Skip to content

Commit

Permalink
Merge branch 'bpftool: Switch to libbpf's hashmap for referencing BPF…
Browse files Browse the repository at this point in the history 
… objects'

Quentin Monnet says:

====================

When listing BPF objects, bpftool can print a number of properties about
items holding references to these objects. For example, it can show pinned
paths for BPF programs, maps, and links; or programs and maps using a given
BTF object; or the names and PIDs of processes referencing BPF objects. To
collect this information, bpftool uses hash maps (to be clear: the data
structures, inside bpftool - we are not talking of BPF maps). It uses the
implementation available from the kernel, and picks it up from
tools/include/linux/hashtable.h.

This patchset converts bpftool's hash maps to a distinct implementation
instead, the one coming with libbpf. The main motivation for this change is
that it should ease the path towards a potential out-of-tree mirror for
bpftool, like the one libbpf already has. Although it's not perfect to
depend on libbpf's internal components, bpftool is intimately tied with the
library anyway, and this looks better than depending too much on (non-UAPI)
kernel headers.

The first two patches contain preparatory work on the Makefile and on the
initialisation of the hash maps for collecting pinned paths for objects.
Then the transition is split into several steps, one for each kind of
properties for which the collection is backed by hash maps.

v2:
  - Move hashmap cleanup for pinned paths for links from do_detach() to
    do_show().
  - Handle errors on hashmap__append() (in three of the patches).
  - Rename bpftool_hash_fn() and bpftool_equal_fn() as hash_fn_for_key_id()
    and equal_fn_for_key_id(), respectively.
  - Add curly braces for hashmap__for_each_key_entry() { } in
    show_btf_plain() and show_btf_json(), where the flow was difficult to
    read.
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
  • Loading branch information
@anakryiko
anakryiko committed Oct 26, 2021
2 parents 57c8d36 + d6699f8 commit 9327acd
Show file tree
Hide file tree
Showing 9 changed files with 262 additions and 228 deletions.
12 changes: 6 additions & 6 deletions tools/bpf/bpftool/Makefile
View file
Original file line number Diff line number Diff line change
Expand Up @@ -31,22 +31,22 @@ LIBBPF = $(LIBBPF_OUTPUT)libbpf.a
LIBBPF_BOOTSTRAP_OUTPUT = $(BOOTSTRAP_OUTPUT)libbpf/
LIBBPF_BOOTSTRAP = $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a

# We need to copy nlattr.h which is not otherwise exported by libbpf, but still
# required by bpftool.
LIBBPF_INTERNAL_HDRS := $(addprefix $(LIBBPF_HDRS_DIR)/,nlattr.h)
# We need to copy hashmap.h and nlattr.h which is not otherwise exported by
# libbpf, but still required by bpftool.
LIBBPF_INTERNAL_HDRS := $(addprefix $(LIBBPF_HDRS_DIR)/,hashmap.h nlattr.h)

ifeq ($(BPFTOOL_VERSION),)
BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
endif

$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT):
$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR):
$(QUIET_MKDIR)mkdir -p $@

$(LIBBPF): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_OUTPUT)
$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_OUTPUT) \
DESTDIR=$(LIBBPF_DESTDIR) prefix= $(LIBBPF) install_headers

$(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h $(LIBBPF)
$(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_DIR)
$(call QUIET_INSTALL, $@)
$(Q)install -m 644 -t $(LIBBPF_HDRS_DIR) $<

Expand Down Expand Up @@ -209,7 +209,7 @@ $(BPFTOOL_BOOTSTRAP): $(BOOTSTRAP_OBJS) $(LIBBPF_BOOTSTRAP)
$(OUTPUT)bpftool: $(OBJS) $(LIBBPF)
$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)

$(BOOTSTRAP_OUTPUT)%.o: %.c | $(BOOTSTRAP_OUTPUT)
$(BOOTSTRAP_OUTPUT)%.o: %.c $(LIBBPF_INTERNAL_HDRS) | $(BOOTSTRAP_OUTPUT)
$(QUIET_CC)$(HOSTCC) $(CFLAGS) -c -MMD -o $@ $<

$(OUTPUT)%.o: %.c
Expand Down
132 changes: 60 additions & 72 deletions tools/bpf/bpftool/btf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,14 +8,15 @@
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <bpf/bpf.h>
#include <bpf/btf.h>
#include <bpf/libbpf.h>
#include <linux/btf.h>
#include <linux/hashtable.h>
#include <sys/types.h>
#include <sys/stat.h>

#include <bpf/bpf.h>
#include <bpf/btf.h>
#include <bpf/hashmap.h>
#include <bpf/libbpf.h>

#include "json_writer.h"
#include "main.h"

Expand All @@ -40,14 +41,9 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
[BTF_KIND_DECL_TAG] = "DECL_TAG",
};

struct btf_attach_table {
DECLARE_HASHTABLE(table, 16);
};

struct btf_attach_point {
__u32 obj_id;
__u32 btf_id;
struct hlist_node hash;
};

static const char *btf_int_enc_str(__u8 encoding)
Expand Down Expand Up @@ -645,29 +641,15 @@ static int btf_parse_fd(int *argc, char ***argv)
return fd;
}

static void delete_btf_table(struct btf_attach_table *tab)
{
struct btf_attach_point *obj;
struct hlist_node *tmp;

unsigned int bkt;

hash_for_each_safe(tab->table, bkt, tmp, obj, hash) {
hash_del(&obj->hash);
free(obj);
}
}

static int
build_btf_type_table(struct btf_attach_table *tab, enum bpf_obj_type type,
build_btf_type_table(struct hashmap *tab, enum bpf_obj_type type,
void *info, __u32 *len)
{
static const char * const names[] = {
[BPF_OBJ_UNKNOWN] = "unknown",
[BPF_OBJ_PROG] = "prog",
[BPF_OBJ_MAP] = "map",
};
struct btf_attach_point *obj_node;
__u32 btf_id, id = 0;
int err;
int fd;
Expand Down Expand Up @@ -741,28 +723,25 @@ build_btf_type_table(struct btf_attach_table *tab, enum bpf_obj_type type,
if (!btf_id)
continue;

obj_node = calloc(1, sizeof(*obj_node));
if (!obj_node) {
p_err("failed to allocate memory: %s", strerror(errno));
err = -ENOMEM;
err = hashmap__append(tab, u32_as_hash_field(btf_id),
u32_as_hash_field(id));
if (err) {
p_err("failed to append entry to hashmap for BTF ID %u, object ID %u: %s",
btf_id, id, strerror(errno));
goto err_free;
}

obj_node->obj_id = id;
obj_node->btf_id = btf_id;
hash_add(tab->table, &obj_node->hash, obj_node->btf_id);
}

return 0;

err_free:
delete_btf_table(tab);
hashmap__free(tab);
return err;
}

static int
build_btf_tables(struct btf_attach_table *btf_prog_table,
struct btf_attach_table *btf_map_table)
build_btf_tables(struct hashmap *btf_prog_table,
struct hashmap *btf_map_table)
{
struct bpf_prog_info prog_info;
__u32 prog_len = sizeof(prog_info);
Expand All @@ -778,7 +757,7 @@ build_btf_tables(struct btf_attach_table *btf_prog_table,
err = build_btf_type_table(btf_map_table, BPF_OBJ_MAP, &map_info,
&map_len);
if (err) {
delete_btf_table(btf_prog_table);
hashmap__free(btf_prog_table);
return err;
}

Expand All @@ -787,10 +766,10 @@ build_btf_tables(struct btf_attach_table *btf_prog_table,

static void
show_btf_plain(struct bpf_btf_info *info, int fd,
struct btf_attach_table *btf_prog_table,
struct btf_attach_table *btf_map_table)
struct hashmap *btf_prog_table,
struct hashmap *btf_map_table)
{
struct btf_attach_point *obj;
struct hashmap_entry *entry;
const char *name = u64_to_ptr(info->name);
int n;

Expand All @@ -804,29 +783,30 @@ show_btf_plain(struct bpf_btf_info *info, int fd,
printf("size %uB", info->btf_size);

n = 0;
hash_for_each_possible(btf_prog_table->table, obj, hash, info->id) {
if (obj->btf_id == info->id)
printf("%s%u", n++ == 0 ? " prog_ids " : ",",
obj->obj_id);
hashmap__for_each_key_entry(btf_prog_table, entry,
u32_as_hash_field(info->id)) {
printf("%s%u", n++ == 0 ? " prog_ids " : ",",
hash_field_as_u32(entry->value));
}

n = 0;
hash_for_each_possible(btf_map_table->table, obj, hash, info->id) {
if (obj->btf_id == info->id)
printf("%s%u", n++ == 0 ? " map_ids " : ",",
obj->obj_id);
hashmap__for_each_key_entry(btf_map_table, entry,
u32_as_hash_field(info->id)) {
printf("%s%u", n++ == 0 ? " map_ids " : ",",
hash_field_as_u32(entry->value));
}
emit_obj_refs_plain(&refs_table, info->id, "\n\tpids ");

emit_obj_refs_plain(refs_table, info->id, "\n\tpids ");

printf("\n");
}

static void
show_btf_json(struct bpf_btf_info *info, int fd,
struct btf_attach_table *btf_prog_table,
struct btf_attach_table *btf_map_table)
struct hashmap *btf_prog_table,
struct hashmap *btf_map_table)
{
struct btf_attach_point *obj;
struct hashmap_entry *entry;
const char *name = u64_to_ptr(info->name);

jsonw_start_object(json_wtr); /* btf object */
Expand All @@ -835,23 +815,21 @@ show_btf_json(struct bpf_btf_info *info, int fd,

jsonw_name(json_wtr, "prog_ids");
jsonw_start_array(json_wtr); /* prog_ids */
hash_for_each_possible(btf_prog_table->table, obj, hash,
info->id) {
if (obj->btf_id == info->id)
jsonw_uint(json_wtr, obj->obj_id);
hashmap__for_each_key_entry(btf_prog_table, entry,
u32_as_hash_field(info->id)) {
jsonw_uint(json_wtr, hash_field_as_u32(entry->value));
}
jsonw_end_array(json_wtr); /* prog_ids */

jsonw_name(json_wtr, "map_ids");
jsonw_start_array(json_wtr); /* map_ids */
hash_for_each_possible(btf_map_table->table, obj, hash,
info->id) {
if (obj->btf_id == info->id)
jsonw_uint(json_wtr, obj->obj_id);
hashmap__for_each_key_entry(btf_map_table, entry,
u32_as_hash_field(info->id)) {
jsonw_uint(json_wtr, hash_field_as_u32(entry->value));
}
jsonw_end_array(json_wtr); /* map_ids */

emit_obj_refs_json(&refs_table, info->id, json_wtr); /* pids */
emit_obj_refs_json(refs_table, info->id, json_wtr); /* pids */

jsonw_bool_field(json_wtr, "kernel", info->kernel_btf);

Expand All @@ -862,8 +840,8 @@ show_btf_json(struct bpf_btf_info *info, int fd,
}

static int
show_btf(int fd, struct btf_attach_table *btf_prog_table,
struct btf_attach_table *btf_map_table)
show_btf(int fd, struct hashmap *btf_prog_table,
struct hashmap *btf_map_table)
{
struct bpf_btf_info info;
__u32 len = sizeof(info);
Expand Down Expand Up @@ -900,8 +878,8 @@ show_btf(int fd, struct btf_attach_table *btf_prog_table,

static int do_show(int argc, char **argv)
{
struct btf_attach_table btf_prog_table;
struct btf_attach_table btf_map_table;
struct hashmap *btf_prog_table;
struct hashmap *btf_map_table;
int err, fd = -1;
__u32 id = 0;

Expand All @@ -917,9 +895,19 @@ static int do_show(int argc, char **argv)
return BAD_ARG();
}

hash_init(btf_prog_table.table);
hash_init(btf_map_table.table);
err = build_btf_tables(&btf_prog_table, &btf_map_table);
btf_prog_table = hashmap__new(hash_fn_for_key_as_id,
equal_fn_for_key_as_id, NULL);
btf_map_table = hashmap__new(hash_fn_for_key_as_id,
equal_fn_for_key_as_id, NULL);
if (!btf_prog_table || !btf_map_table) {
hashmap__free(btf_prog_table);
hashmap__free(btf_map_table);
if (fd >= 0)
close(fd);
p_err("failed to create hashmap for object references");
return -1;
}
err = build_btf_tables(btf_prog_table, btf_map_table);
if (err) {
if (fd >= 0)
close(fd);
Expand All @@ -928,7 +916,7 @@ static int do_show(int argc, char **argv)
build_obj_refs_table(&refs_table, BPF_OBJ_BTF);

if (fd >= 0) {
err = show_btf(fd, &btf_prog_table, &btf_map_table);
err = show_btf(fd, btf_prog_table, btf_map_table);
close(fd);
goto exit_free;
}
Expand Down Expand Up @@ -960,7 +948,7 @@ static int do_show(int argc, char **argv)
break;
}

err = show_btf(fd, &btf_prog_table, &btf_map_table);
err = show_btf(fd, btf_prog_table, btf_map_table);
close(fd);
if (err)
break;
Expand All @@ -970,9 +958,9 @@ static int do_show(int argc, char **argv)
jsonw_end_array(json_wtr); /* root array */

exit_free:
delete_btf_table(&btf_prog_table);
delete_btf_table(&btf_map_table);
delete_obj_refs_table(&refs_table);
hashmap__free(btf_prog_table);
hashmap__free(btf_map_table);
delete_obj_refs_table(refs_table);

return err;
}
Expand Down

0 comments on commit 9327acd

Please sign in to comment.