kernel.git/arch/um, branch linux-6.15.y

um: Re-evaluate thread flags repeatedly

2025-08-20T16:36:05Z

[ Upstream commit b9e2f2246eb2b5617d53af7b5e4e1b8c916f26a8 ] The thread flags may change during their processing. For example a task_work can queue a new signal to be sent. This signal should be delivered before returning to usespace again. Evaluate the flags repeatedly similar to other architectures. Signed-off-by: Thomas Weißschuh Reviewed-by: Nam Cao Link: https://patch.msgid.link/20250704-uml-thread_flags-v1-1-0e293fd8d627@linutronix.de Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: rtc: Avoid shadowing err in uml_rtc_start()

2025-08-15T10:16:29Z

[ Upstream commit 4c916e3b224a02019b3cc3983a15f32bfd9a22df ] Remove the declaration of 'err' inside the 'if (timetravel)' block, as it would otherwise be unavailable outside that block, potentially leading to uml_rtc_start() returning an uninitialized value. Fixes: dde8b58d5127 ("um: add a pseudo RTC") Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20250708090403.1067440-5-tiwei.bie@linux.dev Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: vector: Reduce stack usage in vector_eth_configure()

2025-07-17T16:44:01Z

[ Upstream commit 2d65fc13be85c336c56af7077f08ccd3a3a15a4a ] When compiling with clang (19.1.7), initializing *vp using a compound literal may result in excessive stack usage. Fix it by initializing the required fields of *vp individually. Without this patch: $ objdump -d arch/um/drivers/vector_kern.o | ./scripts/checkstack.pl x86_64 0 ... 0x0000000000000540 vector_eth_configure [vector_kern.o]:1472 ... With this patch: $ objdump -d arch/um/drivers/vector_kern.o | ./scripts/checkstack.pl x86_64 0 ... 0x0000000000000540 vector_eth_configure [vector_kern.o]:208 ... Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202506221017.WtB7Usua-lkp@intel.com/ Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20250623110829.314864-1-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: ubd: Add missing error check in start_io_thread()

2025-07-06T09:04:16Z

[ Upstream commit c55c7a85e02a7bfee20a3ffebdff7cbeb41613ef ] The subsequent call to os_set_fd_block() overwrites the previous return value. OR the two return values together to fix it. Fixes: f88f0bdfc32f ("um: UBD Improvements") Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20250606124428.148164-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: use proper care when taking mmap lock during segfault

2025-07-06T09:04:06Z

[ Upstream commit 6767e8784cd2e8b386a62330ea6864949d983a3e ] Segfaults can occur at times where the mmap lock cannot be taken. If that happens the segfault handler may not be able to take the mmap lock. Fix the code to use the same approach as most other architectures. Unfortunately, this requires copying code from mm/memory.c and modifying it slightly as UML does not have exception tables. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20250408074524.300153-2-benjamin@sipsolutions.net Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: Add cmpxchg8b_emu and checksum functions to asm-prototypes.h

2025-07-06T09:04:06Z

[ Upstream commit 674d03f6bd6b0f8327f1a4920ff5893557facfbd ] With CONFIG_GENDWARFKSYMS, um builds fail due to missing prototypes in asm/asm-prototypes.h. Add declarations for cmpxchg8b_emu and the exported checksum functions, including csum_partial_copy_generic as it's also exported. Cc: Masahiro Yamada Cc: linux-kbuild@vger.kernel.org Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202503251216.lE4t9Ikj-lkp@intel.com/ Signed-off-by: Sami Tolvanen Link: https://patch.msgid.link/20250326190500.847236-2-samitolvanen@google.com Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: Fix tgkill compile error on old host OSes

2025-06-19T13:40:39Z

[ Upstream commit fd054188999ff19746cc09f4e0f196a113964db9 ] tgkill is a quite old syscall since kernel 2.5.75, but unfortunately glibc doesn't support it before 2.30. Thus some systems fail to compile the latest UserMode Linux. Here is the compile error I encountered when I tried to compile UML in my system shipped with glibc-2.28. CALL scripts/checksyscalls.sh CC arch/um/os-Linux/sigio.o In file included from arch/um/os-Linux/sigio.c:17: arch/um/os-Linux/sigio.c: In function ‘write_sigio_thread’: arch/um/os-Linux/sigio.c:49:19: error: implicit declaration of function ‘tgkill’; did you mean ‘kill’? [-Werror=implicit-function-declaration] CATCH_EINTR(r = tgkill(pid, pid, SIGIO)); ^~~~~~ ./arch/um/include/shared/os.h:21:48: note: in definition of macro ‘CATCH_EINTR’ #define CATCH_EINTR(expr) while ((errno = 0, ((expr) < 0)) && (errno == EINTR)) ^~~~ cc1: some warnings being treated as errors Fix it by Replacing glibc call with raw syscall. Fixes: 33c9da5dfb18 ("um: Rewrite the sigio workaround based on epoll and tgkill") Signed-off-by: Yongting Lin Link: https://patch.msgid.link/20250527151222.40371-1-linyongting@gmail.com Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: let 'make clean' properly clean underlying SUBARCH as well

2025-05-12T06:03:42Z

Building the kernel with O= is affected by stale in-tree build artifacts. So, if the source tree is not clean, Kbuild displays the following: $ make ARCH=um O=build defconfig make[1]: Entering directory '/.../linux/build' *** *** The source tree is not clean, please run 'make ARCH=um mrproper' *** in /.../linux *** make[2]: *** [/.../linux/Makefile:673: outputmakefile] Error 1 make[1]: *** [/.../linux/Makefile:248: __sub-make] Error 2 make[1]: Leaving directory '/.../linux/build' make: *** [Makefile:248: __sub-make] Error 2 Usually, running 'make mrproper' is sufficient for cleaning the source tree for out-of-tree builds. However, building UML generates build artifacts not only in arch/um/, but also in the SUBARCH directory (i.e., arch/x86/). If in-tree stale files remain under arch/x86/, Kbuild will reuse them instead of creating new ones under the specified build directory. This commit makes 'make ARCH=um clean' recurse into the SUBARCH directory. Reported-by: Shuah Khan Closes: https://lore.kernel.org/lkml/20250502172459.14175-1-skhan@linuxfoundation.org/ Signed-off-by: Masahiro Yamada Acked-by: Johannes Berg Reviewed-by: David Gow Reviewed-by: Shuah Khan

um: fix _nofault accesses

2025-05-05T08:06:51Z

Nathan reported [1] that when built with clang, the um kernel crashes pretty much immediately. This turned out to be an issue with the inline assembly I had added, when clang used %rax/%eax for both operands. Reorder it so current->thread.segv_continue is written first, and then the lifetime of _faulted won't have overlap with the lifetime of segv_continue. In the email thread Benjamin also pointed out that current->mm is only NULL for true kernel tasks, but we could do this for a userspace task, so the current->thread.segv_continue logic must be lifted out of the mm==NULL check. Finally, while looking at this, put a barrier() so the NULL assignment to thread.segv_continue cannot be reorder before the possibly faulting operation. Reported-by: Nathan Chancellor Closes: https://lore.kernel.org/r/20250402221254.GA384@ax162 [1] Fixes: d1d7f01f7cd3 ("um: mark rodata read-only and implement _nofault accesses") Tested-by: Nathan Chancellor Signed-off-by: Johannes Berg

treewide: Switch/rename to timer_delete[_sync]()

2025-04-05T08:30:12Z

timer_delete[_sync]() replaces del_timer[_sync](). Convert the whole tree over and remove the historical wrapper inlines. Conversion was done with coccinelle plus manual fixups where necessary. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar