[bpf-next,v5,6/9] tools: bpftool: add probes for eBPF helper functions

diff --git a/tools/bpf/bpftool/Documentation/bpftool-feature.rst b/tools/bpf/bpftool/Documentation/bpftool-feature.rst
index 40ac13c0b782..255e3b3629a0 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-feature.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-feature.rst
@@ -30,6 +30,10 @@  DESCRIPTION
 
 		  Keyword **kernel** can be omitted.
 
+		  Note that when probed, some eBPF helpers (e.g.
+		  **bpf_trace_printk**\ () or **bpf_probe_write_user**\ ()) may
+		  print warnings to kernel logs.
+
 	**bpftool feature help**
 		  Print short help message.
 
diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
index cc731475c74b..55c8d215ca44 100644
--- a/tools/bpf/bpftool/feature.c
+++ b/tools/bpf/bpftool/feature.c
@@ -25,6 +25,13 @@  enum probe_component {
 	COMPONENT_KERNEL,
 };
 
+#define BPF_HELPER_MAKE_ENTRY(name)	[BPF_FUNC_ ## name] = "bpf_" # name
+static const char * const helper_name[] = {
+	__BPF_FUNC_MAPPER(BPF_HELPER_MAKE_ENTRY)
+};
+
+#undef BPF_HELPER_MAKE_ENTRY
+
 /* Miscellaneous utility functions */
 
 static bool check_procfs(void)
@@ -458,6 +465,44 @@  static void probe_map_type(enum bpf_map_type map_type)
 	print_bool_feature(feat_name, plain_desc, res);
 }
 
+static void
+probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type)
+{
+	const char *ptype_name = prog_type_name[prog_type];
+	char feat_name[128];
+	unsigned int id;
+	bool res;
+
+	if (json_output) {
+		sprintf(feat_name, "%s_available_helpers", ptype_name);
+		jsonw_name(json_wtr, feat_name);
+		jsonw_start_array(json_wtr);
+	} else {
+		printf("eBPF helpers supported for program type %s:",
+		       ptype_name);
+	}
+
+	for (id = 1; id < ARRAY_SIZE(helper_name); id++) {
+		if (!supported_type)
+			res = false;
+		else
+			res = bpf_probe_helper(id, prog_type, 0);
+
+		if (json_output) {
+			if (res)
+				jsonw_string(json_wtr, helper_name[id]);
+		} else {
+			if (res)
+				printf("\n\t- %s", helper_name[id]);
+		}
+	}
+
+	if (json_output)
+		jsonw_end_array(json_wtr);
+	else
+		printf("\n");
+}
+
 static int do_probe(int argc, char **argv)
 {
 	enum probe_component target = COMPONENT_UNSPEC;
@@ -533,6 +578,12 @@  static int do_probe(int argc, char **argv)
 	for (i = BPF_MAP_TYPE_UNSPEC + 1; i < map_type_name_size; i++)
 		probe_map_type(i);
 
+	print_end_then_start_section("helpers",
+				     "Scanning eBPF helper functions...");
+
+	for (i = BPF_PROG_TYPE_UNSPEC + 1; i < ARRAY_SIZE(prog_type_name); i++)
+		probe_helpers_for_progtype(i, supported_types[i]);
+
 exit_close_json:
 	if (json_output) {
 		/* End current "section" of probes */
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 72385f6f9415..62ae6cb93da1 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -366,6 +366,8 @@  bpf_prog_linfo__lfind(const struct bpf_prog_linfo *prog_linfo,
 LIBBPF_API bool bpf_probe_prog_type(enum bpf_prog_type prog_type,
 				    __u32 ifindex);
 LIBBPF_API bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex);
+LIBBPF_API bool bpf_probe_helper(enum bpf_func_id id,
+				 enum bpf_prog_type prog_type, __u32 ifindex);
 
 #ifdef __cplusplus
 } /* extern "C" */
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index bb2dfc3b2d7b..266bc95d0142 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -127,6 +127,7 @@  LIBBPF_0.0.1 {
 
 LIBBPF_0.0.2 {
 	global:
+		bpf_probe_helper;
 		bpf_probe_map_type;
 		bpf_probe_prog_type;
 } LIBBPF_0.0.1;
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index f511bd317b87..8c3a1c04dcb2 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -2,7 +2,11 @@ 
 /* Copyright (c) 2019 Netronome Systems, Inc. */
 
 #include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
 #include <unistd.h>
+#include <net/if.h>
 #include <sys/utsname.h>
 
 #include <linux/filter.h>
@@ -11,6 +15,37 @@ 
 #include "bpf.h"
 #include "libbpf.h"
 
+static bool grep(const char *buffer, const char *pattern)
+{
+	return !!strstr(buffer, pattern);
+}
+
+static int get_vendor_id(int ifindex)
+{
+	char ifname[IF_NAMESIZE], path[64], buf[8];
+	ssize_t len;
+	int fd;
+
+	if (!if_indextoname(ifindex, ifname))
+		return -1;
+
+	snprintf(path, sizeof(path), "/sys/class/net/%s/device/vendor", ifname);
+
+	fd = open(path, O_RDONLY);
+	if (fd < 0)
+		return -1;
+
+	len = read(fd, buf, sizeof(buf));
+	close(fd);
+	if (len < 0)
+		return -1;
+	if (len >= (ssize_t)sizeof(buf))
+		return -1;
+	buf[len] = '\0';
+
+	return strtol(buf, NULL, 0);
+}
+
 static int get_kernel_version(void)
 {
 	int version, subversion, patchlevel;
@@ -177,3 +212,31 @@  bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex)
 
 	return fd >= 0;
 }
+
+bool bpf_probe_helper(enum bpf_func_id id, enum bpf_prog_type prog_type,
+		      __u32 ifindex)
+{
+	struct bpf_insn insns[2] = {
+		BPF_EMIT_CALL(id),
+		BPF_EXIT_INSN()
+	};
+	char buf[4096] = {};
+	bool res;
+
+	probe_load(prog_type, insns, ARRAY_SIZE(insns), buf, sizeof(buf),
+		   ifindex);
+	res = !grep(buf, "invalid func ") && !grep(buf, "unknown func ");
+
+	if (ifindex) {
+		switch (get_vendor_id(ifindex)) {
+		case 0x19ee: /* Netronome specific */
+			res = res && !grep(buf, "not supported by FW") &&
+				!grep(buf, "unsupported function id");
+			break;
+		default:
+			break;
+		}
+	}
+
+	return res;
+}