linux-kernel - [PATCH 2/2] selftest/bpf: Test returning zero from a perf bpf program suppresses SIGIO.

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Message-Id: <20231204201406.341074-3-khuey@kylehuey.com>
Date:   Mon,  4 Dec 2023 12:14:06 -0800
From:   Kyle Huey <me@...ehuey.com>
To:     Kyle Huey <khuey@...ehuey.com>, linux-kernel@...r.kernel.org
Cc:     Robert O'Callahan <robert@...llahan.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Mykola Lysenko <mykolal@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Shuah Khan <shuah@...nel.org>, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: [PATCH 2/2] selftest/bpf: Test returning zero from a perf bpf program suppresses SIGIO.

The test sets a hardware breakpoint and uses a bpf program to suppress the
I/O availability signal if the ip matches the expected value.

Signed-off-by: Kyle Huey <khuey@...ehuey.com>
---
 .../selftests/bpf/prog_tests/perf_skip.c      | 95 +++++++++++++++++++
 .../selftests/bpf/progs/test_perf_skip.c      | 23 +++++
 2 files changed, 118 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_skip.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_perf_skip.c

diff --git a/tools/testing/selftests/bpf/prog_tests/perf_skip.c b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
new file mode 100644
index 000000000000..b269a31669b7
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/perf_skip.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <test_progs.h>
+#include "test_perf_skip.skel.h"
+#include <linux/hw_breakpoint.h>
+#include <sys/mman.h>
+
+#define BPF_OBJECT            "test_perf_skip.bpf.o"
+
+static void handle_sig(int)
+{
+	ASSERT_OK(1, "perf event not skipped");
+}
+
+static noinline int test_function(void)
+{
+	return 0;
+}
+
+void serial_test_perf_skip(void)
+{
+	sighandler_t previous;
+	int duration = 0;
+	struct test_perf_skip *skel = NULL;
+	int map_fd = -1;
+	long page_size = sysconf(_SC_PAGE_SIZE);
+	uintptr_t *ip = NULL;
+	int prog_fd = -1;
+	struct perf_event_attr attr = {0};
+	int perf_fd = -1;
+	struct f_owner_ex owner;
+	int err;
+
+	previous = signal(SIGIO, handle_sig);
+
+	skel = test_perf_skip__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.handler);
+	if (!ASSERT_OK(prog_fd < 0, "bpf_program__fd"))
+		goto cleanup;
+
+	map_fd = bpf_map__fd(skel->maps.ip);
+	if (!ASSERT_OK(map_fd < 0, "bpf_map__fd"))
+		goto cleanup;
+
+	ip = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
+	if (!ASSERT_OK_PTR(ip, "mmap bpf map"))
+		goto cleanup;
+
+	*ip = (uintptr_t)test_function;
+
+	attr.type = PERF_TYPE_BREAKPOINT;
+	attr.size = sizeof(attr);
+	attr.bp_type = HW_BREAKPOINT_X;
+	attr.bp_addr = (uintptr_t)test_function;
+	attr.bp_len = sizeof(long);
+	attr.sample_period = 1;
+	attr.sample_type = PERF_SAMPLE_IP;
+	attr.pinned = 1;
+	attr.exclude_kernel = 1;
+	attr.exclude_hv = 1;
+	attr.precise_ip = 3;
+
+	perf_fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
+	if (CHECK(perf_fd < 0, "perf_event_open", "err %d\n", perf_fd))
+		goto cleanup;
+
+	err = fcntl(perf_fd, F_SETFL, O_ASYNC);
+	if (!ASSERT_OK(err, "fcntl(F_SETFL, O_ASYNC)"))
+		goto cleanup;
+
+	owner.type = F_OWNER_TID;
+	owner.pid = gettid();
+	err = fcntl(perf_fd, F_SETOWN_EX, &owner);
+	if (!ASSERT_OK(err, "fcntl(F_SETOWN_EX)"))
+		goto cleanup;
+
+	err = ioctl(perf_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
+	if (!ASSERT_OK(err, "ioctl(PERF_EVENT_IOC_SET_BPF)"))
+		goto cleanup;
+
+	test_function();
+
+cleanup:
+	if (perf_fd >= 0)
+		close(perf_fd);
+	if (ip)
+		munmap(ip, page_size);
+	if (skel)
+		test_perf_skip__destroy(skel);
+
+	signal(SIGIO, previous);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_perf_skip.c b/tools/testing/selftests/bpf/progs/test_perf_skip.c
new file mode 100644
index 000000000000..ef01a9161afe
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_perf_skip.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 1);
+	__uint(map_flags, BPF_F_MMAPABLE);
+	__type(key, uint32_t);
+	__type(value, uintptr_t);
+} ip SEC(".maps");
+
+SEC("perf_event")
+int handler(struct bpf_perf_event_data *data)
+{
+	const uint32_t index = 0;
+	uintptr_t *v = bpf_map_lookup_elem(&ip, &index);
+
+	return !(v && *v == PT_REGS_IP(&data->regs));
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.34.1