From mboxrd@z Thu Jan 1 00:00:00 1970 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 143EE33ADA8 for ; Thu, 2 Apr 2026 15:22:14 +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=1775143334; cv=none; b=Uv9NywzNAQwVZdYsdVoEdJnPLQhmd3g0+WbquvnPKSoQm1vY7PeuXpkook96QCJMoinwWIe2fT1mZvnPA2NwuN0eYzSSSL16Pcx6mir5e0BZBWFy66tGx0UQCkU1rX5S+iodat3LMt2QK7JMvw6NG7UTHCHr5K2e9DkD3sJkEA4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775143334; c=relaxed/simple; bh=xrfFjNmTY0Ejf3WJJbqYqcE5921ov1WPIjEhOECQlJM=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=UGSzHPHdf/sG3N+HseVbKRyL/gNut9p/QIsUTnLgkNoMdSoKgXVfom/0qn3eqi3Fv/7s5a1FqvGt4Uqnnv/7esFCf1ovsUi2zQQcNqjl9dHZo9NFoIL6Arg7D72TNqSsGkQHcS6V6/w8RigeKh+ozUv3YsLz+FwVIXAhePKxm0o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iAnatz0/; 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="iAnatz0/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 793FDC116C6; Thu, 2 Apr 2026 15:22:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775143334; bh=xrfFjNmTY0Ejf3WJJbqYqcE5921ov1WPIjEhOECQlJM=; h=Date:From:To:Cc:Subject:References:From; b=iAnatz0/WuCle0bKPppAzW//UlLaCE+gu083d4AWInsuZYoQJe8jMKTL44zptqfJE 4Yt+9y5WdLgliXu5mT66MbEAEO3vFcoe4bKjVilVJ/91pg7OJRkKQCbdqiRNCpoXZU v0Jioi67wSSU8s6GYw2lcSQz9CvmSOOUxHUk98B9fW2TsTfqCfvQkyj7DZaERCx8xq WnfR5k93kWyJde3d10QQhRqG3tw0hVy6WQBjXnnsbuC/NyOWTWBKzJ8EBmnKjge6uq kEI6ib5xVjYD09KAtGR+3jyz56JiN+Eqv528eJdyAr5VD7OiKS+GvzoMy7mu/vD7Cg ajVLVmdWgzVUg== Date: Thu, 02 Apr 2026 17:22:11 +0200 Message-ID: <20260402151940.554181645@kernel.org> User-Agent: quilt/0.68 From: Thomas Gleixner To: LKML Cc: Mathieu Desnoyers , =?UTF-8?q?Andr=C3=A8=20Almeida?= , Sebastian Andrzej Siewior , Carlos O'Donell , Peter Zijlstra , Florian Weimer , Rich Felker , Torvald Riegel , Darren Hart , Ingo Molnar , Davidlohr Bueso , Arnd Bergmann , "Liam R . Howlett" , Uros Bizjak , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= Subject: [patch V4 14/14] selftests: futex: Add tests for robust release operations References: <20260402151131.876492985@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 From: André Almeida Add tests for __vdso_futex_robust_listXX_try_unlock() and for the futex() op FUTEX_ROBUST_UNLOCK. Test the contended and uncontended cases for the vDSO functions and all ops combinations for FUTEX_ROBUST_UNLOCK. [ tglx: Replace the VDSO function lookup ] Signed-off-by: André Almeida Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/20260329-tonyk-vdso_test-v2-2-b7db810e44a1@igalia.com --- V3: Replaced the VDSO lookup Change from v2: - Add test variants for FUTEX_ROBUST_LIST32 - Skip 64 bit tests for 32 bit builds --- tools/testing/selftests/futex/functional/robust_list.c | 239 +++++++++++++++++ tools/testing/selftests/futex/include/futextest.h | 6 2 files changed, 245 insertions(+) --- a/tools/testing/selftests/futex/functional/robust_list.c +++ b/tools/testing/selftests/futex/functional/robust_list.c @@ -27,12 +27,15 @@ #include "futextest.h" #include "../../kselftest_harness.h" +#include #include #include #include +#include #include #include #include +#include #include #include @@ -42,6 +45,10 @@ #define SLEEP_US 100 +#if UINTPTR_MAX == 0xffffffffffffffff +# define BUILD_64 +#endif + static pthread_barrier_t barrier, barrier2; static int set_robust_list(struct robust_list_head *head, size_t len) @@ -54,6 +61,12 @@ static int get_robust_list(int pid, stru return syscall(SYS_get_robust_list, pid, head, len_ptr); } +static int sys_futex_robust_unlock(_Atomic(uint32_t) *uaddr, unsigned int op, int val, + void *list_op_pending, unsigned int val3) +{ + return syscall(SYS_futex, uaddr, op, val, NULL, list_op_pending, val3, 0); +} + /* * Basic lock struct, contains just the futex word and the robust list element * Real implementations have also a *prev to easily walk in the list @@ -549,4 +562,230 @@ TEST(test_circular_list) ksft_test_result_pass("%s\n", __func__); } +/* + * Below are tests for the fix of robust release race condition. Please read the following + * thread to learn more about the issue in the first place and why the following functions fix it: + * https://lore.kernel.org/lkml/20260316162316.356674433@kernel.org/ + */ + +/* + * Auxiliary code for binding the vDSO functions + */ +static void *get_vdso_func_addr(const char *function) +{ + const char *vdso_names[] = { + "linux-vdso.so.1", "linux-gate.so.1", "linux-vdso32.so.1", "linux-vdso64.so.1", + }; + + for (int i = 0; i < ARRAY_SIZE(vdso_names); i++) { + void *vdso = dlopen(vdso_names[i], RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD); + + if (vdso) + return dlsym(vdso, function); + } + return NULL; +} + +/* + * These are the real vDSO function signatures: + * + * __vdso_futex_robust_list64_try_unlock(__u32 *lock, __u32 tid, __u64 *pop) + * __vdso_futex_robust_list32_try_unlock(__u32 *lock, __u32 tid, __u32 *pop) + * + * So for the generic entry point we need to use a void pointer as the last argument + */ +FIXTURE(vdso_unlock) +{ + uint32_t (*vdso)(_Atomic(uint32_t) *lock, uint32_t tid, void *pop); +}; + +FIXTURE_VARIANT(vdso_unlock) +{ + bool is_32; + char func_name[]; +}; + +FIXTURE_SETUP(vdso_unlock) +{ + self->vdso = get_vdso_func_addr(variant->func_name); +} + +FIXTURE_TEARDOWN(vdso_unlock) {} + +FIXTURE_VARIANT_ADD(vdso_unlock, 32) +{ + .func_name = "__vdso_futex_robust_list32_try_unlock", + .is_32 = true, +}; + +FIXTURE_VARIANT_ADD(vdso_unlock, 64) +{ + .func_name = "__vdso_futex_robust_list64_try_unlock", + .is_32 = false, +}; + +/* + * Test the vDSO robust_listXX_try_unlock() for the uncontended case. The virtual syscall should + * return the thread ID of the lock owner, the lock word must be 0 and the list_op_pending should + * be NULL. + */ +TEST_F(vdso_unlock, test_robust_try_unlock_uncontended) +{ + struct lock_struct lock = { .futex = 0 }; + _Atomic(unsigned int) *futex = &lock.futex; + struct robust_list_head head; + uintptr_t exp = (uintptr_t) NULL; + pid_t tid = gettid(); + int ret; + + if (!self->vdso) { + ksft_test_result_skip("%s not found\n", variant->func_name); + return; + } + + *futex = tid; + + ret = set_list(&head); + if (ret) + ksft_test_result_fail("set_robust_list error\n"); + + head.list_op_pending = &lock.list; + + ret = self->vdso(futex, tid, &head.list_op_pending); + + ASSERT_EQ(ret, tid); + ASSERT_EQ(*futex, 0); + + /* Check only the lower 32 bits for the 32-bit entry point */ + if (variant->is_32) { + exp = (uintptr_t)(unsigned long)&lock.list; + exp &= ~0xFFFFFFFFULL; + } + + ASSERT_EQ((uintptr_t)(unsigned long)head.list_op_pending, exp); +} + +/* + * If the lock is contended, the operation fails. The return value is the value found at the + * futex word (tid | FUTEX_WAITERS), the futex word is not modified and the list_op_pending is_32 + * not cleared. + */ +TEST_F(vdso_unlock, test_robust_try_unlock_contended) +{ + struct lock_struct lock = { .futex = 0 }; + _Atomic(unsigned int) *futex = &lock.futex; + struct robust_list_head head; + pid_t tid = gettid(); + int ret; + + if (!self->vdso) { + ksft_test_result_skip("%s not found\n", variant->func_name); + return; + } + + *futex = tid | FUTEX_WAITERS; + + ret = set_list(&head); + if (ret) + ksft_test_result_fail("set_robust_list error\n"); + + head.list_op_pending = &lock.list; + + ret = self->vdso(futex, tid, &head.list_op_pending); + + ASSERT_EQ(ret, tid | FUTEX_WAITERS); + ASSERT_EQ(*futex, tid | FUTEX_WAITERS); + ASSERT_EQ(head.list_op_pending, &lock.list); +} + +FIXTURE(futex_op) {}; + +FIXTURE_VARIANT(futex_op) +{ + unsigned int op; + unsigned int val3; +}; + +FIXTURE_SETUP(futex_op) {} + +FIXTURE_TEARDOWN(futex_op) {} + +FIXTURE_VARIANT_ADD(futex_op, wake) +{ + .op = FUTEX_WAKE, + .val3 = 0, +}; + +FIXTURE_VARIANT_ADD(futex_op, wake_bitset) +{ + .op = FUTEX_WAKE_BITSET, + .val3 = FUTEX_BITSET_MATCH_ANY, +}; + +FIXTURE_VARIANT_ADD(futex_op, unlock_pi) +{ + .op = FUTEX_UNLOCK_PI, + .val3 = 0, +}; + +FIXTURE_VARIANT_ADD(futex_op, wake32) +{ + .op = FUTEX_WAKE | FUTEX_ROBUST_LIST32, + .val3 = 0, +}; + +FIXTURE_VARIANT_ADD(futex_op, wake_bitset32) +{ + .op = FUTEX_WAKE_BITSET | FUTEX_ROBUST_LIST32, + .val3 = FUTEX_BITSET_MATCH_ANY, +}; + +FIXTURE_VARIANT_ADD(futex_op, unlock_pi32) +{ + .op = FUTEX_UNLOCK_PI | FUTEX_ROBUST_LIST32, + .val3 = 0, +}; + +/* + * The syscall should return the number of tasks waken (for this test, 0), clear the futex word and + * clear list_op_pending + */ +TEST_F(futex_op, test_futex_robust_unlock) +{ + struct lock_struct lock = { .futex = 0 }; + _Atomic(unsigned int) *futex = &lock.futex; + uintptr_t exp = (uintptr_t) NULL; + struct robust_list_head head; + pid_t tid = gettid(); + int ret; + +#ifndef BUILD_64 + if (!(variant->op & FUTEX_ROBUST_LIST32)) { + ksft_test_result_skip("Not supported for 32 bit build\n"); + return; + } +#endif + + *futex = tid | FUTEX_WAITERS; + + ret = set_list(&head); + if (ret) + ksft_test_result_fail("set_robust_list error\n"); + + head.list_op_pending = &lock.list; + + ret = sys_futex_robust_unlock(futex, FUTEX_ROBUST_UNLOCK | variant->op, tid, + &head.list_op_pending, variant->val3); + + ASSERT_EQ(ret, 0); + ASSERT_EQ(*futex, 0); + + if (variant->op & FUTEX_ROBUST_LIST32) { + exp = (uint64_t)(unsigned long)&lock.list; + exp &= ~0xFFFFFFFFULL; + } + + ASSERT_EQ((uintptr_t)(unsigned long)head.list_op_pending, exp); +} + TEST_HARNESS_MAIN --- a/tools/testing/selftests/futex/include/futextest.h +++ b/tools/testing/selftests/futex/include/futextest.h @@ -38,6 +38,12 @@ typedef volatile u_int32_t futex_t; #ifndef FUTEX_CMP_REQUEUE_PI #define FUTEX_CMP_REQUEUE_PI 12 #endif +#ifndef FUTEX_ROBUST_UNLOCK +#define FUTEX_ROBUST_UNLOCK 512 +#endif +#ifndef FUTEX_ROBUST_LIST32 +#define FUTEX_ROBUST_LIST32 1024 +#endif #ifndef FUTEX_WAIT_REQUEUE_PI_PRIVATE #define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \ FUTEX_PRIVATE_FLAG)