kernel/linux.git/arch/um/include/shared/kern_util.h, branch v7.1

arch, mm: consolidate empty_zero_page

2026-04-05T20:53:01+00:00

Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of ZERO_PAGE() to 4. Every architecture defines empty_zero_page that way or another, but for the most of them it is always a page aligned page in BSS and most definitions of ZERO_PAGE do virt_to_page(empty_zero_page). Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the core MM and drop these definitions in architectures that do not implement colored zero page (MIPS and s390). ZERO_PAGE() remains a macro because turning it to a wrapper for a static inline causes severe pain in header dependencies. For the most part the change is mechanical, with these being noteworthy: * alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot parameters. Switching to a generic empty_zero_page removes the aliasing and keeps ZERO_PGE for boot parameters only * arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of ZERO_PAGE() is kept intact. * m68k/parisc/um: allocated empty_zero_page from memblock, although they do not support zero page coloring and having it in BSS will work fine. * sparc64 can have empty_zero_page in BSS rather allocate it, but it can't use virt_to_page() for BSS. Keep it's definition of ZERO_PAGE() but instead of allocating it, make mem_map_zero point to empty_zero_page. * sh: used empty_zero_page for boot parameters at the very early boot. Rename the parameters page to boot_params_page and let sh use the generic empty_zero_page. * hexagon: had an amusing comment about empty_zero_page /* A handy thing to have if one has the RAM. Declared in head.S */ that unfortunately had to go :) Link: https://lkml.kernel.org/r/20260211103141.3215197-4-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Acked-by: Helge Deller [parisc] Tested-by: Helge Deller [parisc] Reviewed-by: Christophe Leroy (CS GROUP) Acked-by: Dave Hansen Acked-by: Catalin Marinas Acked-by: Magnus Lindholm [alpha] Acked-by: Dinh Nguyen [nios2] Acked-by: Andreas Larsson [sparc] Acked-by: David Hildenbrand (Arm) Acked-by: Liam R. Howlett Cc: "Borislav Petkov (AMD)" Cc: David S. Miller Cc: Geert Uytterhoeven Cc: Guo Ren Cc: Huacai Chen Cc: Ingo Molnar Cc: Johannes Berg Cc: John Paul Adrian Glaubitz Cc: Lorenzo Stoakes Cc: Madhavan Srinivasan Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Hocko Cc: Michal Simek Cc: Palmer Dabbelt Cc: Richard Weinberger Cc: Russell King Cc: Stafford Horne Cc: Suren Baghdasaryan Cc: Vineet Gupta Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton

um: Determine sleep based on need_resched()

2025-10-27T15:41:15+00:00

With SMP and NO_HZ enabled, the CPU may still need to sleep even if the timer is disarmed. Switch to deciding whether to sleep based on pending resched. Additionally, because disabling IRQs does not block SIGALRM, it is also necessary to check for any pending timer alarms. This is a preparation for adding SMP support. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027001815.1666872-4-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: Remove file-based iomem emulation support

2025-10-27T15:37:12+00:00

The file-based iomem emulation was introduced to support writing paravirtualized drivers based on emulated iomem regions. However, the only driver that makes use of it is an example driver called mmapper, which was written over two decades ago. We now have several modern device emulation mechanisms, such as vhost-user-based virtio-uml. Remove the file-based iomem emulation support to reduce the maintenance burden. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027054519.1996090-5-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

um: Replace UML_ROUND_UP() with PAGE_ALIGN()

2025-10-27T15:37:12+00:00

Although UML_ROUND_UP() is defined in a shared header file, it depends on the PAGE_SIZE and PAGE_MASK macros, so it can only be used in kernel code. Considering its name is not very clear and its functionality is the same as PAGE_ALIGN(), replace its usages with a direct call to PAGE_ALIGN() and remove it. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20251027054519.1996090-4-tiwei.bie@linux.dev 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

um: remove fault_catcher infrastructure

2024-10-23T07:52:46+00:00

This was perhaps intended to do _nofault copies, but the real reason is lost to history. Remove this, it's not needed, and using longjmp() out of the middle of the signal handler with all the state it has modified is not going to be a good idea anyway. Link: https://patch.msgid.link/20241010224513.901c4d390b3e.Ia74742668b44603c1ca23dd36f90e964e6e7ee55@changeid Signed-off-by: Johannes Berg

um: Remove unused ncpus variable

2024-07-03T10:21:57+00:00

It's no longer used. And uml_ncpus_setup doesn't exist anymore. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20240527134024.1539848-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg

um: Fix the declaration of kasan_map_memory

2024-04-30T12:15:42+00:00

Make it match its definition (size_t vs unsigned long). And declare it in a shared header to fix the -Wmissing-prototypes warning, as it is defined in the user code and called in the kernel code. Fixes: 5b301409e8bc ("UML: add support for KASAN under x86_64") Signed-off-by: Tiwei Bie Signed-off-by: Richard Weinberger

um: Move declarations to proper headers

2024-04-22T19:58:48+00:00

This will address below -Wmissing-prototypes warnings: arch/um/kernel/initrd.c:18:12: warning: no previous prototype for ‘read_initrd’ [-Wmissing-prototypes] arch/um/kernel/um_arch.c:408:19: warning: no previous prototype for ‘read_initrd’ [-Wmissing-prototypes] arch/um/os-Linux/start_up.c:301:12: warning: no previous prototype for ‘parse_iomem’ [-Wmissing-prototypes] arch/x86/um/ptrace_32.c:15:6: warning: no previous prototype for ‘arch_switch_to’ [-Wmissing-prototypes] arch/x86/um/ptrace_32.c:101:5: warning: no previous prototype for ‘poke_user’ [-Wmissing-prototypes] arch/x86/um/ptrace_32.c:153:5: warning: no previous prototype for ‘peek_user’ [-Wmissing-prototypes] arch/x86/um/ptrace_64.c:111:5: warning: no previous prototype for ‘poke_user’ [-Wmissing-prototypes] arch/x86/um/ptrace_64.c:171:5: warning: no previous prototype for ‘peek_user’ [-Wmissing-prototypes] arch/x86/um/syscalls_64.c:48:6: warning: no previous prototype for ‘arch_switch_to’ [-Wmissing-prototypes] arch/x86/um/tls_32.c:184:5: warning: no previous prototype for ‘arch_switch_tls’ [-Wmissing-prototypes] Signed-off-by: Tiwei Bie Signed-off-by: Richard Weinberger

um: Drop support for hosts without SYSEMU_SINGLESTEP support

2024-01-04T22:29:11+00:00

These features have existed since Linux 2.6.14 and can be considered widely available at this point. Also drop the backward compatibility code for PTRACE_SETOPTIONS. Signed-off-by: Benjamin Berg ---- v2: * Continue to define PTRACE_SYSEMU_SINGLESTEP as glibc only added it in version 2.27. Signed-off-by: Richard Weinberger