bpf: Support BPF_MAP_TYPE_SK_STORAGE in bpf map probing

This patch supports probing for the new BPF_MAP_TYPE_SK_STORAGE.
BPF_MAP_TYPE_SK_STORAGE enforces BTF usage, so the new probe
requires to create and load a BTF also.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 73 insertions, 1 deletions

diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 80ee922f290c..a2c64a9ce1a6 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -9,6 +9,7 @@
 #include <net/if.h>
 #include <sys/utsname.h>
 
+#include <linux/btf.h>
 #include <linux/filter.h>
 #include <linux/kernel.h>
 
@@ -131,11 +132,65 @@ bool bpf_probe_prog_type(enum bpf_prog_type prog_type, __u32 ifindex)
 	return errno != EINVAL && errno != EOPNOTSUPP;
 }
 
+static int load_btf(void)
+{
+#define BTF_INFO_ENC(kind, kind_flag, vlen) \
+	((!!(kind_flag) << 31) | ((kind) << 24) | ((vlen) & BTF_MAX_VLEN))
+#define BTF_TYPE_ENC(name, info, size_or_type) \
+	(name), (info), (size_or_type)
+#define BTF_INT_ENC(encoding, bits_offset, nr_bits) \
+	((encoding) << 24 | (bits_offset) << 16 | (nr_bits))
+#define BTF_TYPE_INT_ENC(name, encoding, bits_offset, bits, sz) \
+	BTF_TYPE_ENC(name, BTF_INFO_ENC(BTF_KIND_INT, 0, 0), sz), \
+	BTF_INT_ENC(encoding, bits_offset, bits)
+#define BTF_MEMBER_ENC(name, type, bits_offset) \
+	(name), (type), (bits_offset)
+
+	const char btf_str_sec[] = "\0bpf_spin_lock\0val\0cnt\0l";
+	/* struct bpf_spin_lock {
+	 *   int val;
+	 * };
+	 * struct val {
+	 *   int cnt;
+	 *   struct bpf_spin_lock l;
+	 * };
+	 */
+	__u32 btf_raw_types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */
+		/* struct bpf_spin_lock */                      /* [2] */
+		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 4),
+		BTF_MEMBER_ENC(15, 1, 0), /* int val; */
+		/* struct val */                                /* [3] */
+		BTF_TYPE_ENC(15, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 8),
+		BTF_MEMBER_ENC(19, 1, 0), /* int cnt; */
+		BTF_MEMBER_ENC(23, 2, 32),/* struct bpf_spin_lock l; */
+	};
+	struct btf_header btf_hdr = {
+		.magic = BTF_MAGIC,
+		.version = BTF_VERSION,
+		.hdr_len = sizeof(struct btf_header),
+		.type_len = sizeof(btf_raw_types),
+		.str_off = sizeof(btf_raw_types),
+		.str_len = sizeof(btf_str_sec),
+	};
+	__u8 raw_btf[sizeof(struct btf_header) + sizeof(btf_raw_types) +
+		     sizeof(btf_str_sec)];
+
+	memcpy(raw_btf, &btf_hdr, sizeof(btf_hdr));
+	memcpy(raw_btf + sizeof(btf_hdr), btf_raw_types, sizeof(btf_raw_types));
+	memcpy(raw_btf + sizeof(btf_hdr) + sizeof(btf_raw_types),
+	       btf_str_sec, sizeof(btf_str_sec));
+
+	return bpf_load_btf(raw_btf, sizeof(raw_btf), 0, 0, 0);
+}
+
 bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex)
 {
 	int key_size, value_size, max_entries, map_flags;
+	__u32 btf_key_type_id = 0, btf_value_type_id = 0;
 	struct bpf_create_map_attr attr = {};
-	int fd = -1, fd_inner;
+	int fd = -1, btf_fd = -1, fd_inner;
 
 	key_size	= sizeof(__u32);
 	value_size	= sizeof(__u32);
@@ -161,6 +216,16 @@ bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex)
 	case BPF_MAP_TYPE_STACK:
 		key_size	= 0;
 		break;
+	case BPF_MAP_TYPE_SK_STORAGE:
+		btf_key_type_id = 1;
+		btf_value_type_id = 3;
+		value_size = 8;
+		max_entries = 0;
+		map_flags = BPF_F_NO_PREALLOC;
+		btf_fd = load_btf();
+		if (btf_fd < 0)
+			return false;
+		break;
 	case BPF_MAP_TYPE_UNSPEC:
 	case BPF_MAP_TYPE_HASH:
 	case BPF_MAP_TYPE_ARRAY:
@@ -206,11 +271,18 @@ bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex)
 		attr.max_entries = max_entries;
 		attr.map_flags = map_flags;
 		attr.map_ifindex = ifindex;
+		if (btf_fd >= 0) {
+			attr.btf_fd = btf_fd;
+			attr.btf_key_type_id = btf_key_type_id;
+			attr.btf_value_type_id = btf_value_type_id;
+		}
 
 		fd = bpf_create_map_xattr(&attr);
 	}
 	if (fd >= 0)
 		close(fd);
+	if (btf_fd >= 0)
+		close(btf_fd);
 
 	return fd >= 0;
 }