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    Subject[PATCH 12/13] 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 LTO.

    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.

    Signed-off-by: Wang Nan <wangnan0@huawei.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Alexei Starovoitov <ast@kernel.org>
    Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    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 | 34 ++++++++++++++++++++++++++++
    tools/perf/tests/llvm.c | 4 ++++
    tools/perf/tests/llvm.h | 2 ++
    5 files changed, 83 insertions(+), 1 deletion(-)
    create mode 100644 tools/perf/tests/bpf-script-test-prologue.c

    diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
    index f41ebf8..0ff8a97 100644
    --- a/tools/perf/tests/Build
    +++ b/tools/perf/tests/Build
    @@ -31,7 +31,7 @@ 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

    @@ -49,6 +49,13 @@ $(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 ';' >> $@
    +
    ifeq ($(ARCH),$(filter $(ARCH),x86 arm arm64))
    perf-$(CONFIG_DWARF_UNWIND) += dwarf-unwind.o
    endif
    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 ec16f78..c7131fa 100644
    --- a/tools/perf/tests/bpf.c
    +++ b/tools/perf/tests/bpf.c
    @@ -19,6 +19,29 @@ static int epoll_pwait_loop(void)
    return 0;
    }

    +#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 struct {
    enum test_llvm__testcase prog_id;
    const char *desc;
    @@ -37,6 +60,17 @@ static struct {
    &epoll_pwait_loop,
    (NR_ITERS + 1) / 2,
    },
    +#ifdef HAVE_BPF_PROLOGUE
    + {
    + LLVM_TESTCASE_BPF_PROLOGUE,
    + "Test BPF prologue generation",
    + "[bpf_prologue_test]",
    + "fix kbuild first",
    + "check your vmlinux setting?",
    + &llseek_loop,
    + (NR_ITERS + 1) / 4,
    + },
    +#endif
    };

    static int do_test(struct bpf_object *obj, int (*func)(void),
    diff --git a/tools/perf/tests/llvm.c b/tools/perf/tests/llvm.c
    index bc4cf50..7f4f7f7 100644
    --- a/tools/perf/tests/llvm.c
    +++ b/tools/perf/tests/llvm.c
    @@ -44,6 +44,10 @@ static struct {
    .source = test_llvm__bpf_test_kbuild_prog,
    .desc = "Test kbuild searching",
    },
    + [LLVM_TESTCASE_BPF_PROLOGUE] = {
    + .source = test_llvm__bpf_test_prologue_prog,
    + .desc = "Test BPF prologue generation",
    + },
    };


    diff --git a/tools/perf/tests/llvm.h b/tools/perf/tests/llvm.h
    index d91d8f4..5150b4d 100644
    --- a/tools/perf/tests/llvm.h
    +++ b/tools/perf/tests/llvm.h
    @@ -6,10 +6,12 @@

    extern const char test_llvm__bpf_base_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,
    + LLVM_TESTCASE_BPF_PROLOGUE,
    __LLVM_TESTCASE_MAX,
    };

    --
    1.8.3.4


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