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Date: Mon, 1 Jul 2019 16:02:42 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Yonghong Song <yhs@...com>
Cc: Andrii Nakryiko <andriin@...com>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...com>,
"daniel@...earbox.net" <daniel@...earbox.net>,
Kernel Team <Kernel-team@...com>,
"sdf@...ichev.me" <sdf@...ichev.me>,
Song Liu <songliubraving@...com>
Subject: Re: [PATCH v4 bpf-next 8/9] selftests/bpf: add kprobe/uprobe selftests
On Mon, Jul 1, 2019 at 10:18 AM Yonghong Song <yhs@...com> wrote:
>
>
>
> On 6/28/19 8:49 PM, Andrii Nakryiko wrote:
> > Add tests verifying kprobe/kretprobe/uprobe/uretprobe APIs work as
> > expected.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > Reviewed-by: Stanislav Fomichev <sdf@...gle.com>
> > Acked-by: Song Liu <songliubraving@...com>
> > ---
> > .../selftests/bpf/prog_tests/attach_probe.c | 155 ++++++++++++++++++
> > .../selftests/bpf/progs/test_attach_probe.c | 55 +++++++
> > 2 files changed, 210 insertions(+)
> > create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > create mode 100644 tools/testing/selftests/bpf/progs/test_attach_probe.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > new file mode 100644
> > index 000000000000..f22929063c58
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> > @@ -0,0 +1,155 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <test_progs.h>
> > +
> > +ssize_t get_base_addr() {
> > + size_t start;
> > + char buf[256];
> > + FILE *f;
> > +
> > + f = fopen("/proc/self/maps", "r");
> > + if (!f)
> > + return -errno;
> > +
> > + while (fscanf(f, "%zx-%*x %s %*s\n", &start, buf) == 2) {
> > + if (strcmp(buf, "r-xp") == 0) {
> > + fclose(f);
> > + return start;
> > + }
> > + }
> > +
> > + fclose(f);
> > + return -EINVAL;
> > +}
> > +
> > +void test_attach_probe(void)
> > +{
> > + const char *kprobe_name = "kprobe/sys_nanosleep";
> > + const char *kretprobe_name = "kretprobe/sys_nanosleep";
> > + const char *uprobe_name = "uprobe/trigger_func";
> > + const char *uretprobe_name = "uretprobe/trigger_func";
> > + const int kprobe_idx = 0, kretprobe_idx = 1;
> > + const int uprobe_idx = 2, uretprobe_idx = 3;
> > + const char *file = "./test_attach_probe.o";
> > + struct bpf_program *kprobe_prog, *kretprobe_prog;
> > + struct bpf_program *uprobe_prog, *uretprobe_prog;
> > + struct bpf_object *obj;
> > + int err, prog_fd, duration = 0, res;
> > + struct bpf_link *kprobe_link = NULL;
> > + struct bpf_link *kretprobe_link = NULL;
> > + struct bpf_link *uprobe_link = NULL;
> > + struct bpf_link *uretprobe_link = NULL;
> > + int results_map_fd;
> > + size_t uprobe_offset;
> > + ssize_t base_addr;
> > +
> > + base_addr = get_base_addr();
> > + if (CHECK(base_addr < 0, "get_base_addr",
> > + "failed to find base addr: %zd", base_addr))
> > + return;
> > + uprobe_offset = (size_t)&get_base_addr - base_addr;
> > +
> > + /* load programs */
> > + err = bpf_prog_load(file, BPF_PROG_TYPE_KPROBE, &obj, &prog_fd);
> > + if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno))
> > + return;
> > +
> > + kprobe_prog = bpf_object__find_program_by_title(obj, kprobe_name);
> > + if (CHECK(!kprobe_prog, "find_probe",
> > + "prog '%s' not found\n", kprobe_name))
> > + goto cleanup;
> > + kretprobe_prog = bpf_object__find_program_by_title(obj, kretprobe_name);
> > + if (CHECK(!kretprobe_prog, "find_probe",
> > + "prog '%s' not found\n", kretprobe_name))
> > + goto cleanup;
> > + uprobe_prog = bpf_object__find_program_by_title(obj, uprobe_name);
> > + if (CHECK(!uprobe_prog, "find_probe",
> > + "prog '%s' not found\n", uprobe_name))
> > + goto cleanup;
> > + uretprobe_prog = bpf_object__find_program_by_title(obj, uretprobe_name);
> > + if (CHECK(!uretprobe_prog, "find_probe",
> > + "prog '%s' not found\n", uretprobe_name))
> > + goto cleanup;
> > +
> > + /* load maps */
> > + results_map_fd = bpf_find_map(__func__, obj, "results_map");
> > + if (CHECK(results_map_fd < 0, "find_results_map",
> > + "err %d\n", results_map_fd))
> > + goto cleanup;
> > +
> > + kprobe_link = bpf_program__attach_kprobe(kprobe_prog,
> > + false /* retprobe */,
> > + "sys_nanosleep");
> > + if (CHECK(IS_ERR(kprobe_link), "attach_kprobe",
> > + "err %ld\n", PTR_ERR(kprobe_link)))
> > + goto cleanup;
> > +
> > + kretprobe_link = bpf_program__attach_kprobe(kretprobe_prog,
> > + true /* retprobe */,
> > + "sys_nanosleep");
> > + if (CHECK(IS_ERR(kretprobe_link), "attach_kretprobe",
> > + "err %ld\n", PTR_ERR(kretprobe_link)))
> > + goto cleanup;
> > +
> > + uprobe_link = bpf_program__attach_uprobe(uprobe_prog,
> > + false /* retprobe */,
> > + 0 /* self pid */,
> > + "/proc/self/exe",
> > + uprobe_offset);
> > + if (CHECK(IS_ERR(uprobe_link), "attach_uprobe",
> > + "err %ld\n", PTR_ERR(uprobe_link)))
> > + goto cleanup;
> > +
> > + uretprobe_link = bpf_program__attach_uprobe(uretprobe_prog,
> > + true /* retprobe */,
> > + -1 /* any pid */,
> > + "/proc/self/exe",
> > + uprobe_offset);
> > + if (CHECK(IS_ERR(uretprobe_link), "attach_uretprobe",
> > + "err %ld\n", PTR_ERR(uretprobe_link)))
> > + goto cleanup;
> > +
> > + /* trigger & validate kprobe && kretprobe */
> > + usleep(1);
> > +
> > + err = bpf_map_lookup_elem(results_map_fd, &kprobe_idx, &res);
> > + if (CHECK(err, "get_kprobe_res",
> > + "failed to get kprobe res: %d\n", err))
> > + goto cleanup;
> > + if (CHECK(res != kprobe_idx + 1, "check_kprobe_res",
> > + "wrong kprobe res: %d\n", res))
> > + goto cleanup;
> > +
> > + err = bpf_map_lookup_elem(results_map_fd, &kretprobe_idx, &res);
> > + if (CHECK(err, "get_kretprobe_res",
> > + "failed to get kretprobe res: %d\n", err))
> > + goto cleanup;
> > + if (CHECK(res != kretprobe_idx + 1, "check_kretprobe_res",
> > + "wrong kretprobe res: %d\n", res))
> > + goto cleanup;
> > +
> > + /* trigger & validate uprobe & uretprobe */
> > + get_base_addr();
> > +
> > + err = bpf_map_lookup_elem(results_map_fd, &uprobe_idx, &res);
> > + if (CHECK(err, "get_uprobe_res",
> > + "failed to get uprobe res: %d\n", err))
> > + goto cleanup;
> > + if (CHECK(res != uprobe_idx + 1, "check_uprobe_res",
> > + "wrong uprobe res: %d\n", res))
> > + goto cleanup;
> > +
> > + err = bpf_map_lookup_elem(results_map_fd, &uretprobe_idx, &res);
> > + if (CHECK(err, "get_uretprobe_res",
> > + "failed to get uretprobe res: %d\n", err))
> > + goto cleanup;
> > + if (CHECK(res != uretprobe_idx + 1, "check_uretprobe_res",
> > + "wrong uretprobe res: %d\n", res))
> > + goto cleanup;
> > +
> > +cleanup:
> > + bpf_link__destroy(kprobe_link);
> > + bpf_link__destroy(kretprobe_link);
> > + bpf_link__destroy(uprobe_link);
> > + bpf_link__destroy(uretprobe_link);
>
> if any error happens, kprobe_link etc. will be a non-NULL pointer
> indicating an error. the above bpf_link__destroy() won't work
> properly. The same for patch #9.
Yes, you are absolutely right. Fixing.
I just also double-checked patch #9, it doesn't have this problem:
- stacktrace_build_id.c and stacktrace_map.c never call destroy before
bpf_link is successfully established.
- stacktrace_map_raw_tp.c uses if (!IS_ERR_OR_NULL(link)) check before
bpf_link__destroy.
So I think it's just this one.
>
> > + bpf_object__close(obj);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/test_attach_probe.c b/tools/testing/selftests/bpf/progs/test_attach_probe.c
> > new file mode 100644
> > index 000000000000..7a7c5cd728c8
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_attach_probe.c
> > @@ -0,0 +1,55 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +// Copyright (c) 2017 Facebook
> > +
> > +#include <linux/ptrace.h>
> > +#include <linux/bpf.h>
> > +#include "bpf_helpers.h"
> > +
> > +struct {
> > + int type;
> > + int max_entries;
> > + int *key;
> > + int *value;
> > +} results_map SEC(".maps") = {
> > + .type = BPF_MAP_TYPE_ARRAY,
> > + .max_entries = 4,
> > +};
> > +
> > +SEC("kprobe/sys_nanosleep")
> > +int handle_sys_nanosleep_entry(struct pt_regs *ctx)
> > +{
> > + const int key = 0, value = 1;
> > +
> > + bpf_map_update_elem(&results_map, &key, &value, 0);
> > + return 0;
> > +}
> > +
> > +SEC("kretprobe/sys_nanosleep")
> > +int handle_sys_getpid_return(struct pt_regs *ctx)
> > +{
> > + const int key = 1, value = 2;
> > +
> > + bpf_map_update_elem(&results_map, &key, &value, 0);
> > + return 0;
> > +}
> > +
> > +SEC("uprobe/trigger_func")
> > +int handle_uprobe_entry(struct pt_regs *ctx)
> > +{
> > + const int key = 2, value = 3;
> > +
> > + bpf_map_update_elem(&results_map, &key, &value, 0);
> > + return 0;
> > +}
> > +
> > +SEC("uretprobe/trigger_func")
> > +int handle_uprobe_return(struct pt_regs *ctx)
> > +{
> > + const int key = 3, value = 4;
> > +
> > + bpf_map_update_elem(&results_map, &key, &value, 0);
> > + return 0;
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> > +__u32 _version SEC("version") = 1;
> >
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