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From: Martin KaFai Lau <kafai@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	David Miller <davem@davemloft.net>, <kernel-team@fb.com>,
	<netdev@vger.kernel.org>
Subject: [PATCH bpf-next 5/5] bpftool: Support dumping a map with btf_vmlinux_value_type_id
Date: Tue, 14 Jan 2020 14:44:26 -0800
Message-ID: <20200114224426.3028966-1-kafai@fb.com> (raw)
In-Reply-To: <20200114224358.3027079-1-kafai@fb.com>

This patch makes bpftool support dumping a map's value properly
when the map's value type is a type of the running kernel's btf.
(i.e. map_info.btf_vmlinux_value_type_id is set instead of
map_info.btf_value_type_id).  The first usecase is for the
BPF_MAP_TYPE_STRUCT_OPS.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 tools/bpf/bpftool/map.c | 43 +++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 4c5b15d736b6..d25f3b2355ad 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -20,6 +20,7 @@
 #include "btf.h"
 #include "json_writer.h"
 #include "main.h"
+#include "libbpf_internal.h"
 
 const char * const map_type_name[] = {
 	[BPF_MAP_TYPE_UNSPEC]			= "unspec",
@@ -252,6 +253,7 @@ static int do_dump_btf(const struct btf_dumper *d,
 		       struct bpf_map_info *map_info, void *key,
 		       void *value)
 {
+	__u32 value_id;
 	int ret;
 
 	/* start of key-value pair */
@@ -265,9 +267,12 @@ static int do_dump_btf(const struct btf_dumper *d,
 			goto err_end_obj;
 	}
 
+	value_id = map_info->btf_vmlinux_value_type_id ?
+		: map_info->btf_value_type_id;
+
 	if (!map_is_per_cpu(map_info->type)) {
 		jsonw_name(d->jw, "value");
-		ret = btf_dumper_type(d, map_info->btf_value_type_id, value);
+		ret = btf_dumper_type(d, value_id, value);
 	} else {
 		unsigned int i, n, step;
 
@@ -279,8 +284,7 @@ static int do_dump_btf(const struct btf_dumper *d,
 			jsonw_start_object(d->jw);
 			jsonw_int_field(d->jw, "cpu", i);
 			jsonw_name(d->jw, "value");
-			ret = btf_dumper_type(d, map_info->btf_value_type_id,
-					      value + i * step);
+			ret = btf_dumper_type(d, value_id, value + i * step);
 			jsonw_end_object(d->jw);
 			if (ret)
 				break;
@@ -932,6 +936,27 @@ static int maps_have_btf(int *fds, int nb_fds)
 	return 1;
 }
 
+static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
+{
+	struct btf *btf = NULL;
+
+	if (info->btf_vmlinux_value_type_id) {
+		btf = bpf_find_kernel_btf();
+		if (IS_ERR(btf))
+			p_err("failed to get kernel btf");
+	} else if (info->btf_value_type_id) {
+		int err;
+
+		err = btf__get_from_id(info->btf_id, &btf);
+		if (err || !btf) {
+			p_err("failed to get btf");
+			btf = err ? ERR_PTR(err) : ERR_PTR(-ESRCH);
+		}
+	}
+
+	return btf;
+}
+
 static int
 map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 	 bool show_header)
@@ -952,13 +977,11 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 	prev_key = NULL;
 
 	if (wtr) {
-		if (info->btf_id) {
-			err = btf__get_from_id(info->btf_id, &btf);
-			if (err || !btf) {
-				err = err ? : -ESRCH;
-				p_err("failed to get btf");
-				goto exit_free;
-			}
+		btf = get_map_kv_btf(info);
+		if (IS_ERR(btf)) {
+			err = PTR_ERR(btf);
+			btf = NULL;
+			goto exit_free;
 		}
 
 		if (show_header) {
-- 
2.17.1


  parent reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 22:43 [PATCH bpf-next 0/5] " Martin KaFai Lau
2020-01-14 22:44 ` [PATCH bpf-next 1/5] bpftool: Fix a leak of btf object Martin KaFai Lau
2020-01-15  1:10   ` Andrii Nakryiko
2020-01-15  5:46     ` Martin Lau
2020-01-15  6:40       ` Andrii Nakryiko
2020-01-16  8:00       ` Paul Chaignon
2020-01-14 22:44 ` [PATCH bpf-next 2/5] bpftool: Fix missing BTF output for json during map dump Martin KaFai Lau
2020-01-15  1:34   ` Andrii Nakryiko
2020-01-15  5:54     ` Martin Lau
2020-01-15  6:36       ` Andrii Nakryiko
2020-01-14 22:44 ` [PATCH bpf-next 3/5] libbpf: Expose bpf_find_kernel_btf to libbpf_internal.h Martin KaFai Lau
2020-01-15  1:43   ` Andrii Nakryiko
2020-01-15  5:56     ` Martin Lau
2020-01-14 22:44 ` [PATCH bpf-next 4/5] bpftool: Add struct_ops map name Martin KaFai Lau
2020-01-15  1:45   ` Andrii Nakryiko
2020-01-14 22:44 ` Martin KaFai Lau [this message]
2020-01-15  1:49   ` [PATCH bpf-next 5/5] bpftool: Support dumping a map with btf_vmlinux_value_type_id Andrii Nakryiko
2020-01-15  6:04     ` Martin Lau
2020-01-15  6:39       ` Andrii Nakryiko

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