On 10/30/24 4:29 PM, Tejun Heo wrote:
Hello,
On Tue, Oct 29, 2024 at 03:17:23PM -0700, Yonghong Song wrote:
The third test is the same callback function recursing itself. At run time,
the jit trampoline recursion check kicks in to prevent the recursion.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 94 ++++++++++++++++
.../selftests/bpf/bpf_testmod/bpf_testmod.h | 5 +
.../bpf/prog_tests/struct_ops_private_stack.c | 106 ++++++++++++++++++
.../bpf/progs/struct_ops_private_stack.c | 62 ++++++++++
.../bpf/progs/struct_ops_private_stack_fail.c | 62 ++++++++++
.../progs/struct_ops_private_stack_recur.c | 50 +++++++++
6 files changed, 379 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/struct_ops_private_stack.c
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_private_stack.c
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_private_stack_fail.c
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_private_stack_recur.c
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 8835761d9a12..eb761645551a 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
...
+__bpf_kfunc void bpf_testmod_ops3_call_test_1(void)
+{
+ st_ops3->test_1();
+}
...
diff --git a/tools/testing/selftests/bpf/prog_tests/struct_ops_private_stack.c b/tools/testing/selftests/bpf/prog_tests/struct_ops_private_stack.c
new file mode 100644
index 000000000000..4006879ca3fe
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/struct_ops_private_stack.c
...
+static void test_private_stack_recur(void)
+{
+ struct struct_ops_private_stack_recur *skel;
+ struct bpf_link *link;
+ int err;
+
+ skel = struct_ops_private_stack_recur__open();
+ if (!ASSERT_OK_PTR(skel, "struct_ops_private_stack_recur__open"))
+ return;
+
+ if (skel->data->skip) {
+ test__skip();
+ goto cleanup;
+ }
+
+ err = struct_ops_private_stack_recur__load(skel);
+ if (!ASSERT_OK(err, "struct_ops_private_stack_recur__load"))
+ goto cleanup;
+
+ link = bpf_map__attach_struct_ops(skel->maps.testmod_1);
+ if (!ASSERT_OK_PTR(link, "attach_struct_ops"))
+ goto cleanup;
+
+ ASSERT_OK(trigger_module_test_read(256), "trigger_read");
+
+ ASSERT_EQ(skel->bss->val_j, 3, "val_j");
+
+ bpf_link__destroy(link);
+
+cleanup:
+ struct_ops_private_stack_recur__destroy(skel);
+}
...
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_private_stack_recur.c b/tools/testing/selftests/bpf/progs/struct_ops_private_stack_recur.c
new file mode 100644
index 000000000000..15d4e914dc92
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/struct_ops_private_stack_recur.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+#if defined(__TARGET_ARCH_x86)
+bool skip __attribute((__section__(".data"))) = false;
+#else
+bool skip = true;
+#endif
+
+void bpf_testmod_ops3_call_test_1(void) __ksym;
+
+int val_i, val_j;
+
+__noinline static int subprog2(int *a, int *b)
+{
+ return val_i + a[10] + b[20];
+}
+
+__noinline static int subprog1(int *a)
+{
+ /* stack size 400 bytes */
+ int b[100] = {};
+
+ b[20] = 2;
+ return subprog2(a, b);
+}
+
+
+SEC("struct_ops")
+int BPF_PROG(test_1)
+{
+ /* stack size 400 bytes */
+ int a[100] = {};
+
+ a[10] = 1;
+ val_j += subprog1(a);
+ bpf_testmod_ops3_call_test_1();
+ return 0;
+}
+
+SEC(".struct_ops")
+struct bpf_testmod_ops3 testmod_1 = {
+ .test_1 = (void *)test_1,
+};
This is delta, and, while this shouldn't happen for SCX, it'd be great if
SCX can tell BPF to call a function when recursion check triggers and
ignores a call, so that SCX can trigger error, report it and eject the
scheduler.
I had an offline discussion with Tejun. A callback function like
prog->aux->recursion_skipped(prog)
will be provided and if not null the function will be called whenever
a recursion skip happens.
The subsystem requires to define recursion_skipped
callback function and assign it to prog->aux->recursion_skipped if necessary,
if it want to get some error information back.
Thanks.
