linux-stable.git/arch/um, branch linux-6.14.y

um: let 'make clean' properly clean underlying SUBARCH as well

2025-06-04T12:45:09+00:00

[ Upstream commit ab09da75700e9d25c7dfbc7f7934920beb5e39b9 ]

Building the kernel with O= is affected by stale in-tree build artifacts.

So, if the source tree is not clean, Kbuild displays the following:

  $ make ARCH=um O=build defconfig
  make[1]: Entering directory '/.../linux/build'
  ***
  *** The source tree is not clean, please run 'make ARCH=um mrproper'
  *** in /.../linux
  ***
  make[2]: *** [/.../linux/Makefile:673: outputmakefile] Error 1
  make[1]: *** [/.../linux/Makefile:248: __sub-make] Error 2
  make[1]: Leaving directory '/.../linux/build'
  make: *** [Makefile:248: __sub-make] Error 2

Usually, running 'make mrproper' is sufficient for cleaning the source
tree for out-of-tree builds.

However, building UML generates build artifacts not only in arch/um/,
but also in the SUBARCH directory (i.e., arch/x86/). If in-tree stale
files remain under arch/x86/, Kbuild will reuse them instead of creating
new ones under the specified build directory.

This commit makes 'make ARCH=um clean' recurse into the SUBARCH directory.

Reported-by: Shuah Khan 
Closes: https://lore.kernel.org/lkml/20250502172459.14175-1-skhan@linuxfoundation.org/
Signed-off-by: Masahiro Yamada 
Acked-by: Johannes Berg 
Reviewed-by: David Gow 
Reviewed-by: Shuah Khan 
Signed-off-by: Sasha Levin

um: Update min_low_pfn to match changes in uml_reserved

2025-05-29T09:12:37+00:00

[ Upstream commit e82cf3051e6193f61e03898f8dba035199064d36 ]

When uml_reserved is updated, min_low_pfn must also be updated
accordingly. Otherwise, min_low_pfn will not accurately reflect
the lowest available PFN.

Signed-off-by: Tiwei Bie 
Link: https://patch.msgid.link/20250221041855.1156109-1-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg 
Signed-off-by: Sasha Levin

um: work around sched_yield not yielding in time-travel mode

2025-05-02T06:02:02+00:00

[ Upstream commit 887c5c12e80c8424bd471122d2e8b6b462e12874 ]

sched_yield by a userspace may not actually cause scheduling in
time-travel mode as no time has passed. In the case seen it appears to
be a badly implemented userspace spinlock in ASAN. Unfortunately, with
time-travel it causes an extreme slowdown or even deadlock depending on
the kernel configuration (CONFIG_UML_MAX_USERSPACE_ITERATIONS).

Work around it by accounting time to the process whenever it executes a
sched_yield syscall.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250314130815.226872-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Sasha Levin

um: remove copy_from_kernel_nofault_allowed

2025-04-10T12:44:33+00:00

[ Upstream commit 84a6fc378471fbeaf48f8604566a5a33a3d63c18 ]

There is no need to override the default version of this function
anymore as UML now has proper _nofault memory access functions.

Doing this also fixes the fact that the implementation was incorrect as
using mincore() will incorrectly flag pages as inaccessible if they were
swapped out by the host.

Fixes: f75b1b1bedfb ("um: Implement probe_kernel_read()")
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250210160926.420133-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Sasha Levin

um: convert irq_lock to raw spinlock

2025-02-12T22:40:59+00:00

Since this is deep in the architecture, and the code is
called nested into other deep management code, this really
needs to be a raw spinlock. Convert it.

Link: https://patch.msgid.link/20250110125550.32479-8-johannes@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger

um: virtio_uml: use raw spinlock

2025-02-12T22:40:55+00:00

This is needed because at least in time-travel the code
can be called directly from the deep architecture and
IRQ handling code.

Link: https://patch.msgid.link/20250110125550.32479-7-johannes@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger

um: virt-pci: don't use kmalloc()

2025-02-12T22:40:50+00:00

This code can be called deep in the IRQ handling, for
example, and then cannot normally use kmalloc(). Have
its own pre-allocated memory and use from there instead
so this doesn't occur. Only in the (very rare) case of
memcpy_toio() we'd still need to allocate memory.

Link: https://patch.msgid.link/20250110125550.32479-6-johannes@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger

um: fix execve stub execution on old host OSs

2025-02-12T22:40:45+00:00

The stub execution uses the somewhat new close_range and execveat
syscalls. Of these two, the execveat call is essential, but the
close_range call is more about stub process hygiene rather than safety
(and its result is ignored).

Replace both calls with a raw syscall as older machines might not have a
recent enough kernel for close_range (with CLOSE_RANGE_CLOEXEC) or a
libc that does not yet expose both of the syscalls.

Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Reported-by: Glenn Washburn 
Closes: https://lore.kernel.org/20250108022404.05e0de1e@crass-HP-ZBook-15-G2
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250113094107.674738-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger

um: avoid copying FP state from init_task

2025-02-12T22:40:38+00:00

The init_task instance of struct task_struct is statically allocated and
does not contain the dynamic area for the userspace FP registers. As
such, limit the copy to the valid area of init_task and fill the rest
with zero.

Note that the FP state is only needed for userspace, and as such it is
entirely reasonable for init_task to not contain it.

Reported-by: Brian Norris 
Closes: https://lore.kernel.org/Z1ySXmjZm-xOqk90@google.com
Fixes: 3f17fed21491 ("um: switch to regset API and depend on XSTATE")
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20241217202745.1402932-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger

Merge tag 'uml-for-linus-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

2025-01-31T02:29:40+00:00

Pull UML updates from Richard Weinberger:

 - hostfs: Convert to writepages

 - many cleanups: removal of dead macros, missing __init

* tag 'uml-for-linus-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux:
  um: Remove unused asm/archparam.h header
  um: Include missing headers in asm/pgtable.h
  hostfs: Convert to writepages
  um: rtc: use RTC time when calculating the alarm
  um: Remove unused user_context function
  um: Remove unused THREAD_NAME_LEN macro
  um: Remove unused PGD_BOUND macro
  um: Mark setup_env_path as __init
  um: Mark install_fatal_handler as __init
  um: Mark set_stklim as __init
  um: Mark get_top_address as __init
  um: Mark parse_cache_line as __init
  um: Mark parse_host_cpu_flags as __init
  um: Count iomem_size only once in physmem calculation
  um: Remove obsolete fixmap support
  um: Remove unused MODULES_LEN macro