj), err, out);
-	CHECK_ERR(bpf_object__relocate(obj, attr->target_btf_path), err, out);
-	CHECK_ERR(bpf_object__load_progs(obj, attr->log_level), err, out);
+	err = bpf_object__probe_caps(obj);
+	err = err ? : bpf_object__sanitize_and_load_btf(obj);
+	err = err ? : bpf_object__sanitize_maps(obj);
+	err = err ? : bpf_object__create_maps(obj);
+	err = err ? : bpf_object__relocate(obj, attr->target_btf_path);
+	err = err ? : bpf_object__load_progs(obj, attr->log_level);
+	if (err)
+		goto out;
 
 	return 0;
 out:
-- 
2.17.1


  reply	other threads:[~2019-12-04  7:00 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-04  6:59 [RFC PATCH bpf-next 00/16] Add code-generated BPF object skeleton support Andrii Nakryiko
2019-12-04  7:00 ` Andrii Nakryiko [this message]
2019-12-04  7:00 ` [RFC PATCH bpf-next 02/16] libbpf: add generic bpf_program__attach() Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 03/16] libbpf: move non-public APIs from libbpf.h to libbpf_internal.h Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 04/16] libbpf: add BPF_EMBED_OBJ macro for embedding BPF .o files Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 05/16] libbpf: expose field/var declaration emitting API internally Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 06/16] libbpf: expose BPF program's function name Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 07/16] libbpf: refactor global data map initialization Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 08/16] libbpf: postpone BTF ID finding for TRACING programs to load phase Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 09/16] libbpf: reduce log level of supported section names dump Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 10/16] libbpf: add experimental BPF object skeleton support Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 11/16] bpftool: add skeleton codegen command Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 12/16] libbpf/samples: add runqslower sample to libbpf samples Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 13/16] selftests/bpf: add BPF skeletons selftests and convert attach_probe.c Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 14/16] selftests/bpf: convert few more selftest to skeletons Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 15/16] selftests/bpf: add test validating data section to struct convertion layout Andrii Nakryiko
2019-12-04  7:00 ` [RFC PATCH bpf-next 16/16] bpftool: add `gen skeleton` BASH completions Andrii Nakryiko

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