On 9/12/22 11:11 AM, Dave Marchevsky wrote:
This patch adds support for the following pattern:
struct some_data *data = bpf_ringbuf_reserve(&ringbuf, sizeof(struct some_data, 0));
Maybe add:
if (!data)
return;
in the example code? Otherwise, the code looks invalid.
bpf_map_lookup_elem(&another_map, &data->some_field);
bpf_ringbuf_submit(data);
Currently the verifier does not consider bpf_ringbuf_reserve's
PTR_TO_MEM ret type a valid key input to bpf_map_lookup_elem. Since
PTR_TO_MEM is by definition a valid region of memory, it is safe to use
it as a key for lookups.
bpf_ringbuf_reserve return types also has MEM_ALLOC. Maybe should
mention in the above commit message.
Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
---
kernel/bpf/verifier.c | 2 +
tools/testing/selftests/bpf/Makefile | 8 ++-
.../selftests/bpf/prog_tests/ringbuf.c | 10 +++
.../bpf/progs/test_ringbuf_map_key.c | 69 +++++++++++++++++++
4 files changed, 86 insertions(+), 3 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c259d734f863..d093618aed99 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5626,6 +5626,8 @@ static const struct bpf_reg_types map_key_value_types = {
PTR_TO_PACKET_META,
PTR_TO_MAP_KEY,
PTR_TO_MAP_VALUE,
+ PTR_TO_MEM,
PTR_TO_MEM is okay. But bpf_ringbuf_reserve() will trigger
PTR_TO_MEM | MEM_ALLOC. So suggest to add PTR_TO_MEM unless
you find a use case for it.
+ PTR_TO_MEM | MEM_ALLOC,
},
};
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 6cd327f1f216..231d9c1364c9 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -351,9 +351,11 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h \
test_subskeleton.skel.h test_subskeleton_lib.skel.h \
test_usdt.skel.h
-LSKELS := fentry_test.c fexit_test.c fexit_sleep.c \
- test_ringbuf.c atomics.c trace_printk.c trace_vprintk.c \
- map_ptr_kern.c core_kern.c core_kern_overflow.c
+LSKELS := fentry_test.c fexit_test.c fexit_sleep.c atomics.c \
+ trace_printk.c trace_vprintk.c map_ptr_kern.c \
+ core_kern.c core_kern_overflow.c test_ringbuf.c \
+ test_ringbuf_map_key.c
Maybe put the selftest in a separate patch?
+
# Generate both light skeleton and libbpf skeleton for these
LSKELS_EXTRA := test_ksyms_module.c test_ksyms_weak.c kfunc_call_test.c \
kfunc_call_test_subprog.c
diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
index 9a80fe8a6427..1cf458d1a179 100644
--- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
@@ -13,6 +13,7 @@
#include <linux/perf_event.h>
#include <linux/ring_buffer.h>
#include "test_ringbuf.lskel.h"
+#include "test_ringbuf_map_key.lskel.h"
#define EDONE 7777
@@ -297,3 +298,12 @@ void test_ringbuf(void)
ring_buffer__free(ringbuf);
test_ringbuf_lskel__destroy(skel);
}
+
+void test_ringbuf_map_key(void)
+{
+ struct test_ringbuf_map_key_lskel *skel_map_key;
+
+ skel_map_key = test_ringbuf_map_key_lskel__open_and_load();
+ ASSERT_OK_PTR(skel_map_key, "test_ringbuf_map_key_lskel__open_and_load failed");
+ test_ringbuf_map_key_lskel__destroy(skel_map_key);
+}
This adds another *top* test in ringbuf.c.
Should we add test_ringbuf_map_key as a subtest
for test_ringbuf test so in the future more subtests
could be added in the umbrella of test_ringbuf test?
diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c b/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c
new file mode 100644
index 000000000000..96a791a9762e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_ringbuf_map_key.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct sample {
+ int pid;
+ int seq;
+ long value;
+ char comm[16];
+};
+
+struct {
+ __uint(type, BPF_MAP_TYPE_RINGBUF);
+ __uint(max_entries, 4096);
+} ringbuf SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(max_entries, 1000);
+ __type(key, struct sample);
+ __type(value, int);
+} hash_map SEC(".maps");
+
+/* inputs */
+int pid = 0;
+long value = 0;
+long flags = 0;
I didn't see these values are assigned in user space.
So you can simplify the code by remove 'flags'
and manually inline the 'value'.
+
+/* outputs */
+long total = 0;
+long dropped = 0;
'total' is not used. 'dropped' is not checked by user
space application, so it can be dropped too.
+
+/* inner state */
+long seq = 0;
+
+SEC("fentry/" SYS_PREFIX "sys_getpgid")
+int test_ringbuf_mem_map_key(void *ctx)
+{
+ int cur_pid = bpf_get_current_pid_tgid() >> 32;
+ struct sample *sample;
+ int *lookup_val;
+ int zero = 0;
+
+ if (cur_pid != pid)
+ return 0;
+
+ sample = bpf_ringbuf_reserve(&ringbuf, sizeof(*sample), 0);
+ if (!sample) {
+ __sync_fetch_and_add(&dropped, 1);
+ return 0;
+ }
+
+ sample->pid = pid;
+ bpf_get_current_comm(sample->comm, sizeof(sample->comm));
+ sample->value = value;
+ sample->seq = seq++;
+
+ /* This prog is never run, successful load w/ below use of sample mem
+ * as map key is considered success
+ */
+ lookup_val = (int *)bpf_map_lookup_elem(&hash_map, sample);
Maybe add code for bpf_map_update_elem() as well since that is also
common use case?
This way, you can check the result in user space after
bpf_map_update_elem().
+ bpf_ringbuf_submit(sample, 0);
+ return 0;
+}
