From: Thomas Weißschuh Date: Thu, 26 Mar 2026 11:42:30 +0000 (+0100) Subject: vdso/timens: Move functions to new file X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5dc9cf835aba73c882348aa4f99be83b6e45ad9b;p=thirdparty%2Fkernel%2Flinux.git vdso/timens: Move functions to new file As a preparation of the untangling of time namespaces and the vDSO, move the glue functions between those subsystems into a new file. While at it, switch the mutex lock and mmap_read_lock() in the vDSO namespace code to guard(). Signed-off-by: Thomas Weißschuh Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/20260326-vdso-timens-decoupling-v2-1-c82693a7775f@linutronix.de --- diff --git a/MAINTAINERS b/MAINTAINERS index 77fdfcb55f06..6ad74a5196d1 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -10768,6 +10768,7 @@ S: Maintained T: git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/vdso F: include/asm-generic/vdso/vsyscall.h F: include/vdso/ +F: kernel/time/namespace_vdso.c F: kernel/time/vsyscall.c F: lib/vdso/ F: tools/testing/selftests/vDSO/ @@ -21000,6 +21001,7 @@ F: include/trace/events/timer* F: kernel/time/itimer.c F: kernel/time/posix-* F: kernel/time/namespace.c +F: kernel/time/namespace_vdso.c POWER MANAGEMENT CORE M: "Rafael J. Wysocki" diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h index c514d0e5a45c..0421bf1b13d7 100644 --- a/include/linux/time_namespace.h +++ b/include/linux/time_namespace.h @@ -38,8 +38,6 @@ static inline struct time_namespace *to_time_ns(struct ns_common *ns) return container_of(ns, struct time_namespace, ns); } void __init time_ns_init(void); -extern int vdso_join_timens(struct task_struct *task, - struct time_namespace *ns); extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns); static inline struct time_namespace *get_time_ns(struct time_namespace *ns) @@ -117,12 +115,6 @@ static inline void __init time_ns_init(void) { } -static inline int vdso_join_timens(struct task_struct *task, - struct time_namespace *ns) -{ - return 0; -} - static inline void timens_commit(struct task_struct *tsk, struct time_namespace *ns) { diff --git a/kernel/time/Makefile b/kernel/time/Makefile index f7d52d9543cc..662bccb3b7f9 100644 --- a/kernel/time/Makefile +++ b/kernel/time/Makefile @@ -29,6 +29,6 @@ endif obj-$(CONFIG_GENERIC_GETTIMEOFDAY) += vsyscall.o obj-$(CONFIG_DEBUG_FS) += timekeeping_debug.o obj-$(CONFIG_TEST_UDELAY) += test_udelay.o -obj-$(CONFIG_TIME_NS) += namespace.o +obj-$(CONFIG_TIME_NS) += namespace.o namespace_vdso.o obj-$(CONFIG_TEST_CLOCKSOURCE_WATCHDOG) += clocksource-wdtest.o obj-$(CONFIG_TIME_KUNIT_TEST) += time_test.o diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c index 652744e00eb4..903f55a2dfb2 100644 --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -19,7 +19,7 @@ #include #include -#include +#include "namespace_internal.h" ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim, struct timens_offsets *ns_offsets) @@ -138,117 +138,7 @@ struct time_namespace *copy_time_ns(u64 flags, return clone_time_ns(user_ns, old_ns); } -static struct timens_offset offset_from_ts(struct timespec64 off) -{ - struct timens_offset ret; - - ret.sec = off.tv_sec; - ret.nsec = off.tv_nsec; - - return ret; -} - -/* - * A time namespace VVAR page has the same layout as the VVAR page which - * contains the system wide VDSO data. - * - * For a normal task the VVAR pages are installed in the normal ordering: - * VVAR - * PVCLOCK - * HVCLOCK - * TIMENS <- Not really required - * - * Now for a timens task the pages are installed in the following order: - * TIMENS - * PVCLOCK - * HVCLOCK - * VVAR - * - * The check for vdso_clock->clock_mode is in the unlikely path of - * the seq begin magic. So for the non-timens case most of the time - * 'seq' is even, so the branch is not taken. - * - * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check - * for vdso_clock->clock_mode is a non-issue. The task is spin waiting for the - * update to finish and for 'seq' to become even anyway. - * - * Timens page has vdso_clock->clock_mode set to VDSO_CLOCKMODE_TIMENS which - * enforces the time namespace handling path. - */ -static void timens_setup_vdso_clock_data(struct vdso_clock *vc, - struct time_namespace *ns) -{ - struct timens_offset *offset = vc->offset; - struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic); - struct timens_offset boottime = offset_from_ts(ns->offsets.boottime); - - vc->seq = 1; - vc->clock_mode = VDSO_CLOCKMODE_TIMENS; - offset[CLOCK_MONOTONIC] = monotonic; - offset[CLOCK_MONOTONIC_RAW] = monotonic; - offset[CLOCK_MONOTONIC_COARSE] = monotonic; - offset[CLOCK_BOOTTIME] = boottime; - offset[CLOCK_BOOTTIME_ALARM] = boottime; -} - -struct page *find_timens_vvar_page(struct vm_area_struct *vma) -{ - if (likely(vma->vm_mm == current->mm)) - return current->nsproxy->time_ns->vvar_page; - - /* - * VM_PFNMAP | VM_IO protect .fault() handler from being called - * through interfaces like /proc/$pid/mem or - * process_vm_{readv,writev}() as long as there's no .access() - * in special_mapping_vmops(). - * For more details check_vma_flags() and __access_remote_vm() - */ - - WARN(1, "vvar_page accessed remotely"); - - return NULL; -} - -/* - * Protects possibly multiple offsets writers racing each other - * and tasks entering the namespace. - */ -static DEFINE_MUTEX(offset_lock); - -static void timens_set_vvar_page(struct task_struct *task, - struct time_namespace *ns) -{ - struct vdso_time_data *vdata; - struct vdso_clock *vc; - unsigned int i; - - if (ns == &init_time_ns) - return; - - /* Fast-path, taken by every task in namespace except the first. */ - if (likely(ns->frozen_offsets)) - return; - - mutex_lock(&offset_lock); - /* Nothing to-do: vvar_page has been already initialized. */ - if (ns->frozen_offsets) - goto out; - - ns->frozen_offsets = true; - vdata = page_address(ns->vvar_page); - vc = vdata->clock_data; - - for (i = 0; i < CS_BASES; i++) - timens_setup_vdso_clock_data(&vc[i], ns); - - if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS)) { - for (i = 0; i < ARRAY_SIZE(vdata->aux_clock_data); i++) - timens_setup_vdso_clock_data(&vdata->aux_clock_data[i], ns); - } - -out: - mutex_unlock(&offset_lock); -} +DEFINE_MUTEX(timens_offset_lock); void free_time_ns(struct time_namespace *ns) { @@ -298,12 +188,6 @@ static void timens_put(struct ns_common *ns) put_time_ns(to_time_ns(ns)); } -void timens_commit(struct task_struct *tsk, struct time_namespace *ns) -{ - timens_set_vvar_page(tsk, ns); - vdso_join_timens(tsk, ns); -} - static int timens_install(struct nsset *nsset, struct ns_common *new) { struct nsproxy *nsproxy = nsset->nsproxy; @@ -428,7 +312,7 @@ int proc_timens_set_offset(struct file *file, struct task_struct *p, goto out; } - mutex_lock(&offset_lock); + mutex_lock(&timens_offset_lock); if (time_ns->frozen_offsets) { err = -EACCES; goto out_unlock; @@ -453,7 +337,7 @@ int proc_timens_set_offset(struct file *file, struct task_struct *p, } out_unlock: - mutex_unlock(&offset_lock); + mutex_unlock(&timens_offset_lock); out: put_time_ns(time_ns); diff --git a/kernel/time/namespace_internal.h b/kernel/time/namespace_internal.h new file mode 100644 index 000000000000..e85da11abb4d --- /dev/null +++ b/kernel/time/namespace_internal.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _TIME_NAMESPACE_INTERNAL_H +#define _TIME_NAMESPACE_INTERNAL_H + +#include + +/* + * Protects possibly multiple offsets writers racing each other + * and tasks entering the namespace. + */ +extern struct mutex timens_offset_lock; + +#endif /* _TIME_NAMESPACE_INTERNAL_H */ diff --git a/kernel/time/namespace_vdso.c b/kernel/time/namespace_vdso.c new file mode 100644 index 000000000000..0e154f901501 --- /dev/null +++ b/kernel/time/namespace_vdso.c @@ -0,0 +1,146 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Author: Andrei Vagin + * Author: Dmitry Safonov + */ + +#include +#include +#include +#include +#include + +#include +#include + +#include "namespace_internal.h" + +static struct timens_offset offset_from_ts(struct timespec64 off) +{ + struct timens_offset ret; + + ret.sec = off.tv_sec; + ret.nsec = off.tv_nsec; + + return ret; +} + +/* + * A time namespace VVAR page has the same layout as the VVAR page which + * contains the system wide VDSO data. + * + * For a normal task the VVAR pages are installed in the normal ordering: + * VVAR + * PVCLOCK + * HVCLOCK + * TIMENS <- Not really required + * + * Now for a timens task the pages are installed in the following order: + * TIMENS + * PVCLOCK + * HVCLOCK + * VVAR + * + * The check for vdso_clock->clock_mode is in the unlikely path of + * the seq begin magic. So for the non-timens case most of the time + * 'seq' is even, so the branch is not taken. + * + * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check + * for vdso_clock->clock_mode is a non-issue. The task is spin waiting for the + * update to finish and for 'seq' to become even anyway. + * + * Timens page has vdso_clock->clock_mode set to VDSO_CLOCKMODE_TIMENS which + * enforces the time namespace handling path. + */ +static void timens_setup_vdso_clock_data(struct vdso_clock *vc, + struct time_namespace *ns) +{ + struct timens_offset *offset = vc->offset; + struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic); + struct timens_offset boottime = offset_from_ts(ns->offsets.boottime); + + vc->seq = 1; + vc->clock_mode = VDSO_CLOCKMODE_TIMENS; + offset[CLOCK_MONOTONIC] = monotonic; + offset[CLOCK_MONOTONIC_RAW] = monotonic; + offset[CLOCK_MONOTONIC_COARSE] = monotonic; + offset[CLOCK_BOOTTIME] = boottime; + offset[CLOCK_BOOTTIME_ALARM] = boottime; +} + +struct page *find_timens_vvar_page(struct vm_area_struct *vma) +{ + if (likely(vma->vm_mm == current->mm)) + return current->nsproxy->time_ns->vvar_page; + + /* + * VM_PFNMAP | VM_IO protect .fault() handler from being called + * through interfaces like /proc/$pid/mem or + * process_vm_{readv,writev}() as long as there's no .access() + * in special_mapping_vmops(). + * For more details check_vma_flags() and __access_remote_vm() + */ + + WARN(1, "vvar_page accessed remotely"); + + return NULL; +} + +static void timens_set_vvar_page(struct task_struct *task, + struct time_namespace *ns) +{ + struct vdso_time_data *vdata; + struct vdso_clock *vc; + unsigned int i; + + if (ns == &init_time_ns) + return; + + /* Fast-path, taken by every task in namespace except the first. */ + if (likely(ns->frozen_offsets)) + return; + + guard(mutex)(&timens_offset_lock); + /* Nothing to-do: vvar_page has been already initialized. */ + if (ns->frozen_offsets) + return; + + ns->frozen_offsets = true; + vdata = page_address(ns->vvar_page); + vc = vdata->clock_data; + + for (i = 0; i < CS_BASES; i++) + timens_setup_vdso_clock_data(&vc[i], ns); + + if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS)) { + for (i = 0; i < ARRAY_SIZE(vdata->aux_clock_data); i++) + timens_setup_vdso_clock_data(&vdata->aux_clock_data[i], ns); + } +} + +/* + * The vvar page layout depends on whether a task belongs to the root or + * non-root time namespace. Whenever a task changes its namespace, the VVAR + * page tables are cleared and then they will be re-faulted with a + * corresponding layout. + * See also the comment near timens_setup_vdso_clock_data() for details. + */ +static int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) +{ + struct mm_struct *mm = task->mm; + struct vm_area_struct *vma; + VMA_ITERATOR(vmi, mm, 0); + + guard(mmap_read_lock)(mm); + for_each_vma(vmi, vma) { + if (vma_is_special_mapping(vma, &vdso_vvar_mapping)) + zap_vma_pages(vma); + } + return 0; +} + +void timens_commit(struct task_struct *tsk, struct time_namespace *ns) +{ + timens_set_vvar_page(tsk, ns); + vdso_join_timens(tsk, ns); +} diff --git a/lib/vdso/datastore.c b/lib/vdso/datastore.c index faebf5b7cd6e..cf5d784a4a5a 100644 --- a/lib/vdso/datastore.c +++ b/lib/vdso/datastore.c @@ -132,28 +132,3 @@ struct vm_area_struct *vdso_install_vvar_mapping(struct mm_struct *mm, unsigned VM_MIXEDMAP | VM_SEALED_SYSMAP, &vdso_vvar_mapping); } - -#ifdef CONFIG_TIME_NS -/* - * The vvar page layout depends on whether a task belongs to the root or - * non-root time namespace. Whenever a task changes its namespace, the VVAR - * page tables are cleared and then they will be re-faulted with a - * corresponding layout. - * See also the comment near timens_setup_vdso_clock_data() for details. - */ -int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) -{ - struct mm_struct *mm = task->mm; - struct vm_area_struct *vma; - VMA_ITERATOR(vmi, mm, 0); - - mmap_read_lock(mm); - for_each_vma(vmi, vma) { - if (vma_is_special_mapping(vma, &vdso_vvar_mapping)) - zap_vma_pages(vma); - } - mmap_read_unlock(mm); - - return 0; -} -#endif