Re: [PATCH v4 17/18] kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec()

[Iurii Zaikin <yzaikin@google.com>]

On Fri, May 17, 2019 at 11:22 AM Stephen Boyd <sboyd@kernel.org> wrote:
>
> Quoting Brendan Higgins (2019-05-14 15:17:10)
> > diff --git a/kernel/sysctl-test.c b/kernel/sysctl-test.c
> > new file mode 100644
> > index 0000000000000..fe0f2bae66085
> > --- /dev/null
> > +++ b/kernel/sysctl-test.c
> > @@ -0,0 +1,293 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * KUnit test of proc sysctl.
> > + */
> > +
> > +#include <kunit/test.h>
> > +#include <linux/printk.h>
>
> Is this include used?
  Deleted.
>
> > +#include <linux/sysctl.h>
> > +#include <linux/uaccess.h>
>
> Is this include used?
Deleted.
>
> > +
> > +
> > +static void sysctl_test_dointvec_happy_single_negative(struct kunit *test)
> > +{
> > +       struct ctl_table table = {
> > +               .procname = "foo",
> > +               .data           = &test_data.int_0001,
> > +               .maxlen         = sizeof(int),
> > +               .mode           = 0644,
> > +               .proc_handler   = proc_dointvec,
> > +               .extra1         = &i_zero,
> > +               .extra2         = &i_one_hundred,
> > +       };
> > +       char input[] = "-9";
> > +       size_t len = sizeof(input) - 1;
> > +       loff_t pos = 0;
> > +
> > +       table.data = kunit_kzalloc(test, sizeof(int), GFP_USER);
> > +       KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, 1, input, &len, &pos));
> > +       KUNIT_EXPECT_EQ(test, sizeof(input) - 1, len);
> > +       KUNIT_EXPECT_EQ(test, sizeof(input) - 1, pos);
> > +       KUNIT_EXPECT_EQ(test, -9, *(int *)table.data);
>
> Is the casting necessary? Or can the macro do a type coercion of the
> second parameter based on the first type?
 Data field is defined as void* so I believe casting is necessary to
dereference it as a pointer to an array of ints. I don't think the
macro should do any type coercion that == operator wouldn't do.
 I did change the cast to make it more clear that it's a pointer to an
array of ints being dereferenced.
>
> > +}
> > +
> > +static void sysctl_test_dointvec_single_less_int_min(struct kunit *test)
> > +{
> > +       struct ctl_table table = {
> > +               .procname = "foo",
> > +               .data           = &test_data.int_0001,
> > +               .maxlen         = sizeof(int),
> > +               .mode           = 0644,
> > +               .proc_handler   = proc_dointvec,
> > +               .extra1         = &i_zero,
> > +               .extra2         = &i_one_hundred,
> > +       };
> > +       char input[32];
> > +       size_t len = sizeof(input) - 1;
> > +       loff_t pos = 0;
> > +       unsigned long abs_of_less_than_min = (unsigned long)INT_MAX
> > +                                            - (INT_MAX + INT_MIN) + 1;
> > +
> > +       KUNIT_EXPECT_LT(test,
> > +                       snprintf(input, sizeof(input), "-%lu",
> > +                                abs_of_less_than_min),
> > +                       sizeof(input));
> > +
> > +       table.data = kunit_kzalloc(test, sizeof(int), GFP_USER);
> > +       KUNIT_EXPECT_EQ(test, -EINVAL,
> > +                       proc_dointvec(&table, 1, input, &len, &pos));
> > +       KUNIT_EXPECT_EQ(test, sizeof(input) - 1, len);
> > +       KUNIT_EXPECT_EQ(test, 0, *(int *)table.data);
> > +}
> > +
> > +static void sysctl_test_dointvec_single_greater_int_max(struct kunit *test)
> > +{
> > +       struct ctl_table table = {
> > +               .procname = "foo",
> > +               .data           = &test_data.int_0001,
> > +               .maxlen         = sizeof(int),
> > +               .mode           = 0644,
> > +               .proc_handler   = proc_dointvec,
> > +               .extra1         = &i_zero,
> > +               .extra2         = &i_one_hundred,
> > +       };
> > +       char input[32];
> > +       size_t len = sizeof(input) - 1;
> > +       loff_t pos = 0;
> > +       unsigned long greater_than_max = (unsigned long)INT_MAX + 1;
> > +
> > +       KUNIT_EXPECT_GT(test, greater_than_max, INT_MAX);
> > +       KUNIT_EXPECT_LT(test, snprintf(input, sizeof(input), "%lu",
> > +                                      greater_than_max),
> > +                       sizeof(input));
> > +       table.data = kunit_kzalloc(test, sizeof(int), GFP_USER);
> > +       KUNIT_EXPECT_EQ(test, -EINVAL,
> > +                       proc_dointvec(&table, 1, input, &len, &pos));
> > +       KUNIT_EXPECT_EQ(test, sizeof(input) - 1, len);
> > +       KUNIT_EXPECT_EQ(test, 0, *(int *)table.data);
> > +}
> > +
> > +static int sysctl_test_init(struct kunit *test)
> > +{
> > +       return 0;
> > +}
> > +
> > +/*
> > + * This is run once after each test case, see the comment on example_test_module
> > + * for more information.
> > + */
> > +static void sysctl_test_exit(struct kunit *test)
> > +{
> > +}
> Can the above two be omitted? If they can be empty sometimes it would be
> nice to avoid the extra symbols and code by letting them be assigned to
> NULL in the kunit_module.
 Deleted.
>
> > +
> > +/*
> > + * Here we make a list of all the test cases we want to add to the test module
> > + * below.
> > + */
> > +static struct kunit_case sysctl_test_cases[] = {
> > +       /*
> > +        * This is a helper to create a test case object from a test case
> > +        * function; its exact function is not important to understand how to
> > +        * use KUnit, just know that this is how you associate test cases with a
> > +        * test module.
> > +        */
> > +       KUNIT_CASE(sysctl_test_dointvec_null_tbl_data),
> > +       KUNIT_CASE(sysctl_test_dointvec_table_maxlen_unset),
> > +       KUNIT_CASE(sysctl_test_dointvec_table_len_is_zero),
> > +       KUNIT_CASE(sysctl_test_dointvec_table_read_but_position_set),
> > +       KUNIT_CASE(sysctl_test_dointvec_happy_single_positive),
> > +       KUNIT_CASE(sysctl_test_dointvec_happy_single_negative),
> > +       KUNIT_CASE(sysctl_test_dointvec_single_less_int_min),
> > +       KUNIT_CASE(sysctl_test_dointvec_single_greater_int_max),
> > +       {},
> > +};
> > +
> > +/*
> > + * This defines a suite or grouping of tests.
> > + *
> > + * Test cases are defined as belonging to the suite by adding them to
> > + * `test_cases`.
> > + *
> > + * Often it is desirable to run some function which will set up things which
> > + * will be used by every test; this is accomplished with an `init` function
> > + * which runs before each test case is invoked. Similarly, an `exit` function
> > + * may be specified which runs after every test case and can be used to for
> > + * cleanup. For clarity, running tests in a test module would behave as follows:
> > + *
> > + * module.init(test);
> > + * module.test_case[0](test);
> > + * module.exit(test);
> > + * module.init(test);
> > + * module.test_case[1](test);
> > + * module.exit(test);
> > + * ...;
>
> This comment (and the one above for "this is a helper") looks generic
> and should probably only be in some documentation somewhere and not for
> a sysctl test?
>
Deleted.
> > + */
> > +static struct kunit_module sysctl_test_module = {
> > +       .name = "sysctl_test",
> > +       .init = sysctl_test_init,
> > +       .exit = sysctl_test_exit,
> > +       .test_cases = sysctl_test_cases,
> > +};
> > +
> > +/*
> > + * This registers the above test module telling KUnit that this is a suite of
> > + * tests that need to be run.
> > + */
>
> Same comment about generic comment.
>
Deleted.
> > +module_test(sysctl_test_module);
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index d5a4a4036d2f8..772af4ec70111 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -1908,6 +1908,12 @@ config TEST_SYSCTL
> >
> >           If unsure, say N.
> >
> > +config SYSCTL_KUNIT_TEST
> > +       bool "KUnit test for sysctl"
>
> Why not tristate?
>
I don't believe KUnit as a module is currently supported.
> > +       depends on KUNIT
> > +       help
> > +         Enables KUnit sysctl test.
> > +