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: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211023205154.6710-4-quentin@isovalent.com

1 files changed, 17 insertions, 12 deletions

diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index baf607cd5924..0d64e39573f2 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -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