On Tue, Dec 5, 2023 at 8:54 AM Yonghong Song yonghong.song@linux.dev wrote:
On 12/4/23 3:14 PM, Kyle Huey wrote:
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@kylehuey.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)
I hit a warning here: home/yhs/work/bpf-next/tools/testing/selftests/bpf/prog_tests/perf_skip.c:10:27: error: omitting the parameter name in a function definition is a C23 extension [-Werror,-Wc23-extensions]
Yeah, Meta's kernel-ci bot sent me off-list email about this one.
10 | static void handle_sig(int) |Add a parameter and marked as unused can resolve the issue.
#define __always_unused __attribute__((__unused__))
static void handle_sig(int unused __always_unused) { ASSERT_OK(1, "perf event not skipped"); }
+{
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();I hit a compilation failure here:
/home/yhs/work/bpf-next/tools/testing/selftests/bpf/prog_tests/perf_skip.c:75:14: error: call to undeclared function 'gettid'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] 75 | owner.pid = gettid(); | ^
If you looked at some other examples, the common usage is do 'syscall(SYS_gettid)'.
Not clear why this works for me but sure I'll change that.
So the following patch should fix the compilation error:
#include <sys/syscall.h> ... owner.pid = syscall(SYS_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();As Andrii has mentioned in previous comments, we will have issue is RELEASE version of selftest is built RELEASE=1 make ...
See https://lore.kernel.org/bpf/20231127050342.1945270-1-yonghong.song@linux.dev
Not sure I follow this one. Are you saying adding asm volatile ("") in test_function() is *not* sufficient?
- Kyle
+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";