Add selftest with few subtests testing proper user_ctx usage.
Kprobe and uprobe subtests are pretty straightforward and just validate that
the same BPF program attached with different user_ctx will be triggered with
those different user_ctx values.
Tracepoint subtest is a bit more interesting, as it is the only
perf_event-based BPF hook that shares bpf_prog_array between multiple
perf_events internally. This means that the same BPF program can't be attached
to the same tracepoint multiple times. So we have 3 identical copies. This
arrangement allows to test bpf_prog_array_copy()'s handling of bpf_prog_array
list manipulation logic when programs are attached and detached. The test
validates that user_ctx isn't mixed up and isn't lost during such list
manipulations.
Perf_event subtest validates that two BPF links can be created against the
same perf_event (but not at the same time, only one BPF program can be
attached to perf_event itself), and that for each we can specify different
user_ctx value.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/user_ctx.c | 254 ++++++++++++++++++
.../selftests/bpf/progs/test_user_ctx.c | 85 ++++++
2 files changed, 339 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/user_ctx.c
create mode 100644 tools/testing/selftests/bpf/progs/test_user_ctx.c
diff --git a/tools/testing/selftests/bpf/prog_tests/user_ctx.c b/tools/testing/selftests/bpf/prog_tests/user_ctx.c
new file mode 100644
index 000000000000..86374c8666dd
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/user_ctx.c
@@ -0,0 +1,254 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <sched.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <test_progs.h>
+#include "test_user_ctx.skel.h"
+
+static void kprobe_subtest(struct test_user_ctx *skel)
+{
+ DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, opts);
+ struct bpf_link *link1 = NULL, *link2 = NULL;
+ struct bpf_link *retlink1 = NULL, *retlink2 = NULL;
+
+ /* attach two kprobes */
+ opts.user_ctx = 0x1;
+ opts.retprobe = false;
+ link1 = bpf_program__attach_kprobe_opts(skel->progs.handle_kprobe,
+ SYS_NANOSLEEP_KPROBE_NAME, &opts);
+ if (!ASSERT_OK_PTR(link1, "link1"))
+ goto cleanup;
+
+ opts.user_ctx = 0x2;
+ opts.retprobe = false;
+ link2 = bpf_program__attach_kprobe_opts(skel->progs.handle_kprobe,
+ SYS_NANOSLEEP_KPROBE_NAME, &opts);
+ if (!ASSERT_OK_PTR(link2, "link2"))
+ goto cleanup;
+
+ /* attach two kretprobes */
+ opts.user_ctx = 0x10;
+ opts.retprobe = true;
+ retlink1 = bpf_program__attach_kprobe_opts(skel->progs.handle_kretprobe,
+ SYS_NANOSLEEP_KPROBE_NAME, &opts);
+ if (!ASSERT_OK_PTR(retlink1, "retlink1"))
+ goto cleanup;
+
+ opts.user_ctx = 0x20;
+ opts.retprobe = true;
+ retlink2 = bpf_program__attach_kprobe_opts(skel->progs.handle_kretprobe,
+ SYS_NANOSLEEP_KPROBE_NAME, &opts);
+ if (!ASSERT_OK_PTR(retlink2, "retlink2"))
+ goto cleanup;
+
+ /* trigger kprobe && kretprobe */
+ usleep(1);
+
+ ASSERT_EQ(skel->bss->kprobe_res, 0x1 | 0x2, "kprobe_res");
+ ASSERT_EQ(skel->bss->kretprobe_res, 0x10 | 0x20, "kretprobe_res");
+
+cleanup:
+ bpf_link__destroy(link1);
+ bpf_link__destroy(link2);
+ bpf_link__destroy(retlink1);
+ bpf_link__destroy(retlink2);
+}
+
+static void uprobe_subtest(struct test_user_ctx *skel)
+{
+ DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts);
+ struct bpf_link *link1 = NULL, *link2 = NULL;
+ struct bpf_link *retlink1 = NULL, *retlink2 = NULL;
+ size_t uprobe_offset;
+ ssize_t base_addr;
+
+ base_addr = get_base_addr();
+ uprobe_offset = get_uprobe_offset(&get_base_addr, base_addr);
+
+ /* attach two uprobes */
+ opts.user_ctx = 0x100;
+ opts.retprobe = false;
+ link1 = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe, 0 /* self pid */,
+ "/proc/self/exe", uprobe_offset, &opts);
+ if (!ASSERT_OK_PTR(link1, "link1"))
+ goto cleanup;
+
+ opts.user_ctx = 0x200;
+ opts.retprobe = false;
+ link2 = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe, -1 /* any pid */,
+ "/proc/self/exe", uprobe_offset, &opts);
+ if (!ASSERT_OK_PTR(link2, "link2"))
+ goto cleanup;
+
+ /* attach two uretprobes */
+ opts.user_ctx = 0x1000;
+ opts.retprobe = true;
+ retlink1 = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe, -1 /* any pid */,
+ "/proc/self/exe", uprobe_offset, &opts);
+ if (!ASSERT_OK_PTR(retlink1, "retlink1"))
+ goto cleanup;
+
+ opts.user_ctx = 0x2000;
+ opts.retprobe = true;
+ retlink2 = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe, 0 /* self pid */,
+ "/proc/self/exe", uprobe_offset, &opts);
+ if (!ASSERT_OK_PTR(retlink2, "retlink2"))
+ goto cleanup;
+
+ /* trigger uprobe && uretprobe */
+ get_base_addr();
+
+ ASSERT_EQ(skel->bss->uprobe_res, 0x100 | 0x200, "uprobe_res");
+ ASSERT_EQ(skel->bss->uretprobe_res, 0x1000 | 0x2000, "uretprobe_res");
+
+cleanup:
+ bpf_link__destroy(link1);
+ bpf_link__destroy(link2);
+ bpf_link__destroy(retlink1);
+ bpf_link__destroy(retlink2);
+}
+
+static void tp_subtest(struct test_user_ctx *skel)
+{
+ DECLARE_LIBBPF_OPTS(bpf_tracepoint_opts, opts);
+ struct bpf_link *link1 = NULL, *link2 = NULL, *link3 = NULL;
+
+ /* attach first tp prog */
+ opts.user_ctx = 0x10000;
+ link1 = bpf_program__attach_tracepoint_opts(skel->progs.handle_tp1,
+ "syscalls", "sys_enter_nanosleep", &opts);
+ if (!ASSERT_OK_PTR(link1, "link1"))
+ goto cleanup;
+
+ /* attach second tp prog */
+ opts.user_ctx = 0x20000;
+ link2 = bpf_program__attach_tracepoint_opts(skel->progs.handle_tp2,
+ "syscalls", "sys_enter_nanosleep", &opts);
+ if (!ASSERT_OK_PTR(link2, "link2"))
+ goto cleanup;
+
+ /* trigger tracepoints */
+ usleep(1);
+
+ ASSERT_EQ(skel->bss->tp_res, 0x10000 | 0x20000, "tp_res1");
+
+ /* now we detach first prog and will attach third one, which causes
+ * two internal calls to bpf_prog_array_copy(), shuffling
+ * bpf_prog_array_items around. We test here that we don't lose track
+ * of associated user_ctxs.
+ */
+ bpf_link__destroy(link1);
+ link1 = NULL;
+ kern_sync_rcu();
+ skel->bss->tp_res = 0;
+
+ /* attach third tp prog */
+ opts.user_ctx = 0x40000;
+ link3 = bpf_program__attach_tracepoint_opts(skel->progs.handle_tp3,
+ "syscalls", "sys_enter_nanosleep", &opts);
+ if (!ASSERT_OK_PTR(link3, "link3"))
+ goto cleanup;
+
+ /* trigger tracepoints */
+ usleep(1);
+
+ ASSERT_EQ(skel->bss->tp_res, 0x20000 | 0x40000, "tp_res2");
+
+cleanup:
+ bpf_link__destroy(link1);
+ bpf_link__destroy(link2);
+ bpf_link__destroy(link3);
+}
+
+static void burn_cpu(void)
+{
+ volatile int j = 0;
+ cpu_set_t cpu_set;
+ int i, err;
+
+ /* generate some branches on cpu 0 */
+ CPU_ZERO(&cpu_set);
+ CPU_SET(0, &cpu_set);
+ err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set);
+ ASSERT_OK(err, "set_thread_affinity");
+
+ /* spin the loop for a while (random high number) */
+ for (i = 0; i < 1000000; ++i)
+ ++j;
+}
+
+static void pe_subtest(struct test_user_ctx *skel)
+{
+ DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, opts);
+ struct bpf_link *link = NULL;
+ struct perf_event_attr attr;
+ int pfd = -1;
+
+ /* create perf event */
+ memset(&attr, 0, sizeof(attr));
+ attr.size = sizeof(attr);
+ attr.type = PERF_TYPE_SOFTWARE;
+ attr.config = PERF_COUNT_SW_CPU_CLOCK;
+ attr.freq = 1;
+ attr.sample_freq = 4000;
+ pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
+ if (!ASSERT_GE(pfd, 0, "perf_fd"))
+ goto cleanup;
+
+ opts.user_ctx = 0x100000;
+ link = bpf_program__attach_perf_event_opts(skel->progs.handle_pe, pfd, &opts);
+ if (!ASSERT_OK_PTR(link, "link1"))
+ goto cleanup;
+
+ burn_cpu(); /* trigger BPF prog */
+
+ ASSERT_EQ(skel->bss->pe_res, 0x100000, "pe_res1");
+
+ /* prevent bpf_link__destroy() closing pfd itself */
+ bpf_link__disconnect(link);
+ /* close BPF link's FD explicitly */
+ close(bpf_link__fd(link));
+ /* free up memory used by struct bpf_link */
+ bpf_link__destroy(link);
+ link = NULL;
+ kern_sync_rcu();
+ skel->bss->pe_res = 0;
+
+ opts.user_ctx = 0x200000;
+ link = bpf_program__attach_perf_event_opts(skel->progs.handle_pe, pfd, &opts);
+ if (!ASSERT_OK_PTR(link, "link2"))
+ goto cleanup;
+
+ burn_cpu(); /* trigger BPF prog */
+
+ ASSERT_EQ(skel->bss->pe_res, 0x200000, "pe_res2");
+
+cleanup:
+ close(pfd);
+ bpf_link__destroy(link);
+}
+
+void test_user_ctx(void)
+{
+ struct test_user_ctx *skel;
+
+ skel = test_user_ctx__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ return;
+
+ skel->bss->my_tid = syscall(SYS_gettid);
+
+ if (test__start_subtest("kprobe"))
+ kprobe_subtest(skel);
+ if (test__start_subtest("uprobe"))
+ uprobe_subtest(skel);
+ if (test__start_subtest("tracepoint"))
+ tp_subtest(skel);
+ if (test__start_subtest("perf_event"))
+ pe_subtest(skel);
+
+ test_user_ctx__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_user_ctx.c b/tools/testing/selftests/bpf/progs/test_user_ctx.c
new file mode 100644
index 000000000000..e641bb5e1774
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_user_ctx.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+int my_tid;
+
+int kprobe_res;
+int kprobe_multi_res;
+int kretprobe_res;
+int uprobe_res;
+int uretprobe_res;
+int tp_res;
+int pe_res;
+
+static void update(void *ctx, int *res)
+{
+ if (my_tid != (u32)bpf_get_current_pid_tgid())
+ return;
+
+ *res |= bpf_get_user_ctx(ctx);
+}
+
+SEC("kprobe/sys_nanosleep")
+int handle_kprobe(struct pt_regs *ctx)
+{
+ update(ctx, &kprobe_res);
+ return 0;
+}
+
+SEC("kretprobe/sys_nanosleep")
+int handle_kretprobe(struct pt_regs *ctx)
+{
+ update(ctx, &kretprobe_res);
+ return 0;
+}
+
+SEC("uprobe/trigger_func")
+int handle_uprobe(struct pt_regs *ctx)
+{
+ update(ctx, &uprobe_res);
+ return 0;
+}
+
+SEC("uretprobe/trigger_func")
+int handle_uretprobe(struct pt_regs *ctx)
+{
+ update(ctx, &uretprobe_res);
+ return 0;
+}
+
+/* bpf_prog_array, used by kernel internally to keep track of attached BPF
+ * programs to a given BPF hook (e.g., for tracepoints) doesn't allow the same
+ * BPF program to be attached multiple times. So have three identical copies
+ * ready to attach to the same tracepoint.
+ */
+SEC("tp/syscalls/sys_enter_nanosleep")
+int handle_tp1(struct pt_regs *ctx)
+{
+ update(ctx, &tp_res);
+ return 0;
+}
+SEC("tp/syscalls/sys_enter_nanosleep")
+int handle_tp2(struct pt_regs *ctx)
+{
+ update(ctx, &tp_res);
+ return 0;
+}
+SEC("tp/syscalls/sys_enter_nanosleep")
+int handle_tp3(void *ctx)
+{
+ update(ctx, &tp_res);
+ return 1;
+}
+
+SEC("perf_event")
+int handle_pe(struct pt_regs *ctx)
+{
+ update(ctx, &pe_res);
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.30.2
