linux.git/arch/um/include/shared, branch v6.15

Merge tag 'uml-for-linux-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

2025-04-02T19:25:03+00:00

Pull UML updates from Johannes Berg:

 - proper nofault accesses and read-only rodata

 - hostfs fix for host inode number reuse

 - fixes for host errno handling

 - various cleanups/small fixes

* tag 'uml-for-linux-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux:
  um: Rewrite the sigio workaround based on epoll and tgkill
  um: Prohibit the VM_CLONE flag in run_helper_thread()
  um: Switch to the pthread-based helper in sigio workaround
  um: ubd: Switch to the pthread-based helper
  um: Add pthread-based helper support
  um: x86: clean up elf specific definitions
  um: Store full CSGSFS and SS register from mcontext
  um: virt-pci: Refactor virtio_pcidev into its own module
  um: work around sched_yield not yielding in time-travel mode
  um/locking: Remove semicolon from "lock" prefix
  um: Update min_low_pfn to match changes in uml_reserved
  um: use str_yes_no() to remove hardcoded "yes" and "no"
  um: hostfs: avoid issues on inode number reuse by host
  um: Allocate vdso page pointer statically
  um: remove copy_from_kernel_nofault_allowed
  um: mark rodata read-only and implement _nofault accesses
  um: Pass the correct Rust target and options with gcc

um: Rewrite the sigio workaround based on epoll and tgkill

2025-03-20T08:28:44+00:00

The existing sigio workaround implementation removes FDs from the
poll when events are triggered, requiring users to re-add them via
add_sigio_fd() after processing. This introduces a potential race
condition between FD removal in write_sigio_thread() and next_poll
update in __add_sigio_fd(), and is inefficient due to frequent FD
removal and re-addition. Rewrite the implementation based on epoll
and tgkill for improved efficiency and reliability.

Signed-off-by: Tiwei Bie 
Link: https://patch.msgid.link/20250315161910.4082396-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg

um: Add pthread-based helper support

2025-03-20T08:26:38+00:00

Introduce a new set of utility functions that can be used to create
pthread-based helpers. Helper threads created in this way will ensure
thread safety for errno while sharing the same memory space.

Signed-off-by: Tiwei Bie 
Link: https://patch.msgid.link/20250319135523.97050-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg

um: remove copy_from_kernel_nofault_allowed

2025-03-18T10:03:29+00:00

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

um: mark rodata read-only and implement _nofault accesses

2025-03-18T10:03:14+00:00

Mark read-only data actually read-only (simple mprotect), and
to be able to test it also implement _nofault accesses. This
works by setting up a new "segv_continue" pointer in current,
and then when we hit a segfault we change the signal return
context so that we continue at that address. The code using
this sets it up so that it jumps to a label and then aborts
the access that way, returning -EFAULT.

It's possible to optimize the ___backtrack_faulted() thing by
using asm goto (compiler version dependent) and/or gcc's (not
sure if clang has it) &&label extension, but at least in one
attempt I made the && caused the compiler to not load -EFAULT
into the register in case of jumping to the &&label from the
fault handler. So leave it like this for now.

Signed-off-by: Johannes Berg 
Co-developed-by: Benjamin Berg 
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250210160926.420133-2-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

arch, mm: set max_mapnr when allocating memory map for FLATMEM

2025-03-18T05:06:52+00:00

max_mapnr is essentially the size of the memory map for systems that use
FLATMEM. There is no reason to calculate it in each and every architecture
when it's anyway calculated in alloc_node_mem_map().

Drop setting of max_mapnr from architecture code and set it once in
alloc_node_mem_map().

While on it, move definition of mem_map and max_mapnr to mm/mm_init.c so
there won't be two copies for MMU and !MMU variants.

Link: https://lkml.kernel.org/r/20250313135003.836600-10-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) 
Acked-by: Dave Hansen 	[x86]
Tested-by: Mark Brown 
Cc: Alexander Gordeev 
Cc: Andreas Larsson 
Cc: Andy Lutomirski 
Cc: Ard Biesheuvel 
Cc: Arnd Bergmann 
Cc: Borislav Betkov 
Cc: Catalin Marinas 
Cc: David S. Miller 
Cc: Dinh Nguyen 
Cc: Geert Uytterhoeven 
Cc: Gerald Schaefer 
Cc: Guo Ren (csky) 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Huacai Chen 
Cc: Ingo Molnar 
Cc: Jiaxun Yang 
Cc: Johannes Berg 
Cc: John Paul Adrian Glaubitz 
Cc: Madhavan Srinivasan 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Palmer Dabbelt 
Cc: Richard Weinberger 
Cc: Russel King 
Cc: Stafford Horne 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleinxer 
Cc: Vasily Gorbik 
Cc: Vineet Gupta 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

um: move thread info into task

2024-11-12T13:50:31+00:00

This selects the THREAD_INFO_IN_TASK option for UM and changes the way
that the current task is discovered. This is trivial though, as UML
already tracks the current task in cpu_tasks[] and this can be used to
retrieve it.

Also remove the signal handler code that copies the thread information
into the IRQ stack. It is obsolete now, which also means that the
mentioned race condition cannot happen anymore.

Signed-off-by: Benjamin Berg 
Reviewed-by: Hajime Tazaki 
Link: https://patch.msgid.link/20241111102910.46512-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: remove broken double fault detection

2024-11-07T16:36:31+00:00

The show_stack function had some code to detect double faults. However,
the logic is wrong and it would e.g. trigger if a WARNING happened
inside an IRQ.

Remove it without trying to add a new logic. The current behaviour,
which will just fault repeatedly until the IRQ stack is used up and the
host kills UML, seems to be good enough.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20241103150506.1367695-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: remove duplicate UM_NSEC_PER_SEC definition

2024-11-07T16:36:31+00:00

Just remove the first entry as there is a second later on.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20241103150506.1367695-4-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: remove file sync for stub data

2024-11-07T16:36:30+00:00

There is no need to sync the stub code to "disk" for the other process
to see the correct memory. Drop the fsync there and remove the helper
function.

Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20241103150506.1367695-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg