kernel/arch/um/include/asm/mmu_context.h, branch linux-rolling-stable

um: Stop tracking virtual CPUs via mm_cpumask()

2025-09-10T12:23:53Z

In UML, each user address space is represented as a separate stub process on the host. Therefore, user address spaces do not require TLB management on UML virtual CPUs, and it's unnecessary to track which virtual CPUs they have executed on. Signed-off-by: Tiwei Bie Signed-off-by: Johannes Berg

um: Stop tracking stub's PID via userspace_pid[]

2025-07-13T17:42:49Z

The PID of the stub process can be obtained from current_mm_id(). There is no need to track it via userspace_pid[]. Stop doing that to simplify the code. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20250711065021.2535362-4-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: remove force_flush_all from fork_handler

2024-07-03T15:09:50Z

There should be no need for this. It may be that this used to work around another issue where after a clone the MM was in a bad state. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-11-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: remove process stub VMA

2021-02-12T20:37:38Z

This mostly reverts the old commit 3963333fe676 ("uml: cover stubs with a VMA") which had added a VMA to the existing PTEs. However, there's no real reason to have the PTEs in the first place and the VMA cannot be 'fixed' in place, which leads to bugs that userspace could try to unmap them and be forcefully killed, or such. Also, there's a bit of an ugly hole in userspace's address space. Simplify all this: just install the stub code/page at the top of the (inner) address space, i.e. put it just above TASK_SIZE. The pages are simply hard-coded to be mapped in the userspace process we use to implement an mm context, and they're out of reach of the inner mmap/munmap/mprotect etc. since they're above TASK_SIZE. Getting rid of the VMA also makes vma_merge() no longer hit one of the VM_WARN_ON()s there because we installed a VMA while the code assumes the stack VMA is the first one. It also removes a lockdep warning about mmap_sem usage since we no longer have uml_setup_stubs() and thus no longer need to do any manipulation that would require mmap_sem in activate_mm(). Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: use asm-generic/mmu_context.h for no-op implementations

2020-10-27T15:02:39Z

Signed-off-by: Nicholas Piggin Cc: Jeff Dike Cc: Richard Weinberger Cc: Anton Ivanov Cc: linux-um@lists.infradead.org Signed-off-by: Arnd Bergmann

mmap locking API: convert nested write lock sites

2020-06-09T16:39:14Z

Add API for nested write locks and convert the few call sites doing that. 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/20200520052908.204642-7-walken@google.com Signed-off-by: Linus Torvalds

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

2020-06-09T16:39:14Z

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

mm: remove arch_bprm_mm_init() hook

2020-01-23T18:41:16Z

From: Dave Hansen MPX is being removed from the kernel due to a lack of support in the toolchain going forward (gcc). arch_bprm_mm_init() is used at execve() time. The only non-stub implementation is on x86 for MPX. Remove the hook entirely from all architectures and generic code. Cc: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: x86@kernel.org Cc: Linus Torvalds Cc: linux-arch@vger.kernel.org Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Jeff Dike Cc: Richard Weinberger Cc: Anton Ivanov Cc: Guan Xuetao Cc: Andrew Morton Signed-off-by: Dave Hansen

um: Add SPDX headers for files in arch/um/include

2019-09-15T19:37:17Z

Convert files to use SPDX header. All files are licensed under the GPLv2. Signed-off-by: Alex Dewar Signed-off-by: Richard Weinberger

um: Silence lockdep complaint about mmap_sem

2019-07-02T21:27:11Z

When we get into activate_mm(), lockdep complains that we're doing something strange: WARNING: possible circular locking dependency detected 5.1.0-10252-gb00152307319-dirty #121 Not tainted ------------------------------------------------------ inside.sh/366 is trying to acquire lock: (____ptrval____) (&(&p->alloc_lock)->rlock){+.+.}, at: flush_old_exec+0x703/0x8d7 but task is already holding lock: (____ptrval____) (&mm->mmap_sem){++++}, at: flush_old_exec+0x6c5/0x8d7 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&mm->mmap_sem){++++}: [...] __lock_acquire+0x12ab/0x139f lock_acquire+0x155/0x18e down_write+0x3f/0x98 flush_old_exec+0x748/0x8d7 load_elf_binary+0x2ca/0xddb [...] -> #0 (&(&p->alloc_lock)->rlock){+.+.}: [...] __lock_acquire+0x12ab/0x139f lock_acquire+0x155/0x18e _raw_spin_lock+0x30/0x83 flush_old_exec+0x703/0x8d7 load_elf_binary+0x2ca/0xddb [...] other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&mm->mmap_sem); lock(&(&p->alloc_lock)->rlock); lock(&mm->mmap_sem); lock(&(&p->alloc_lock)->rlock); *** DEADLOCK *** 2 locks held by inside.sh/366: #0: (____ptrval____) (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file+0x12d/0x869 #1: (____ptrval____) (&mm->mmap_sem){++++}, at: flush_old_exec+0x6c5/0x8d7 stack backtrace: CPU: 0 PID: 366 Comm: inside.sh Not tainted 5.1.0-10252-gb00152307319-dirty #121 Stack: [...] Call Trace: [<600420de>] show_stack+0x13b/0x155 [<6048906b>] dump_stack+0x2a/0x2c [<6009ae64>] print_circular_bug+0x332/0x343 [<6009c5c6>] check_prev_add+0x669/0xdad [<600a06b4>] __lock_acquire+0x12ab/0x139f [<6009f3d0>] lock_acquire+0x155/0x18e [<604a07e0>] _raw_spin_lock+0x30/0x83 [<60151e6a>] flush_old_exec+0x703/0x8d7 [<601a8eb8>] load_elf_binary+0x2ca/0xddb [...] I think it's because in exec_mmap() we have down_read(&old_mm->mmap_sem); ... task_lock(tsk); ... activate_mm(active_mm, mm); (which does down_write(&mm->mmap_sem)) I'm not really sure why lockdep throws in the whole knowledge about the task lock, but it seems that old_mm and mm shouldn't ever be the same (and it doesn't deadlock) so tell lockdep that they're different. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger