1 files changed, 38 insertions, 11 deletions

diff --git a/tools/lib/bpf/features.c b/tools/lib/bpf/features.c
index 4e783cc7fc4b..760657f5224c 100644
--- a/tools/lib/bpf/features.c
+++ b/tools/lib/bpf/features.c
@@ -22,7 +22,7 @@ int probe_fd(int fd)
 
 static int probe_kern_prog_name(int token_fd)
 {
-	const size_t attr_sz = offsetofend(union bpf_attr, prog_name);
+	const size_t attr_sz = offsetofend(union bpf_attr, prog_token_fd);
 	struct bpf_insn insns[] = {
 		BPF_MOV64_IMM(BPF_REG_0, 0),
 		BPF_EXIT_INSN(),
@@ -47,7 +47,6 @@ static int probe_kern_prog_name(int token_fd)
 
 static int probe_kern_global_data(int token_fd)
 {
-	char *cp, errmsg[STRERR_BUFSIZE];
 	struct bpf_insn insns[] = {
 		BPF_LD_MAP_VALUE(BPF_REG_1, 0, 16),
 		BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 42),
@@ -67,9 +66,8 @@ static int probe_kern_global_data(int token_fd)
 	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_global", sizeof(int), 32, 1, &map_opts);
 	if (map < 0) {
 		ret = -errno;
-		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
-		pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
-			__func__, cp, -ret);
+		pr_warn("Error in %s(): %s. Couldn't create simple array map.\n",
+			__func__, errstr(ret));
 		return ret;
 	}
 
@@ -267,7 +265,6 @@ static int probe_kern_probe_read_kernel(int token_fd)
 
 static int probe_prog_bind_map(int token_fd)
 {
-	char *cp, errmsg[STRERR_BUFSIZE];
 	struct bpf_insn insns[] = {
 		BPF_MOV64_IMM(BPF_REG_0, 0),
 		BPF_EXIT_INSN(),
@@ -285,9 +282,8 @@ static int probe_prog_bind_map(int token_fd)
 	map = bpf_map_create(BPF_MAP_TYPE_ARRAY, "libbpf_det_bind", sizeof(int), 32, 1, &map_opts);
 	if (map < 0) {
 		ret = -errno;
-		cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
-		pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
-			__func__, cp, -ret);
+		pr_warn("Error in %s(): %s. Couldn't create simple array map.\n",
+			__func__, errstr(ret));
 		return ret;
 	}
 
@@ -392,11 +388,41 @@ static int probe_uprobe_multi_link(int token_fd)
 	link_fd = bpf_link_create(prog_fd, -1, BPF_TRACE_UPROBE_MULTI, &link_opts);
 	err = -errno; /* close() can clobber errno */
 
+	if (link_fd >= 0 || err != -EBADF) {
+		if (link_fd >= 0)
+			close(link_fd);
+		close(prog_fd);
+		return 0;
+	}
+
+	/* Initial multi-uprobe support in kernel didn't handle PID filtering
+	 * correctly (it was doing thread filtering, not process filtering).
+	 * So now we'll detect if PID filtering logic was fixed, and, if not,
+	 * we'll pretend multi-uprobes are not supported, if not.
+	 * Multi-uprobes are used in USDT attachment logic, and we need to be
+	 * conservative here, because multi-uprobe selection happens early at
+	 * load time, while the use of PID filtering is known late at
+	 * attachment time, at which point it's too late to undo multi-uprobe
+	 * selection.
+	 *
+	 * Creating uprobe with pid == -1 for (invalid) '/' binary will fail
+	 * early with -EINVAL on kernels with fixed PID filtering logic;
+	 * otherwise -ESRCH would be returned if passed correct binary path
+	 * (but we'll just get -BADF, of course).
+	 */
+	link_opts.uprobe_multi.pid = -1; /* invalid PID */
+	link_opts.uprobe_multi.path = "/"; /* invalid path */
+	link_opts.uprobe_multi.offsets = &offset;
+	link_opts.uprobe_multi.cnt = 1;
+
+	link_fd = bpf_link_create(prog_fd, -1, BPF_TRACE_UPROBE_MULTI, &link_opts);
+	err = -errno; /* close() can clobber errno */
+
 	if (link_fd >= 0)
 		close(link_fd);
 	close(prog_fd);
 
-	return link_fd < 0 && err == -EBADF;
+	return link_fd < 0 && err == -EINVAL;
 }
 
 static int probe_kern_bpf_cookie(int token_fd)
@@ -574,7 +600,8 @@ bool feat_supported(struct kern_feature_cache *cache, enum kern_feature_id feat_
 		} else if (ret == 0) {
 			WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
 		} else {
-			pr_warn("Detection of kernel %s support failed: %d\n", feat->desc, ret);
+			pr_warn("Detection of kernel %s support failed: %s\n",
+				feat->desc, errstr(ret));
 			WRITE_ONCE(cache->res[feat_id], FEAT_MISSING);
 		}
 	}