From e8386c4e1fa3b5486487fa4d6c350a0d5e300aaf Mon Sep 17 00:00:00 2001

From: Andrea Claudi <aclaudi@redhat.com>

Date: Thu, 13 Jun 2019 14:37:56 +0200

Subject: [PATCH] bpf: implement btf handling and map annotation

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1716361

Upstream Status: iproute2.git commit f823f36012fb5

commit f823f36012fb5ab4ddfca6ed4ff56188730f281e

Author: Daniel Borkmann <daniel@iogearbox.net>

Date:   Wed Jul 18 01:31:22 2018 +0200

    bpf: implement btf handling and map annotation

    Implement loading of .BTF section from object file and build up

    internal table for retrieving key/value id related to maps in

    the BPF program. Latter is done by setting up struct btf_type

    table.

    One of the issues is that there's a disconnect between the data

    types used in the map and struct bpf_elf_map, meaning the underlying

    types are unknown from the map description. One way to overcome

    this is to add a annotation such that the loader will recognize

    the relation to both. BPF_ANNOTATE_KV_PAIR(map_foo, struct key,

    struct val); has been added to the API that programs can use.

    The loader will then pick the corresponding key/value type ids and

    attach it to the maps for creation. This can later on be dumped via

    bpftool for introspection.

    Example with test_xdp_noinline.o from kernel selftests:

      [...]

      struct ctl_value {

            union {

                    __u64 value;

                    __u32 ifindex;

                    __u8 mac[6];

            };

      };

      struct bpf_map_def __attribute__ ((section("maps"), used)) ctl_array = {

            .type           = BPF_MAP_TYPE_ARRAY,

            .key_size       = sizeof(__u32),

            .value_size     = sizeof(struct ctl_value),

            .max_entries    = 16,

            .map_flags      = 0,

      };

      BPF_ANNOTATE_KV_PAIR(ctl_array, __u32, struct ctl_value);

      [...]

    Above could also further be wrapped in a macro. Compiling through LLVM and

    converting to BTF:

      # llc --version

      LLVM (http://llvm.org/):

        LLVM version 7.0.0svn

        Optimized build.

        Default target: x86_64-unknown-linux-gnu

        Host CPU: skylake

        Registered Targets:

          bpf    - BPF (host endian)

          bpfeb  - BPF (big endian)

          bpfel  - BPF (little endian)

      [...]

      # clang [...] -O2 -target bpf -g -emit-llvm -c test_xdp_noinline.c -o - |

        llc -march=bpf -mcpu=probe -mattr=dwarfris -filetype=obj -o test_xdp_noinline.o

      # pahole -J test_xdp_noinline.o

    Checking pahole dump of BPF object file:

      # file test_xdp_noinline.o

      test_xdp_noinline.o: ELF 64-bit LSB relocatable, *unknown arch 0xf7* version 1 (SYSV), with debug_info, not stripped

      # pahole test_xdp_noinline.o

      [...]

      struct ctl_value {

            union {

                    __u64              value;                /*     0     8 */

                    __u32              ifindex;              /*     0     4 */

                    __u8               mac[0];               /*     0     0 */

            };                                               /*     0     8 */

            /* size: 8, cachelines: 1, members: 1 */

            /* last cacheline: 8 bytes */

      };

    Now loading into kernel and dumping the map via bpftool:

      # ip -force link set dev lo xdp obj test_xdp_noinline.o sec xdp-test

      # ip a

      1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 xdpgeneric/id:227 qdisc noqueue state UNKNOWN group default qlen 1000

          link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

          inet 127.0.0.1/8 scope host lo

             valid_lft forever preferred_lft forever

          inet6 ::1/128 scope host

             valid_lft forever preferred_lft forever

      [...]

      # bpftool prog show id 227

      227: xdp  tag a85e060c275c5616  gpl

          loaded_at 2018-07-17T14:41:29+0000  uid 0

          xlated 8152B  not jited  memlock 12288B  map_ids 381,385,386,382,384,383

      # bpftool map dump id 386

       [{

            "key": 0,

            "value": {

                "": {

                    "value": 0,

                    "ifindex": 0,

                    "mac": []

                }

            }

        },{

            "key": 1,

            "value": {

                "": {

                    "value": 0,

                    "ifindex": 0,

                    "mac": []

                }

            }

        },{

      [...]

    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

    Signed-off-by: David Ahern <dsahern@gmail.com>

---

 include/bpf_elf.h  |   9 ++

 include/bpf_util.h |   1 +

 lib/bpf.c          | 332 ++++++++++++++++++++++++++++++++++++++++++++-

 3 files changed, 338 insertions(+), 4 deletions(-)

diff --git a/include/bpf_elf.h b/include/bpf_elf.h

index a8e360f3bbb28..84e8ae00834c8 100644

--- a/include/bpf_elf.h

+++ b/include/bpf_elf.h

@@ -41,4 +41,13 @@ struct bpf_elf_map {

 	__u32 inner_idx;

 };

+#define BPF_ANNOTATE_KV_PAIR(name, type_key, type_val)		\

+	struct ____btf_map_##name {				\

+		type_key key;					\

+		type_val value;					\

+	};							\

+	struct ____btf_map_##name				\

+	    __attribute__ ((section(".maps." #name), used))	\

+	    ____btf_map_##name = { }

+

 #endif /* __BPF_ELF__ */

diff --git a/include/bpf_util.h b/include/bpf_util.h

index 219beb40cd253..63837a04e56fe 100644

--- a/include/bpf_util.h

+++ b/include/bpf_util.h

@@ -14,6 +14,7 @@

 #define __BPF_UTIL__

 #include <linux/bpf.h>

+#include <linux/btf.h>

 #include <linux/filter.h>

 #include <linux/magic.h>

 #include <linux/elf-em.h>

diff --git a/lib/bpf.c b/lib/bpf.c

index 1b87490555050..d093d0bd86eae 100644

--- a/lib/bpf.c

+++ b/lib/bpf.c

@@ -393,6 +393,8 @@ struct bpf_prog_data {

 struct bpf_map_ext {

 	struct bpf_prog_data owner;

+	unsigned int btf_id_key;

+	unsigned int btf_id_val;

 };

 static int bpf_derive_elf_map_from_fdinfo(int fd, struct bpf_elf_map *map,

@@ -1125,24 +1127,36 @@ struct bpf_config {

 	unsigned int		jit_enabled;

 };

+struct bpf_btf {

+	const struct btf_header	*hdr;

+	const void		*raw;

+	const char		*strings;

+	const struct btf_type	**types;

+	int			types_num;

+};

+

 struct bpf_elf_ctx {

 	struct bpf_config	cfg;

 	Elf			*elf_fd;

 	GElf_Ehdr		elf_hdr;

 	Elf_Data		*sym_tab;

 	Elf_Data		*str_tab;

+	Elf_Data		*btf_data;

 	char			obj_uid[64];

 	int			obj_fd;

+	int			btf_fd;

 	int			map_fds[ELF_MAX_MAPS];

 	struct bpf_elf_map	maps[ELF_MAX_MAPS];

 	struct bpf_map_ext	maps_ext[ELF_MAX_MAPS];

 	struct bpf_elf_prog	prog_text;

+	struct bpf_btf		btf;

 	int			sym_num;

 	int			map_num;

 	int			map_len;

 	bool			*sec_done;

 	int			sec_maps;

 	int			sec_text;

+	int			sec_btf;

 	char			license[ELF_MAX_LICENSE_LEN];

 	enum bpf_prog_type	type;

 	__u32			ifindex;

@@ -1167,6 +1181,11 @@ struct bpf_map_data {

 	struct bpf_elf_map	*ent;

 };

+static bool bpf_log_has_data(struct bpf_elf_ctx *ctx)

+{

+	return ctx->log && ctx->log[0];

+}

+

 static __check_format_string(2, 3) void

 bpf_dump_error(struct bpf_elf_ctx *ctx, const char *format, ...)

 {

@@ -1176,7 +1195,7 @@ bpf_dump_error(struct bpf_elf_ctx *ctx, const char *format, ...)

 	vfprintf(stderr, format, vl);

 	va_end(vl);

-	if (ctx->log && ctx->log[0]) {

+	if (bpf_log_has_data(ctx)) {

 		if (ctx->verbose) {

 			fprintf(stderr, "%s\n", ctx->log);

 		} else {

@@ -1223,7 +1242,9 @@ static int bpf_log_realloc(struct bpf_elf_ctx *ctx)

 static int bpf_map_create(enum bpf_map_type type, uint32_t size_key,

 			  uint32_t size_value, uint32_t max_elem,

-			  uint32_t flags, int inner_fd, uint32_t ifindex)

+			  uint32_t flags, int inner_fd, int btf_fd,

+			  uint32_t ifindex, uint32_t btf_id_key,

+			  uint32_t btf_id_val)

 {

 	union bpf_attr attr = {};

@@ -1234,10 +1255,30 @@ static int bpf_map_create(enum bpf_map_type type, uint32_t size_key,

 	attr.map_flags = flags;

 	attr.inner_map_fd = inner_fd;

 	attr.map_ifindex = ifindex;

+	attr.btf_fd = btf_fd;

+	attr.btf_key_type_id = btf_id_key;

+	attr.btf_value_type_id = btf_id_val;

 	return bpf(BPF_MAP_CREATE, &attr, sizeof(attr));

 }

+static int bpf_btf_load(void *btf, size_t size_btf,

+			char *log, size_t size_log)

+{

+	union bpf_attr attr = {};

+

+	attr.btf = bpf_ptr_to_u64(btf);

+	attr.btf_size = size_btf;

+

+	if (size_log > 0) {

+		attr.btf_log_buf = bpf_ptr_to_u64(log);

+		attr.btf_log_size = size_log;

+		attr.btf_log_level = 1;

+	}

+

+	return bpf(BPF_BTF_LOAD, &attr, sizeof(attr));

+}

+

 static int bpf_obj_pin(int fd, const char *pathname)

 {

 	union bpf_attr attr = {};

@@ -1613,7 +1654,8 @@ static int bpf_map_attach(const char *name, struct bpf_elf_ctx *ctx,

 	ifindex = bpf_map_offload_neutral(map->type) ? 0 : ctx->ifindex;

 	errno = 0;

 	fd = bpf_map_create(map->type, map->size_key, map->size_value,

-			    map->max_elem, map->flags, map_inner_fd, ifindex);

+			    map->max_elem, map->flags, map_inner_fd, ctx->btf_fd,

+			    ifindex, ext->btf_id_key, ext->btf_id_val);

 	if (fd < 0 || ctx->verbose) {

 		bpf_map_report(fd, name, map, ctx, map_inner_fd);

@@ -1638,8 +1680,80 @@ static const char *bpf_str_tab_name(const struct bpf_elf_ctx *ctx,

 	return ctx->str_tab->d_buf + sym->st_name;

 }

+static int bpf_btf_find(struct bpf_elf_ctx *ctx, const char *name)

+{

+	const struct btf_type *type;

+	const char *res;

+	int id;

+

+	for (id = 1; id < ctx->btf.types_num; id++) {

+		type = ctx->btf.types[id];

+		if (type->name_off >= ctx->btf.hdr->str_len)

+			continue;

+		res = &ctx->btf.strings[type->name_off];

+		if (!strcmp(res, name))

+			return id;

+	}

+

+	return -ENOENT;

+}

+

+static int bpf_btf_find_kv(struct bpf_elf_ctx *ctx, const struct bpf_elf_map *map,

+			   const char *name, uint32_t *id_key, uint32_t *id_val)

+{

+	const struct btf_member *key, *val;

+	const struct btf_type *type;

+	char btf_name[512];

+	const char *res;

+	int id;

+

+	snprintf(btf_name, sizeof(btf_name), "____btf_map_%s", name);

+	id = bpf_btf_find(ctx, btf_name);

+	if (id < 0)

+		return id;

+

+	type = ctx->btf.types[id];

+	if (BTF_INFO_KIND(type->info) != BTF_KIND_STRUCT)

+		return -EINVAL;

+	if (BTF_INFO_VLEN(type->info) != 2)

+		return -EINVAL;

+

+	key = ((void *) type) + sizeof(*type);

+	val = key + 1;

+	if (!key->type || key->type >= ctx->btf.types_num ||

+	    !val->type || val->type >= ctx->btf.types_num)

+		return -EINVAL;

+

+	if (key->name_off >= ctx->btf.hdr->str_len ||

+	    val->name_off >= ctx->btf.hdr->str_len)

+		return -EINVAL;

+

+	res = &ctx->btf.strings[key->name_off];

+	if (strcmp(res, "key"))

+		return -EINVAL;

+

+	res = &ctx->btf.strings[val->name_off];

+	if (strcmp(res, "value"))

+		return -EINVAL;

+

+	*id_key = key->type;

+	*id_val = val->type;

+	return 0;

+}

+

+static void bpf_btf_annotate(struct bpf_elf_ctx *ctx, int which, const char *name)

+{

+	uint32_t id_key = 0, id_val = 0;

+

+	if (!bpf_btf_find_kv(ctx, &ctx->maps[which], name, &id_key, &id_val)) {

+		ctx->maps_ext[which].btf_id_key = id_key;

+		ctx->maps_ext[which].btf_id_val = id_val;

+	}

+}

+

 static const char *bpf_map_fetch_name(struct bpf_elf_ctx *ctx, int which)

 {

+	const char *name;

 	GElf_Sym sym;

 	int i;

@@ -1653,7 +1767,9 @@ static const char *bpf_map_fetch_name(struct bpf_elf_ctx *ctx, int which)

 		    sym.st_value / ctx->map_len != which)

 			continue;

-		return bpf_str_tab_name(ctx, &sym);

+		name = bpf_str_tab_name(ctx, &sym);

+		bpf_btf_annotate(ctx, which, name);

+		return name;

 	}

 	return NULL;

@@ -1915,11 +2031,210 @@ static int bpf_fetch_text(struct bpf_elf_ctx *ctx, int section,

 	return 0;

 }

+static void bpf_btf_report(int fd, struct bpf_elf_ctx *ctx)

+{

+	fprintf(stderr, "\nBTF debug data section \'.BTF\' %s%s (%d)!\n",

+		fd < 0 ? "rejected: " : "loaded",

+		fd < 0 ? strerror(errno) : "",

+		fd < 0 ? errno : fd);

+

+	fprintf(stderr, " - Length:       %zu\n", ctx->btf_data->d_size);

+

+	bpf_dump_error(ctx, "Verifier analysis:\n\n");

+}

+

+static int bpf_btf_attach(struct bpf_elf_ctx *ctx)

+{

+	int tries = 0, fd;

+retry:

+	errno = 0;

+	fd = bpf_btf_load(ctx->btf_data->d_buf, ctx->btf_data->d_size,

+			  ctx->log, ctx->log_size);

+	if (fd < 0 || ctx->verbose) {

+		if (fd < 0 && (errno == ENOSPC || !ctx->log_size)) {

+			if (tries++ < 10 && !bpf_log_realloc(ctx))

+				goto retry;

+

+			fprintf(stderr, "Log buffer too small to dump verifier log %zu bytes (%d tries)!\n",

+				ctx->log_size, tries);

+			return fd;

+		}

+

+		if (bpf_log_has_data(ctx))

+			bpf_btf_report(fd, ctx);

+	}

+

+	return fd;

+}

+

+static int bpf_fetch_btf_begin(struct bpf_elf_ctx *ctx, int section,

+			       struct bpf_elf_sec_data *data)

+{

+	ctx->btf_data = data->sec_data;

+	ctx->sec_btf = section;

+	ctx->sec_done[section] = true;

+	return 0;

+}

+

+static int bpf_btf_check_header(struct bpf_elf_ctx *ctx)

+{

+	const struct btf_header *hdr = ctx->btf_data->d_buf;

+	const char *str_start, *str_end;

+	unsigned int data_len;

+

+	if (hdr->magic != BTF_MAGIC) {

+		fprintf(stderr, "Object has wrong BTF magic: %x, expected: %x!\n",

+			hdr->magic, BTF_MAGIC);

+		return -EINVAL;

+	}

+

+	if (hdr->version != BTF_VERSION) {

+		fprintf(stderr, "Object has wrong BTF version: %u, expected: %u!\n",

+			hdr->version, BTF_VERSION);

+		return -EINVAL;

+	}

+

+	if (hdr->flags) {

+		fprintf(stderr, "Object has unsupported BTF flags %x!\n",

+			hdr->flags);

+		return -EINVAL;

+	}

+

+	data_len = ctx->btf_data->d_size - sizeof(*hdr);

+	if (data_len < hdr->type_off ||

+	    data_len < hdr->str_off ||

+	    data_len < hdr->type_len + hdr->str_len ||

+	    hdr->type_off >= hdr->str_off ||

+	    hdr->type_off + hdr->type_len != hdr->str_off ||

+	    hdr->str_off + hdr->str_len != data_len ||

+	    (hdr->type_off & (sizeof(uint32_t) - 1))) {

+		fprintf(stderr, "Object has malformed BTF data!\n");

+		return -EINVAL;

+	}

+

+	ctx->btf.hdr = hdr;

+	ctx->btf.raw = hdr + 1;

+

+	str_start = ctx->btf.raw + hdr->str_off;

+	str_end = str_start + hdr->str_len;

+	if (!hdr->str_len ||

+	    hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||

+	    str_start[0] || str_end[-1]) {

+		fprintf(stderr, "Object has malformed BTF string data!\n");

+		return -EINVAL;

+	}

+

+	ctx->btf.strings = str_start;

+	return 0;

+}

+

+static int bpf_btf_register_type(struct bpf_elf_ctx *ctx,

+				 const struct btf_type *type)

+{

+	int cur = ctx->btf.types_num, num = cur + 1;

+	const struct btf_type **types;

+

+	types = realloc(ctx->btf.types, num * sizeof(type));

+	if (!types) {

+		free(ctx->btf.types);

+		ctx->btf.types = NULL;

+		ctx->btf.types_num = 0;

+		return -ENOMEM;

+	}

+

+	ctx->btf.types = types;

+	ctx->btf.types[cur] = type;

+	ctx->btf.types_num = num;

+	return 0;

+}

+

+static struct btf_type btf_type_void;

+

+static int bpf_btf_prep_type_data(struct bpf_elf_ctx *ctx)

+{

+	const void *type_cur = ctx->btf.raw + ctx->btf.hdr->type_off;

+	const void *type_end = ctx->btf.raw + ctx->btf.hdr->str_off;

+	const struct btf_type *type;

+	uint16_t var_len;

+	int ret, kind;

+

+	ret = bpf_btf_register_type(ctx, &btf_type_void);

+	if (ret < 0)

+		return ret;

+

+	while (type_cur < type_end) {

+		type = type_cur;

+		type_cur += sizeof(*type);

+

+		var_len = BTF_INFO_VLEN(type->info);

+		kind = BTF_INFO_KIND(type->info);

+

+		switch (kind) {

+		case BTF_KIND_INT:

+			type_cur += sizeof(int);

+			break;

+		case BTF_KIND_ARRAY:

+			type_cur += sizeof(struct btf_array);

+			break;

+		case BTF_KIND_STRUCT:

+		case BTF_KIND_UNION:

+			type_cur += var_len * sizeof(struct btf_member);

+			break;

+		case BTF_KIND_ENUM:

+			type_cur += var_len * sizeof(struct btf_enum);

+			break;

+		case BTF_KIND_TYPEDEF:

+		case BTF_KIND_PTR:

+		case BTF_KIND_FWD:

+		case BTF_KIND_VOLATILE:

+		case BTF_KIND_CONST:

+		case BTF_KIND_RESTRICT:

+			break;

+		default:

+			fprintf(stderr, "Object has unknown BTF type: %u!\n", kind);

+			return -EINVAL;

+		}

+

+		ret = bpf_btf_register_type(ctx, type);

+		if (ret < 0)

+			return ret;

+	}

+

+	return 0;

+}

+

+static int bpf_btf_prep_data(struct bpf_elf_ctx *ctx)

+{

+	int ret = bpf_btf_check_header(ctx);

+

+	if (!ret)

+		return bpf_btf_prep_type_data(ctx);

+	return ret;

+}

+

+static void bpf_fetch_btf_end(struct bpf_elf_ctx *ctx)

+{

+	int fd = bpf_btf_attach(ctx);

+

+	if (fd < 0)

+		return;

+	ctx->btf_fd = fd;

+	if (bpf_btf_prep_data(ctx) < 0) {

+		close(ctx->btf_fd);

+		ctx->btf_fd = 0;

+	}

+}

+

 static bool bpf_has_map_data(const struct bpf_elf_ctx *ctx)

 {

 	return ctx->sym_tab && ctx->str_tab && ctx->sec_maps;

 }

+static bool bpf_has_btf_data(const struct bpf_elf_ctx *ctx)

+{

+	return ctx->sec_btf;

+}

+

 static bool bpf_has_call_data(const struct bpf_elf_ctx *ctx)

 {

 	return ctx->sec_text;

@@ -1952,6 +2267,9 @@ static int bpf_fetch_ancillary(struct bpf_elf_ctx *ctx, bool check_text_sec)

 		else if (data.sec_hdr.sh_type == SHT_STRTAB &&

 			 !strcmp(data.sec_name, ".strtab"))

 			ret = bpf_fetch_strtab(ctx, i, &data);

+		else if (data.sec_hdr.sh_type == SHT_PROGBITS &&

+			 !strcmp(data.sec_name, ".BTF"))

+			ret = bpf_fetch_btf_begin(ctx, i, &data);

 		if (ret < 0) {

 			fprintf(stderr, "Error parsing section %d! Perhaps check with readelf -a?\n",

 				i);

@@ -1959,6 +2277,8 @@ static int bpf_fetch_ancillary(struct bpf_elf_ctx *ctx, bool check_text_sec)

 		}

 	}

+	if (bpf_has_btf_data(ctx))

+		bpf_fetch_btf_end(ctx);

 	if (bpf_has_map_data(ctx)) {

 		ret = bpf_fetch_maps_end(ctx);

 		if (ret < 0) {

@@ -2596,6 +2916,10 @@ static void bpf_maps_teardown(struct bpf_elf_ctx *ctx)

 		if (ctx->map_fds[i])

 			close(ctx->map_fds[i]);

 	}

+

+	if (ctx->btf_fd)

+		close(ctx->btf_fd);

+	free(ctx->btf.types);

 }

 static void bpf_elf_ctx_destroy(struct bpf_elf_ctx *ctx, bool failure)

-- 

2.20.1