[PATCHv2 bpf-next 0/2] selftests/bpf: Add more uprobe multi tests

[PATCHv2 bpf-next 0/2] selftests/bpf: Add more uprobe multi tests

[Jiri Olsa]

hi,
adding more uprobe multi tests for failed attachments
inside the uprobe register code.

v2 changes:
  - addressed review comments [Andrii]
  - added new test

thanks,
jirka


---
Jiri Olsa (2):
      selftests/bpf: Add uprobe fail tests for uprobe multi
      selftests/bpf: Add uprobe multi consumers test

 tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c | 318 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/uprobe_multi_consumers.c |  39 ++++++++++++
 2 files changed, 357 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/uprobe_multi_consumers.c

[PATCHv2 bpf-next 1/2] selftests/bpf: Add uprobe fail tests for uprobe multi

[Jiri Olsa]

Addig tests for checking on recovery after failing to
attach uprobe.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../bpf/prog_tests/uprobe_multi_test.c        | 109 ++++++++++++++++++
 1 file changed, 109 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
index bf6ca8e3eb13..da8873f24a53 100644
--- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
@@ -516,6 +516,113 @@ static void test_attach_api_fails(void)
 	uprobe_multi__destroy(skel);
 }
 
+#ifdef __x86_64__
+noinline __attribute__((naked)) void uprobe_multi_error_func(void)
+{
+	asm volatile ("int3");
+}
+
+/*
+ * Attaching uprobe on uprobe_multi_error_func results in error
+ * because it already starts with int3 instruction.
+ */
+static void attach_uprobe_fail_trap(struct uprobe_multi *skel)
+{
+	LIBBPF_OPTS(bpf_uprobe_multi_opts, opts);
+	const char *syms[4] = {
+		"uprobe_multi_func_1",
+		"uprobe_multi_func_2",
+		"uprobe_multi_func_3",
+		"uprobe_multi_error_func",
+	};
+
+	opts.syms = syms;
+	opts.cnt = ARRAY_SIZE(syms);
+
+	skel->links.uprobe = bpf_program__attach_uprobe_multi(skel->progs.uprobe, -1,
+							      "/proc/self/exe", NULL, &opts);
+	if (!ASSERT_ERR_PTR(skel->links.uprobe, "bpf_program__attach_uprobe_multi")) {
+		bpf_link__destroy(skel->links.uprobe);
+		skel->links.uprobe = NULL;
+	}
+}
+#else
+static void attach_uprobe_fail_trap(struct uprobe_multi *skel) { }
+#endif
+
+static short sema_1 __maybe_unused, sema_2 __maybe_unused;
+
+static void attach_uprobe_fail_refctr(struct uprobe_multi *skel)
+{
+	unsigned long *tmp_offsets = NULL, *tmp_ref_ctr_offsets = NULL;
+	unsigned long offsets[3], ref_ctr_offsets[3];
+	LIBBPF_OPTS(bpf_link_create_opts, opts);
+	const char *path = "/proc/self/exe";
+	const char *syms[3] = {
+		"uprobe_multi_func_1",
+		"uprobe_multi_func_2",
+	};
+	const char *sema[3] = {
+		"sema_1",
+		"sema_2",
+	};
+	int prog_fd, link_fd, err;
+
+	prog_fd = bpf_program__fd(skel->progs.uprobe_extra);
+
+	err = elf_resolve_syms_offsets("/proc/self/exe", 2, (const char **) &syms,
+				       &tmp_offsets, STT_FUNC);
+	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_func"))
+		return;
+
+	err = elf_resolve_syms_offsets("/proc/self/exe", 2, (const char **) &sema,
+				       &tmp_ref_ctr_offsets, STT_OBJECT);
+	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_sema"))
+		goto cleanup;
+
+	/*
+	 * We attach to 3 uprobes on 2 functions so 2 uprobes share single function,
+	 * but with different ref_ctr_offset which is not allowed and results in fail.
+	 */
+	offsets[0] = tmp_offsets[0]; /* uprobe_multi_func_1 */
+	offsets[1] = tmp_offsets[1]; /* uprobe_multi_func_2 */
+	offsets[2] = tmp_offsets[1]; /* uprobe_multi_func_2 */
+
+	ref_ctr_offsets[0] = tmp_ref_ctr_offsets[0]; /* sema_1 */
+	ref_ctr_offsets[1] = tmp_ref_ctr_offsets[1]; /* sema_2 */
+	ref_ctr_offsets[2] = tmp_ref_ctr_offsets[0]; /* sema_1, error */
+
+	opts.uprobe_multi.path = path;
+	opts.uprobe_multi.offsets = (const unsigned long *) &offsets;
+	opts.uprobe_multi.ref_ctr_offsets = (const unsigned long *) &ref_ctr_offsets;
+	opts.uprobe_multi.cnt = 3;
+
+	link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_UPROBE_MULTI, &opts);
+	if (!ASSERT_ERR(link_fd, "link_fd"))
+		close(link_fd);
+
+cleanup:
+	free(tmp_ref_ctr_offsets);
+	free(tmp_offsets);
+}
+
+static void test_attach_uprobe_fails(void)
+{
+	struct uprobe_multi *skel = NULL;
+
+	skel = uprobe_multi__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "uprobe_multi__open_and_load"))
+		return;
+
+	/* attach fails due to adding uprobe on trap instruction, x86_64 only */
+	attach_uprobe_fail_trap(skel);
+
+	/* attach fail due to wrong ref_ctr_offs on one of the uprobes */
+	attach_uprobe_fail_refctr(skel);
+
+	uprobe_multi__destroy(skel);
+}
+
 static void __test_link_api(struct child *child)
 {
 	int prog_fd, link1_fd = -1, link2_fd = -1, link3_fd = -1, link4_fd = -1;
@@ -703,4 +810,6 @@ void test_uprobe_multi_test(void)
 		test_bench_attach_usdt();
 	if (test__start_subtest("attach_api_fails"))
 		test_attach_api_fails();
+	if (test__start_subtest("attach_uprobe_fails"))
+		test_attach_uprobe_fails();
 }
-- 
2.45.2

Re: [PATCHv2 bpf-next 1/2] selftests/bpf: Add uprobe fail tests for uprobe multi

[Andrii Nakryiko]

On Thu, Jul 18, 2024 at 6:28 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Addig tests for checking on recovery after failing to

typo: Adding

> attach uprobe.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  .../bpf/prog_tests/uprobe_multi_test.c        | 109 ++++++++++++++++++
>  1 file changed, 109 insertions(+)
>

LGTM, thanks for adding these failing test cases! CI is failing, so
please check what's wrong

pw-bot: cr

> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> index bf6ca8e3eb13..da8873f24a53 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> @@ -516,6 +516,113 @@ static void test_attach_api_fails(void)
>         uprobe_multi__destroy(skel);
>  }
>

[...]

[PATCHv2 bpf-next 2/2] selftests/bpf: Add uprobe multi consumers test

[Jiri Olsa]

Adding test that attached/detaches multiple consumers on
single uprobe and verifies all were hit as expected.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../bpf/prog_tests/uprobe_multi_test.c        | 211 +++++++++++++++++-
 .../bpf/progs/uprobe_multi_consumers.c        |  39 ++++
 2 files changed, 249 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/uprobe_multi_consumers.c

diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
index da8873f24a53..5228085c2240 100644
--- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
@@ -6,6 +6,7 @@
 #include "uprobe_multi.skel.h"
 #include "uprobe_multi_bench.skel.h"
 #include "uprobe_multi_usdt.skel.h"
+#include "uprobe_multi_consumers.skel.h"
 #include "bpf/libbpf_internal.h"
 #include "testing_helpers.h"
 #include "../sdt.h"
@@ -581,7 +582,7 @@ static void attach_uprobe_fail_refctr(struct uprobe_multi *skel)
 		goto cleanup;
 
 	/*
-	 * We attach to 3 uprobes on 2 functions so 2 uprobes share single function,
+	 * We attach to 3 uprobes on 2 functions, so 2 uprobes share single function,
 	 * but with different ref_ctr_offset which is not allowed and results in fail.
 	 */
 	offsets[0] = tmp_offsets[0]; /* uprobe_multi_func_1 */
@@ -722,6 +723,212 @@ static void test_link_api(void)
 	__test_link_api(child);
 }
 
+static struct bpf_program *
+get_program(struct uprobe_multi_consumers *skel, int prog)
+{
+	switch (prog) {
+	case 0:
+		return skel->progs.uprobe_0;
+	case 1:
+		return skel->progs.uprobe_1;
+	case 2:
+		return skel->progs.uprobe_2;
+	case 3:
+		return skel->progs.uprobe_3;
+	default:
+		ASSERT_FAIL("get_program");
+		return NULL;
+	}
+}
+
+static struct bpf_link **
+get_link(struct uprobe_multi_consumers *skel, int link)
+{
+	switch (link) {
+	case 0:
+		return &skel->links.uprobe_0;
+	case 1:
+		return &skel->links.uprobe_1;
+	case 2:
+		return &skel->links.uprobe_2;
+	case 3:
+		return &skel->links.uprobe_3;
+	default:
+		ASSERT_FAIL("get_link");
+		return NULL;
+	}
+}
+
+static int uprobe_attach(struct uprobe_multi_consumers *skel, int idx)
+{
+	struct bpf_program *prog = get_program(skel, idx);
+	struct bpf_link **link = get_link(skel, idx);
+	LIBBPF_OPTS(bpf_uprobe_multi_opts, opts);
+
+	/*
+	 * bit/prog: 0,1 uprobe entry
+	 * bit/prog: 2,3 uprobe return
+	 */
+	opts.retprobe = idx == 2 || idx == 3;
+
+	*link = bpf_program__attach_uprobe_multi(prog, 0, "/proc/self/exe",
+						"uprobe_session_consumer_test",
+						&opts);
+	if (!ASSERT_OK_PTR(*link, "bpf_program__attach_uprobe_multi"))
+		return -1;
+	return 0;
+}
+
+static void uprobe_detach(struct uprobe_multi_consumers *skel, int idx)
+{
+	struct bpf_link **link = get_link(skel, idx);
+
+	bpf_link__destroy(*link);
+	*link = NULL;
+}
+
+static bool test_bit(int bit, unsigned long val)
+{
+	return val & (1 << bit);
+}
+
+noinline int
+uprobe_session_consumer_test(struct uprobe_multi_consumers *skel,
+			     unsigned long before, unsigned long after)
+{
+	int idx;
+
+	/* detach uprobe for each unset programs in 'before' state ... */
+	for (idx = 0; idx < 4; idx++) {
+		if (test_bit(idx, before) && !test_bit(idx, after))
+			uprobe_detach(skel, idx);
+	}
+
+	/* ... and attach all new programs in 'after' state */
+	for (idx = 0; idx < 4; idx++) {
+		if (!test_bit(idx, before) && test_bit(idx, after)) {
+			if (!ASSERT_OK(uprobe_attach(skel, idx), "uprobe_attach_after"))
+				return -1;
+		}
+	}
+	return 0;
+}
+
+static void session_consumer_test(struct uprobe_multi_consumers *skel,
+				  unsigned long before, unsigned long after)
+{
+	int err, idx;
+
+	printf("session_consumer_test before %lu after %lu\n", before, after);
+
+	/* 'before' is each, we attach uprobe for every set idx */
+	for (idx = 0; idx < 4; idx++) {
+		if (test_bit(idx, before)) {
+			if (!ASSERT_OK(uprobe_attach(skel, idx), "uprobe_attach_before"))
+				goto cleanup;
+		}
+	}
+
+	err = uprobe_session_consumer_test(skel, before, after);
+	if (!ASSERT_EQ(err, 0, "uprobe_session_consumer_test"))
+		goto cleanup;
+
+	for (idx = 0; idx < 4; idx++) {
+		const char *fmt = "BUG";
+		__u64 val = 0;
+
+		if (idx < 2) {
+			/*
+			 * uprobe entry
+			 *   +1 if define in 'before'
+			 */
+			if (test_bit(idx, before))
+				val++;
+			fmt = "prog 0/1: uprobe";
+		} else {
+			/* uprobe return is tricky ;-)
+			 *
+			 * to trigger uretprobe consumer, the uretprobe needs to be installed,
+			 * which means one of the 'return' uprobes was alive when probe was hit:
+			 *
+			 *   idxs: 2/3 uprobe return in 'installed' mask
+			 *
+			 * in addition if 'after' state removes everything that was installed in
+			 * 'before' state, then uprobe kernel object goes away and return uprobe
+			 * is not installed and we won't hit it even if it's in 'after' state.
+			 */
+			unsigned long installed = before & 0b1100; // is uretprobe installed
+			unsigned long exists    = before & after;  // did uprobe go away
+
+			if (installed && exists && test_bit(idx, after))
+				val++;
+			fmt = "idx 2/3: uretprobe";
+		}
+
+		ASSERT_EQ(skel->bss->uprobe_result[idx], val, fmt);
+		skel->bss->uprobe_result[idx] = 0;
+	}
+
+cleanup:
+	for (idx = 0; idx < 4; idx++)
+		uprobe_detach(skel, idx);
+}
+
+static void test_consumers(void)
+{
+	struct uprobe_multi_consumers *skel;
+	int before, after;
+
+	skel = uprobe_multi_consumers__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "uprobe_multi_consumers__open_and_load"))
+		return;
+
+	/*
+	 * The idea of this test is to try all possible combinations of
+	 * uprobes consumers attached on single function.
+	 *
+	 *  - 2 uprobe entry consumer
+	 *  - 2 uprobe exit consumers
+	 *
+	 * The test uses 4 uprobes attached on single function, but that
+	 * translates into single uprobe with 4 consumers in kernel.
+	 *
+	 * The before/after values present the state of attached consumers
+	 * before and after the probed function:
+	 *
+	 *  bit/prog 0,1 : uprobe entry
+	 *  bit/prog 2,3 : uprobe return
+	 *
+	 * For example for:
+	 *
+	 *   before = 0b0101
+	 *   after  = 0b0110
+	 *
+	 * it means that before we call 'uprobe_session_consumer_test' we
+	 * attach uprobes defined in 'before' value:
+	 *
+	 *   - bit/prog 0: uprobe entry
+	 *   - bit/prog 2: uprobe return
+	 *
+	 * uprobe_session_consumer_test is called and inside it we attach
+	 * and detach * uprobes based on 'after' value:
+	 *
+	 *   - bit/prog 0: stays untouched
+	 *   - bit/prog 2: uprobe return is detached
+	 *
+	 * uprobe_session_consumer_test returns and we check counters values
+	 * increased by bpf programs on each uprobe to match the expected
+	 * count based on before/after bits.
+	 */
+
+	for (before = 0; before < 16; before++) {
+		for (after = 0; after < 16; after++)
+			session_consumer_test(skel, before, after);
+	}
+
+	uprobe_multi_consumers__destroy(skel);
+}
+
 static void test_bench_attach_uprobe(void)
 {
 	long attach_start_ns = 0, attach_end_ns = 0;
@@ -812,4 +1019,6 @@ void test_uprobe_multi_test(void)
 		test_attach_api_fails();
 	if (test__start_subtest("attach_uprobe_fails"))
 		test_attach_uprobe_fails();
+	if (test__start_subtest("consumers"))
+		test_consumers();
 }
diff --git a/tools/testing/selftests/bpf/progs/uprobe_multi_consumers.c b/tools/testing/selftests/bpf/progs/uprobe_multi_consumers.c
new file mode 100644
index 000000000000..7e0fdcbbd242
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/uprobe_multi_consumers.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <stdbool.h>
+#include "bpf_kfuncs.h"
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+__u64 uprobe_result[4];
+
+SEC("uprobe.multi")
+int uprobe_0(struct pt_regs *ctx)
+{
+	uprobe_result[0]++;
+	return 0;
+}
+
+SEC("uprobe.multi")
+int uprobe_1(struct pt_regs *ctx)
+{
+	uprobe_result[1]++;
+	return 0;
+}
+
+SEC("uprobe.multi")
+int uprobe_2(struct pt_regs *ctx)
+{
+	uprobe_result[2]++;
+	return 0;
+}
+
+SEC("uprobe.multi")
+int uprobe_3(struct pt_regs *ctx)
+{
+	uprobe_result[3]++;
+	return 0;
+}
-- 
2.45.2

Re: [PATCHv2 bpf-next 2/2] selftests/bpf: Add uprobe multi consumers test

[Andrii Nakryiko]

On Thu, Jul 18, 2024 at 6:28 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding test that attached/detaches multiple consumers on

typo: attaches

> single uprobe and verifies all were hit as expected.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  .../bpf/prog_tests/uprobe_multi_test.c        | 211 +++++++++++++++++-
>  .../bpf/progs/uprobe_multi_consumers.c        |  39 ++++
>  2 files changed, 249 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/bpf/progs/uprobe_multi_consumers.c
>

LGTM, took me a bit of extra time to validate the counting logic, but
it looks correct.

> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> index da8873f24a53..5228085c2240 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> @@ -6,6 +6,7 @@
>  #include "uprobe_multi.skel.h"
>  #include "uprobe_multi_bench.skel.h"
>  #include "uprobe_multi_usdt.skel.h"
> +#include "uprobe_multi_consumers.skel.h"
>  #include "bpf/libbpf_internal.h"
>  #include "testing_helpers.h"
>  #include "../sdt.h"
> @@ -581,7 +582,7 @@ static void attach_uprobe_fail_refctr(struct uprobe_multi *skel)
>                 goto cleanup;
>
>         /*
> -        * We attach to 3 uprobes on 2 functions so 2 uprobes share single function,
> +        * We attach to 3 uprobes on 2 functions, so 2 uprobes share single function,

this probably belongs in patch #1

>          * but with different ref_ctr_offset which is not allowed and results in fail.
>          */
>         offsets[0] = tmp_offsets[0]; /* uprobe_multi_func_1 */
> @@ -722,6 +723,212 @@ static void test_link_api(void)
>         __test_link_api(child);
>  }
>
> +static struct bpf_program *
> +get_program(struct uprobe_multi_consumers *skel, int prog)
> +{
> +       switch (prog) {
> +       case 0:
> +               return skel->progs.uprobe_0;
> +       case 1:
> +               return skel->progs.uprobe_1;
> +       case 2:
> +               return skel->progs.uprobe_2;
> +       case 3:
> +               return skel->progs.uprobe_3;
> +       default:
> +               ASSERT_FAIL("get_program");
> +               return NULL;
> +       }
> +}
> +
> +static struct bpf_link **
> +get_link(struct uprobe_multi_consumers *skel, int link)
> +{
> +       switch (link) {
> +       case 0:
> +               return &skel->links.uprobe_0;
> +       case 1:
> +               return &skel->links.uprobe_1;
> +       case 2:
> +               return &skel->links.uprobe_2;
> +       case 3:
> +               return &skel->links.uprobe_3;
> +       default:
> +               ASSERT_FAIL("get_link");
> +               return NULL;
> +       }
> +}
> +
> +static int uprobe_attach(struct uprobe_multi_consumers *skel, int idx)
> +{
> +       struct bpf_program *prog = get_program(skel, idx);
> +       struct bpf_link **link = get_link(skel, idx);
> +       LIBBPF_OPTS(bpf_uprobe_multi_opts, opts);
> +
> +       /*
> +        * bit/prog: 0,1 uprobe entry
> +        * bit/prog: 2,3 uprobe return
> +        */
> +       opts.retprobe = idx == 2 || idx == 3;
> +
> +       *link = bpf_program__attach_uprobe_multi(prog, 0, "/proc/self/exe",


this will crash if idx is wrong, let's add explicit NULL checks for
link and prog, just to fail gracefully?


> +                                               "uprobe_session_consumer_test",
> +                                               &opts);
> +       if (!ASSERT_OK_PTR(*link, "bpf_program__attach_uprobe_multi"))
> +               return -1;
> +       return 0;
> +}
> +
> +static void uprobe_detach(struct uprobe_multi_consumers *skel, int idx)
> +{
> +       struct bpf_link **link = get_link(skel, idx);
> +
> +       bpf_link__destroy(*link);
> +       *link = NULL;
> +}
> +
> +static bool test_bit(int bit, unsigned long val)
> +{
> +       return val & (1 << bit);
> +}
> +
> +noinline int
> +uprobe_session_consumer_test(struct uprobe_multi_consumers *skel,

this gave me pause, I was frantically recalling when did we end up
landing uprobe sessions support :)


> +                            unsigned long before, unsigned long after)
> +{
> +       int idx;
> +
> +       /* detach uprobe for each unset programs in 'before' state ... */
> +       for (idx = 0; idx < 4; idx++) {
> +               if (test_bit(idx, before) && !test_bit(idx, after))
> +                       uprobe_detach(skel, idx);
> +       }
> +
> +       /* ... and attach all new programs in 'after' state */
> +       for (idx = 0; idx < 4; idx++) {
> +               if (!test_bit(idx, before) && test_bit(idx, after)) {
> +                       if (!ASSERT_OK(uprobe_attach(skel, idx), "uprobe_attach_after"))
> +                               return -1;
> +               }
> +       }
> +       return 0;
> +}
> +
> +static void session_consumer_test(struct uprobe_multi_consumers *skel,
> +                                 unsigned long before, unsigned long after)
> +{
> +       int err, idx;
> +
> +       printf("session_consumer_test before %lu after %lu\n", before, after);
> +
> +       /* 'before' is each, we attach uprobe for every set idx */
> +       for (idx = 0; idx < 4; idx++) {
> +               if (test_bit(idx, before)) {
> +                       if (!ASSERT_OK(uprobe_attach(skel, idx), "uprobe_attach_before"))
> +                               goto cleanup;
> +               }
> +       }
> +
> +       err = uprobe_session_consumer_test(skel, before, after);
> +       if (!ASSERT_EQ(err, 0, "uprobe_session_consumer_test"))
> +               goto cleanup;
> +
> +       for (idx = 0; idx < 4; idx++) {
> +               const char *fmt = "BUG";
> +               __u64 val = 0;
> +
> +               if (idx < 2) {
> +                       /*
> +                        * uprobe entry
> +                        *   +1 if define in 'before'
> +                        */
> +                       if (test_bit(idx, before))
> +                               val++;
> +                       fmt = "prog 0/1: uprobe";
> +               } else {
> +                       /* uprobe return is tricky ;-)
> +                        *
> +                        * to trigger uretprobe consumer, the uretprobe needs to be installed,
> +                        * which means one of the 'return' uprobes was alive when probe was hit:
> +                        *
> +                        *   idxs: 2/3 uprobe return in 'installed' mask
> +                        *
> +                        * in addition if 'after' state removes everything that was installed in
> +                        * 'before' state, then uprobe kernel object goes away and return uprobe
> +                        * is not installed and we won't hit it even if it's in 'after' state.
> +                        */

yeah, this is tricky, thanks for writing this out, seems correct to me

> +                       unsigned long installed = before & 0b1100; // is uretprobe installed
> +                       unsigned long exists    = before & after;  // did uprobe go away
> +
> +                       if (installed && exists && test_bit(idx, after))

nit: naming didn't really help (actually probably hurt the analysis).
installed is whether we had any uretprobes, so "had_uretprobes"?
exists is whether uprobe stayed attached during function call, right,
so maybe "probe_preserved" or something like that?

I.e., the condition should say "if we had any uretprobes, and the
probe instance stayed alive, and the program is still attached at
return".

> +                               val++;
> +                       fmt = "idx 2/3: uretprobe";
> +               }
> +
> +               ASSERT_EQ(skel->bss->uprobe_result[idx], val, fmt);
> +               skel->bss->uprobe_result[idx] = 0;
> +       }
> +
> +cleanup:
> +       for (idx = 0; idx < 4; idx++)
> +               uprobe_detach(skel, idx);
> +}
> +

[...]

Re: [PATCHv2 bpf-next 2/2] selftests/bpf: Add uprobe multi consumers test

[Jiri Olsa]

On Fri, Jul 19, 2024 at 10:58:07AM -0700, Andrii Nakryiko wrote:
> On Thu, Jul 18, 2024 at 6:28 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding test that attached/detaches multiple consumers on
> 
> typo: attaches
> 
> > single uprobe and verifies all were hit as expected.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  .../bpf/prog_tests/uprobe_multi_test.c        | 211 +++++++++++++++++-
> >  .../bpf/progs/uprobe_multi_consumers.c        |  39 ++++
> >  2 files changed, 249 insertions(+), 1 deletion(-)
> >  create mode 100644 tools/testing/selftests/bpf/progs/uprobe_multi_consumers.c
> >
> 
> LGTM, took me a bit of extra time to validate the counting logic, but
> it looks correct.
> 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> > index da8873f24a53..5228085c2240 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> > @@ -6,6 +6,7 @@
> >  #include "uprobe_multi.skel.h"
> >  #include "uprobe_multi_bench.skel.h"
> >  #include "uprobe_multi_usdt.skel.h"
> > +#include "uprobe_multi_consumers.skel.h"
> >  #include "bpf/libbpf_internal.h"
> >  #include "testing_helpers.h"
> >  #include "../sdt.h"
> > @@ -581,7 +582,7 @@ static void attach_uprobe_fail_refctr(struct uprobe_multi *skel)
> >                 goto cleanup;
> >
> >         /*
> > -        * We attach to 3 uprobes on 2 functions so 2 uprobes share single function,
> > +        * We attach to 3 uprobes on 2 functions, so 2 uprobes share single function,
> 
> this probably belongs in patch #1

ugh yep

SNIP

> > +static int uprobe_attach(struct uprobe_multi_consumers *skel, int idx)
> > +{
> > +       struct bpf_program *prog = get_program(skel, idx);
> > +       struct bpf_link **link = get_link(skel, idx);
> > +       LIBBPF_OPTS(bpf_uprobe_multi_opts, opts);
> > +
> > +       /*
> > +        * bit/prog: 0,1 uprobe entry
> > +        * bit/prog: 2,3 uprobe return
> > +        */
> > +       opts.retprobe = idx == 2 || idx == 3;
> > +
> > +       *link = bpf_program__attach_uprobe_multi(prog, 0, "/proc/self/exe",
> 
> 
> this will crash if idx is wrong, let's add explicit NULL checks for
> link and prog, just to fail gracefully?

ok

> 
> 
> > +                                               "uprobe_session_consumer_test",
> > +                                               &opts);
> > +       if (!ASSERT_OK_PTR(*link, "bpf_program__attach_uprobe_multi"))
> > +               return -1;
> > +       return 0;
> > +}
> > +
> > +static void uprobe_detach(struct uprobe_multi_consumers *skel, int idx)
> > +{
> > +       struct bpf_link **link = get_link(skel, idx);
> > +
> > +       bpf_link__destroy(*link);
> > +       *link = NULL;
> > +}
> > +
> > +static bool test_bit(int bit, unsigned long val)
> > +{
> > +       return val & (1 << bit);
> > +}
> > +
> > +noinline int
> > +uprobe_session_consumer_test(struct uprobe_multi_consumers *skel,
> 
> this gave me pause, I was frantically recalling when did we end up
> landing uprobe sessions support :)

rename leftover sry ;-)


SNIP

> > +               } else {
> > +                       /* uprobe return is tricky ;-)
> > +                        *
> > +                        * to trigger uretprobe consumer, the uretprobe needs to be installed,
> > +                        * which means one of the 'return' uprobes was alive when probe was hit:
> > +                        *
> > +                        *   idxs: 2/3 uprobe return in 'installed' mask
> > +                        *
> > +                        * in addition if 'after' state removes everything that was installed in
> > +                        * 'before' state, then uprobe kernel object goes away and return uprobe
> > +                        * is not installed and we won't hit it even if it's in 'after' state.
> > +                        */
> 
> yeah, this is tricky, thanks for writing this out, seems correct to me
> 
> > +                       unsigned long installed = before & 0b1100; // is uretprobe installed
> > +                       unsigned long exists    = before & after;  // did uprobe go away
> > +
> > +                       if (installed && exists && test_bit(idx, after))
> 
> nit: naming didn't really help (actually probably hurt the analysis).
> installed is whether we had any uretprobes, so "had_uretprobes"?
> exists is whether uprobe stayed attached during function call, right,
> so maybe "probe_preserved" or something like that?
> 
> I.e., the condition should say "if we had any uretprobes, and the
> probe instance stayed alive, and the program is still attached at
> return".

yep, looks much better, will rename, thanks

jirka

> 
> > +                               val++;
> > +                       fmt = "idx 2/3: uretprobe";
> > +               }
> > +
> > +               ASSERT_EQ(skel->bss->uprobe_result[idx], val, fmt);
> > +               skel->bss->uprobe_result[idx] = 0;
> > +       }
> > +
> > +cleanup:
> > +       for (idx = 0; idx < 4; idx++)
> > +               uprobe_detach(skel, idx);
> > +}
> > +
> 
> [...]