On Fri, 11 Feb 2022, Andrii Nakryiko wrote:
> Add a selftest validating various aspects of libbpf's handling of custom
> SEC() handlers. It also demonstrates how libraries can ensure very early
> callbacks registration and unregistration using
> __attribute__((constructor))/__attribute__((destructor)) functions.
>
> Reviewed-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Thanks for adding the additional tests, looks great!
> ---
> .../bpf/prog_tests/custom_sec_handlers.c | 176 ++++++++++++++++++
> .../bpf/progs/test_custom_sec_handlers.c | 63 +++++++
> 2 files changed, 239 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/custom_sec_handlers.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_custom_sec_handlers.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/custom_sec_handlers.c b/tools/testing/selftests/bpf/prog_tests/custom_sec_handlers.c
> new file mode 100644
> index 000000000000..28264528280d
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/custom_sec_handlers.c
> @@ -0,0 +1,176 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2022 Facebook */
> +
> +#include <test_progs.h>
> +#include "test_custom_sec_handlers.skel.h"
> +
> +#define COOKIE_ABC1 1
> +#define COOKIE_ABC2 2
> +#define COOKIE_CUSTOM 3
> +#define COOKIE_FALLBACK 4
> +#define COOKIE_KPROBE 5
> +
> +static int custom_init_prog(struct bpf_program *prog, long cookie)
> +{
> + if (cookie == COOKIE_ABC1)
> + bpf_program__set_autoload(prog, false);
> +
> + return 0;
> +}
> +
> +static int custom_preload_prog(struct bpf_program *prog,
> + struct bpf_prog_load_opts *opts, long cookie)
> +{
> + if (cookie == COOKIE_FALLBACK)
> + opts->prog_flags |= BPF_F_SLEEPABLE;
> + else if (cookie == COOKIE_ABC1)
> + ASSERT_FALSE(true, "unexpected preload for abc");
> +
> + return 0;
> +}
> +
> +static int custom_attach_prog(const struct bpf_program *prog, long cookie,
> + struct bpf_link **link)
> +{
> + switch (cookie) {
> + case COOKIE_ABC2:
> + *link = bpf_program__attach_raw_tracepoint(prog, "sys_enter");
> + return libbpf_get_error(*link);
> + case COOKIE_CUSTOM:
> + *link = bpf_program__attach_tracepoint(prog, "syscalls", "sys_enter_nanosleep");
> + return libbpf_get_error(*link);
> + case COOKIE_KPROBE:
> + case COOKIE_FALLBACK:
> + /* no auto-attach for SEC("xyz") and SEC("kprobe") */
> + *link = NULL;
> + return 0;
> + default:
> + ASSERT_FALSE(true, "unexpected cookie");
> + return -EINVAL;
> + }
> +}
> +
> +static int abc1_id;
> +static int abc2_id;
> +static int custom_id;
> +static int fallback_id;
> +static int kprobe_id;
> +
> +__attribute__((constructor))
> +static void register_sec_handlers(void)
> +{
> + LIBBPF_OPTS(libbpf_prog_handler_opts, abc1_opts,
> + .cookie = COOKIE_ABC1,
> + .init_fn = custom_init_prog,
> + .preload_fn = custom_preload_prog,
> + .attach_fn = NULL,
> + );
> + LIBBPF_OPTS(libbpf_prog_handler_opts, abc2_opts,
> + .cookie = COOKIE_ABC2,
> + .init_fn = custom_init_prog,
> + .preload_fn = custom_preload_prog,
> + .attach_fn = custom_attach_prog,
> + );
> + LIBBPF_OPTS(libbpf_prog_handler_opts, custom_opts,
> + .cookie = COOKIE_CUSTOM,
> + .init_fn = NULL,
> + .preload_fn = NULL,
> + .attach_fn = custom_attach_prog,
> + );
> +
> + abc1_id = libbpf_register_prog_handler("abc", BPF_PROG_TYPE_RAW_TRACEPOINT, 0, &abc1_opts);
> + abc2_id = libbpf_register_prog_handler("abc/", BPF_PROG_TYPE_RAW_TRACEPOINT, 0, &abc2_opts);
> + custom_id = libbpf_register_prog_handler("custom+", BPF_PROG_TYPE_TRACEPOINT, 0, &custom_opts);
> +}
> +
> +__attribute__((destructor))
> +static void unregister_sec_handlers(void)
> +{
> + libbpf_unregister_prog_handler(abc1_id);
> + libbpf_unregister_prog_handler(abc2_id);
> + libbpf_unregister_prog_handler(custom_id);
> +}
> +
> +void test_custom_sec_handlers(void)
> +{
> + LIBBPF_OPTS(libbpf_prog_handler_opts, opts,
> + .init_fn = custom_init_prog,
> + .preload_fn = custom_preload_prog,
> + .attach_fn = custom_attach_prog,
> + );
> + struct test_custom_sec_handlers* skel;
> + int err;
> +
> + ASSERT_GT(abc1_id, 0, "abc1_id");
> + ASSERT_GT(abc2_id, 0, "abc2_id");
> + ASSERT_GT(custom_id, 0, "custom_id");
> +
> + /* override libbpf's handle of SEC("kprobe/...") but also allow pure
> + * SEC("kprobe") due to "kprobe+" specifier. Register it as
> + * TRACEPOINT, just for fun.
> + */
> + opts.cookie = COOKIE_KPROBE;
> + kprobe_id = libbpf_register_prog_handler("kprobe+", BPF_PROG_TYPE_TRACEPOINT, 0, &opts);
> + /* fallback treats everything as BPF_PROG_TYPE_SYSCALL program to test
> + * setting custom BPF_F_SLEEPABLE bit in preload handler
> + */
> + opts.cookie = COOKIE_FALLBACK;
> + fallback_id = libbpf_register_prog_handler(NULL, BPF_PROG_TYPE_SYSCALL, 0, &opts);
> +
> + if (!ASSERT_GT(fallback_id, 0, "fallback_id") /* || !ASSERT_GT(kprobe_id, 0, "kprobe_id")*/) {
> + if (fallback_id > 0)
> + libbpf_unregister_prog_handler(fallback_id);
> + if (kprobe_id > 0)
> + libbpf_unregister_prog_handler(kprobe_id);
> + return;
> + }
> +
> + /* open skeleton and validate assumptions */
> + skel = test_custom_sec_handlers__open();
> + if (!ASSERT_OK_PTR(skel, "skel_open"))
> + goto cleanup;
> +
> + ASSERT_EQ(bpf_program__type(skel->progs.abc1), BPF_PROG_TYPE_RAW_TRACEPOINT, "abc1_type");
> + ASSERT_FALSE(bpf_program__autoload(skel->progs.abc1), "abc1_autoload");
> +
> + ASSERT_EQ(bpf_program__type(skel->progs.abc2), BPF_PROG_TYPE_RAW_TRACEPOINT, "abc2_type");
> + ASSERT_EQ(bpf_program__type(skel->progs.custom1), BPF_PROG_TYPE_TRACEPOINT, "custom1_type");
> + ASSERT_EQ(bpf_program__type(skel->progs.custom2), BPF_PROG_TYPE_TRACEPOINT, "custom2_type");
> + ASSERT_EQ(bpf_program__type(skel->progs.kprobe1), BPF_PROG_TYPE_TRACEPOINT, "kprobe1_type");
> + ASSERT_EQ(bpf_program__type(skel->progs.xyz), BPF_PROG_TYPE_SYSCALL, "xyz_type");
> +
> + skel->rodata->my_pid = getpid();
> +
> + /* now attempt to load everything */
> + err = test_custom_sec_handlers__load(skel);
> + if (!ASSERT_OK(err, "skel_load"))
> + goto cleanup;
> +
> + /* now try to auto-attach everything */
> + err = test_custom_sec_handlers__attach(skel);
> + if (!ASSERT_OK(err, "skel_attach"))
> + goto cleanup;
> +
> + skel->links.xyz = bpf_program__attach(skel->progs.kprobe1);
> + ASSERT_EQ(errno, EOPNOTSUPP, "xyz_attach_err");
> + ASSERT_ERR_PTR(skel->links.xyz, "xyz_attach");
> +
> + /* trigger programs */
> + usleep(1);
> +
> + /* SEC("abc") is set to not auto-loaded */
> + ASSERT_FALSE(skel->bss->abc1_called, "abc1_called");
> + ASSERT_TRUE(skel->bss->abc2_called, "abc2_called");
> + ASSERT_TRUE(skel->bss->custom1_called, "custom1_called");
> + ASSERT_TRUE(skel->bss->custom2_called, "custom2_called");
> + /* SEC("kprobe") shouldn't be auto-attached */
> + ASSERT_FALSE(skel->bss->kprobe1_called, "kprobe1_called");
> + /* SEC("xyz") shouldn't be auto-attached */
> + ASSERT_FALSE(skel->bss->xyz_called, "xyz_called");
> +
> +cleanup:
> + test_custom_sec_handlers__destroy(skel);
> +
> + ASSERT_OK(libbpf_unregister_prog_handler(fallback_id), "unregister_fallback");
> + ASSERT_OK(libbpf_unregister_prog_handler(kprobe_id), "unregister_kprobe");
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_custom_sec_handlers.c b/tools/testing/selftests/bpf/progs/test_custom_sec_handlers.c
> new file mode 100644
> index 000000000000..4061f701ca50
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_custom_sec_handlers.c
> @@ -0,0 +1,63 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2022 Facebook */
> +
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +const volatile int my_pid;
> +
> +bool abc1_called;
> +bool abc2_called;
> +bool custom1_called;
> +bool custom2_called;
> +bool kprobe1_called;
> +bool xyz_called;
> +
> +SEC("abc")
> +int abc1(void *ctx)
> +{
> + abc1_called = true;
> + return 0;
> +}
> +
> +SEC("abc/whatever")
> +int abc2(void *ctx)
> +{
> + abc2_called = true;
> + return 0;
> +}
> +
> +SEC("custom")
> +int custom1(void *ctx)
> +{
> + custom1_called = true;
> + return 0;
> +}
> +
> +SEC("custom/something")
> +int custom2(void *ctx)
> +{
> + custom2_called = true;
> + return 0;
> +}
> +
> +SEC("kprobe")
> +int kprobe1(void *ctx)
> +{
> + kprobe1_called = true;
> + return 0;
> +}
> +
> +SEC("xyz/blah")
> +int xyz(void *ctx)
> +{
> + int whatever;
> +
> + /* use sleepable helper, custom handler should set sleepable flag */
> + bpf_copy_from_user(&whatever, sizeof(whatever), NULL);
> + xyz_called = true;
> + return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.30.2
>
>
