selftests/bpf: Add kprobe write ctx attach test

Adding test to check we can't attach standard kprobe program that
writes to the context.

It's x86_64 specific test.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20250916215301.664963-6-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index cabc51c2ca6bd5c6d291e44c27e7ad923b3e455f..9e77e5da7097c3dc9c40c08ac752c13299b4fbce 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
@@ -3,6 +3,7 @@
 #include "test_attach_kprobe_sleepable.skel.h"
 #include "test_attach_probe_manual.skel.h"
 #include "test_attach_probe.skel.h"
+#include "kprobe_write_ctx.skel.h"
 
 /* this is how USDT semaphore is actually defined, except volatile modifier */
 volatile unsigned short uprobe_ref_ctr __attribute__((unused)) __attribute((section(".probes")));
@@ -201,6 +202,31 @@ cleanup:
        test_attach_probe_manual__destroy(skel);
 }
 
+#ifdef __x86_64__
+/* attach kprobe/kretprobe long event name testings */
+static void test_attach_kprobe_write_ctx(void)
+{
+       struct kprobe_write_ctx *skel = NULL;
+       struct bpf_link *link = NULL;
+
+       skel = kprobe_write_ctx__open_and_load();
+       if (!ASSERT_OK_PTR(skel, "kprobe_write_ctx__open_and_load"))
+               return;
+
+       link = bpf_program__attach_kprobe_opts(skel->progs.kprobe_write_ctx,
+                                            "bpf_fentry_test1", NULL);
+       if (!ASSERT_ERR_PTR(link, "bpf_program__attach_kprobe_opts"))
+               bpf_link__destroy(link);
+
+       kprobe_write_ctx__destroy(skel);
+}
+#else
+static void test_attach_kprobe_write_ctx(void)
+{
+       test__skip();
+}
+#endif
+
 static void test_attach_probe_auto(struct test_attach_probe *skel)
 {
        struct bpf_link *uprobe_err_link;
@@ -406,6 +432,8 @@ void test_attach_probe(void)
                test_attach_uprobe_long_event_name();
        if (test__start_subtest("kprobe-long_name"))
                test_attach_kprobe_long_event_name();
+       if (test__start_subtest("kprobe-write-ctx"))
+               test_attach_kprobe_write_ctx();
 
 cleanup:
        test_attach_probe__destroy(skel);

diff --git a/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c b/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c
new file mode 100644 (file)
index 0000000..4621a5b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c
@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+#if defined(__TARGET_ARCH_x86)
+SEC("kprobe")
+int kprobe_write_ctx(struct pt_regs *ctx)
+{
+       ctx->ax = 0;
+       return 0;
+}
+#endif