Commit 8f184732 authored by Quentin Monnet's avatar Quentin Monnet Committed by Andrii Nakryiko
Browse files

bpftool: Switch to libbpf's hashmap for pinned paths of BPF objects 



In order to show pinned paths for BPF programs, maps, or links when
listing them with the "-f" option, bpftool creates hash maps to store
all relevant paths under the bpffs. So far, it would rely on the
kernel implementation (from tools/include/linux/hashtable.h).

We can make bpftool rely on libbpf's implementation instead. The
motivation is to make bpftool less dependent of kernel headers, to ease
the path to a potential out-of-tree mirror, like libbpf has.

This commit is the first step of the conversion: the hash maps for
pinned paths for programs, maps, and links are converted to libbpf's
hashmap.{c,h}. Other hash maps used for the PIDs of process holding
references to BPF objects are left unchanged for now. On the build side,
this requires adding a dependency to a second header internal to libbpf,
and making it a dependency for the bootstrap bpftool version as well.
The rest of the changes are a rather straightforward conversion.

Signed-off-by: default avatarQuentin Monnet <quentin@isovalent.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211023205154.6710-4-quentin@isovalent.com
parent 46241271

tools/bpf/bpftool/Makefile

+4 −4
Original line number Diff line number Diff line
@@ -31,9 +31,9 @@ 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)
@@ -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

tools/bpf/bpftool/common.c

+30 −20
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <sys/vfs.h>



#include <bpf/bpf.h>

#include <bpf/hashmap.h>

#include <bpf/libbpf.h> /* libbpf_num_possible_cpus */



#include "main.h"
@@ -393,7 +394,7 @@ void print_hex_data_json(uint8_t *data, size_t len) 
}



/* extra params for nftw cb */

static struct pinned_obj_table *build_fn_table;

static struct hashmap *build_fn_table;

static enum bpf_obj_type build_fn_type;



static int do_build_table_cb(const char *fpath, const struct stat *sb,
@@ -401,9 +402,9 @@ static int do_build_table_cb(const char *fpath, const struct stat *sb, 
{

	struct bpf_prog_info pinned_info;

	__u32 len = sizeof(pinned_info);

	struct pinned_obj *obj_node;

	enum bpf_obj_type objtype;

	int fd, err = 0;

	char *path;



	if (typeflag != FTW_F)

		goto out_ret;
@@ -420,28 +421,26 @@ static int do_build_table_cb(const char *fpath, const struct stat *sb, 
	if (bpf_obj_get_info_by_fd(fd, &pinned_info, &len))

		goto out_close;



	obj_node = calloc(1, sizeof(*obj_node));

	if (!obj_node) {

	path = strdup(fpath);

	if (!path) {

		err = -1;

		goto out_close;

	}



	obj_node->id = pinned_info.id;

	obj_node->path = strdup(fpath);

	if (!obj_node->path) {

		err = -1;

		free(obj_node);

	err = hashmap__append(build_fn_table, u32_as_hash_field(pinned_info.id), path);

	if (err) {

		p_err("failed to append entry to hashmap for ID %u, path '%s': %s",

		      pinned_info.id, path, strerror(errno));

		goto out_close;

	}



	hash_add(build_fn_table->table, &obj_node->hash, obj_node->id);

out_close:

	close(fd);

out_ret:

	return err;

}



int build_pinned_obj_table(struct pinned_obj_table *tab,

int build_pinned_obj_table(struct hashmap *tab,

			   enum bpf_obj_type type)

{

	struct mntent *mntent = NULL;
@@ -470,17 +469,18 @@ int build_pinned_obj_table(struct pinned_obj_table *tab, 
	return err;

}



void delete_pinned_obj_table(struct pinned_obj_table *tab)

void delete_pinned_obj_table(struct hashmap *map)

{

	struct pinned_obj *obj;

	struct hlist_node *tmp;

	unsigned int bkt;

	struct hashmap_entry *entry;

	size_t bkt;



	hash_for_each_safe(tab->table, bkt, tmp, obj, hash) {

		hash_del(&obj->hash);

		free(obj->path);

		free(obj);

	}

	if (!map)

		return;



	hashmap__for_each_entry(map, entry, bkt)

		free(entry->value);



	hashmap__free(map);

}



unsigned int get_page_size(void)
@@ -962,3 +962,13 @@ int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len) 


	return fd;

}



size_t hash_fn_for_key_as_id(const void *key, void *ctx)

{

	return (size_t)key;

}



bool equal_fn_for_key_as_id(const void *k1, const void *k2, void *ctx)

{

	return k1 == k2;

}

tools/bpf/bpftool/link.c

+20 −16
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#include <unistd.h>



#include <bpf/bpf.h>

#include <bpf/hashmap.h>



#include "json_writer.h"

#include "main.h"
@@ -20,7 +21,7 @@ static const char * const link_type_name[] = { 
	[BPF_LINK_TYPE_NETNS]			= "netns",

};



static struct pinned_obj_table link_table;

static struct hashmap *link_table;



static int link_parse_fd(int *argc, char ***argv)

{
@@ -158,15 +159,14 @@ static int show_link_close_json(int fd, struct bpf_link_info *info) 
		break;

	}



	if (!hash_empty(link_table.table)) {

		struct pinned_obj *obj;

	if (!hashmap__empty(link_table)) {

		struct hashmap_entry *entry;



		jsonw_name(json_wtr, "pinned");

		jsonw_start_array(json_wtr);

		hash_for_each_possible(link_table.table, obj, hash, info->id) {

			if (obj->id == info->id)

				jsonw_string(json_wtr, obj->path);

		}

		hashmap__for_each_key_entry(link_table, entry,

					    u32_as_hash_field(info->id))

			jsonw_string(json_wtr, entry->value);

		jsonw_end_array(json_wtr);

	}
@@ -246,13 +246,12 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info) 
		break;

	}



	if (!hash_empty(link_table.table)) {

		struct pinned_obj *obj;

	if (!hashmap__empty(link_table)) {

		struct hashmap_entry *entry;



		hash_for_each_possible(link_table.table, obj, hash, info->id) {

			if (obj->id == info->id)

				printf("\n\tpinned %s", obj->path);

		}

		hashmap__for_each_key_entry(link_table, entry,

					    u32_as_hash_field(info->id))

			printf("\n\tpinned %s", (char *)entry->value);

	}

	emit_obj_refs_plain(&refs_table, info->id, "\n\tpids ");
@@ -305,8 +304,13 @@ static int do_show(int argc, char **argv) 
	int err, fd;



	if (show_pinned) {

		hash_init(link_table.table);

		build_pinned_obj_table(&link_table, BPF_OBJ_LINK);

		link_table = hashmap__new(hash_fn_for_key_as_id,

					  equal_fn_for_key_as_id, NULL);

		if (!link_table) {

			p_err("failed to create hashmap for pinned paths");

			return -1;

		}

		build_pinned_obj_table(link_table, BPF_OBJ_LINK);

	}

	build_obj_refs_table(&refs_table, BPF_OBJ_LINK);
@@ -351,7 +355,7 @@ static int do_show(int argc, char **argv) 
	delete_obj_refs_table(&refs_table);



	if (show_pinned)

		delete_pinned_obj_table(&link_table);

		delete_pinned_obj_table(link_table);



	return errno == ENOENT ? 0 : -1;

}

tools/bpf/bpftool/main.h

+17 −12
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/hashtable.h>

#include <tools/libc_compat.h>



#include <bpf/hashmap.h>

#include <bpf/libbpf.h>



#include "json_writer.h"
@@ -105,16 +106,6 @@ void set_max_rlimit(void); 


int mount_tracefs(const char *target);



struct pinned_obj_table {

	DECLARE_HASHTABLE(table, 16);

};



struct pinned_obj {

	__u32 id;

	char *path;

	struct hlist_node hash;

};



struct obj_refs_table {

	DECLARE_HASHTABLE(table, 16);

};
@@ -134,9 +125,9 @@ struct obj_refs { 
struct btf;

struct bpf_line_info;



int build_pinned_obj_table(struct pinned_obj_table *table,

int build_pinned_obj_table(struct hashmap *table,

			   enum bpf_obj_type type);

void delete_pinned_obj_table(struct pinned_obj_table *tab);

void delete_pinned_obj_table(struct hashmap *table);

__weak int build_obj_refs_table(struct obj_refs_table *table,

				enum bpf_obj_type type);

__weak void delete_obj_refs_table(struct obj_refs_table *table);
@@ -256,4 +247,18 @@ int do_filter_dump(struct tcmsg *ifinfo, struct nlattr **tb, const char *kind, 


int print_all_levels(__maybe_unused enum libbpf_print_level level,

		     const char *format, va_list args);



size_t hash_fn_for_key_as_id(const void *key, void *ctx);

bool equal_fn_for_key_as_id(const void *k1, const void *k2, void *ctx);



static inline void *u32_as_hash_field(__u32 x)

{

	return (void *)(uintptr_t)x;

}



static inline bool hashmap__empty(struct hashmap *map)

{

	return map ? hashmap__size(map) == 0 : true;

}



#endif

tools/bpf/bpftool/map.c

+20 −16
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 


#include <bpf/bpf.h>

#include <bpf/btf.h>

#include <bpf/hashmap.h>



#include "json_writer.h"

#include "main.h"
@@ -56,7 +57,7 @@ const char * const map_type_name[] = { 


const size_t map_type_name_size = ARRAY_SIZE(map_type_name);



static struct pinned_obj_table map_table;

static struct hashmap *map_table;



static bool map_is_per_cpu(__u32 type)

{
@@ -537,15 +538,14 @@ static int show_map_close_json(int fd, struct bpf_map_info *info) 
	if (info->btf_id)

		jsonw_int_field(json_wtr, "btf_id", info->btf_id);



	if (!hash_empty(map_table.table)) {

		struct pinned_obj *obj;

	if (!hashmap__empty(map_table)) {

		struct hashmap_entry *entry;



		jsonw_name(json_wtr, "pinned");

		jsonw_start_array(json_wtr);

		hash_for_each_possible(map_table.table, obj, hash, info->id) {

			if (obj->id == info->id)

				jsonw_string(json_wtr, obj->path);

		}

		hashmap__for_each_key_entry(map_table, entry,

					    u32_as_hash_field(info->id))

			jsonw_string(json_wtr, entry->value);

		jsonw_end_array(json_wtr);

	}
@@ -612,13 +612,12 @@ static int show_map_close_plain(int fd, struct bpf_map_info *info) 
	}

	close(fd);



	if (!hash_empty(map_table.table)) {

		struct pinned_obj *obj;

	if (!hashmap__empty(map_table)) {

		struct hashmap_entry *entry;



		hash_for_each_possible(map_table.table, obj, hash, info->id) {

			if (obj->id == info->id)

				printf("\n\tpinned %s", obj->path);

		}

		hashmap__for_each_key_entry(map_table, entry,

					    u32_as_hash_field(info->id))

			printf("\n\tpinned %s", (char *)entry->value);

	}

	printf("\n");
@@ -697,8 +696,13 @@ static int do_show(int argc, char **argv) 
	int fd;



	if (show_pinned) {

		hash_init(map_table.table);

		build_pinned_obj_table(&map_table, BPF_OBJ_MAP);

		map_table = hashmap__new(hash_fn_for_key_as_id,

					 equal_fn_for_key_as_id, NULL);

		if (!map_table) {

			p_err("failed to create hashmap for pinned paths");

			return -1;

		}

		build_pinned_obj_table(map_table, BPF_OBJ_MAP);

	}

	build_obj_refs_table(&refs_table, BPF_OBJ_MAP);
@@ -747,7 +751,7 @@ static int do_show(int argc, char **argv) 
	delete_obj_refs_table(&refs_table);



	if (show_pinned)

		delete_pinned_obj_table(&map_table);

		delete_pinned_obj_table(map_table);



	return errno == ENOENT ? 0 : -1;

}