Re: [PATCH v2 1/2] kunit: support failure from dynamic analysis tools

[Alan Maguire]

On Fri, 5 Feb 2021, Daniel Latypov wrote:

> From: Uriel Guajardo <urielguajardo@xxxxxxxxxx>
> 
> 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
> 

Thanks for doing this!

> * Declare it as a function for nice __printf() warnings about mismatched
> format strings even when KUnit is not enabled.
>

One thing I _think_ this assumes is that KUnit is builtin;
don't we need an

EXPORT_SYMBOL_GPL(_kunit_fail_current_test);

?

Without it, if an analysis tool (or indeed if KUnit) is built
as a module, it won't be possible to use this functionality.

> 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@xxxxxxxxxx>
> Signed-off-by: Uriel Guajardo <urielguajardo@xxxxxxxxxx>
> Signed-off-by: Daniel Latypov <dlatypov@xxxxxxxxxx>
> ---
>  include/kunit/test-bug.h | 30 ++++++++++++++++++++++++++++++
>  lib/kunit/test.c         | 36 ++++++++++++++++++++++++++++++++----
>  2 files changed, 62 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..4963ed52c2df
> --- /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.

nit; might want to update copyright year.

> + * Author: Uriel Guajardo <urielguajardo@xxxxxxxxxx>
> + */
> +
> +#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)
> +
> +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..7b16aae0ccae 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 +17,37 @@
>  #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);
> +}
> +
>  /*
>   * Append formatted message to log, size of which is limited to
>   * KUNIT_LOG_SIZE bytes (including null terminating byte).
> @@ -273,9 +305,7 @@ 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 +654,7 @@ 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
> 
>