vdso: Remove remnants of architecture-specific time storage

All users of the time releated parts of the vDSO are now using the generic
storage implementation. Remove the therefore unnecessary compat

vdso: Remove remnants of architecture-specific time storage

All users of the time releated parts of the vDSO are now using the generic
storage implementation. Remove the therefore unnecessary compatibility
accessor functions and symbols.

Co-developed-by: Nam Cao <[email protected]>
Signed-off-by: Nam Cao <[email protected]>
Signed-off-by: Thomas Weißschuh <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

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vdso: Add generic time data storage

Historically each architecture defined their own way to store the vDSO
data page. Add a generic mechanism to provide storage for that page.

Furthermore this gene

vdso: Add generic time data storage

Historically each architecture defined their own way to store the vDSO
data page. Add a generic mechanism to provide storage for that page.

Furthermore this generic storage will be extended to also provide
uniform storage for *non*-time-related data, like the random state or
architecture-specific data. These will have their own pages and data
structures, so rename 'vdso_data' into 'vdso_time_data' to make that
split clear from the name.

Also introduce a new consistent naming scheme for the symbols related to
the vDSO, which makes it clear if the symbol is accessible from
userspace or kernel space and the type of data behind the symbol.

The generic fault handler contains an optimization to prefault the vvar
page when the timens page is accessed. This was lifted from s390 and x86.

Co-developed-by: Nam Cao <[email protected]>
Signed-off-by: Nam Cao <[email protected]>
Signed-off-by: Thomas Weißschuh <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

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timekeeping: Kill percpu.h dependency

Slimming down recursive header includes.

Signed-off-by: Kent Overstreet <[email protected]>
Cc: Thomas Gleixner <[email protected]>

time_namespace.h: fix missing include

Signed-off-by: Kent Overstreet <[email protected]>

time_namespace: always provide arch_get_vdso_data() prototype for vdso

The arch_get_vdso_data() function is defined separately on each
architecture, but only called when CONFIG_TIME_NS is set. If t

time_namespace: always provide arch_get_vdso_data() prototype for vdso

The arch_get_vdso_data() function is defined separately on each
architecture, but only called when CONFIG_TIME_NS is set. If the
definition is a global function, this causes a W=1 warning without
TIME_NS:

arch/x86/entry/vdso/vma.c:35:19: error: no previous prototype for 'arch_get_vdso_data' [-Werror=missing-prototypes]

Move the prototype out of the #ifdef block to reliably turn off that
warning.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnd Bergmann <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: Eric Paris <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Paul Moore <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Cc: Russell King <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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vdso/timens: Always provide arch_get_vdso_data() prototype for vdso

The arch_get_vdso_data() function is defined separately on each architecture,
but only called when CONFIG_TIME_NS is set. If the d

vdso/timens: Always provide arch_get_vdso_data() prototype for vdso

The arch_get_vdso_data() function is defined separately on each architecture,
but only called when CONFIG_TIME_NS is set. If the definition is a global
function, this causes a W=1 warning without TIME_NS:

arch/x86/entry/vdso/vma.c:35:19: error: no previous prototype for 'arch_get_vdso_data' [-Werror=missing-prototypes]

Move the prototype out of the #ifdef block to reliably turn off that
warning.

Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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vdso/timens: Refactor copy-pasted find_timens_vvar_page() helper into one copy

find_timens_vvar_page() is not architecture-specific, as can be seen from
how all five per-architecture versions of it

vdso/timens: Refactor copy-pasted find_timens_vvar_page() helper into one copy

find_timens_vvar_page() is not architecture-specific, as can be seen from
how all five per-architecture versions of it are the same.

(arm64, powerpc and riscv are exactly the same; x86 and s390 have two
characters difference inside a comment, less blank lines, and mark the
!CONFIG_TIME_NS version as inline.)

Refactor the five copies into a central copy in kernel/time/namespace.c.

Signed-off-by: Jann Horn <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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namespace: make timens_on_fork() return nothing

timens_on_fork() always return 0, and maybe not
need to judge the return value in copy_namespaces().

So make timens_on_fork() return nothing and do n

namespace: make timens_on_fork() return nothing

timens_on_fork() always return 0, and maybe not
need to judge the return value in copy_namespaces().

So make timens_on_fork() return nothing and do not
judge its return val in copy_namespaces().

Signed-off-by: Hui Su <[email protected]>
Link: https://lore.kernel.org/r/20201117161750.GA45121@rlk
Signed-off-by: Christian Brauner <[email protected]>

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timens: additional helper functions for boottime offset handling

Provide functions for time_namespace to subtract the boottime offset
from a timespec64 as well as to apply the boottime offset to u64

timens: additional helper functions for boottime offset handling

Provide functions for time_namespace to subtract the boottime offset
from a timespec64 as well as to apply the boottime offset to u64 types in
nanoseconds.

Signed-off-by: Michael Weiß <[email protected]>
Reviewed-by: Andrei Vagin <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Acked-by: Christian Brauner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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time: Use generic ns_common::count

Switch over time namespaces to use the newly introduced common lifetime
counter.

Currently every namespace type has its own lifetime counter which is stored
in th

time: Use generic ns_common::count

Switch over time namespaces to use the newly introduced common lifetime
counter.

Currently every namespace type has its own lifetime counter which is stored
in the specific namespace struct. The lifetime counters are used
identically for all namespaces types. Namespaces may of course have
additional unrelated counters and these are not altered.

This introduces a common lifetime counter into struct ns_common. The
ns_common struct encompasses information that all namespaces share. That
should include the lifetime counter since its common for all of them.

It also allows us to unify the type of the counters across all namespaces.
Most of them use refcount_t but one uses atomic_t and at least one uses
kref. Especially the last one doesn't make much sense since it's just a
wrapper around refcount_t since 2016 and actually complicates cleanup
operations by having to use container_of() to cast the correct namespace
struct out of struct ns_common.

Having the lifetime counter for the namespaces in one place reduces
maintenance cost. Not just because after switching all namespaces over we
will have removed more code than we added but also because the logic is
more easily understandable and we indicate to the user that the basic
lifetime requirements for all namespaces are currently identical.

Signed-off-by: Kirill Tkhai <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Acked-by: Christian Brauner <[email protected]>
Link: https://lore.kernel.org/r/159644982033.604812.9406853013011123238.stgit@localhost.localdomain
Signed-off-by: Christian Brauner <[email protected]>

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nsproxy: support CLONE_NEWTIME with setns()

So far setns() was missing time namespace support. This was partially due
to it simply not being implemented but also because vdso_join_timens()
could sti

nsproxy: support CLONE_NEWTIME with setns()

So far setns() was missing time namespace support. This was partially due
to it simply not being implemented but also because vdso_join_timens()
could still fail which made switching to multiple namespaces atomically
problematic. This is now fixed so support CLONE_NEWTIME with setns()

Signed-off-by: Christian Brauner <[email protected]>
Reviewed-by: Andrei Vagin <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Serge Hallyn <[email protected]>
Cc: Dmitry Safonov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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fs/proc: Introduce /proc/pid/timens_offsets

API to set time namespace offsets for children processes, i.e.:
echo "$clockid $offset_sec $offset_nsec" > /proc/self/timens_offsets

Co-developed-by: Dmi

fs/proc: Introduce /proc/pid/timens_offsets

API to set time namespace offsets for children processes, i.e.:
echo "$clockid $offset_sec $offset_nsec" > /proc/self/timens_offsets

Co-developed-by: Dmitry Safonov <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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x86/vdso: Zap vvar pages when switching to a time namespace

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

x86/vdso: Zap vvar pages when switching to a time namespace

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.

Co-developed-by: Andrei Vagin <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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time: Allocate per-timens vvar page

VDSO support for Time namespace needs to set up a page with the same
layout as VVAR. That timens page will be placed on position of VVAR page
inside namespace. Th

time: Allocate per-timens vvar page

VDSO support for Time namespace needs to set up a page with the same
layout as VVAR. That timens page will be placed on position of VVAR page
inside namespace. That page contains time namespace clock offsets and it
has vdso_data->seq set to 1 to enforce the slow path and
vdso_data->clock_mode set to VCLOCK_TIMENS to enforce the time namespace
handling path.

Allocate the timens page during namespace creation. Setup the offsets
when the first task enters the ns and freeze them to guarantee the pace
of monotonic/boottime clocks and to avoid breakage of applications.

The design decision is to have a global offset_lock which is used during
namespace offsets setup and to freeze offsets when the first task joins the
new time namespace. That is better in terms of memory usage compared to
having a per namespace mutex that's used only during the setup period.

Suggested-by: Andy Lutomirski <[email protected]>
Based-on-work-by: Thomas Gleixner <[email protected]>
Co-developed-by: Andrei Vagin <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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x86/vdso: Provide vdso_data offset on vvar_page

VDSO support for time namespaces needs to set up a page with the same
layout as VVAR. That timens page will be placed on position of VVAR page
inside

x86/vdso: Provide vdso_data offset on vvar_page

VDSO support for time namespaces needs to set up a page with the same
layout as VVAR. That timens page will be placed on position of VVAR page
inside namespace. That page has vdso_data->seq set to 1 to enforce
the slow path and vdso_data->clock_mode set to VCLOCK_TIMENS to enforce
the time namespace handling path.

To prepare the time namespace page the kernel needs to know the vdso_data
offset. Provide arch_get_vdso_data() helper for locating vdso_data on VVAR
page.

Co-developed-by: Andrei Vagin <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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time: Add do_timens_ktime_to_host() helper

The helper subtracts namespace's clock offset from the given time
and ensures that the result is within [0, KTIME_MAX].

Co-developed-by: Dmitry Safonov <d

time: Add do_timens_ktime_to_host() helper

The helper subtracts namespace's clock offset from the given time
and ensures that the result is within [0, KTIME_MAX].

Co-developed-by: Dmitry Safonov <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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time: Add timens_offsets to be used for tasks in time namespace

Introduce offsets for time namespace. They will contain an adjustment
needed to convert clocks to/from host's.

A new namespace is cre

time: Add timens_offsets to be used for tasks in time namespace

Introduce offsets for time namespace. They will contain an adjustment
needed to convert clocks to/from host's.

A new namespace is created with the same offsets as the time namespace
of the current process.

Co-developed-by: Dmitry Safonov <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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ns: Introduce Time Namespace

Time Namespace isolates clock values.

The kernel provides access to several clocks CLOCK_REALTIME,
CLOCK_MONOTONIC, CLOCK_BOOTTIME, etc.

CLOCK_REALTIME
System-wi

ns: Introduce Time Namespace

Time Namespace isolates clock values.

The kernel provides access to several clocks CLOCK_REALTIME,
CLOCK_MONOTONIC, CLOCK_BOOTTIME, etc.

CLOCK_REALTIME
System-wide clock that measures real (i.e., wall-clock) time.

CLOCK_MONOTONIC
Clock that cannot be set and represents monotonic time since
some unspecified starting point.

CLOCK_BOOTTIME
Identical to CLOCK_MONOTONIC, except it also includes any time
that the system is suspended.

For many users, the time namespace means the ability to changes date and
time in a container (CLOCK_REALTIME). Providing per namespace notions of
CLOCK_REALTIME would be complex with a massive overhead, but has a dubious
value.

But in the context of checkpoint/restore functionality, monotonic and
boottime clocks become interesting. Both clocks are monotonic with
unspecified starting points. These clocks are widely used to measure time
slices and set timers. After restoring or migrating processes, it has to be
guaranteed that they never go backward. In an ideal case, the behavior of
these clocks should be the same as for a case when a whole system is
suspended. All this means that it is required to set CLOCK_MONOTONIC and
CLOCK_BOOTTIME clocks, which can be achieved by adding per-namespace
offsets for clocks.

A time namespace is similar to a pid namespace in the way how it is
created: unshare(CLONE_NEWTIME) system call creates a new time namespace,
but doesn't set it to the current process. Then all children of the process
will be born in the new time namespace, or a process can use the setns()
system call to join a namespace.

This scheme allows setting clock offsets for a namespace, before any
processes appear in it.

All available clone flags have been used, so CLONE_NEWTIME uses the highest
bit of CSIGNAL. It means that it can be used only with the unshare() and
the clone3() system calls.

[ tglx: Adjusted paragraph about clone3() to reality and massaged the
changelog a bit. ]

Co-developed-by: Dmitry Safonov <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://criu.org/Time_namespace
Link: https://lists.openvz.org/pipermail/criu/2018-June/041504.html
Link: https://lore.kernel.org/r/[email protected]

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