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[v12,00/13] nommu UML

Message ID cover.1762075876.git.thehajime@gmail.com
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Series nommu UML | expand

Message

Hajime Tazaki Nov. 2, 2025, 9:49 a.m. UTC 
This patchset is another spin of nommu mode addition to UML.  It would
be nice to hear about your opinions on that.

There are still several limitations/issues which we already found;
here is the list of those issues.

- memory mapped by loadable modules are not distinguished from
  userspace memory.
- CONFIG_SMP is disabled as host_fs handling doesn't work with thread
  local storage.

-- Hajime

v12:
- rebase with the latest uml/next branch
- disable SMP and tls as those doesn't work with host_fs handling ([11/13])

v11:
- clean up userspace return routine and integrate to userspace() ([04/13])
- fix direction flag issue on using nolibc memcpy ([04/13])
- fix a crash issue when using usermode helper ([06/13])
- test with out-of-tree kunit-uapi patches (which uses umh)
 - https://lore.kernel.org/all/20250626-kunit-kselftests-v4-0-48760534fef5@linutronix.de/
 - https://lore.kernel.org/all/20250626195714.2123694-3-benjamin@sipsolutions.net/
- https://lore.kernel.org/all/cover.1758181109.git.thehajime@gmail.com/

v10:
- fix wrong comment on gs register handling ([09/13])
- remove unnecessary code of early syscall implementation ([04/13])
- https://lore.kernel.org/all/cover.1750594487.git.thehajime@gmail.com/

v9:
- rebase with the latest uml/next branch
- add performance numbers of new SECCOMP mode, and update results ([12/13])
- add a workaround for upstream change on MMU depedency to PCI drivers ([10/13])
- https://lore.kernel.org/all/cover.1750294482.git.thehajime@gmail.com/

v8:
- rebase with the latest uml/next branch
- clean up segv_handler to align with the latest uml ([9/12])
- https://lore.kernel.org/all/cover.1745980082.git.thehajime@gmail.com/

v7:
- properly handle FP register upon signal delivery [10/13]
- update benchmark result with new FP register handling [12/13]
- fix arch_has_single_step() for !MMU case [07/13]
- revert stack alignment as it is in uml/fixes tree [10/13]
- https://lore.kernel.org/all/cover.1737348399.git.thehajime@gmail.com/

v6:
- rebase to the latest uml/next tree
- more clean up on mmu/nommu for signal handling [10/13]
- rename functions of mcontext routines [06,10/13]
- added Acked-by tag for binfmt_elf_fdpic [02/13]
- https://lore.kernel.org/linux-um/cover.1736853925.git.thehajime@gmail.com/

v5:
- clean up stack manipulation code [05,06,07,10/13]
- https://lore.kernel.org/linux-um/cover.1733998168.git.thehajime@gmail.com/

v4:
- add arch/um/nommu, arch/x86/um/nommu to contain !MMU specific codes
- remove zpoline patch
- drop binfmt_elf_fdpic patch
- reduce ifndef CONFIG_MMU if possible
- split to elf header cleanup patch [01/13]
- fix kernel test robot warnings [06/13]
- fix coding styles [07/13]
- move task_top_of_stack definition [05/13]
- https://lore.kernel.org/linux-um/cover.1733652929.git.thehajime@gmail.com/

v3:
- https://lore.kernel.org/linux-um/cover.1733199769.git.thehajime@gmail.com/
- add seccomp-based syscall hook in addition to zpoline [06/13]
- remove RFC, add a line to MAINTAINERS file
- fix kernel test robot warnings [02/13,08/13,10/13]
- add base-commit tag to cover letter
- pull the latest uml/next
- clean up SIGSEGV handling [10/13]
- detect fsgsbase availability with elf aux vector [08/13]
- simplify vdso code with macros [09/13]

RFC v2:
- https://lore.kernel.org/linux-um/cover.1731290567.git.thehajime@gmail.com/
- base branch is now uml/linux.git instead of torvalds/linux.git.
- reorganize the patch series to clean up
- fixed various coding styles issues
- clean up exec code path [07/13]
- fixed the crash/SIGSEGV case on userspace programs [10/13]
- add seccomp filter to limit syscall caller address [06/13]
- detect fsgsbase availability with sigsetjmp/siglongjmp [08/13]
- removes unrelated changes
- removes unneeded ifndef CONFIG_MMU
- convert UML_CONFIG_MMU to CONFIG_MMU as using uml/linux.git
- proposed a patch of maple-tree issue (resolving a limitation in RFC v1)
  https://lore.kernel.org/linux-mm/20241108222834.3625217-1-thehajime@gmail.com/

RFC:
- https://lore.kernel.org/linux-um/cover.1729770373.git.thehajime@gmail.com/

Hajime Tazaki (13):
  x86/um: nommu: elf loader for fdpic
  um: decouple MMU specific code from the common part
  um: nommu: memory handling
  x86/um: nommu: syscall handling
  um: nommu: seccomp syscalls hook
  x86/um: nommu: process/thread handling
  um: nommu: configure fs register on host syscall invocation
  x86/um/vdso: nommu: vdso memory update
  x86/um: nommu: signal handling
  um: change machine name for uname output
  um: nommu: disable SMP on nommu UML
  um: nommu: add documentation of nommu UML
  um: nommu: plug nommu code into build system

 Documentation/virt/uml/nommu-uml.rst   | 180 ++++++++++++++++++++++
 MAINTAINERS                            |   1 +
 arch/um/Kconfig                        |  14 +-
 arch/um/Makefile                       |  10 ++
 arch/um/configs/x86_64_nommu_defconfig |  54 +++++++
 arch/um/include/asm/futex.h            |   4 +
 arch/um/include/asm/mmu.h              |   8 +
 arch/um/include/asm/mmu_context.h      |   2 +
 arch/um/include/asm/ptrace-generic.h   |   8 +-
 arch/um/include/asm/uaccess.h          |   7 +-
 arch/um/include/shared/kern_util.h     |   6 +
 arch/um/include/shared/os.h            |  16 ++
 arch/um/kernel/Makefile                |   5 +-
 arch/um/kernel/mem-pgtable.c           |  55 +++++++
 arch/um/kernel/mem.c                   |  38 +----
 arch/um/kernel/process.c               |  38 +++++
 arch/um/kernel/skas/process.c          |  37 -----
 arch/um/kernel/um_arch.c               |   3 +
 arch/um/nommu/Makefile                 |   3 +
 arch/um/nommu/os-Linux/Makefile        |   7 +
 arch/um/nommu/os-Linux/seccomp.c       |  87 +++++++++++
 arch/um/nommu/os-Linux/signal.c        |  24 +++
 arch/um/nommu/trap.c                   | 201 +++++++++++++++++++++++++
 arch/um/os-Linux/Makefile              |   3 +-
 arch/um/os-Linux/internal.h            |   8 +
 arch/um/os-Linux/mem.c                 |   4 +
 arch/um/os-Linux/process.c             | 139 ++++++++++++++++-
 arch/um/os-Linux/signal.c              |  11 +-
 arch/um/os-Linux/skas/process.c        | 127 ----------------
 arch/um/os-Linux/start_up.c            |  25 ++-
 arch/um/os-Linux/util.c                |   3 +-
 arch/x86/um/Kconfig                    |   2 +-
 arch/x86/um/Makefile                   |   7 +-
 arch/x86/um/asm/elf.h                  |   8 +-
 arch/x86/um/asm/syscall.h              |   6 +
 arch/x86/um/nommu/Makefile             |   8 +
 arch/x86/um/nommu/do_syscall_64.c      |  75 +++++++++
 arch/x86/um/nommu/entry_64.S           | 114 ++++++++++++++
 arch/x86/um/nommu/os-Linux/Makefile    |   6 +
 arch/x86/um/nommu/os-Linux/mcontext.c  |  26 ++++
 arch/x86/um/nommu/syscalls.h           |  18 +++
 arch/x86/um/nommu/syscalls_64.c        | 121 +++++++++++++++
 arch/x86/um/shared/sysdep/mcontext.h   |   5 +
 arch/x86/um/shared/sysdep/ptrace.h     |   2 +-
 arch/x86/um/vdso/vma.c                 |  17 ++-
 fs/Kconfig.binfmt                      |   2 +-
 46 files changed, 1322 insertions(+), 223 deletions(-)
 create mode 100644 Documentation/virt/uml/nommu-uml.rst
 create mode 100644 arch/um/configs/x86_64_nommu_defconfig
 create mode 100644 arch/um/kernel/mem-pgtable.c
 create mode 100644 arch/um/nommu/Makefile
 create mode 100644 arch/um/nommu/os-Linux/Makefile
 create mode 100644 arch/um/nommu/os-Linux/seccomp.c
 create mode 100644 arch/um/nommu/os-Linux/signal.c
 create mode 100644 arch/um/nommu/trap.c
 create mode 100644 arch/x86/um/nommu/Makefile
 create mode 100644 arch/x86/um/nommu/do_syscall_64.c
 create mode 100644 arch/x86/um/nommu/entry_64.S
 create mode 100644 arch/x86/um/nommu/os-Linux/Makefile
 create mode 100644 arch/x86/um/nommu/os-Linux/mcontext.c
 create mode 100644 arch/x86/um/nommu/syscalls.h
 create mode 100644 arch/x86/um/nommu/syscalls_64.c


base-commit: 8e03c195cc4d82100291500f772f85c686653748