From patchwork Fri Mar 18 02:13:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Gow X-Patchwork-Id: 12784770 X-Patchwork-Delegate: brendanhiggins@google.com Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F73BC4332F for ; Fri, 18 Mar 2022 02:13:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230527AbiCRCO7 (ORCPT ); Thu, 17 Mar 2022 22:14:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58120 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231738AbiCRCO5 (ORCPT ); Thu, 17 Mar 2022 22:14:57 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 929A614FFC5 for ; Thu, 17 Mar 2022 19:13:38 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-2e599f0c613so60443947b3.3 for ; Thu, 17 Mar 2022 19:13:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=mPa+N3L2y3VpMLYvKGR04UJEK5knMdloLonQKnMZnCM=; b=b8t1MTiw2eHXOlvtgtcnQrF06MYxklfxRCFYyKHU7JoA1XGJClI+Ocx4Whixxnq/a6 syNqOUg8tVgmTPakDxrfRQidH2gNJyc3utlG8lIBQ96boigK1tp3wRL9lde4WsjK6uKp WditUPnQJQlkzcMyJ/72g6TM8bjkd00Cd/5XSt9vIv4pxjl4GcJPORcGXCL3IfFO0tDz jB1lFpnkxn5P9lQH+Ms7v7YPB1+GxU8R0AWMX0T7lbLkjuD3Daio/AFiB6GnxcPIq1z8 E3NSJFnioELXIYtsGZ1gYKIhl3nlexl6QvkbY5F0Voi+s8D21V0Fp++PbRavyTNDs5Iv 2e8A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=mPa+N3L2y3VpMLYvKGR04UJEK5knMdloLonQKnMZnCM=; b=2+FAyGdJrRTG0ePowEtgKHsZ+JpX91oc3qrXbzbj50+dox3Jv5KLG6rNuxLoeRfQaQ qe3ZTZlb8lHUGYGIwPa+WqNMzWJWIJKH61NHK30wC7yXzrnCF3MFvlljBZzfOKfn5DC1 M/+q8VoeqSV8tlXx7RvCvdC8I1YVsjdkwqctc2JM174QO5G2uDqmsVHgoeYrhV7JFE8a IGi0TLNUv0g8wHmMk6xfjZIp8vXQjKWHq+Q0iGkdi2fr1RFO8kO76O+PeSxmTIKo9rcb eVx1KCDYbuAf6vIChuolgxRtMDiirlUkkIuXvbuch/zIu6ya6hnml2LxO5wees8EeTRV 172A== X-Gm-Message-State: AOAM5327LV2jATMR3Y68eXfKkQ5n/Nb4RQcR6oVPmPkuIL9Z+sR+uXQU 3aqw4kCzjW9aB3g5SyzsIKUKKzh2YlqdBA== X-Google-Smtp-Source: ABdhPJxStsn2NAG6uC6iu1aljL3f45if8t9PJJwceQCOBd9/7QA1OOzhbqLxWgrNdyfhseQrdml7iqswyCxfLg== X-Received: from slicestar.c.googlers.com ([fda3:e722:ac3:cc00:4f:4b78:c0a8:20a1]) (user=davidgow job=sendgmr) by 2002:a25:664f:0:b0:629:2387:cd3c with SMTP id z15-20020a25664f000000b006292387cd3cmr8235091ybm.593.1647569617787; Thu, 17 Mar 2022 19:13:37 -0700 (PDT) Date: Fri, 18 Mar 2022 10:13:13 +0800 In-Reply-To: <20220318021314.3225240-1-davidgow@google.com> Message-Id: <20220318021314.3225240-2-davidgow@google.com> Mime-Version: 1.0 References: <20220318021314.3225240-1-davidgow@google.com> X-Mailer: git-send-email 2.35.1.894.gb6a874cedc-goog Subject: [RFC PATCH 1/2] kunit: Expose 'static stub' API to redirect functions From: David Gow To: Brendan Higgins , Daniel Latypov , Kees Cook , Shuah Khan Cc: David Gow , Steven Rostedt , kunit-dev@googlegroups.com, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Add a simple way of redirecting calls to functions by including a special prologue in the "real" function which checks to see if the replacement function should be called (and, if so, calls it). To redirect calls to a function, make the first (non-declaration) line of the function: KUNIT_STATIC_STUB_REDIRECT(function_name, [function arguments]); (This will compile away to nothing if KUnit is not enabled, otherwise it will check if a redirection is active, call the replacement function, and return.) Calls to the real function can be redirected to a replacement using: kunit_activate_static_stub(test, real_fn, replacement_fn); The redirection will only affect calls made from within the kthread of the current test, and will be automatically disabled when the test completes. It can also be manually disabled with kunit_deactivate_static_stub(). The 'example' KUnit test suite has a more complete example. This is intended to be an alternative to ftrace-based stubbing (see the next patch), with different tradeoffs. In particular: - 'static stubs' work on all architectures, and don't have any dependencies. - There's no separate Kconfig option to enable them, they always exist. - They must be explicitly opted-into by the function being replaced (which can be good or bad depending on your POV) - They have a greater performance penalty when not in active use (as every call to the real function must check to see if the stub is enabled) - They could more easily be extended to pass additional context to replacement functions. Co-developed-by: Daniel Latypov Signed-off-by: Daniel Latypov Signed-off-by: David Gow --- include/kunit/static_stub.h | 106 ++++++++++++++++++++++++++++ lib/kunit/Makefile | 1 + lib/kunit/kunit-example-test.c | 39 ++++++++++ lib/kunit/static_stub.c | 125 +++++++++++++++++++++++++++++++++ 4 files changed, 271 insertions(+) create mode 100644 include/kunit/static_stub.h create mode 100644 lib/kunit/static_stub.c diff --git a/include/kunit/static_stub.h b/include/kunit/static_stub.h new file mode 100644 index 000000000000..020e0e9110f2 --- /dev/null +++ b/include/kunit/static_stub.h @@ -0,0 +1,106 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * KUnit function redirection (static stubbing) API. + * + * Copyright (C) 2022, Google LLC. + * Author: David Gow + */ +#ifndef _KUNIT_STATIC_STUB_H +#define _KUNIT_STATIC_STUB_H + +#if !IS_REACHABLE(CONFIG_KUNIT) + +/* If CONFIG_KUNIT is not enabled, these stubs quietly disappear. */ +#define KUNIT_TRIGGER_STATIC_STUB(real_fn_name, args...) do {} while (0) + +#else + +#include + +#include /* for {un,}likely() */ +#include /* for task_struct */ + +/* Returns the address of the replacement function. */ +void *__kunit_get_static_stub_address(struct kunit *test, void *real_fn_addr); + +/** + * KUNIT_STATIC_STUB_REDIRECT() - call a replacement 'static stub' if one exists + * @real_fn_name: The name of this function (as an identifier, not a string) + * @args: All of the arguments passed to this function + * + * This is a function prologue which is used to allow calls to the current + * function to be redirected by a KUnit test. KUnit tests can call + * kunit_activate_static_stub() to pass a replacement function in. The + * replacement function will be called by KUNIT_TRIGGER_STATIC_STUB(), which + * will then return from the function. If the caller is not in a KUnit context, + * the function will continue execution as normal. + * + * Example: + * + * .. code-block:: c + * int real_func(int n) + * { + * KUNIT_STATIC_STUB_REDIRECT(real_func, n); + * return 0; + * } + * + * void replacement_func(int n) + * { + * return 42; + * } + * + * void example_test(struct kunit *test) + * { + * kunit_activate_static_stub(test, real_func, replacement_func); + * KUNIT_EXPECT_EQ(test, real_func(1), 42); + * } + * + */ +#define KUNIT_STATIC_STUB_REDIRECT(real_fn_name, args...) \ +do { \ + typeof(&real_fn_name) replacement; \ + struct kunit *current_test = current->kunit_test; \ + \ + if (likely(!current_test)) \ + break; \ + \ + KUNIT_ASSERT_STREQ_MSG(current_test, __func__, #real_fn_name, \ + "Static stub function name mismatch"); \ + \ + replacement = __kunit_get_static_stub_address(current_test, \ + &real_fn_name); \ + \ + if (unlikely(replacement)) \ + return replacement(args); \ +} while (0) + +/* Helper function for kunit_activate_static_stub(). The macro does + * typechecking, so use it instead. + */ +void __kunit_activate_static_stub(struct kunit *test, + void *real_fn_addr, + void *replacement_addr); + +/** + * kunit_activate_static_stub() - replace a function using static stubs. + * @test: A pointer to the 'struct kunit' test context for the current test. + * @real_fn_addr: The address of the function to replace. + * @replacement_addr: The address of the function to replace it with. + * + * When activated, calls to real_fn_addr from within this test (even if called + * indirectly) will instead call replacement_addr. The function pointed to by + * real_fn_addr must begin with the static stub prologue in + * KUNIT_TRIGGER_STATIC_STUB() for this to work. real_fn_addr and + * replacement_addr must have the same type. + * + * The redirection can be disabled again with kunit_deactivate_static_stub(). + */ +#define kunit_activate_static_stub(test, real_fn_addr, replacement_addr) do { \ + typecheck(typeof(real_fn_addr), replacement_addr); \ + __kunit_activate_static_stub(test, real_fn_addr, replacement_addr); \ +} while (0) + +void kunit_deactivate_static_stub(struct kunit *test, void *real_fn_addr); + +#endif +#endif diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile index c49f4ffb6273..f9e929700782 100644 --- a/lib/kunit/Makefile +++ b/lib/kunit/Makefile @@ -1,6 +1,7 @@ obj-$(CONFIG_KUNIT) += kunit.o kunit-objs += test.o \ + static_stub.o \ string-stream.o \ assert.o \ try-catch.o \ diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c index 51099b0ca29c..670c21e74446 100644 --- a/lib/kunit/kunit-example-test.c +++ b/lib/kunit/kunit-example-test.c @@ -7,6 +7,7 @@ */ #include +#include /* * This is the most fundamental element of KUnit, the test case. A test case @@ -69,6 +70,43 @@ static void example_mark_skipped_test(struct kunit *test) /* This line should run */ kunit_info(test, "You should see this line."); } + +/* This is a function we'll replace with static stubs. */ +static int add_one(int i) +{ + /* This will trigger the stub if active. */ + KUNIT_STATIC_STUB_REDIRECT(add_one, i); + + return i + 1; +} + +/* This is used as a replacement for the above function. */ +static int subtract_one(int i) +{ + /* We don't need to trigger the stub from the replacement. */ + + return i - 1; +} + +/* + * This test shows the use of static stubs. + */ +static void example_static_stub_test(struct kunit *test) +{ + /* By default, function is not stubbed. */ + KUNIT_EXPECT_EQ(test, add_one(1), 2); + + /* Replace add_one() with subtract_one(). */ + kunit_activate_static_stub(test, add_one, subtract_one); + + /* add_one() is now replaced. */ + KUNIT_EXPECT_EQ(test, add_one(1), 0); + + /* Return add_one() to normal. */ + kunit_deactivate_static_stub(test, add_one); + KUNIT_EXPECT_EQ(test, add_one(1), 2); +} + /* * Here we make a list of all the test cases we want to add to the test suite * below. @@ -83,6 +121,7 @@ static struct kunit_case example_test_cases[] = { KUNIT_CASE(example_simple_test), KUNIT_CASE(example_skip_test), KUNIT_CASE(example_mark_skipped_test), + KUNIT_CASE(example_static_stub_test), {} }; diff --git a/lib/kunit/static_stub.c b/lib/kunit/static_stub.c new file mode 100644 index 000000000000..b06b88f82dd7 --- /dev/null +++ b/lib/kunit/static_stub.c @@ -0,0 +1,125 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KUnit function redirection (static stubbing) API. + * + * Copyright (C) 2022, Google LLC. + * Author: David Gow + */ + +#include +#include + + +/* Context for a static stub. This is stored in the resource data. */ +struct kunit_static_stub_ctx { + void *real_fn_addr; + void *replacement_addr; +}; + +static void __kunit_static_stub_resource_free(struct kunit_resource *res) +{ + kfree(res->data); +} + +/* Matching function for kunit_find_resource(). match_data is real_fn_addr. */ +static bool __kunit_static_stub_resource_match(struct kunit *test, + struct kunit_resource *res, + void *match_real_fn_addr) +{ + /* This pointer is only valid if res is a static stub resource. */ + struct kunit_static_stub_ctx *ctx = res->data; + + /* Make sure the resource is a static stub resource. */ + if (res->free != &__kunit_static_stub_resource_free) + return false; + + return ctx->real_fn_addr == match_real_fn_addr; +} + +/* Returns the address of the replacement function. */ +void *__kunit_get_static_stub_address(struct kunit *test, void *real_fn_addr) +{ + struct kunit_resource *res; + struct kunit_static_stub_ctx *ctx; + void *replacement_addr; + + res = kunit_find_resource(test, + __kunit_static_stub_resource_match, + real_fn_addr); + + if (!res) + return NULL; + + ctx = res->data; + replacement_addr = ctx->replacement_addr; + kunit_put_resource(res); + return replacement_addr; +} +EXPORT_SYMBOL_GPL(__kunit_get_static_stub_address); + +void kunit_deactivate_static_stub(struct kunit *test, void *real_fn_addr) +{ + struct kunit_resource *res; + + KUNIT_ASSERT_PTR_NE_MSG(test, real_fn_addr, NULL, + "Tried to deactivate a NULL stub."); + + /* Look up the existing stub for this function. */ + res = kunit_find_resource(test, + __kunit_static_stub_resource_match, + real_fn_addr); + + /* Error out if the stub doesn't exist. */ + KUNIT_ASSERT_PTR_NE_MSG(test, res, NULL, + "Tried to deactivate a nonexistent stub."); + + /* Free the stub. We 'put' twice, as we got a reference + * from kunit_find_resource() + */ + kunit_remove_resource(test, res); + kunit_put_resource(res); +} +EXPORT_SYMBOL_GPL(kunit_deactivate_static_stub); + +/* Helper function for kunit_activate_static_stub(). The macro does + * typechecking, so use it instead. + */ +void __kunit_activate_static_stub(struct kunit *test, + void *real_fn_addr, + void *replacement_addr) +{ + struct kunit_static_stub_ctx *ctx; + struct kunit_resource *res; + + KUNIT_ASSERT_PTR_NE_MSG(test, real_fn_addr, NULL, + "Tried to activate a stub for function NULL"); + + /* If the replacement address is NULL, deactivate the stub. */ + if (!replacement_addr) { + kunit_deactivate_static_stub(test, replacement_addr); + return; + } + + /* Look up any existing stubs for this function, and replace them. */ + res = kunit_find_resource(test, + __kunit_static_stub_resource_match, + real_fn_addr); + if (res) { + ctx = res->data; + ctx->replacement_addr = replacement_addr; + + /* We got an extra reference from find_resource(), so put it. */ + kunit_put_resource(res); + } else { + ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx); + ctx->real_fn_addr = real_fn_addr; + ctx->replacement_addr = replacement_addr; + res = kunit_alloc_resource(test, NULL, + &__kunit_static_stub_resource_free, + GFP_KERNEL, ctx); + } +} +EXPORT_SYMBOL_GPL(__kunit_activate_static_stub); + +