linux.git/arch/arm64/kernel/vdso.c, branch v5.11

mm: forbid splitting special mappings

2020-12-15T20:13:41+00:00

Don't allow splitting of vm_special_mapping's.  It affects vdso/vvar
areas.  Uprobes have only one page in xol_area so they aren't affected.

Those restrictions were enforced by checks in .mremap() callbacks.
Restrict resizing with generic .split() callback.

Link: https://lkml.kernel.org/r/20201013013416.390574-7-dima@arista.com
Signed-off-by: Dmitry Safonov 
Cc: Alexander Viro 
Cc: Andy Lutomirski 
Cc: Brian Geffon 
Cc: Catalin Marinas 
Cc: Dan Carpenter 
Cc: Dan Williams 
Cc: Dave Jiang 
Cc: Hugh Dickins 
Cc: Ingo Molnar 
Cc: Jason Gunthorpe 
Cc: John Hubbard 
Cc: "Kirill A. Shutemov" 
Cc: Mike Kravetz 
Cc: Minchan Kim 
Cc: Ralph Campbell 
Cc: Russell King 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Vishal Verma 
Cc: Vlastimil Babka 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

arm64: vdso: Fix unusual formatting in *setup_additional_pages()

2020-09-01T12:37:57+00:00

There's really no need to put every parameter on a new line when calling
a function with a long name, so reformat the *setup_additional_pages()
functions in the vDSO setup code to follow the usual conventions.

Acked-by: Mark Rutland 
Reviewed-by: Vincenzo Frascino 
Reviewed-by: Ard Biesheuvel 
Signed-off-by: Will Deacon

arm64: vdso32: Remove a bunch of #ifdef CONFIG_COMPAT_VDSO guards

2020-09-01T12:37:56+00:00

Most of the compat vDSO code can be built and guarded using IS_ENABLED,
so drop the unnecessary #ifdefs.

Reviewed-by: Vincenzo Frascino 
Reviewed-by: Ard Biesheuvel 
Reviewed-by: Mark Rutland 
Signed-off-by: Will Deacon

arm64/vdso: Restrict splitting VVAR VMA

2020-07-24T17:06:52+00:00

Forbid splitting VVAR VMA resulting in a stricter ABI and reducing the
amount of corner-cases to consider while working further on VDSO time
namespace support.

As the offset from timens to VVAR page is computed compile-time, the pages
in VVAR should stay together and not being partically mremap()'ed.

Signed-off-by: Andrei Vagin 
Reviewed-by: Vincenzo Frascino 
Reviewed-by: Dmitry Safonov 
Link: https://lore.kernel.org/r/20200624083321.144975-6-avagin@gmail.com
Signed-off-by: Catalin Marinas

arm64/vdso: Handle faults on timens page

2020-07-24T17:06:45+00:00

If a task belongs to a time namespace then the VVAR page which contains
the system wide VDSO data is replaced with a namespace specific page
which has the same layout as the VVAR page.

Signed-off-by: Andrei Vagin 
Reviewed-by: Vincenzo Frascino 
Reviewed-by: Dmitry Safonov 
Link: https://lore.kernel.org/r/20200624083321.144975-5-avagin@gmail.com
Signed-off-by: Catalin Marinas

arm64/vdso: Add time namespace page

2020-07-24T12:15:20+00:00

Allocate the time namespace page among VVAR pages.  Provide
__arch_get_timens_vdso_data() helper for VDSO code to get the
code-relative position of VVARs on that special page.

If a task belongs to a time namespace then the VVAR page which contains
the system wide VDSO data is replaced with a namespace specific page
which has the same layout as the VVAR page. 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.

The extra check in the case that vdso_data->seq is odd, e.g. a concurrent
update of the VDSO data is in progress, is not really affecting regular
tasks which are not part of a time namespace as the task is spin waiting
for the update to finish and vdso_data->seq to become even again.

If a time namespace task hits that code path, it invokes the corresponding
time getter function which retrieves the real VVAR page, reads host time
and then adds the offset for the requested clock which is stored in the
special VVAR page.

The time-namespace page isn't allocated on !CONFIG_TIME_NAMESPACE, but
vma is the same size, which simplifies criu/vdso migration between
different kernel configs.

Signed-off-by: Andrei Vagin 
Reviewed-by: Vincenzo Frascino 
Reviewed-by: Dmitry Safonov 
Cc: Mark Rutland 
Link: https://lore.kernel.org/r/20200624083321.144975-4-avagin@gmail.com
Signed-off-by: Catalin Marinas

arm64/vdso: Zap vvar pages when switching to a time namespace

2020-07-24T12:15:20+00:00

The order of vvar pages depends on whether a task belongs to the root
time namespace or not. In the root time namespace, a task doesn't have a
per-namespace page. In a non-root namespace, the VVAR page which contains
the system-wide VDSO data is replaced with a namespace specific page
that contains clock offsets.

Whenever a task changes its namespace, the VVAR page tables are cleared
and then they will be re-faulted with a corresponding layout.

A task can switch its time namespace only if its ->mm isn't shared with
another task.

Signed-off-by: Andrei Vagin 
Reviewed-by: Vincenzo Frascino 
Reviewed-by: Dmitry Safonov 
Reviewed-by: Christian Brauner 
Link: https://lore.kernel.org/r/20200624083321.144975-3-avagin@gmail.com
Signed-off-by: Catalin Marinas

arm64/vdso: use the fault callback to map vvar pages

2020-07-24T12:15:20+00:00

Currently the vdso has no awareness of time namespaces, which may
apply distinct offsets to processes in different namespaces. To handle
this within the vdso, we'll need to expose a per-namespace data page.

As a preparatory step, this patch separates the vdso data page from
the code pages, and has it faulted in via its own fault callback.
Subsquent patches will extend this to support distinct pages per time
namespace.

The vvar vma has to be installed with the VM_PFNMAP flag to handle
faults via its vma fault callback.

Signed-off-by: Andrei Vagin 
Reviewed-by: Vincenzo Frascino 
Reviewed-by: Dmitry Safonov 
Link: https://lore.kernel.org/r/20200624083321.144975-2-avagin@gmail.com
Signed-off-by: Catalin Marinas

arm64: compat: Allow 32-bit vdso and sigpage to co-exist

2020-06-23T13:47:03+00:00

In preparation for removing the signal trampoline from the compat vDSO,
allow the sigpage and the compat vDSO to co-exist.

For the moment the vDSO signal trampoline will still be used when built.
Subsequent patches will move to the sigpage consistently.

Acked-by: Dave Martin 
Reviewed-by: Vincenzo Frascino 
Reviewed-by: Ard Biesheuvel 
Reviewed-by: Mark Rutland 
Signed-off-by: Will Deacon

mmap locking API: use coccinelle to convert mmap_sem rwsem call sites

2020-06-09T16:39:14+00:00

This change converts the existing mmap_sem rwsem calls to use the new mmap
locking API instead.

The change is generated using coccinelle with the following rule:

// spatch --sp-file mmap_lock_api.cocci --in-place --include-headers --dir .

@@
expression mm;
@@
(
-init_rwsem
+mmap_init_lock
|
-down_write
+mmap_write_lock
|
-down_write_killable
+mmap_write_lock_killable
|
-down_write_trylock
+mmap_write_trylock
|
-up_write
+mmap_write_unlock
|
-downgrade_write
+mmap_write_downgrade
|
-down_read
+mmap_read_lock
|
-down_read_killable
+mmap_read_lock_killable
|
-down_read_trylock
+mmap_read_trylock
|
-up_read
+mmap_read_unlock
)
-(&mm->mmap_sem)
+(mm)

Signed-off-by: Michel Lespinasse 
Signed-off-by: Andrew Morton 
Reviewed-by: Daniel Jordan 
Reviewed-by: Laurent Dufour 
Reviewed-by: Vlastimil Babka 
Cc: Davidlohr Bueso 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Jason Gunthorpe 
Cc: Jerome Glisse 
Cc: John Hubbard 
Cc: Liam Howlett 
Cc: Matthew Wilcox 
Cc: Peter Zijlstra 
Cc: Ying Han 
Link: http://lkml.kernel.org/r/20200520052908.204642-5-walken@google.com
Signed-off-by: Linus Torvalds