Commit 1b6c8928 authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Thomas Gleixner
Browse files

timens: Remove dependency on the vDSO 



Previously, missing time namespace support in the vDSO meant that time
namespaces needed to be disabled globally. This was expressed in a hard
dependency on the generic vDSO library. This also meant that architectures
without any vDSO or only a stub vDSO could not enable time namespaces.
Now that all architectures using a real vDSO are using the generic library,
that dependency is not necessary anymore.

Remove the dependency and let all architectures enable time namespaces.

Signed-off-by: default avatarThomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260326-vdso-timens-decoupling-v2-2-c82693a7775f@linutronix.de
parent 5dc9cf83

include/linux/time_namespace.h

+16 −12
Original line number Diff line number Diff line
@@ -25,7 +25,9 @@ struct time_namespace { 
	struct ucounts		*ucounts;

	struct ns_common	ns;

	struct timens_offsets	offsets;

#ifdef CONFIG_TIME_NS_VDSO

	struct page		*vvar_page;

#endif

	/* If set prevents changing offsets after any task joined namespace. */

	bool			frozen_offsets;

} __randomize_layout;
@@ -38,7 +40,6 @@ 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 void timens_commit(struct task_struct *tsk, struct time_namespace *ns);



static inline struct time_namespace *get_time_ns(struct time_namespace *ns)

{
@@ -51,7 +52,6 @@ struct time_namespace *copy_time_ns(u64 flags, 
				    struct time_namespace *old_ns);

void free_time_ns(struct time_namespace *ns);

void timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk);

struct page *find_timens_vvar_page(struct vm_area_struct *vma);



static inline void put_time_ns(struct time_namespace *ns)

{
@@ -115,11 +115,6 @@ static inline void __init time_ns_init(void) 
{

}



static inline void timens_commit(struct task_struct *tsk,

				 struct time_namespace *ns)

{

}



static inline struct time_namespace *get_time_ns(struct time_namespace *ns)

{

	return NULL;
@@ -146,11 +141,6 @@ static inline void timens_on_fork(struct nsproxy *nsproxy, 
	return;

}



static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)

{

	return NULL;

}



static inline void timens_add_monotonic(struct timespec64 *ts) { }

static inline void timens_add_boottime(struct timespec64 *ts) { }
@@ -167,4 +157,18 @@ static inline ktime_t timens_ktime_to_host(clockid_t clockid, ktime_t tim) 
}

#endif



#ifdef CONFIG_TIME_NS_VDSO

extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns);

struct page *find_timens_vvar_page(struct vm_area_struct *vma);

#else /* !CONFIG_TIME_NS_VDSO */

static inline void timens_commit(struct task_struct *tsk, struct time_namespace *ns)

{

}



static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)

{

	return NULL;

}

#endif /* CONFIG_TIME_NS_VDSO */



#endif /* _LINUX_TIMENS_H */

init/Kconfig

+3 −1
Original line number Diff line number Diff line
@@ -1386,12 +1386,14 @@ config UTS_NS 


config TIME_NS

	bool "TIME namespace"

	depends on GENERIC_GETTIMEOFDAY

	default y

	help

	  In this namespace boottime and monotonic clocks can be set.

	  The time will keep going with the same pace.



config TIME_NS_VDSO

	def_bool TIME_NS && GENERIC_GETTIMEOFDAY



config IPC_NS

	bool "IPC namespace"

	depends on (SYSVIPC || POSIX_MQUEUE)

kernel/time/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ 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 namespace_vdso.o

obj-$(CONFIG_TIME_NS)				+= namespace.o

obj-$(CONFIG_TIME_NS_VDSO)			+= namespace_vdso.o

obj-$(CONFIG_TEST_CLOCKSOURCE_WATCHDOG)		+= clocksource-wdtest.o

obj-$(CONFIG_TIME_KUNIT_TEST)			+= time_test.o

kernel/time/namespace.c

+4 −4
Original line number Diff line number Diff line
@@ -93,8 +93,8 @@ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns, 
	if (!ns)

		goto fail_dec;



	ns->vvar_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);

	if (!ns->vvar_page)

	err = timens_vdso_alloc_vvar_page(ns);

	if (err)

		goto fail_free;



	err = ns_common_init(ns);
@@ -109,7 +109,7 @@ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns, 
	return ns;



fail_free_page:

	__free_page(ns->vvar_page);

	timens_vdso_free_vvar_page(ns);

fail_free:

	kfree(ns);

fail_dec:
@@ -146,7 +146,7 @@ void free_time_ns(struct time_namespace *ns) 
	dec_time_namespaces(ns->ucounts);

	put_user_ns(ns->user_ns);

	ns_common_free(ns);

	__free_page(ns->vvar_page);

	timens_vdso_free_vvar_page(ns);

	/* Concurrent nstree traversal depends on a grace period. */

	kfree_rcu(ns, ns.ns_rcu);

}

kernel/time/namespace_internal.h

+15 −0
Original line number Diff line number Diff line
@@ -4,10 +4,25 @@ 


#include <linux/mutex.h>



struct time_namespace;



/*

 * Protects possibly multiple offsets writers racing each other

 * and tasks entering the namespace.

 */

extern struct mutex timens_offset_lock;



#ifdef CONFIG_TIME_NS_VDSO

int timens_vdso_alloc_vvar_page(struct time_namespace *ns);

void timens_vdso_free_vvar_page(struct time_namespace *ns);

#else /* !CONFIG_TIME_NS_VDSO */

static inline int timens_vdso_alloc_vvar_page(struct time_namespace *ns)

{

	return 0;

}

static inline void timens_vdso_free_vvar_page(struct time_namespace *ns)

{

}

#endif /* CONFIG_TIME_NS_VDSO */



#endif /* _TIME_NAMESPACE_INTERNAL_H */