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 DF9EC3C3430 for ; Mon, 30 Mar 2026 12:03:14 +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=1774872194; cv=none; b=asHCCfhNxbM1biP4uGVxK3TQChSs0EUtcBjV4lP+hLYd3Tui9T2Xt5LDwb5WAaB53cjpi3jmGHQKV4qKofqyxlLPWfQ3DfBvpKaG/sCBlDB07DMuw355jS+1Lo8J5R7oaYZiGKV4s3KoKGbiVyc1Swk7pwh65XKPnCyHv3sZa4Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774872194; c=relaxed/simple; bh=/7zAtkSdBspPrw3upuJaIEaGzuZL77t3uFPcttGVBls=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=nCOMhcj6BamBsjcoXuYnJ2+NrX4kRcKxLmoUnHr5GSW36ic7F/cZvo9rr/hbib0nUXF3N4YJy72z/q7TqeAGGe/GJOkNYg0ECD24ZTGVfPQDgjRmGXlVikez6+9z6Sk2bAWEA9V7BXcxi+5d7TDFntf4QzUwx9oOoAXsdi61Y5k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oP5xpsb/; 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="oP5xpsb/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F054AC2BCB0; Mon, 30 Mar 2026 12:03:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774872194; bh=/7zAtkSdBspPrw3upuJaIEaGzuZL77t3uFPcttGVBls=; h=Date:From:To:Cc:Subject:References:From; b=oP5xpsb/+f/3tF3bWO5Slcnr74HfTKUZFRGQw4A3rmfVTfdtEyRDIAcGYf1hwIIRk 7s3+XEKd77SZ/pampi9yWtsid7ZLaAZX++tfIT43MOBvKh+DeWHmBRsDGU0Xx6TQ2P QGYhFtxQP047yDuf6mXHf/xQAgf+3KhsAuNnA/HPhvUOsvS5M3fbaMJVsgQozj9PPn ucxYLxokBr/COHgdbJ+qlTCpyUYQ2WUQjNPIJ+wtaebjz9xvcmnD1YCJB1dplS2DKE dzRGp0QhOIhdmkKnyCokXwT0rXVWB3J7Ij5Gkdzxv/r2sVSqK6ETzOa0GXXjRP97Fx weseNBOVNskUg== Date: Mon, 30 Mar 2026 14:03:11 +0200 Message-ID: <20260330120118.012924430@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 V3 14/14] selftests: futex: Add tests for robust release operations References: <20260330114212.927686587@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. Signed-off-by: André Almeida Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/20260326-tonyk-vdso_test-v1-2-30a6f78c8bc3@igalia.com --- tools/testing/selftests/futex/functional/robust_list.c | 203 +++++++++++++++++ tools/testing/selftests/futex/include/futextest.h | 3 2 files changed, 206 insertions(+) --- a/tools/testing/selftests/futex/functional/robust_list.c +++ b/tools/testing/selftests/futex/functional/robust_list.c @@ -27,12 +27,14 @@ #include "futextest.h" #include "../../kselftest_harness.h" +#include #include #include #include #include #include #include +#include #include #include @@ -54,6 +56,12 @@ 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 +557,199 @@ 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 loading the vDSO functions + */ +#define VDSO_SIZE 0x4000 + +void *get_vdso_func_addr(const char *str) +{ + void *vdso_base = (void *) getauxval(AT_SYSINFO_EHDR), *addr; + Dl_info info; + + if (!vdso_base) { + perror("Error to get AT_SYSINFO_EHDR"); + return NULL; + } + + for (addr = vdso_base; addr < vdso_base + VDSO_SIZE; addr += sizeof(addr)) { + if (dladdr(addr, &info) == 0 || !info.dli_sname) + continue; + + if (!strcmp(info.dli_sname, str)) + return info.dli_saddr; + } + + 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); + + if (!self->vdso) + ksft_test_result_skip("%s not found\n", 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; + uint64_t exp = (uint64_t) NULL; + pid_t tid = gettid(); + int ret; + + *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 = (uint64_t)(unsigned long)&lock.list; + exp &= ~0xFFFFFFFFULL; + } + + ASSERT_EQ((uint64_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; + + *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, +}; + +/* + * 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; + struct robust_list_head head; + pid_t tid = gettid(); + int ret; + + *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); + ASSERT_EQ(head.list_op_pending, NULL); +} + TEST_HARNESS_MAIN --- a/tools/testing/selftests/futex/include/futextest.h +++ b/tools/testing/selftests/futex/include/futextest.h @@ -38,6 +38,9 @@ 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_WAIT_REQUEUE_PI_PRIVATE #define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \ FUTEX_PRIVATE_FLAG)