netdev - [PATCH iproute2-next 2/2] bpf: increase verifier verbosity when in verbose mode

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Date: Wed, 18 Oct 2023 14:22:34 +0800
From: Shung-Hsi Yu <shung-hsi.yu@...e.com>
To: netdev@...r.kernel.org
Cc: Shung-Hsi Yu <shung-hsi.yu@...e.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	David Ahern <dsahern@...nel.org>,
	Toke Høiland-Jørgensen <toke@...hat.com>
Subject: [PATCH iproute2-next 2/2] bpf: increase verifier verbosity when in verbose mode

The BPF verifier allows setting a higher verbosity level, which is
helpful when it comes to debugging verifier issue, specially when used
to BPF program that loads successfully (but should not have passed the
verifier in the first place). Increase the BPF verifier log level in
when in verbose mode to help with such cases.

Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@...e.com>
---
 include/bpf_util.h |  4 ++--
 ip/ipvrf.c         |  3 ++-
 lib/bpf_legacy.c   | 10 ++++++----
 lib/bpf_libbpf.c   |  9 ++++++---
 4 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/include/bpf_util.h b/include/bpf_util.h
index 1c924f50..8951a5e8 100644
--- a/include/bpf_util.h
+++ b/include/bpf_util.h
@@ -273,10 +273,10 @@ void bpf_print_ops(struct rtattr *bpf_ops, __u16 len);
 
 int bpf_prog_load_dev(enum bpf_prog_type type, const struct bpf_insn *insns,
 		      size_t size_insns, const char *license, __u32 ifindex,
-		      char *log, size_t size_log);
+		      char *log, size_t size_log, bool verbose);
 int bpf_program_load(enum bpf_prog_type type, const struct bpf_insn *insns,
 		     size_t size_insns, const char *license, char *log,
-		     size_t size_log);
+		     size_t size_log, bool verbose);
 
 int bpf_prog_attach_fd(int prog_fd, int target_fd, enum bpf_attach_type type);
 int bpf_prog_detach_fd(int target_fd, enum bpf_attach_type type);
diff --git a/ip/ipvrf.c b/ip/ipvrf.c
index 12beaec3..e7c702ab 100644
--- a/ip/ipvrf.c
+++ b/ip/ipvrf.c
@@ -253,7 +253,8 @@ static int prog_load(int idx)
 	};
 
 	return bpf_program_load(BPF_PROG_TYPE_CGROUP_SOCK, prog, sizeof(prog),
-				"GPL", bpf_log_buf, sizeof(bpf_log_buf));
+				"GPL", bpf_log_buf, sizeof(bpf_log_buf),
+				false);
 }
 
 static int vrf_configure_cgroup(const char *path, int ifindex)
diff --git a/lib/bpf_legacy.c b/lib/bpf_legacy.c
index 3542b12f..844974e9 100644
--- a/lib/bpf_legacy.c
+++ b/lib/bpf_legacy.c
@@ -1098,7 +1098,7 @@ int bpf_prog_detach_fd(int target_fd, enum bpf_attach_type type)
 
 int bpf_prog_load_dev(enum bpf_prog_type type, const struct bpf_insn *insns,
 		      size_t size_insns, const char *license, __u32 ifindex,
-		      char *log, size_t size_log)
+		      char *log, size_t size_log, bool verbose)
 {
 	union bpf_attr attr = {};
 
@@ -1112,6 +1112,8 @@ int bpf_prog_load_dev(enum bpf_prog_type type, const struct bpf_insn *insns,
 		attr.log_buf = bpf_ptr_to_u64(log);
 		attr.log_size = size_log;
 		attr.log_level = 1;
+		if (verbose)
+			attr.log_level |= 2;
 	}
 
 	return bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
@@ -1119,9 +1121,9 @@ int bpf_prog_load_dev(enum bpf_prog_type type, const struct bpf_insn *insns,
 
 int bpf_program_load(enum bpf_prog_type type, const struct bpf_insn *insns,
 		     size_t size_insns, const char *license, char *log,
-		     size_t size_log)
+		     size_t size_log, bool verbose)
 {
-	return bpf_prog_load_dev(type, insns, size_insns, license, 0, log, size_log);
+	return bpf_prog_load_dev(type, insns, size_insns, license, 0, log, size_log, verbose);
 }
 
 #ifdef HAVE_ELF
@@ -1543,7 +1545,7 @@ retry:
 	errno = 0;
 	fd = bpf_prog_load_dev(prog->type, prog->insns, prog->size,
 			       prog->license, ctx->ifindex,
-			       ctx->log, ctx->log_size);
+			       ctx->log, ctx->log_size, ctx->verbose);
 	if (fd < 0 || ctx->verbose) {
 		/* The verifier log is pretty chatty, sometimes so chatty
 		 * on larger programs, that we could fail to dump everything
diff --git a/lib/bpf_libbpf.c b/lib/bpf_libbpf.c
index f678a710..08692d30 100644
--- a/lib/bpf_libbpf.c
+++ b/lib/bpf_libbpf.c
@@ -285,11 +285,14 @@ static int load_bpf_object(struct bpf_cfg_in *cfg)
 	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, open_opts,
 			.relaxed_maps = true,
 			.pin_root_path = root_path,
-#ifdef (LIBBPF_MAJOR_VERSION > 0) || (LIBBPF_MINOR_VERSION >= 7)
-			.kernel_log_level = 1,
-#endif
 	);
 
+#if (LIBBPF_MAJOR_VERSION > 0) || (LIBBPF_MINOR_VERSION >= 7)
+	open_opts.kernel_log_level = 1;
+	if (cfg->verbose)
+		open_opts.kernel_log_level |= 2;
+#endif
+
 	obj = bpf_object__open_file(cfg->object, &open_opts);
 	if (libbpf_get_error(obj)) {
 		fprintf(stderr, "ERROR: opening BPF object file failed\n");
-- 
2.42.0