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    Subject[PATCH] perf test: Test BPF prologue
    Date
    This patch introduces a new BPF script to test BPF prologue. The new
    script probes at null_lseek, which is the function pointer when we try
    to lseek on '/dev/null'.

    null_lseek is chosen because it is a function pointer, so we don't need
    to consider inlining and LTP.

    By extracting file->f_mode, bpf-script-test-prologue.c should know whether
    the file is writable or readonly. According to llseek_loop() and
    bpf-script-test-prologue.c, one forth of total lseeks should be collected.

    This patch improve test__bpf so it can run multiple BPF programs on
    different test functions.

    Signed-off-by: Wang Nan <wangnan0@huawei.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Alexei Starovoitov <ast@plumgrid.com>
    Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
    Cc: Daniel Borkmann <daniel@iogearbox.net>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: He Kuang <hekuang@huawei.com>
    Cc: Jiri Olsa <jolsa@kernel.org>
    Cc: Kaixu Xia <xiakaixu@huawei.com>
    Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Zefan Li <lizefan@huawei.com>
    Cc: pi3orama@163.com
    ---
    tools/perf/tests/Build | 9 ++-
    tools/perf/tests/bpf-script-test-prologue.c | 35 +++++++++++
    tools/perf/tests/bpf.c | 93 +++++++++++++++++++++++------
    tools/perf/tests/llvm.c | 5 ++
    tools/perf/tests/llvm.h | 8 +++
    5 files changed, 130 insertions(+), 20 deletions(-)
    create mode 100644 tools/perf/tests/bpf-script-test-prologue.c

    diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
    index 2bd5f37..3e98a97 100644
    --- a/tools/perf/tests/Build
    +++ b/tools/perf/tests/Build
    @@ -32,7 +32,7 @@ perf-y += sample-parsing.o
    perf-y += parse-no-sample-id-all.o
    perf-y += kmod-path.o
    perf-y += thread-map.o
    -perf-y += llvm.o llvm-src-base.o llvm-src-kbuild.o
    +perf-y += llvm.o llvm-src-base.o llvm-src-kbuild.o llvm-src-prologue.o
    perf-y += bpf.o
    perf-y += topology.o

    @@ -50,6 +50,13 @@ $(OUTPUT)tests/llvm-src-kbuild.c: tests/bpf-script-test-kbuild.c
    $(Q)sed -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/g' $< >> $@
    $(Q)echo ';' >> $@

    +$(OUTPUT)tests/llvm-src-prologue.c: tests/bpf-script-test-prologue.c
    + $(call rule_mkdir)
    + $(Q)echo '#include <tests/llvm.h>' > $@
    + $(Q)echo 'const char test_llvm__bpf_test_prologue_prog[] =' >> $@
    + $(Q)sed -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/g' $< >> $@
    + $(Q)echo ';' >> $@
    +
    perf-$(CONFIG_X86) += perf-time-to-tsc.o
    ifdef CONFIG_AUXTRACE
    perf-$(CONFIG_X86) += insn-x86.o
    diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
    new file mode 100644
    index 0000000..7230e62
    --- /dev/null
    +++ b/tools/perf/tests/bpf-script-test-prologue.c
    @@ -0,0 +1,35 @@
    +/*
    + * bpf-script-test-prologue.c
    + * Test BPF prologue
    + */
    +#ifndef LINUX_VERSION_CODE
    +# error Need LINUX_VERSION_CODE
    +# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
    +#endif
    +#define SEC(NAME) __attribute__((section(NAME), used))
    +
    +#include <uapi/linux/fs.h>
    +
    +#define FMODE_READ 0x1
    +#define FMODE_WRITE 0x2
    +
    +static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
    + (void *) 6;
    +
    +SEC("func=null_lseek file->f_mode offset orig")
    +int bpf_func__null_lseek(void *ctx, int err, unsigned long f_mode,
    + unsigned long offset, unsigned long orig)
    +{
    + if (err)
    + return 0;
    + if (f_mode & FMODE_WRITE)
    + return 0;
    + if (offset & 1)
    + return 0;
    + if (orig == SEEK_CUR)
    + return 0;
    + return 1;
    +}
    +
    +char _license[] SEC("license") = "GPL";
    +int _version SEC("version") = LINUX_VERSION_CODE;
    diff --git a/tools/perf/tests/bpf.c b/tools/perf/tests/bpf.c
    index 64aaab68..6305b3d 100644
    --- a/tools/perf/tests/bpf.c
    +++ b/tools/perf/tests/bpf.c
    @@ -19,14 +19,37 @@ static int epoll_pwait_loop(void)
    return 0;
    }

    -static int prepare_bpf(void *obj_buf, size_t obj_buf_sz)
    +#ifdef HAVE_BPF_PROLOGUE
    +
    +static int llseek_loop(void)
    +{
    + int fds[2], i;
    +
    + fds[0] = open("/dev/null", O_RDONLY);
    + fds[1] = open("/dev/null", O_RDWR);
    +
    + if (fds[0] < 0 || fds[1] < 0)
    + return -1;
    +
    + for (i = 0; i < NR_ITERS; i++) {
    + lseek(fds[i % 2], i, (i / 2) % 2 ? SEEK_CUR : SEEK_SET);
    + lseek(fds[(i + 1) % 2], i, (i / 2) % 2 ? SEEK_CUR : SEEK_SET);
    + }
    + close(fds[0]);
    + close(fds[1]);
    + return 0;
    +}
    +
    +#endif
    +
    +static int prepare_bpf(const char *name, void *obj_buf, size_t obj_buf_sz)
    {
    int err;
    char errbuf[BUFSIZ];

    - err = bpf__prepare_load_buffer(obj_buf, obj_buf_sz, NULL);
    + err = bpf__prepare_load_buffer(obj_buf, obj_buf_sz, name);
    if (err) {
    - bpf__strerror_prepare_load("[buffer]", false, err, errbuf,
    + bpf__strerror_prepare_load(name, false, err, errbuf,
    sizeof(errbuf));
    fprintf(stderr, " (%s)", errbuf);
    return TEST_FAIL;
    @@ -49,7 +72,7 @@ static int prepare_bpf(void *obj_buf, size_t obj_buf_sz)
    return 0;
    }

    -static int do_test(void)
    +static int do_test(int (*func)(void), int expect)
    {
    struct record_opts opts = {
    .target = {
    @@ -106,7 +129,7 @@ static int do_test(void)
    }

    perf_evlist__enable(evlist);
    - epoll_pwait_loop();
    + (*func)();
    perf_evlist__disable(evlist);

    for (i = 0; i < evlist->nr_mmaps; i++) {
    @@ -120,8 +143,8 @@ static int do_test(void)
    }
    }

    - if (count != (NR_ITERS + 1) / 2) {
    - fprintf(stderr, " (filter result incorrect)");
    + if (count != expect) {
    + fprintf(stderr, " (filter result incorrect: %d != %d)", count, expect);
    err = -EBADF;
    }

    @@ -132,30 +155,30 @@ out_delete_evlist:
    return 0;
    }

    -int test__bpf(void)
    +static int __test__bpf(int index, const char *name,
    + const char *message_compile,
    + const char *message_load,
    + int (*func)(void), int expect)
    {
    int err;
    void *obj_buf;
    size_t obj_buf_sz;

    - if (geteuid() != 0) {
    - fprintf(stderr, " (try run as root)");
    - return TEST_SKIP;
    - }
    -
    - test_llvm__fetch_bpf_obj(&obj_buf, &obj_buf_sz, LLVM_TESTCASE_BASE);
    -
    + test_llvm__fetch_bpf_obj(&obj_buf, &obj_buf_sz, index);
    if (!obj_buf || !obj_buf_sz) {
    if (verbose == 0)
    - fprintf(stderr, " (fix 'perf test LLVM' first)");
    + fprintf(stderr, " (%s)", message_compile);
    return TEST_SKIP;
    }

    - err = prepare_bpf(obj_buf, obj_buf_sz);
    - if (err)
    + err = prepare_bpf(name, obj_buf, obj_buf_sz);
    + if (err) {
    + if ((verbose == 0) && (message_load[0] != '\0'))
    + fprintf(stderr, " (%s)", message_load);
    goto out;
    + }

    - err = do_test();
    + err = do_test(func, expect);
    if (err)
    goto out;
    out:
    @@ -166,6 +189,38 @@ out:
    return 0;
    }

    +int test__bpf(void)
    +{
    + int err;
    +
    + if (geteuid() != 0) {
    + fprintf(stderr, " (try run as root)");
    + return TEST_SKIP;
    + }
    +
    + err = __test__bpf(LLVM_TESTCASE_BASE,
    + "[basic_bpf_test]",
    + "fix 'perf test LLVM' first",
    + "load bpf object failed",
    + &epoll_pwait_loop,
    + (NR_ITERS + 1) / 2);
    + if (err)
    + return err;
    +
    +#ifdef HAVE_BPF_PROLOGUE
    + err = __test__bpf(LLVM_TESTCASE_BPF_PROLOGUE,
    + "[bpf_prologue_test]",
    + "fix kbuild first",
    + "check your vmlinux setting?",
    + &llseek_loop,
    + (NR_ITERS + 1) / 4);
    + return err;
    +#else
    + fprintf(stderr, " (skip BPF prologue test)");
    + return TEST_OK;
    +#endif
    +}
    +
    #else
    int test__bpf(void)
    {
    diff --git a/tools/perf/tests/llvm.c b/tools/perf/tests/llvm.c
    index 75cd99f..e722e8a 100644
    --- a/tools/perf/tests/llvm.c
    +++ b/tools/perf/tests/llvm.c
    @@ -22,6 +22,11 @@ struct llvm_testcase {
    [LLVM_TESTCASE_KBUILD] = {.source = test_llvm__bpf_test_kbuild_prog,
    .errmsg = "llvm.kbuild-dir can be fixed",
    .tried = false},
    + /* Don't output if this one fail. */
    + [LLVM_TESTCASE_BPF_PROLOGUE] = {
    + .source = test_llvm__bpf_test_prologue_prog,
    + .errmsg = "failed for unknown reason",
    + .tried = false},
    {.source = NULL}
    };

    diff --git a/tools/perf/tests/llvm.h b/tools/perf/tests/llvm.h
    index 78ec01d..c00c1be 100644
    --- a/tools/perf/tests/llvm.h
    +++ b/tools/perf/tests/llvm.h
    @@ -10,10 +10,18 @@ struct test_llvm__bpf_result {

    extern const char test_llvm__bpf_prog[];
    extern const char test_llvm__bpf_test_kbuild_prog[];
    +extern const char test_llvm__bpf_test_prologue_prog[];

    enum test_llvm__testcase {
    LLVM_TESTCASE_BASE,
    LLVM_TESTCASE_KBUILD,
    + /*
    + * We must put LLVM_TESTCASE_BPF_PROLOGUE after
    + * LLVM_TESTCASE_KBUILD, so if kbuild test failed,
    + * don't need to try this one, because it depend on
    + * kernel header.
    + */
    + LLVM_TESTCASE_BPF_PROLOGUE,
    NR_LLVM_TESTCASES,
    };
    void test_llvm__fetch_bpf_obj(void **p_obj_buf, size_t *p_obj_buf_sz, int index);
    --
    1.8.3.4


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