x86 atomic instructions are used for um on UML_X86, therefore atomics
on UML_X86 support native atomic RmW as x86 does, hence select
ARCH_SUPPORTS_ATOMIC_RMW.

Reviewed-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Acked-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20260106034034.60074-1-boqun.feng@gmail.com

Historically the code to set up AT_HWCAP and AT_PLATFORM was only built
for 32bit x86 as it was intermingled with the vDSO passthrough code.

Now that vDSO passthrough has been removed, always pass through AT_HWCAP
and AT_PLATFORM.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://patch.msgid.link/20251028-uml-remove-32bit-pseudo-vdso-v1-10-e930063eff5f@weissschuh.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Inheriting the vDSO from the host is problematic. The values read
from the time functions will not be correct for the UML kernel.
Furthermore the start and end of the vDSO are not stable or
detectable by userspace. Specifically the vDSO datapages start
before AT_SYSINFO_EHDR and the vDSO itself is larger than a single page.

This codepath is only used on 32bit x86 UML. In my testing with both
32bit and 64bit hosts the passthrough functionality has always been
disabled anyways due to the checks against envp in scan_elf_aux().

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://patch.msgid.link/20251028-uml-remove-32bit-pseudo-vdso-v1-4-e930063eff5f@weissschuh.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Implement spinlock support for SMP on UML/x86, leveraging x86's
spinlock implementation. In addition, to support SMP on CPUs that
do not support CX8, some additional work is required. However,
considering that such CPUs are already very outdated, and x86 is
also removing support for them [1], let's enable SMP support only
on CPUs that support CX8.

[1] https://lore.kernel.org/lkml/20250515085708.2510123-1-mingo@kernel.org/

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20251027001815.1666872-9-tiwei.bie@linux.dev
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

The larger memory space is useful to support more applications inside
UML. One example for this is ASAN instrumentation of userspace
applications which requires addresses that would otherwise not be
available.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240919124511.282088-11-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

The highmem support has been removed by commit a98a6d864d3b ("um:
Remove broken highmem support"). The 2-level page table is sufficient
on UML/i386 now. Remove the 3-level page table support on UML/i386
which is still marked as experimental.

Suggested-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20240918061702.614837-1-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

The x86 port of UM has efficient unaligned access. Set the option as it
is appropriate and will e.g. cause UBSAN to not enable unaligned memory
access checking by default.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240913134442.967599-6-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

The convention for indentation seems to be a single tab. Help text is
further indented by an additional two whitespaces. Fix the lines that
violate these rules.

Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Pull vfs updates from Al Viro:
 "Assorted bits and pieces"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  aio: drop needless assignment in aio_read()
  clean overflow checks in count_mounts() a bit
  seq_file: fix NULL pointer arithmetic warning
  uml/x86: use x86 load_unaligned_zeropad()
  asm/user.h: killed unused macros
  constify struct path argument of finish_automount()/do_add_mount()
  fs: Remove FIXME comment in generic_write_checks()

As arm64 is about to introduce MTE-specific phdrs in the core dump, add
a common CONFIG_ARCH_BINFMT_ELF_EXTRA_PHDRS option currently selectable
by UML_X86 and IA64.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Link: https://lore.kernel.org/r/20220131165456.2160675-2-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>