Re: [PATCH v10 12/12] fprobe: Add a selftest for fprobe

[Andrii Nakryiko]

On Wed, Mar 9, 2022 at 4:17 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
>
> Hi,
>
> On Tue,  8 Mar 2022 20:10:48 +0900
> Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
>
> > Add a KUnit based selftest for fprobe interface.
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > ---
> >  Changes in v9:
> >   - Rename fprobe_target* to fprobe_selftest_target*.
> >   - Find the correct expected ip by ftrace_location_range().
> >   - Since the ftrace_location_range() is not exposed to module, make
> >     this test only for embedded.
> >   - Add entry only test.
> >   - Reset the fprobe structure before reuse it.
> > ---
> >  lib/Kconfig.debug |   12 ++++
> >  lib/Makefile      |    2 +
> >  lib/test_fprobe.c |  174 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 188 insertions(+)
> >  create mode 100644 lib/test_fprobe.c
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 14b89aa37c5c..ffc469a12afc 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -2100,6 +2100,18 @@ config KPROBES_SANITY_TEST
> >
> >         Say N if you are unsure.
> >
> > +config FPROBE_SANITY_TEST
> > +     bool "Self test for fprobe"
> > +     depends on DEBUG_KERNEL
> > +     depends on FPROBE
> > +     depends on KUNIT
>
> Hmm, this caused a build error with allmodconfig because KUNIT=m but FPROBE_SANITY_TEST=y.
> Let me fix this issue.

Please base on top of bpf-next and add [PATCH v11 bpf-next] to subject.

>
> Thank you,
>
> > +     help
> > +       This option will enable testing the fprobe when the system boot.
> > +       A series of tests are made to verify that the fprobe is functioning
> > +       properly.
> > +
> > +       Say N if you are unsure.
> > +
> >  config BACKTRACE_SELF_TEST
> >       tristate "Self test for the backtrace code"
> >       depends on DEBUG_KERNEL
> > diff --git a/lib/Makefile b/lib/Makefile
> > index 300f569c626b..154008764b16 100644
> > --- a/lib/Makefile
> > +++ b/lib/Makefile
> > @@ -103,6 +103,8 @@ obj-$(CONFIG_TEST_HMM) += test_hmm.o
> >  obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o
> >  obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
> >  obj-$(CONFIG_TEST_REF_TRACKER) += test_ref_tracker.o
> > +CFLAGS_test_fprobe.o += $(CC_FLAGS_FTRACE)
> > +obj-$(CONFIG_FPROBE_SANITY_TEST) += test_fprobe.o
> >  #
> >  # CFLAGS for compiling floating point code inside the kernel. x86/Makefile turns
> >  # off the generation of FPU/SSE* instructions for kernel proper but FPU_FLAGS
> > diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
> > new file mode 100644
> > index 000000000000..ed70637a2ffa
> > --- /dev/null
> > +++ b/lib/test_fprobe.c
> > @@ -0,0 +1,174 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * test_fprobe.c - simple sanity test for fprobe
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/fprobe.h>
> > +#include <linux/random.h>
> > +#include <kunit/test.h>
> > +
> > +#define div_factor 3
> > +
> > +static struct kunit *current_test;
> > +
> > +static u32 rand1, entry_val, exit_val;
> > +
> > +/* Use indirect calls to avoid inlining the target functions */
> > +static u32 (*target)(u32 value);
> > +static u32 (*target2)(u32 value);
> > +static unsigned long target_ip;
> > +static unsigned long target2_ip;
> > +
> > +static noinline u32 fprobe_selftest_target(u32 value)
> > +{
> > +     return (value / div_factor);
> > +}
> > +
> > +static noinline u32 fprobe_selftest_target2(u32 value)
> > +{
> > +     return (value / div_factor) + 1;
> > +}
> > +
> > +static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
> > +{
> > +     KUNIT_EXPECT_FALSE(current_test, preemptible());
> > +     /* This can be called on the fprobe_selftest_target and the fprobe_selftest_target2 */
> > +     if (ip != target_ip)
> > +             KUNIT_EXPECT_EQ(current_test, ip, target2_ip);
> > +     entry_val = (rand1 / div_factor);
> > +}
> > +
> > +static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
> > +{
> > +     unsigned long ret = regs_return_value(regs);
> > +
> > +     KUNIT_EXPECT_FALSE(current_test, preemptible());
> > +     if (ip != target_ip) {
> > +             KUNIT_EXPECT_EQ(current_test, ip, target2_ip);
> > +             KUNIT_EXPECT_EQ(current_test, ret, (rand1 / div_factor) + 1);
> > +     } else
> > +             KUNIT_EXPECT_EQ(current_test, ret, (rand1 / div_factor));
> > +     KUNIT_EXPECT_EQ(current_test, entry_val, (rand1 / div_factor));
> > +     exit_val = entry_val + div_factor;
> > +}
> > +
> > +/* Test entry only (no rethook) */
> > +static void test_fprobe_entry(struct kunit *test)
> > +{
> > +     struct fprobe fp_entry = {
> > +             .entry_handler = fp_entry_handler,
> > +     };
> > +
> > +     current_test = test;
> > +
> > +     /* Before register, unregister should be failed. */
> > +     KUNIT_EXPECT_NE(test, 0, unregister_fprobe(&fp_entry));
> > +     KUNIT_EXPECT_EQ(test, 0, register_fprobe(&fp_entry, "fprobe_selftest_target*", NULL));
> > +
> > +     entry_val = 0;
> > +     exit_val = 0;
> > +     target(rand1);
> > +     KUNIT_EXPECT_NE(test, 0, entry_val);
> > +     KUNIT_EXPECT_EQ(test, 0, exit_val);
> > +
> > +     entry_val = 0;
> > +     exit_val = 0;
> > +     target2(rand1);
> > +     KUNIT_EXPECT_NE(test, 0, entry_val);
> > +     KUNIT_EXPECT_EQ(test, 0, exit_val);
> > +
> > +     KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp_entry));
> > +}
> > +
> > +static void test_fprobe(struct kunit *test)
> > +{
> > +     struct fprobe fp = {
> > +             .entry_handler = fp_entry_handler,
> > +             .exit_handler = fp_exit_handler,
> > +     };
> > +
> > +     current_test = test;
> > +     KUNIT_EXPECT_EQ(test, 0, register_fprobe(&fp, "fprobe_selftest_target*", NULL));
> > +
> > +     entry_val = 0;
> > +     exit_val = 0;
> > +     target(rand1);
> > +     KUNIT_EXPECT_NE(test, 0, entry_val);
> > +     KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
> > +
> > +     entry_val = 0;
> > +     exit_val = 0;
> > +     target2(rand1);
> > +     KUNIT_EXPECT_NE(test, 0, entry_val);
> > +     KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
> > +
> > +     KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
> > +}
> > +
> > +static void test_fprobe_syms(struct kunit *test)
> > +{
> > +     static const char *syms[] = {"fprobe_selftest_target", "fprobe_selftest_target2"};
> > +     struct fprobe fp = {
> > +             .entry_handler = fp_entry_handler,
> > +             .exit_handler = fp_exit_handler,
> > +     };
> > +
> > +     current_test = test;
> > +     KUNIT_EXPECT_EQ(test, 0, register_fprobe_syms(&fp, syms, 2));
> > +
> > +     entry_val = 0;
> > +     exit_val = 0;
> > +     target(rand1);
> > +     KUNIT_EXPECT_NE(test, 0, entry_val);
> > +     KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
> > +
> > +     entry_val = 0;
> > +     exit_val = 0;
> > +     target2(rand1);
> > +     KUNIT_EXPECT_NE(test, 0, entry_val);
> > +     KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
> > +
> > +     KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
> > +}
> > +
> > +static unsigned long get_ftrace_location(void *func)
> > +{
> > +     unsigned long size, addr = (unsigned long)func;
> > +
> > +     if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size)
> > +             return 0;
> > +
> > +     return ftrace_location_range(addr, addr + size - 1);
> > +}
> > +
> > +static int fprobe_test_init(struct kunit *test)
> > +{
> > +     do {
> > +             rand1 = prandom_u32();
> > +     } while (rand1 <= div_factor);
> > +
> > +     target = fprobe_selftest_target;
> > +     target2 = fprobe_selftest_target2;
> > +     target_ip = get_ftrace_location(target);
> > +     target2_ip = get_ftrace_location(target2);
> > +
> > +     return 0;
> > +}
> > +
> > +static struct kunit_case fprobe_testcases[] = {
> > +     KUNIT_CASE(test_fprobe_entry),
> > +     KUNIT_CASE(test_fprobe),
> > +     KUNIT_CASE(test_fprobe_syms),
> > +     {}
> > +};
> > +
> > +static struct kunit_suite fprobe_test_suite = {
> > +     .name = "fprobe_test",
> > +     .init = fprobe_test_init,
> > +     .test_cases = fprobe_testcases,
> > +};
> > +
> > +kunit_test_suites(&fprobe_test_suite);
> > +
> > +MODULE_LICENSE("GPL");
> >
>
>
> --
> Masami Hiramatsu <mhiramat@xxxxxxxxxx>