Date:   Thu, 11 Feb 2021 16:54:59 +0800
From:   David Gow <davidgow@...gle.com>
To:     Daniel Latypov <dlatypov@...gle.com>
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Alan Maguire <alan.maguire@...cle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Uriel Guajardo <urielguajardo@...gle.com>
Subject: Re: [PATCH v3 1/2] kunit: support failure from dynamic analysis tools

On Wed, Feb 10, 2021 at 6:14 AM Daniel Latypov <dlatypov@...gle.com> wrote:
>
> From: Uriel Guajardo <urielguajardo@...gle.com>
>
> Add a kunit_fail_current_test() function to fail the currently running
> test, if any, with an error message.
>
> This is largely intended for dynamic analysis tools like UBSAN and for
> fakes.
> E.g. say I had a fake ops struct for testing and I wanted my `free`
> function to complain if it was called with an invalid argument, or
> caught a double-free. Most return void and have no normal means of
> signalling failure (e.g. super_operations, iommu_ops, etc.).
>
> Key points:
> * Always update current->kunit_test so anyone can use it.
>   * commit 83c4e7a0363b ("KUnit: KASAN Integration") only updated it for
>   CONFIG_KASAN=y
>
> * Create a new header <kunit/test-bug.h> so non-test code doesn't have
> to include all of <kunit/test.h> (e.g. lib/ubsan.c)
>
> * Forward the file and line number to make it easier to track down
> failures
>
> * Declare the helper function for nice __printf() warnings about mismatched
> format strings even when KUnit is not enabled.
>
> Example output from kunit_fail_current_test("message"):
> [15:19:34] [FAILED] example_simple_test
> [15:19:34]     # example_simple_test: initializing
> [15:19:34]     # example_simple_test: lib/kunit/kunit-example-test.c:24: message
> [15:19:34]     not ok 1 - example_simple_test
>
> Co-developed-by: Daniel Latypov <dlatypov@...gle.com>
> Signed-off-by: Uriel Guajardo <urielguajardo@...gle.com>
> Signed-off-by: Daniel Latypov <dlatypov@...gle.com>
> ---
>  include/kunit/test-bug.h | 30 ++++++++++++++++++++++++++++++
>  lib/kunit/test.c         | 37 +++++++++++++++++++++++++++++++++----
>  2 files changed, 63 insertions(+), 4 deletions(-)
>  create mode 100644 include/kunit/test-bug.h
>
> diff --git a/include/kunit/test-bug.h b/include/kunit/test-bug.h
> new file mode 100644
> index 000000000000..18b1034ec43a
> --- /dev/null
> +++ b/include/kunit/test-bug.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * KUnit API allowing dynamic analysis tools to interact with KUnit tests
> + *
> + * Copyright (C) 2020, Google LLC.
> + * Author: Uriel Guajardo <urielguajardo@...gle.com>
> + */
> +
> +#ifndef _KUNIT_TEST_BUG_H
> +#define _KUNIT_TEST_BUG_H
> +
> +#define kunit_fail_current_test(fmt, ...) \
> +       __kunit_fail_current_test(__FILE__, __LINE__, fmt, ##__VA_ARGS__)
> +
> +#if IS_ENABLED(CONFIG_KUNIT)

As the kernel test robot has pointed out on the second patch, this
probably should be IS_BUILTIN(), otherwise this won't build if KUnit
is a module, and the code calling it isn't.

This does mean that things like UBSAN integration won't work if KUnit
is a module, which is a shame.

(It's worth noting that the KASAN integration worked around this by
only calling inline functions, which would therefore be built-in even
if the rest of KUnit was built as a module. I don't think it's quite
as convenient to do that here, though.)

> +
> +extern __printf(3, 4) void __kunit_fail_current_test(const char *file, int line,
> +                                                   const char *fmt, ...);
> +
> +#else
> +
> +static __printf(3, 4) void __kunit_fail_current_test(const char *file, int line,
> +                                                   const char *fmt, ...)
> +{
> +}
> +
> +#endif
> +
> +
> +#endif /* _KUNIT_TEST_BUG_H */
> diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> index ec9494e914ef..5794059505cf 100644
> --- a/lib/kunit/test.c
> +++ b/lib/kunit/test.c
> @@ -7,6 +7,7 @@
>   */
>
>  #include <kunit/test.h>
> +#include <kunit/test-bug.h>
>  #include <linux/kernel.h>
>  #include <linux/kref.h>
>  #include <linux/sched/debug.h>
> @@ -16,6 +17,38 @@
>  #include "string-stream.h"
>  #include "try-catch-impl.h"
>
> +/*
> + * Fail the current test and print an error message to the log.
> + */
> +void __kunit_fail_current_test(const char *file, int line, const char *fmt, ...)
> +{
> +       va_list args;
> +       int len;
> +       char *buffer;
> +
> +       if (!current->kunit_test)
> +               return;
> +
> +       kunit_set_failure(current->kunit_test);
> +
> +       /* kunit_err() only accepts literals, so evaluate the args first. */
> +       va_start(args, fmt);
> +       len = vsnprintf(NULL, 0, fmt, args) + 1;
> +       va_end(args);
> +
> +       buffer = kunit_kmalloc(current->kunit_test, len, GFP_KERNEL);
> +       if (!buffer)
> +               return;
> +
> +       va_start(args, fmt);
> +       vsnprintf(buffer, len, fmt, args);
> +       va_end(args);
> +
> +       kunit_err(current->kunit_test, "%s:%d: %s", file, line, buffer);
> +       kunit_kfree(current->kunit_test, buffer);
> +}
> +EXPORT_SYMBOL_GPL(__kunit_fail_current_test);
> +
>  /*
>   * Append formatted message to log, size of which is limited to
>   * KUNIT_LOG_SIZE bytes (including null terminating byte).
> @@ -273,9 +306,7 @@ static void kunit_try_run_case(void *data)
>         struct kunit_suite *suite = ctx->suite;
>         struct kunit_case *test_case = ctx->test_case;
>
> -#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
>         current->kunit_test = test;
> -#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT) */
>
>         /*
>          * kunit_run_case_internal may encounter a fatal error; if it does,
> @@ -624,9 +655,7 @@ void kunit_cleanup(struct kunit *test)
>                 spin_unlock(&test->lock);
>                 kunit_remove_resource(test, res);
>         }
> -#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
>         current->kunit_test = NULL;
> -#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT)*/
>  }
>  EXPORT_SYMBOL_GPL(kunit_cleanup);
>
> --
> 2.30.0.478.g8a0d178c01-goog
>

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