While mlockall() is meant to lock page *memory*, effectively it will
also create and lock the corresponding page table entries.
Latency-sensitive applications expect not to experience any pagefaults
after calling mlockall(). However mlockall() ignores VM_IO mappings,
which is used by the generic vDSO datastore.
While the fault handler itself is very fast, going through the full
pagefault exception handling is much slower, on the order of 20us in a
test machine.
Since the memory behind the datastore mappings is always present and
accessible it is not necessary to use VM_IO for them.
The data page mapping is now also aligned with the architecture-specific
code pages. Some architecture-specific data pages, like the x86 VCLOCK
pages, continue to use VM_IO as they are not always mappable. They will
require their own special handling later when the general approach has
been agreed upon.
As a side-effect this will allow GUP on these pages and allow more ways
to access the data in them. This is fine, as all data in this mapping
is globally visible anyways. Either because it is mapped into all tasks,
or in the case of the time namespace pages, can be read from procfs.
Regular mlock() would also work, but userspace does not know the boundaries
of the vDSO.
Reported-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Nam Cao <namcao@linutronix.de>
Link: https://patch.msgid.link/20260630-vdso-mlockall-v4-5-6c93708ce723@linutronix.de
The fault handler for the timens page does not have access to the target
task and therefore can not be invoked remotely.
Currently the handler relies on the fact that the vvar mapping is marked as
VM_IO and VM_PFNMAP for which the mm core always prevents remote access.
However the VM_IO and VM_PFNMAP flags are going to be removed.
Add an explicit check to prevent remote access to the mapping.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Nam Cao <namcao@linutronix.de>
Link: https://patch.msgid.link/20260630-vdso-mlockall-v4-4-6c93708ce723@linutronix.de
mlockall() stops if a page in a VMA is unmappable. As the datastore VMA
can contain holes, mlockall() would not process all data pages.
Replace the mapping error VM_FAULT_SIGBUS by just mapping the underlying
unused and zeroed-out data page. The vDSO will not access these pages in
any case and for other userspace these pages have undefined contents.
This will allow mlockall() to process all pages within the VMA as soon
as VM_IO is removed from the VMA.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Nam Cao <namcao@linutronix.de>
Link: https://patch.msgid.link/20260630-vdso-mlockall-v4-3-6c93708ce723@linutronix.de
To support mlockall() on the datapages the VMA can have no holes where
inner pages return VM_FAULT_SIGBUS. An upcoming change will avoid these
holes by mapping a zeroed pages into these holes. That logic will be
simpler when the mapping logic is based on vmf->pgoff instead of the
vdso_k_ symbols.
Switch to the equivalent vmf->pgoff logic.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Nam Cao <namcao@linutronix.de>
Link: https://patch.msgid.link/20260630-vdso-mlockall-v4-2-6c93708ce723@linutronix.de
Pull vdso updates from Thomas Gleixner:
- Remove the redundant CONFIG_GENERIC_TIME_VSYSCALL after converting
the remaining users over.
- Rework and sanitize the MIPS VDSO handling, so it does not handle the
time related VDSO if there is no VDSO capable clocksource available.
Also stop mapping VDSO data pages unconditionally even if there is no
usage possible.
* tag 'timers-vdso-2026-06-13' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip:
MIPS: VDSO: Fold MIPS_CLOCK_VSYSCALL into MIPS_GENERIC_GETTIMEOFDAY
MIPS: VDSO: Gate microMIPS restriction on GCC version
MIPS: VDSO: Fold MIPS_DISABLE_VDSO into MIPS_GENERIC_GETTIMEOFDAY
clocksource/drivers/mips-gic-timer: Only use VDSO_CLOCKMODE_GIC when it is a available
MIPS: csrc-r4k: Only use VDSO_CLOCKMODE_R4K when it is a available
MIPS: VDSO: Only map the data pages when the vDSO is used
MIPS: Introduce Kconfig MIPS_GENERIC_GETTIMEOFDAY
vdso/datastore: Always provide symbol declarations
MAINTAINERS: Add include/linux/vdso_datastore.h to vDSO block
vdso/gettimeofday: Rename __arch_get_vdso_u_timens_data()
vdso/treewide: Drop GENERIC_TIME_VSYSCALL
vdso/vsyscall: Gate update_vsyscall() behind CONFIG_GENERIC_GETTIMEOFDAY
riscv: vdso: Drop CONFIG_GENERIC_TIME_VSYSCALL guard around syscall fallbacks
After switching to the real data pages, the sequence counter needs to be
reloaded from there. The code using vdso_read_begin_timens() assumed
this worked by 'continue' jumping to the *beginning* of the do-while
retry loop. However the 'continue' jumps to the *end* of said loop,
evaluating the exit condition. If the data page has a sequence counter
of '1' it will match the one from the time namespace page and prematurely
exit the retry loop. This would result in garbage returned to the caller.
Reload the sequence counter after switching the pages by using an inner
while loop again, which will loop at most once.
The loop generates slightly better code than an explicit reload through
'seq = vdso_read_begin()'.
Fixes: ed78b7b2c5 ("vdso/gettimeofday: Add a helper to read the sequence lock of a time namespace aware clock")
Reported-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Link: https://patch.msgid.link/20260422-vdso-aux-timens-loop-v1-1-e2dd8c7164cc@linutronix.de
Closes: https://lore.kernel.org/lkml/CANiDSCsOy0P1if-gJZqOM5pTJ0RDcwVfru1B7KFbTOEMqjPKJw@mail.gmail.com/
Currently there are three different open-coded variants of a time
namespace aware variant of vdso_read_begin(). They make the code hard to
read and introduce an inconsistency, as only the first copy uses
unlikely().
Split the code into a shared helper function.
Move that next to the definition of the regular vdso_read_begin(), so
that any future changes can be kept in sync easily.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260227-vdso-cleanups-v1-2-c848b4bc4850@linutronix.de
Allocating the data pages as part of the kernel image does not work on
SPARC. The MMU will raise a fault when userspace tries to access them.
Allocate the data pages through the page allocator instead.
Unused pages in the vDSO VMA are still allocated to keep the virtual
addresses aligned. Switch the mapping from PFNs to 'struct page' as that is
required for dynamically allocated pages. This also aligns the allocation
of the datapages with the code pages and is a prerequisite for mlockall()
support.
VM_MIXEDMAP is necessary for the call to vmf_insert_page() in the timens
prefault path to work.
The data pages need to be order-0, non-compound pages so that the mapping
to userspace and the different orderings work.
These pages are also used by the timekeeping, random pool and architecture
initialization code. Some of these are running before the page allocator is
available. To keep these subsytems working without changes, introduce
early, statically data storage which will then replaced by the real one as
soon as that is available.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Link: https://patch.msgid.link/20260304-vdso-sparc64-generic-2-v6-3-d8eb3b0e1410@linutronix.de
With CONFIG_CC_OPTIMIZE_FOR_SIZE=y, GCC may decide not to inline
__cvdso_clock_getres_common(). This introduces spurious internal
function calls in the vDSO fastpath.
Furthermore, with automatic stack variable initialization
(CONFIG_INIT_STACK_ALL_ZERO or CONFIG_INIT_STACK_ALL_PATTERN) GCC can emit
a call to memset() which is not valid in the vDSO.
Mark __cvdso_clock_getres_common() as __always_inline to avoid both issues.
Paradoxically the inlining even reduces the size of the code:
$ ./scripts/bloat-o-meter arch/powerpc/kernel/vdso/vgettimeofday-32.o.before arch/powerpc/kernel/vdso/vgettimeofday-32.o.after
add/remove: 0/1 grow/shrink: 1/1 up/down: 52/-148 (-96)
Function old new delta
__c_kernel_clock_getres_time64 92 144 +52
__c_kernel_clock_getres 136 132 -4
__cvdso_clock_getres_common 144 - -144
Total: Before=2788, After=2692, chg -3.44%
With CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y the functions are always inlined
and therefore the behaviour stays the same.
See also the equivalent change for clock_gettime() in commit b91c8c42ff
("lib/vdso: Force inlining of __cvdso_clock_gettime_common()").
Fixes: 21bbfd7404 ("x86/vdso: Provide clock_getres_time64() for x86-32")
Fixes: 1149dcdfc9 ("ARM: VDSO: Provide clock_getres_time64()")
Fixes: f10c2e72b5 ("arm64: vdso32: Provide clock_getres_time64()")
Fixes: bec06cd6a1 ("MIPS: vdso: Provide getres_time64() for 32-bit ABIs")
Fixes: 759a1f9737 ("powerpc/vdso: Provide clock_getres_time64()")
Reported-by: Sverdlin, Alexander <alexander.sverdlin@siemens.com>
Suggested-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://lore.kernel.org/lkml/230c749f-ebd6-4829-93ee-601d88000a45@kernel.org/
Link: https://patch.msgid.link/20260123-vdso-clock_getres-inline-v1-1-4d6203b90cd3@linutronix.de
Closes: https://lore.kernel.org/lkml/f45316f65a46da638b3c6aa69effd8980e6677b9.camel@siemens.com/
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be an array of VDSO clocks.
Now that all preparatory changes are in place:
Split the clock related struct members into a separate struct
vdso_clock. Make sure all users are aware, that vdso_time_data is no longer
initialized as an array and vdso_clock is now the array inside
vdso_data. Remove the vdso_clock define, which mapped it to vdso_time_data
for the transition.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-19-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
For time namespaces, vdso_time_data needs to be set up. But only the clock
related part of the vdso_data thats requires this setup. To reflect the
future struct vdso_clock, rename timens_setup_vdso_data() to
timns_setup_vdso_clock_data().
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-13-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
To prepare for the rework of the data structures, replace the struct
vdso_time_data pointer argument of the helper functions with struct
vdso_clock pointer where applicable.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-11-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
Prepare for the rework of these structures by adding a struct vdso_clock
pointer argument to do_coarse_time_ns(), and replace the struct
vdso_time_data pointer with the new pointer argument where applicable.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-10-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
Prepare for the rework of these structures by adding a struct vdso_clock
pointer argument to do_coarse(), and replace the struct vdso_time_data
pointer with the new pointer argument where applicable.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-9-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
Prepare for the rework of these structures by adding a struct vdso_clock
pointer argument to do_hres_timens(), and replace the struct vdso_time_data
pointer with the new pointer argument where applicable.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-8-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
Prepare for the rework of these structures by adding a struct vdso_clock
pointer argument to do_hres(), and replace the struct vdso_time_data
pointer with the new pointer argument where applicable.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-7-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
Prepare all functions which need the pointer to the vdso_clock array to
work correctly after introducing the new struct. Where applicable, replace
the struct vdso_time_data pointer by a struct vdso_clock pointer.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-6-c1b5c69a166f@linutronix.de
Thomas Weißschuh