From nobody Sun Feb 8 08:27:37 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 072322E2EF2; Fri, 16 Jan 2026 08:03:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768550603; cv=none; b=KAIhlSieyGTk7Z5Tg96NDw9QwRgjdVdyv+Su9rhEwXiRzy2B3LIU8ZJ7QN58oIrebC2fa1rnsg9p4DmBstq+djhFtk69GLOMdXRHTEu30I4+JESnE2iBSHA5tgfp8dwX5iZ/JKvKpRlV8sAYvt/TzKc/eia9X8pWTMyL9/Wk4Lw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768550603; c=relaxed/simple; bh=NGlLg2wfkaS/UD8ySu81w3opwQk+z7hVmTBbWkqUS+4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rZZkP7omd3YjQvqxo/sveJx9i2e8jueEbAoGF68rYzIQPqcz0PePhtqRY8JGRMeIJ320vLJigWaG5arZV+eeEPa87r49S19DSwg/IEl70rOPEWoxsstKR+QTxWLI6VmFsVi8uBO498zpMkGqC6QvE4Soj3nRNGZE4cA2IU9JkXc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GMq0yuIf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GMq0yuIf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE9A9C19421; Fri, 16 Jan 2026 08:03:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768550600; bh=NGlLg2wfkaS/UD8ySu81w3opwQk+z7hVmTBbWkqUS+4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GMq0yuIf/NGHWZFDOYpdwZiaEWSZDEGuCYz6UmHMzhv15PNm2h0l9pq+sN39LrY/e rxDnm5c2tYfbmnXdYAiCMw1aX8SBzDsYNb1dpFRetD+4S39D73aRjkw+7MDTE32cXj wnKUUOLYEAObvBDPcG/LJAdYRwtj9zvgbUbBA9DEzQ8RTCBIUP/AiGsXUKSKfMA05M syffKYZY7dBi6pHtnH8J0eJd+1dMXNkffjyNqern2Z9uJzoaImNWmc0HQzWhwl5wLZ EOM/HpJXedJQXVyjTzfopLqV6lv//qAs2yLBaL9RrF86MXN/L2JXDz/aBqnwj7uh88 L4laBYD8mqGgA== From: Tzung-Bi Shih To: Benson Leung , Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , Bartosz Golaszewski , Linus Walleij Cc: Jonathan Corbet , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, chrome-platform@lists.linux.dev, linux-kselftest@vger.kernel.org, tzungbi@kernel.org, Laurent Pinchart , Wolfram Sang , Simona Vetter , Dan Williams , Jason Gunthorpe , linux-gpio@vger.kernel.org Subject: [PATCH v7 1/3] revocable: Revocable resource management Date: Fri, 16 Jan 2026 08:02:33 +0000 Message-ID: <20260116080235.350305-2-tzungbi@kernel.org> X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog In-Reply-To: <20260116080235.350305-1-tzungbi@kernel.org> References: <20260116080235.350305-1-tzungbi@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Some resources can be removed asynchronously, for example, resources provided by a hot-pluggable device like USB. When holding a reference to such a resource, it's possible for the resource to be removed and its memory freed, leading to use-after-free errors on subsequent access. The "revocable" mechanism addresses this by establishing a weak reference to a resource that might be freed at any time. It allows a resource consumer to safely attempt to access the resource, guaranteeing that the access is valid for the duration of its use, or it fails safely if the resource has already been revoked. The implementation uses a provider/consumer model built on Sleepable RCU (SRCU) to guarantee safe memory access: - A resource provider, such as a driver for a hot-pluggable device, allocates a struct revocable_provider and initializes it with a pointer to the resource. - A resource consumer that wants to access the resource allocates a struct revocable which acts as a handle containing a reference to the provider. - To access the resource, the consumer uses revocable_try_access(). This function enters an SRCU read-side critical section and returns the pointer to the resource. If the provider has already freed the resource, it returns NULL. After use, the consumer calls revocable_withdraw_access() to exit the SRCU critical section. The REVOCABLE_TRY_ACCESS_WITH() and REVOCABLE_TRY_ACCESS_SCOPED() are convenient helpers for doing that. - When the provider needs to remove the resource, it calls revocable_provider_revoke(). This function sets the internal resource pointer to NULL and then calls synchronize_srcu() to wait for all current readers to finish before the resource can be completely torn down. Acked-by: Danilo Krummrich Signed-off-by: Tzung-Bi Shih --- v7: - "2025" -> "2026" in copyright. - Documentation/ - Rephrase section "Revocable vs. Devres (devm)". - Include sections for struct revocable_provider and struct revocable. - Minor rename: "revocable" -> "access_rev" for DEFINE_FREE(). - Add Acked-by tag. v6: https://lore.kernel.org/chrome-platform/20251106152330.11733-2-tzungbi@= kernel.org - Rename REVOCABLE_TRY_ACCESS_WITH() -> REVOCABLE_TRY_ACCESS_SCOPED(). - Add new REVOCABLE_TRY_ACCESS_WITH(). - Remove Acked-by tags as the API names changed a bit. v5: https://lore.kernel.org/chrome-platform/20251016054204.1523139-2-tzungb= i@kernel.org - No changes. v4: https://lore.kernel.org/chrome-platform/20250923075302.591026-2-tzungbi= @kernel.org - Rename: - revocable_provider_free() -> revocable_provider_revoke(). - REVOCABLE() -> REVOCABLE_TRY_ACCESS_WITH(). - revocable_release() -> revocable_withdraw_access(). - rcu_dereference() -> srcu_dereference() to fix a warning from lock debugg= ing. - Move most docs to kernel-doc, include them in Documentation/, and modify = the commit message accordingly. - Fix some doc errors. - Add Acked-by tags. v3: https://lore.kernel.org/chrome-platform/20250912081718.3827390-2-tzungb= i@kernel.org - No changes. v2: https://lore.kernel.org/chrome-platform/20250820081645.847919-2-tzungbi= @kernel.org - Rename "ref_proxy" -> "revocable". - Add introduction in kernel-doc format in revocable.c. - Add MAINTAINERS entry. - Add copyright. - Move from lib/ to drivers/base/. - EXPORT_SYMBOL() -> EXPORT_SYMBOL_GPL(). - Add Documentation/. - Rename _get() -> try_access(); _put() -> release(). - Fix a sparse warning by removing the redundant __rcu annotations. - Fix a sparse warning by adding __acquires() and __releases() annotations. v1: https://lore.kernel.org/chrome-platform/20250814091020.1302888-2-tzungb= i@kernel.org Note (for my reference): - An optional .release() callback for revocable provider-managed resource hasn't added. - `make O=3Dbuild SPHINXDIRS=3Ddriver-api/driver-model/ htmldocs` a way to verify the Documentation/. .../driver-api/driver-model/index.rst | 1 + .../driver-api/driver-model/revocable.rst | 152 +++++++++++ MAINTAINERS | 7 + drivers/base/Makefile | 2 +- drivers/base/revocable.c | 242 ++++++++++++++++++ include/linux/revocable.h | 69 +++++ 6 files changed, 472 insertions(+), 1 deletion(-) create mode 100644 Documentation/driver-api/driver-model/revocable.rst create mode 100644 drivers/base/revocable.c create mode 100644 include/linux/revocable.h diff --git a/Documentation/driver-api/driver-model/index.rst b/Documentatio= n/driver-api/driver-model/index.rst index 4831bdd92e5c..8e1ee21185df 100644 --- a/Documentation/driver-api/driver-model/index.rst +++ b/Documentation/driver-api/driver-model/index.rst @@ -14,6 +14,7 @@ Driver Model overview platform porting + revocable =20 .. only:: subproject and html =20 diff --git a/Documentation/driver-api/driver-model/revocable.rst b/Document= ation/driver-api/driver-model/revocable.rst new file mode 100644 index 000000000000..22a442cc8d7f --- /dev/null +++ b/Documentation/driver-api/driver-model/revocable.rst @@ -0,0 +1,152 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D +Revocable Resource Management +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D + +Overview +=3D=3D=3D=3D=3D=3D=3D=3D + +.. kernel-doc:: drivers/base/revocable.c + :doc: Overview + +Revocable vs. Devres (devm) +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D + +It's important to understand the distinct roles of the Revocable and Devre= s, +and how they can complement each other. They address different problems in +resource management: + +* **Devres:** Primarily address **resource leaks**. The lifetime of the + resources is tied to the lifetime of the device. The resource is + automatically freed when the device is unbound. This cleanup happens + irrespective of any potential active users. + +* **Revocable:** Primarily addresses **invalid memory access**, + such as Use-After-Free (UAF). It's an independent synchronization + primitive that decouples consumer access from the resource's actual + presence. Consumers interact with a "revocable object" (an intermedia= ry), + not the underlying resource directly. This revocable object persists = as + long as there are active references to it from consumer handles. + +**Key Distinctions & How They Complement Each Other:** + +1. **Reference Target:** Consumers of a resource managed by the Revocable + mechanism hold a reference to the *revocable object*, not the + encapsulated resource itself. + +2. **Resource Lifetime vs. Access:** The underlying resource's lifetime is + independent of the number of references to the revocable object. The + resource can be freed at any point. A common scenario is the resource + being freed by `devres` when the providing device is unbound. + +3. **Safe Access:** Revocable provides a safe way to attempt access. Bef= ore + using the resource, a consumer uses the Revocable API (e.g., + revocable_try_access()). This function checks if the resource is still + valid. It returns a pointer to the resource only if it hasn't been + revoked; otherwise, it returns NULL. This prevents UAF by providing a + clear signal that the resource is gone. + +4. **Complementary Usage:** `devres` and Revocable work well together. + `devres` can handle the automatic allocation and deallocation of a + resource tied to a device. The Revocable mechanism can be layered on = top + to provide safe access for consumers whose lifetimes might extend beyo= nd + the provider device's lifetime. For instance, a userspace program mig= ht + keep a character device file open even after the physical device has b= een + removed. In this case: + + * `devres` frees the device-specific resource upon unbinding. + * The Revocable mechanism ensures that any subsequent operations on = the + open file handle, which attempt to access the now-freed resource, + will fail gracefully (e.g., revocable_try_access() returns NULL) + instead of causing a UAF. + +In summary, `devres` ensures resources are *released* to prevent leaks, wh= ile +the Revocable mechanism ensures that attempts to *access* these resources = are +done safely, even if the resource has been released. + +API and Usage +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +For Resource Providers +---------------------- +.. kernel-doc:: drivers/base/revocable.c + :identifiers: revocable_provider + +.. kernel-doc:: drivers/base/revocable.c + :identifiers: revocable_provider_alloc + +.. kernel-doc:: drivers/base/revocable.c + :identifiers: devm_revocable_provider_alloc + +.. kernel-doc:: drivers/base/revocable.c + :identifiers: revocable_provider_revoke + +For Resource Consumers +---------------------- +.. kernel-doc:: drivers/base/revocable.c + :identifiers: revocable + +.. kernel-doc:: drivers/base/revocable.c + :identifiers: revocable_alloc + +.. kernel-doc:: drivers/base/revocable.c + :identifiers: revocable_free + +.. kernel-doc:: drivers/base/revocable.c + :identifiers: revocable_try_access + +.. kernel-doc:: drivers/base/revocable.c + :identifiers: revocable_withdraw_access + +.. kernel-doc:: include/linux/revocable.h + :identifiers: REVOCABLE_TRY_ACCESS_WITH + +Example Usage +~~~~~~~~~~~~~ + +.. code-block:: c + + void consumer_use_resource(struct revocable *rev) + { + struct foo_resource *res; + + REVOCABLE_TRY_ACCESS_WITH(rev, res); + // Always check if the resource is valid. + if (!res) { + pr_warn("Resource is not available\n"); + return; + } + + // At this point, 'res' is guaranteed to be valid until + // this block exits. + do_something_with(res); + + } // revocable_withdraw_access() is automatically called here. + +.. kernel-doc:: include/linux/revocable.h + :identifiers: REVOCABLE_TRY_ACCESS_SCOPED + +Example Usage +~~~~~~~~~~~~~ + +.. code-block:: c + + void consumer_use_resource(struct revocable *rev) + { + struct foo_resource *res; + + REVOCABLE_TRY_ACCESS_SCOPED(rev, res) { + // Always check if the resource is valid. + if (!res) { + pr_warn("Resource is not available\n"); + return; + } + + // At this point, 'res' is guaranteed to be valid until + // this block exits. + do_something_with(res); + } + + // revocable_withdraw_access() is automatically called here. + } diff --git a/MAINTAINERS b/MAINTAINERS index a671e3d4e8be..fd683c62012a 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -22517,6 +22517,13 @@ F: include/uapi/linux/rseq.h F: kernel/rseq.c F: tools/testing/selftests/rseq/ =20 +REVOCABLE RESOURCE MANAGEMENT +M: Tzung-Bi Shih +L: linux-kernel@vger.kernel.org +S: Maintained +F: drivers/base/revocable.c +F: include/linux/revocable.h + RFKILL M: Johannes Berg L: linux-wireless@vger.kernel.org diff --git a/drivers/base/Makefile b/drivers/base/Makefile index 8074a10183dc..bdf854694e39 100644 --- a/drivers/base/Makefile +++ b/drivers/base/Makefile @@ -6,7 +6,7 @@ obj-y :=3D component.o core.o bus.o dd.o syscore.o \ cpu.o firmware.o init.o map.o devres.o \ attribute_container.o transport_class.o \ topology.o container.o property.o cacheinfo.o \ - swnode.o faux.o + swnode.o faux.o revocable.o obj-$(CONFIG_AUXILIARY_BUS) +=3D auxiliary.o obj-$(CONFIG_DEVTMPFS) +=3D devtmpfs.o obj-y +=3D power/ diff --git a/drivers/base/revocable.c b/drivers/base/revocable.c new file mode 100644 index 000000000000..f6cece275aac --- /dev/null +++ b/drivers/base/revocable.c @@ -0,0 +1,242 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright 2026 Google LLC + * + * Revocable resource management + */ + +#include +#include +#include +#include +#include + +/** + * DOC: Overview + * + * The "revocable" mechanism is a synchronization primitive designed to ma= nage + * safe access to resources that can be asynchronously removed or invalida= ted. + * Its primary purpose is to prevent Use-After-Free (UAF) errors when + * interacting with resources whose lifetimes are not guaranteed to outlast + * their consumers. + * + * This is particularly useful in systems where resources can disappear + * unexpectedly, such as those provided by hot-pluggable devices like USB. + * When a consumer holds a reference to such a resource, the underlying de= vice + * might be removed, causing the resource's memory to be freed. Subsequent + * access attempts by the consumer would then lead to UAF errors. + * + * Revocable addresses this by providing a form of "weak reference" and a + * controlled access method. It allows a resource consumer to safely atte= mpt to + * access the resource. The mechanism guarantees that any access granted = is + * valid for the duration of its use. If the resource has already been + * revoked (i.e., freed), the access attempt will fail safely, typically by + * returning NULL, instead of causing a crash. + * + * The implementation uses a provider/consumer model built on Sleepable + * RCU (SRCU) to guarantee safe memory access: + * + * - A resource provider, such as a driver for a hot-pluggable device, + * allocates a struct revocable_provider and initializes it with a point= er + * to the resource. + * + * - A resource consumer that wants to access the resource allocates a + * struct revocable which acts as a handle containing a reference to the + * provider. + * + * - To access the resource, the consumer uses revocable_try_access(). + * This function enters an SRCU read-side critical section and returns + * the pointer to the resource. If the provider has already freed the + * resource, it returns NULL. After use, the consumer calls + * revocable_withdraw_access() to exit the SRCU critical section. The + * REVOCABLE_TRY_ACCESS_WITH() and REVOCABLE_TRY_ACCESS_SCOPED() are + * convenient helpers for doing that. + * + * - When the provider needs to remove the resource, it calls + * revocable_provider_revoke(). This function sets the internal resource + * pointer to NULL and then calls synchronize_srcu() to wait for all + * current readers to finish before the resource can be completely torn + * down. + */ + +/** + * struct revocable_provider - A handle for resource provider. + * @srcu: The SRCU to protect the resource. + * @res: The pointer of resource. It can point to anything. + * @kref: The refcount for this handle. + */ +struct revocable_provider { + struct srcu_struct srcu; + void __rcu *res; + struct kref kref; +}; + +/** + * struct revocable - A handle for resource consumer. + * @rp: The pointer of resource provider. + * @idx: The index for the RCU critical section. + */ +struct revocable { + struct revocable_provider *rp; + int idx; +}; + +/** + * revocable_provider_alloc() - Allocate struct revocable_provider. + * @res: The pointer of resource. + * + * This holds an initial refcount to the struct. + * + * Return: The pointer of struct revocable_provider. NULL on errors. + */ +struct revocable_provider *revocable_provider_alloc(void *res) +{ + struct revocable_provider *rp; + + rp =3D kzalloc(sizeof(*rp), GFP_KERNEL); + if (!rp) + return NULL; + + init_srcu_struct(&rp->srcu); + rcu_assign_pointer(rp->res, res); + synchronize_srcu(&rp->srcu); + kref_init(&rp->kref); + + return rp; +} +EXPORT_SYMBOL_GPL(revocable_provider_alloc); + +static void revocable_provider_release(struct kref *kref) +{ + struct revocable_provider *rp =3D container_of(kref, + struct revocable_provider, kref); + + cleanup_srcu_struct(&rp->srcu); + kfree(rp); +} + +/** + * revocable_provider_revoke() - Revoke the managed resource. + * @rp: The pointer of resource provider. + * + * This sets the resource `(struct revocable_provider *)->res` to NULL to + * indicate the resource has gone. + * + * This drops the refcount to the resource provider. If it is the final + * reference, revocable_provider_release() will be called to free the stru= ct. + */ +void revocable_provider_revoke(struct revocable_provider *rp) +{ + rcu_assign_pointer(rp->res, NULL); + synchronize_srcu(&rp->srcu); + kref_put(&rp->kref, revocable_provider_release); +} +EXPORT_SYMBOL_GPL(revocable_provider_revoke); + +static void devm_revocable_provider_revoke(void *data) +{ + struct revocable_provider *rp =3D data; + + revocable_provider_revoke(rp); +} + +/** + * devm_revocable_provider_alloc() - Dev-managed revocable_provider_alloc(= ). + * @dev: The device. + * @res: The pointer of resource. + * + * It is convenient to allocate providers via this function if the @res is + * also tied to the lifetime of the @dev. revocable_provider_revoke() will + * be called automatically when the device is unbound. + * + * This holds an initial refcount to the struct. + * + * Return: The pointer of struct revocable_provider. NULL on errors. + */ +struct revocable_provider *devm_revocable_provider_alloc(struct device *de= v, + void *res) +{ + struct revocable_provider *rp; + + rp =3D revocable_provider_alloc(res); + if (!rp) + return NULL; + + if (devm_add_action_or_reset(dev, devm_revocable_provider_revoke, rp)) + return NULL; + + return rp; +} +EXPORT_SYMBOL_GPL(devm_revocable_provider_alloc); + +/** + * revocable_alloc() - Allocate struct revocable. + * @rp: The pointer of resource provider. + * + * This holds a refcount to the resource provider. + * + * Return: The pointer of struct revocable. NULL on errors. + */ +struct revocable *revocable_alloc(struct revocable_provider *rp) +{ + struct revocable *rev; + + rev =3D kzalloc(sizeof(*rev), GFP_KERNEL); + if (!rev) + return NULL; + + rev->rp =3D rp; + kref_get(&rp->kref); + + return rev; +} +EXPORT_SYMBOL_GPL(revocable_alloc); + +/** + * revocable_free() - Free struct revocable. + * @rev: The pointer of struct revocable. + * + * This drops a refcount to the resource provider. If it is the final + * reference, revocable_provider_release() will be called to free the stru= ct. + */ +void revocable_free(struct revocable *rev) +{ + struct revocable_provider *rp =3D rev->rp; + + kref_put(&rp->kref, revocable_provider_release); + kfree(rev); +} +EXPORT_SYMBOL_GPL(revocable_free); + +/** + * revocable_try_access() - Try to access the resource. + * @rev: The pointer of struct revocable. + * + * This tries to de-reference to the resource and enters a RCU critical + * section. + * + * Return: The pointer to the resource. NULL if the resource has gone. + */ +void *revocable_try_access(struct revocable *rev) __acquires(&rev->rp->src= u) +{ + struct revocable_provider *rp =3D rev->rp; + + rev->idx =3D srcu_read_lock(&rp->srcu); + return srcu_dereference(rp->res, &rp->srcu); +} +EXPORT_SYMBOL_GPL(revocable_try_access); + +/** + * revocable_withdraw_access() - Stop accessing to the resource. + * @rev: The pointer of struct revocable. + * + * Call this function to indicate the resource is no longer used. It exits + * the RCU critical section. + */ +void revocable_withdraw_access(struct revocable *rev) __releases(&rev->rp-= >srcu) +{ + struct revocable_provider *rp =3D rev->rp; + + srcu_read_unlock(&rp->srcu, rev->idx); +} +EXPORT_SYMBOL_GPL(revocable_withdraw_access); diff --git a/include/linux/revocable.h b/include/linux/revocable.h new file mode 100644 index 000000000000..659ba01c58db --- /dev/null +++ b/include/linux/revocable.h @@ -0,0 +1,69 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright 2026 Google LLC + */ + +#ifndef __LINUX_REVOCABLE_H +#define __LINUX_REVOCABLE_H + +#include +#include + +struct device; +struct revocable; +struct revocable_provider; + +struct revocable_provider *revocable_provider_alloc(void *res); +void revocable_provider_revoke(struct revocable_provider *rp); +struct revocable_provider *devm_revocable_provider_alloc(struct device *de= v, + void *res); + +struct revocable *revocable_alloc(struct revocable_provider *rp); +void revocable_free(struct revocable *rev); +void *revocable_try_access(struct revocable *rev) __acquires(&rev->rp->src= u); +void revocable_withdraw_access(struct revocable *rev) __releases(&rev->rp-= >srcu); + +DEFINE_FREE(access_rev, struct revocable *, if (_T) revocable_withdraw_acc= ess(_T)) + +/** + * REVOCABLE_TRY_ACCESS_WITH() - A helper for accessing revocable resource + * @_rev: The consumer's ``struct revocable *`` handle. + * @_res: A pointer variable that will be assigned the resource. + * + * The macro simplifies the access-release cycle for consumers, ensuring t= hat + * revocable_withdraw_access() is always called, even in the case of an ea= rly + * exit. + * + * It creates a local variable in the current scope. @_res is populated w= ith + * the result of revocable_try_access(). The consumer code **must** check= if + * @_res is ``NULL`` before using it. The revocable_withdraw_access() fun= ction + * is automatically called when the scope is exited. + * + * Note: It shares the same issue with guard() in cleanup.h. No goto stat= ements + * are allowed before the helper. Otherwise, the compiler fails with + * "jump bypasses initialization of variable with __attribute__((cleanup))= ". + */ +#define REVOCABLE_TRY_ACCESS_WITH(_rev, _res) \ + struct revocable *__UNIQUE_ID(name) __free(access_rev) =3D _rev; \ + _res =3D revocable_try_access(_rev) + +#define _REVOCABLE_TRY_ACCESS_SCOPED(_rev, _label, _res) \ + for (struct revocable *__UNIQUE_ID(name) __free(access_rev) =3D _rev; \ + (_res =3D revocable_try_access(_rev)) || true; ({ goto _label; })) \ + if (0) { \ +_label: \ + break; \ + } else + +/** + * REVOCABLE_TRY_ACCESS_SCOPED() - A helper for accessing revocable resour= ce + * @_rev: The consumer's ``struct revocable *`` handle. + * @_res: A pointer variable that will be assigned the resource. + * + * Similar to REVOCABLE_TRY_ACCESS_WITH() but with an explicit scope from a + * temporary ``for`` loop. + */ +#define REVOCABLE_TRY_ACCESS_SCOPED(_rev, _res) \ + _REVOCABLE_TRY_ACCESS_SCOPED(_rev, __UNIQUE_ID(label), _res) + +#endif /* __LINUX_REVOCABLE_H */ --=20 2.52.0.457.g6b5491de43-goog From nobody Sun Feb 8 08:27:37 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0CADE2EA16A; Fri, 16 Jan 2026 08:03:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768550604; cv=none; b=UOLp9GZdaKKIJnXnf2EGZL2IcTJoaWxeoSo6IOaurkn34+PgMizYdTCwsC3jD6fJhVNvAz5EDIHBAahHe/zaxHCnUugugbWSqAv7wTwfF0oTGFsTKMWUvhdlIw55MAQqZbncRZzKi8id1OxXDyXTtzCDD18yc3bXsExaf9e5N6w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768550604; c=relaxed/simple; bh=34BVjBvX5lK3lNQk7gr0ARLP4Kd8ezVIdxO/YL4kztc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JvSUDNoD5e6MXjlG/VMLzFhIh0kDpgnK6f01R1uSIlfuuoxOGSV0HFpV6444EI8sgbjtXhZRuiR4D81RaZzVBZ3aOsxmKStAQ4Weu80p28Zncknw54fJyxQxUL6fKJ6eqMlyzDHofdtjFxPSy0PE5KVBvSkHTPqfSSK9XJpzS6I= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DzNaGfMs; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DzNaGfMs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 024D0C19424; Fri, 16 Jan 2026 08:03:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768550603; bh=34BVjBvX5lK3lNQk7gr0ARLP4Kd8ezVIdxO/YL4kztc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DzNaGfMsj1eX/guULntLgkaQeqRjgljFyoQuYxesbL89YA+/tWCPtG82wBEhUJWc1 zlXUYKEazeLJqmC92xxzo6J3ZxXLImi/Io1GtC7eM+Qj7Eby2DflGfv2EashoJawRL 6LBva/RlqIZsQeIB1KjZyHPVRd+3D+aC0e564G3XtokNQn7nFf0cQUeE1y/Yvh9v1z uK/fmP49XAotNxlqILPSFRBEeLWbzg0ieBLTJ41IsWsUFRWcQ52SWSE7WRpU8MiyK/ tVAKPDlx06Fy1RdIdKtQ9geS0eH1TafruYjgCt52dCEcIWZyH6+WqX6ZdL97n6vE1G beZUUWyzFcE2A== From: Tzung-Bi Shih To: Benson Leung , Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , Bartosz Golaszewski , Linus Walleij Cc: Jonathan Corbet , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, chrome-platform@lists.linux.dev, linux-kselftest@vger.kernel.org, tzungbi@kernel.org, Laurent Pinchart , Wolfram Sang , Simona Vetter , Dan Williams , Jason Gunthorpe , linux-gpio@vger.kernel.org Subject: [PATCH v7 2/3] revocable: Add Kunit test cases Date: Fri, 16 Jan 2026 08:02:34 +0000 Message-ID: <20260116080235.350305-3-tzungbi@kernel.org> X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog In-Reply-To: <20260116080235.350305-1-tzungbi@kernel.org> References: <20260116080235.350305-1-tzungbi@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add Kunit test cases for the revocable API. The test cases cover the following scenarios: - Basic: Verifies that a consumer can successfully access the resource provided via the provider. - Revocation: Verifies that after the provider revokes the resource, the consumer correctly receives a NULL pointer on a subsequent access. - Try Access Macro: Same as "Revocation" but uses the REVOCABLE_TRY_ACCESS_WITH() and REVOCABLE_TRY_ACCESS_SCOPED(). A way to run the test: $ ./tools/testing/kunit/kunit.py run \ --kconfig_add CONFIG_REVOCABLE_KUNIT_TEST=3Dy \ revocable_test Signed-off-by: Tzung-Bi Shih --- v7: - "2025" -> "2026" in copyright. - Rename the test name "macro" -> "try_access_macro". v6: https://lore.kernel.org/chrome-platform/20251106152330.11733-3-tzungbi@= kernel.org - Rename REVOCABLE_TRY_ACCESS_WITH() -> REVOCABLE_TRY_ACCESS_SCOPED(). - Add tests for new REVOCABLE_TRY_ACCESS_WITH(). v5: https://lore.kernel.org/chrome-platform/20251016054204.1523139-3-tzungb= i@kernel.org - No changes. v4: https://lore.kernel.org/chrome-platform/20250923075302.591026-3-tzungbi= @kernel.org - REVOCABLE() -> REVOCABLE_TRY_ACCESS_WITH(). - revocable_release() -> revocable_withdraw_access(). v3: https://lore.kernel.org/chrome-platform/20250912081718.3827390-3-tzungb= i@kernel.org - No changes. v2: https://lore.kernel.org/chrome-platform/20250820081645.847919-3-tzungbi= @kernel.org - New in the series. MAINTAINERS | 1 + drivers/base/Kconfig | 8 ++ drivers/base/Makefile | 3 + drivers/base/revocable_test.c | 139 ++++++++++++++++++++++++++++++++++ 4 files changed, 151 insertions(+) create mode 100644 drivers/base/revocable_test.c diff --git a/MAINTAINERS b/MAINTAINERS index fd683c62012a..8e237833a17a 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -22522,6 +22522,7 @@ M: Tzung-Bi Shih L: linux-kernel@vger.kernel.org S: Maintained F: drivers/base/revocable.c +F: drivers/base/revocable_test.c F: include/linux/revocable.h =20 RFKILL diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index 1786d87b29e2..8f7d7b9d81ac 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -250,3 +250,11 @@ config FW_DEVLINK_SYNC_STATE_TIMEOUT work on. =20 endmenu + +# Kunit test cases +config REVOCABLE_KUNIT_TEST + tristate "Kunit tests for revocable" if !KUNIT_ALL_TESTS + depends on KUNIT + default KUNIT_ALL_TESTS + help + Kunit tests for the revocable API. diff --git a/drivers/base/Makefile b/drivers/base/Makefile index bdf854694e39..4185aaa9bbb9 100644 --- a/drivers/base/Makefile +++ b/drivers/base/Makefile @@ -35,3 +35,6 @@ ccflags-$(CONFIG_DEBUG_DRIVER) :=3D -DDEBUG # define_trace.h needs to know how to find our header CFLAGS_trace.o :=3D -I$(src) obj-$(CONFIG_TRACING) +=3D trace.o + +# Kunit test cases +obj-$(CONFIG_REVOCABLE_KUNIT_TEST) +=3D revocable_test.o diff --git a/drivers/base/revocable_test.c b/drivers/base/revocable_test.c new file mode 100644 index 000000000000..28d46ce1ba0c --- /dev/null +++ b/drivers/base/revocable_test.c @@ -0,0 +1,139 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright 2026 Google LLC + * + * Kunit tests for the revocable API. + * + * The test cases cover the following scenarios: + * + * - Basic: Verifies that a consumer can successfully access the resource + * provided via the provider. + * + * - Revocation: Verifies that after the provider revokes the resource, + * the consumer correctly receives a NULL pointer on a subsequent access. + * + * - Try Access Macro: Same as "Revocation" but uses the + * REVOCABLE_TRY_ACCESS_WITH() and REVOCABLE_TRY_ACCESS_SCOPED(). + */ + +#include +#include + +static void revocable_test_basic(struct kunit *test) +{ + struct revocable_provider *rp; + struct revocable *rev; + void *real_res =3D (void *)0x12345678, *res; + + rp =3D revocable_provider_alloc(real_res); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rp); + + rev =3D revocable_alloc(rp); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rev); + + res =3D revocable_try_access(rev); + KUNIT_EXPECT_PTR_EQ(test, res, real_res); + revocable_withdraw_access(rev); + + revocable_free(rev); + revocable_provider_revoke(rp); +} + +static void revocable_test_revocation(struct kunit *test) +{ + struct revocable_provider *rp; + struct revocable *rev; + void *real_res =3D (void *)0x12345678, *res; + + rp =3D revocable_provider_alloc(real_res); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rp); + + rev =3D revocable_alloc(rp); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rev); + + res =3D revocable_try_access(rev); + KUNIT_EXPECT_PTR_EQ(test, res, real_res); + revocable_withdraw_access(rev); + + revocable_provider_revoke(rp); + + res =3D revocable_try_access(rev); + KUNIT_EXPECT_PTR_EQ(test, res, NULL); + revocable_withdraw_access(rev); + + revocable_free(rev); +} + +static void revocable_test_try_access_macro(struct kunit *test) +{ + struct revocable_provider *rp; + struct revocable *rev; + void *real_res =3D (void *)0x12345678, *res; + + rp =3D revocable_provider_alloc(real_res); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rp); + + rev =3D revocable_alloc(rp); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rev); + + { + REVOCABLE_TRY_ACCESS_WITH(rev, res); + KUNIT_EXPECT_PTR_EQ(test, res, real_res); + } + + revocable_provider_revoke(rp); + + { + REVOCABLE_TRY_ACCESS_WITH(rev, res); + KUNIT_EXPECT_PTR_EQ(test, res, NULL); + } + + revocable_free(rev); +} + +static void revocable_test_try_access_macro2(struct kunit *test) +{ + struct revocable_provider *rp; + struct revocable *rev; + void *real_res =3D (void *)0x12345678, *res; + bool accessed; + + rp =3D revocable_provider_alloc(real_res); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rp); + + rev =3D revocable_alloc(rp); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rev); + + accessed =3D false; + REVOCABLE_TRY_ACCESS_SCOPED(rev, res) { + KUNIT_EXPECT_PTR_EQ(test, res, real_res); + accessed =3D true; + } + KUNIT_EXPECT_TRUE(test, accessed); + + revocable_provider_revoke(rp); + + accessed =3D false; + REVOCABLE_TRY_ACCESS_SCOPED(rev, res) { + KUNIT_EXPECT_PTR_EQ(test, res, NULL); + accessed =3D true; + } + KUNIT_EXPECT_TRUE(test, accessed); + + revocable_free(rev); +} + +static struct kunit_case revocable_test_cases[] =3D { + KUNIT_CASE(revocable_test_basic), + KUNIT_CASE(revocable_test_revocation), + KUNIT_CASE(revocable_test_try_access_macro), + KUNIT_CASE(revocable_test_try_access_macro2), + {} +}; + +static struct kunit_suite revocable_test_suite =3D { + .name =3D "revocable_test", + .test_cases =3D revocable_test_cases, +}; + +kunit_test_suite(revocable_test_suite); --=20 2.52.0.457.g6b5491de43-goog From nobody Sun Feb 8 08:27:37 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2799E2DC359; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="LW6tdlKj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1B42BC19421; Fri, 16 Jan 2026 08:03:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768550606; bh=ISjk0mF+kvy32Y01Ja6qoG3N9ZRVPpKla32G/KY/fyk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LW6tdlKjCOO/OHgMvfo6fkXujDIH5023ASwEQSNmf6654m6IJSvlxXyZLsV5nVBJj 1mDf6MLeGZIGzpOFWM6uzKeCT/IFRxqFDnU3OiHI3ltRTRaZJpG7IyEoC9EskN8mi+ 0YJtTqvQXnWdCiSygkYi2EXSkfwMCn11FBhP3AyZxcJ/upitpp48XE9P6JAKeOzmy6 5HP1YwaqGdSHbzXIk9y8HK7ZC5nvtkdoNwaXiJrfqU8auPRWBG8nP2CwNH4XeUry8P Qc1nrpH6lVTAJjoPcjfkytEfvGZ4MUjhejII1OThzGDj+eLk/sY0FcMVucZW5ok7yW 54YjxHs6afoUQ== From: Tzung-Bi Shih To: Benson Leung , Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , Bartosz Golaszewski , Linus Walleij Cc: Jonathan Corbet , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, chrome-platform@lists.linux.dev, linux-kselftest@vger.kernel.org, tzungbi@kernel.org, Laurent Pinchart , Wolfram Sang , Simona Vetter , Dan Williams , Jason Gunthorpe , linux-gpio@vger.kernel.org Subject: [PATCH v7 3/3] selftests: revocable: Add kselftest cases Date: Fri, 16 Jan 2026 08:02:35 +0000 Message-ID: <20260116080235.350305-4-tzungbi@kernel.org> X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog In-Reply-To: <20260116080235.350305-1-tzungbi@kernel.org> References: <20260116080235.350305-1-tzungbi@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add kselftest cases for the revocable API. The test consists of three parts: - A kernel module (revocable_test.ko) that creates a debugfs interface with `/provider` and `/consumer` files. - A user-space C program (revocable_test) that uses the kselftest harness to interact with the debugfs files. - An orchestrating shell script (test-revocable.sh) that loads the module, runs the C program, and unloads the module. The test cases cover the following scenarios: - Basic: Verifies that a consumer can successfully access the resource provided via the provider. - Revocation: Verifies that after the provider revokes the resource, the consumer correctly receives a NULL pointer on a subsequent access. - Try Access Macro: Same as "Revocation" but uses the REVOCABLE_TRY_ACCESS_WITH() and REVOCABLE_TRY_ACCESS_SCOPED(). Signed-off-by: Tzung-Bi Shih --- v7: - "2025" -> "2026" in copyright. - Rename the test name "macro" -> "try_access_macro". v6: https://lore.kernel.org/chrome-platform/20251106152330.11733-4-tzungbi@= kernel.org - Rename REVOCABLE_TRY_ACCESS_WITH() -> REVOCABLE_TRY_ACCESS_SCOPED(). - Add tests for new REVOCABLE_TRY_ACCESS_WITH(). v5: https://lore.kernel.org/chrome-platform/20251016054204.1523139-4-tzungb= i@kernel.org - No changes. v4: https://lore.kernel.org/chrome-platform/20250923075302.591026-4-tzungbi= @kernel.org - REVOCABLE() -> REVOCABLE_TRY_ACCESS_WITH(). - revocable_release() -> revocable_withdraw_access(). v3: https://lore.kernel.org/chrome-platform/20250912081718.3827390-4-tzungb= i@kernel.org - No changes. v2: https://lore.kernel.org/chrome-platform/20250820081645.847919-4-tzungbi= @kernel.org - New in the series. A way to run the kselftest (for my reference): - Update kernel to the DUT. - `mkdir build` and copy the kernel config to build/. - `make O=3Dbuild LLVM=3D1 -j32` (for generated headers and built-in symbol= s). - `make O=3Dbuild LLVM=3D1 KDIR=3D$(pwd) -C tools/testing/selftests/ TARGETS=3Ddrivers/base/revocable gen_tar`. - Copy build/kselftest/kselftest_install/kselftest-packages/kselftest.tar.gz to the DUT, extract, and execute the run_kselftest.sh. MAINTAINERS | 1 + tools/testing/selftests/Makefile | 1 + .../selftests/drivers/base/revocable/Makefile | 7 + .../drivers/base/revocable/revocable_test.c | 136 ++++++++++++ .../drivers/base/revocable/test-revocable.sh | 39 ++++ .../base/revocable/test_modules/Makefile | 10 + .../revocable/test_modules/revocable_test.c | 195 ++++++++++++++++++ 7 files changed, 389 insertions(+) create mode 100644 tools/testing/selftests/drivers/base/revocable/Makefile create mode 100644 tools/testing/selftests/drivers/base/revocable/revocabl= e_test.c create mode 100755 tools/testing/selftests/drivers/base/revocable/test-rev= ocable.sh create mode 100644 tools/testing/selftests/drivers/base/revocable/test_mod= ules/Makefile create mode 100644 tools/testing/selftests/drivers/base/revocable/test_mod= ules/revocable_test.c diff --git a/MAINTAINERS b/MAINTAINERS index 8e237833a17a..51426922c88e 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -22524,6 +22524,7 @@ S: Maintained F: drivers/base/revocable.c F: drivers/base/revocable_test.c F: include/linux/revocable.h +F: tools/testing/selftests/drivers/base/revocable/ =20 RFKILL M: Johannes Berg diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Mak= efile index 56e44a98d6a5..11b6515ce3d0 100644 --- a/tools/testing/selftests/Makefile +++ b/tools/testing/selftests/Makefile @@ -17,6 +17,7 @@ TARGETS +=3D damon TARGETS +=3D devices/error_logs TARGETS +=3D devices/probe TARGETS +=3D dmabuf-heaps +TARGETS +=3D drivers/base/revocable TARGETS +=3D drivers/dma-buf TARGETS +=3D drivers/ntsync TARGETS +=3D drivers/s390x/uvdevice diff --git a/tools/testing/selftests/drivers/base/revocable/Makefile b/tool= s/testing/selftests/drivers/base/revocable/Makefile new file mode 100644 index 000000000000..afa5ca0fa452 --- /dev/null +++ b/tools/testing/selftests/drivers/base/revocable/Makefile @@ -0,0 +1,7 @@ +# SPDX-License-Identifier: GPL-2.0 + +TEST_GEN_MODS_DIR :=3D test_modules +TEST_GEN_PROGS_EXTENDED :=3D revocable_test +TEST_PROGS :=3D test-revocable.sh + +include ../../../lib.mk diff --git a/tools/testing/selftests/drivers/base/revocable/revocable_test.= c b/tools/testing/selftests/drivers/base/revocable/revocable_test.c new file mode 100644 index 000000000000..f024164e9273 --- /dev/null +++ b/tools/testing/selftests/drivers/base/revocable/revocable_test.c @@ -0,0 +1,136 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright 2026 Google LLC + * + * A selftest for the revocable API. + * + * The test cases cover the following scenarios: + * + * - Basic: Verifies that a consumer can successfully access the resource + * provided via the provider. + * + * - Revocation: Verifies that after the provider revokes the resource, + * the consumer correctly receives a NULL pointer on a subsequent access. + * + * - Try Access Macro: Same as "Revocation" but uses the + * REVOCABLE_TRY_ACCESS_WITH() and REVOCABLE_TRY_ACCESS_SCOPED(). + */ + +#include +#include + +#include "../../../kselftest_harness.h" + +#define DEBUGFS_PATH "/sys/kernel/debug/revocable_test" +#define TEST_CMD_RESOURCE_GONE "resource_gone" +#define TEST_DATA "12345678" +#define TEST_MAGIC_OFFSET 0x1234 +#define TEST_MAGIC_OFFSET2 0x5678 + +FIXTURE(revocable_fixture) { + int pfd; + int cfd; +}; + +FIXTURE_SETUP(revocable_fixture) { + int ret; + + self->pfd =3D open(DEBUGFS_PATH "/provider", O_WRONLY); + ASSERT_NE(-1, self->pfd) + TH_LOG("failed to open provider fd"); + + ret =3D write(self->pfd, TEST_DATA, strlen(TEST_DATA)); + ASSERT_NE(-1, ret) { + close(self->pfd); + TH_LOG("failed to write test data"); + } + + self->cfd =3D open(DEBUGFS_PATH "/consumer", O_RDONLY); + ASSERT_NE(-1, self->cfd) + TH_LOG("failed to open consumer fd"); +} + +FIXTURE_TEARDOWN(revocable_fixture) { + close(self->cfd); + close(self->pfd); +} + +/* + * ASSERT_* is only available in TEST or TEST_F block. Use + * macro for the helper. + */ +#define READ_TEST_DATA(_fd, _offset, _data, _msg) \ + do { \ + int ret; \ + \ + ret =3D lseek(_fd, _offset, SEEK_SET); \ + ASSERT_NE(-1, ret) \ + TH_LOG("failed to lseek"); \ + \ + ret =3D read(_fd, _data, sizeof(_data) - 1); \ + ASSERT_NE(-1, ret) \ + TH_LOG(_msg); \ + data[ret] =3D '\0'; \ + } while (0) + +TEST_F(revocable_fixture, basic) { + char data[16]; + + READ_TEST_DATA(self->cfd, 0, data, "failed to read test data"); + EXPECT_STREQ(TEST_DATA, data); +} + +TEST_F(revocable_fixture, revocation) { + char data[16]; + int ret; + + READ_TEST_DATA(self->cfd, 0, data, "failed to read test data"); + EXPECT_STREQ(TEST_DATA, data); + + ret =3D write(self->pfd, TEST_CMD_RESOURCE_GONE, + strlen(TEST_CMD_RESOURCE_GONE)); + ASSERT_NE(-1, ret) + TH_LOG("failed to write resource gone cmd"); + + READ_TEST_DATA(self->cfd, 0, data, + "failed to read test data after resource gone"); + EXPECT_STREQ("(null)", data); +} + +TEST_F(revocable_fixture, try_access_macro) { + char data[16]; + int ret; + + READ_TEST_DATA(self->cfd, TEST_MAGIC_OFFSET, data, + "failed to read test data"); + EXPECT_STREQ(TEST_DATA, data); + + ret =3D write(self->pfd, TEST_CMD_RESOURCE_GONE, + strlen(TEST_CMD_RESOURCE_GONE)); + ASSERT_NE(-1, ret) + TH_LOG("failed to write resource gone cmd"); + + READ_TEST_DATA(self->cfd, TEST_MAGIC_OFFSET, data, + "failed to read test data after resource gone"); + EXPECT_STREQ("(null)", data); +} + +TEST_F(revocable_fixture, try_access_macro2) { + char data[16]; + int ret; + + READ_TEST_DATA(self->cfd, TEST_MAGIC_OFFSET2, data, + "failed to read test data"); + EXPECT_STREQ(TEST_DATA, data); + + ret =3D write(self->pfd, TEST_CMD_RESOURCE_GONE, + strlen(TEST_CMD_RESOURCE_GONE)); + ASSERT_NE(-1, ret) + TH_LOG("failed to write resource gone cmd"); + + READ_TEST_DATA(self->cfd, TEST_MAGIC_OFFSET2, data, + "failed to read test data after resource gone"); + EXPECT_STREQ("(null)", data); +} + +TEST_HARNESS_MAIN diff --git a/tools/testing/selftests/drivers/base/revocable/test-revocable.= sh b/tools/testing/selftests/drivers/base/revocable/test-revocable.sh new file mode 100755 index 000000000000..3a34be28001a --- /dev/null +++ b/tools/testing/selftests/drivers/base/revocable/test-revocable.sh @@ -0,0 +1,39 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 + +mod_name=3D"revocable_test" +ksft_fail=3D1 +ksft_skip=3D4 + +if [ "$(id -u)" -ne 0 ]; then + echo "$0: Must be run as root" + exit "$ksft_skip" +fi + +if ! which insmod > /dev/null 2>&1; then + echo "$0: Need insmod" + exit "$ksft_skip" +fi + +if ! which rmmod > /dev/null 2>&1; then + echo "$0: Need rmmod" + exit "$ksft_skip" +fi + +insmod test_modules/"${mod_name}".ko + +if [ ! -d /sys/kernel/debug/revocable_test/ ]; then + mount -t debugfs none /sys/kernel/debug/ + + if [ ! -d /sys/kernel/debug/revocable_test/ ]; then + echo "$0: Error mounting debugfs" + exit "$ksft_fail" + fi +fi + +./revocable_test +ret=3D$? + +rmmod "${mod_name}" + +exit "${ret}" diff --git a/tools/testing/selftests/drivers/base/revocable/test_modules/Ma= kefile b/tools/testing/selftests/drivers/base/revocable/test_modules/Makefi= le new file mode 100644 index 000000000000..f29e4f909402 --- /dev/null +++ b/tools/testing/selftests/drivers/base/revocable/test_modules/Makefile @@ -0,0 +1,10 @@ +TESTMODS_DIR :=3D $(realpath $(dir $(abspath $(lastword $(MAKEFILE_LIST)))= )) +KDIR ?=3D /lib/modules/$(shell uname -r)/build + +obj-m +=3D revocable_test.o + +all: + $(Q)$(MAKE) -C $(KDIR) M=3D$(TESTMODS_DIR) + +clean: + $(Q)$(MAKE) -C $(KDIR) M=3D$(TESTMODS_DIR) clean diff --git a/tools/testing/selftests/drivers/base/revocable/test_modules/re= vocable_test.c b/tools/testing/selftests/drivers/base/revocable/test_module= s/revocable_test.c new file mode 100644 index 000000000000..1b0692eb75f3 --- /dev/null +++ b/tools/testing/selftests/drivers/base/revocable/test_modules/revocable= _test.c @@ -0,0 +1,195 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright 2026 Google LLC + * + * A kernel module for testing the revocable API. + */ + +#include +#include +#include +#include + +#define TEST_CMD_RESOURCE_GONE "resource_gone" +#define TEST_MAGIC_OFFSET 0x1234 +#define TEST_MAGIC_OFFSET2 0x5678 + +static struct dentry *debugfs_dir; + +struct revocable_test_provider_priv { + struct revocable_provider *rp; + struct dentry *dentry; + char res[16]; +}; + +static int revocable_test_consumer_open(struct inode *inode, struct file *= filp) +{ + struct revocable *rev; + struct revocable_provider *rp =3D inode->i_private; + + rev =3D revocable_alloc(rp); + if (!rev) + return -ENOMEM; + filp->private_data =3D rev; + + return 0; +} + +static int revocable_test_consumer_release(struct inode *inode, + struct file *filp) +{ + struct revocable *rev =3D filp->private_data; + + revocable_free(rev); + return 0; +} + +static ssize_t revocable_test_consumer_read(struct file *filp, + char __user *buf, + size_t count, loff_t *offset) +{ + char *res; + char data[16]; + size_t len; + struct revocable *rev =3D filp->private_data; + + switch (*offset) { + case 0: + res =3D revocable_try_access(rev); + snprintf(data, sizeof(data), "%s", res ?: "(null)"); + revocable_withdraw_access(rev); + break; + case TEST_MAGIC_OFFSET: + { + REVOCABLE_TRY_ACCESS_WITH(rev, res); + snprintf(data, sizeof(data), "%s", res ?: "(null)"); + } + break; + case TEST_MAGIC_OFFSET2: + REVOCABLE_TRY_ACCESS_SCOPED(rev, res) + snprintf(data, sizeof(data), "%s", res ?: "(null)"); + break; + default: + return 0; + } + + len =3D min_t(size_t, strlen(data), count); + if (copy_to_user(buf, data, len)) + return -EFAULT; + + *offset =3D len; + return len; +} + +static const struct file_operations revocable_test_consumer_fops =3D { + .open =3D revocable_test_consumer_open, + .release =3D revocable_test_consumer_release, + .read =3D revocable_test_consumer_read, + .llseek =3D default_llseek, +}; + +static int revocable_test_provider_open(struct inode *inode, struct file *= filp) +{ + struct revocable_test_provider_priv *priv; + + priv =3D kzalloc(sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + filp->private_data =3D priv; + + return 0; +} + +static int revocable_test_provider_release(struct inode *inode, + struct file *filp) +{ + struct revocable_test_provider_priv *priv =3D filp->private_data; + + debugfs_remove(priv->dentry); + if (priv->rp) + revocable_provider_revoke(priv->rp); + kfree(priv); + + return 0; +} + +static ssize_t revocable_test_provider_write(struct file *filp, + const char __user *buf, + size_t count, loff_t *offset) +{ + size_t copied; + char data[64]; + struct revocable_test_provider_priv *priv =3D filp->private_data; + + copied =3D strncpy_from_user(data, buf, sizeof(data)); + if (copied < 0) + return copied; + if (copied =3D=3D sizeof(data)) + data[sizeof(data) - 1] =3D '\0'; + + /* + * Note: The test can't just close the FD for signaling the + * resource gone. Subsequent file operations on the opening + * FD of debugfs return -EIO after calling debugfs_remove(). + * See also debugfs_file_get(). + * + * Here is a side command channel for signaling the resource + * gone. + */ + if (!strcmp(data, TEST_CMD_RESOURCE_GONE)) { + revocable_provider_revoke(priv->rp); + priv->rp =3D NULL; + } else { + if (priv->res[0] !=3D '\0') + return 0; + + strscpy(priv->res, data); + + priv->rp =3D revocable_provider_alloc(&priv->res); + if (!priv->rp) + return -ENOMEM; + + priv->dentry =3D debugfs_create_file("consumer", 0400, + debugfs_dir, priv->rp, + &revocable_test_consumer_fops); + if (!priv->dentry) { + revocable_provider_revoke(priv->rp); + return -ENOMEM; + } + } + + return copied; +} + +static const struct file_operations revocable_test_provider_fops =3D { + .open =3D revocable_test_provider_open, + .release =3D revocable_test_provider_release, + .write =3D revocable_test_provider_write, +}; + +static int __init revocable_test_init(void) +{ + debugfs_dir =3D debugfs_create_dir("revocable_test", NULL); + if (!debugfs_dir) + return -ENOMEM; + + if (!debugfs_create_file("provider", 0200, debugfs_dir, NULL, + &revocable_test_provider_fops)) { + debugfs_remove_recursive(debugfs_dir); + return -ENOMEM; + } + + return 0; +} + +static void __exit revocable_test_exit(void) +{ + debugfs_remove_recursive(debugfs_dir); +} + +module_init(revocable_test_init); +module_exit(revocable_test_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Tzung-Bi Shih "); +MODULE_DESCRIPTION("Revocable Kselftest"); --=20 2.52.0.457.g6b5491de43-goog