On 12/3/23 3:48 PM, Jiri Olsa wrote:
Adding test that tries to trigger the BUG_ON during early map update
in prog_array_map_poke_run function.
The idea is to share prog array map between thread that constantly
updates it and another one loading a program that uses that prog
array.
Eventually we will hit a place where the program is ok to be updated
(poke->tailcall_target_stable check) but the address is still not
registered in kallsyms, so the bpf_arch_text_poke returns -EINVAL
and cause imbalance for the next tail call update check, which will
fail with -EBUSY in bpf_arch_text_poke as described in previous fix.
Acked-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/tailcall_poke.c | 74 +++++++++++++++++++
.../selftests/bpf/progs/tailcall_poke.c | 32 ++++++++
2 files changed, 106 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/tailcall_poke.c
create mode 100644 tools/testing/selftests/bpf/progs/tailcall_poke.c
diff --git a/tools/testing/selftests/bpf/prog_tests/tailcall_poke.c b/tools/testing/selftests/bpf/prog_tests/tailcall_poke.c
new file mode 100644
index 000000000000..f7e2c09fd772
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/tailcall_poke.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <unistd.h>
+#include <test_progs.h>
+#include "tailcall_poke.skel.h"
+
+#define JMP_TABLE "/sys/fs/bpf/jmp_table"
+
+static int thread_exit;
+
+static void *update(void *arg)
+{
+ __u32 zero = 0, prog1_fd, prog2_fd, map_fd;
+ struct tailcall_poke *call = arg;
+
+ map_fd = bpf_map__fd(call->maps.jmp_table);
+ prog1_fd = bpf_program__fd(call->progs.call1);
+ prog2_fd = bpf_program__fd(call->progs.call2);
+
+ while (!thread_exit) {
+ bpf_map_update_elem(map_fd, &zero, &prog1_fd, BPF_ANY);
+ bpf_map_update_elem(map_fd, &zero, &prog2_fd, BPF_ANY);
+ }
+
+ return NULL;
+}
+
+void test_tailcall_poke(void)
+{
+ struct tailcall_poke *call, *test;
+ int err, cnt = 10;
+ pthread_t thread;
+
+ unlink(JMP_TABLE);
+
+ call = tailcall_poke__open_and_load();
+ if (!ASSERT_OK_PTR(call, "tailcall_poke__open"))
+ return;
+
+ err = bpf_map__pin(call->maps.jmp_table, JMP_TABLE);
+ if (!ASSERT_OK(err, "bpf_map__pin"))
+ goto out;
Just curious. What is the reason having bpf_map__pin() here
and below? I tried and it looks like removing bpf_map__pin()
and below bpf_map__set_pin_path() will make reproducing
the failure hard/impossible.
+
+ err = pthread_create(&thread, NULL, update, call);
+ if (!ASSERT_OK(err, "new toggler"))
+ goto out;
+
+ while (cnt--) {
+ test = tailcall_poke__open();
+ if (!ASSERT_OK_PTR(test, "tailcall_poke__open"))
+ break;
+
+ err = bpf_map__set_pin_path(test->maps.jmp_table, JMP_TABLE);
+ if (!ASSERT_OK(err, "bpf_map__pin")) {
+ tailcall_poke__destroy(test);
+ break;
+ }
+
+ bpf_program__set_autoload(test->progs.test, true);
+ bpf_program__set_autoload(test->progs.call1, false);
+ bpf_program__set_autoload(test->progs.call2, false);
+
+ err = tailcall_poke__load(test);
+ tailcall_poke__destroy(test);
+ if (!ASSERT_OK(err, "tailcall_poke__load"))
+ break;
+ }
+
+ thread_exit = 1;
+ ASSERT_OK(pthread_join(thread, NULL), "pthread_join");
+
+out:
+ bpf_map__unpin(call->maps.jmp_table, JMP_TABLE);
+ tailcall_poke__destroy(call);
+}
diff --git a/tools/testing/selftests/bpf/progs/tailcall_poke.c b/tools/testing/selftests/bpf/progs/tailcall_poke.c
new file mode 100644
index 000000000000..c78b94b75e83
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tailcall_poke.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+ __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+ __uint(max_entries, 1);
+ __uint(key_size, sizeof(__u32));
+ __uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+SEC("?fentry/bpf_fentry_test1")
+int BPF_PROG(test, int a)
+{
+ bpf_tail_call_static(ctx, &jmp_table, 0);
+ return 0;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(call1, int a)
+{
+ return 0;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(call2, int a)
+{
+ return 0;
+}
