linux-kernel - [PATCH 2/5] bpf: convert queue and stack map to map_copy

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Message-Id: <20200310174711.7490-3-lmb@cloudflare.com>
Date:   Tue, 10 Mar 2020 17:47:08 +0000
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     kernel-team@...udflare.com, Lorenz Bauer <lmb@...udflare.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/5] bpf: convert queue and stack map to map_copy_value

Migrate BPF_MAP_TYPE_QUEUE and BPF_MAP_TYPE_STACK to map_copy_value,
by introducing small wrappers that discard the (unused) key argument.

Signed-off-by: Lorenz Bauer <lmb@...udflare.com>
---
 kernel/bpf/queue_stack_maps.c | 18 ++++++++++++++++++
 kernel/bpf/syscall.c          |  5 +----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/queue_stack_maps.c b/kernel/bpf/queue_stack_maps.c
index f697647ceb54..5c89b7583cd2 100644
--- a/kernel/bpf/queue_stack_maps.c
+++ b/kernel/bpf/queue_stack_maps.c
@@ -262,11 +262,28 @@ static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
 	return -EINVAL;
 }
 
+/* Called from syscall */
+static int queue_map_copy_value(struct bpf_map *map, void *key, void *value)
+{
+	(void)key;
+
+	return queue_map_peek_elem(map, value);
+}
+
+/* Called from syscall */
+static int stack_map_copy_value(struct bpf_map *map, void *key, void *value)
+{
+	(void)key;
+
+	return stack_map_peek_elem(map, value);
+}
+
 const struct bpf_map_ops queue_map_ops = {
 	.map_alloc_check = queue_stack_map_alloc_check,
 	.map_alloc = queue_stack_map_alloc,
 	.map_free = queue_stack_map_free,
 	.map_lookup_elem = queue_stack_map_lookup_elem,
+	.map_copy_value = queue_map_copy_value,
 	.map_update_elem = queue_stack_map_update_elem,
 	.map_delete_elem = queue_stack_map_delete_elem,
 	.map_push_elem = queue_stack_map_push_elem,
@@ -280,6 +297,7 @@ const struct bpf_map_ops stack_map_ops = {
 	.map_alloc = queue_stack_map_alloc,
 	.map_free = queue_stack_map_free,
 	.map_lookup_elem = queue_stack_map_lookup_elem,
+	.map_copy_value = stack_map_copy_value,
 	.map_update_elem = queue_stack_map_update_elem,
 	.map_delete_elem = queue_stack_map_delete_elem,
 	.map_push_elem = queue_stack_map_push_elem,
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6503824e81e9..20c6cdace275 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -218,10 +218,7 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value,
 		return bpf_map_offload_lookup_elem(map, key, value);
 
 	bpf_disable_instrumentation();
-	if (map->map_type == BPF_MAP_TYPE_QUEUE ||
-	    map->map_type == BPF_MAP_TYPE_STACK) {
-		err = map->ops->map_peek_elem(map, value);
-	} else if (map->ops->map_copy_value) {
+	if (map->ops->map_copy_value) {
 		err = map->ops->map_copy_value(map, key, value);
 	} else {
 		rcu_read_lock();
-- 
2.20.1