kernel/linux.git/arch/um/os-Linux/process.c, branch v6.18.21

um: Track userspace children dying in SECCOMP mode

2025-06-02T13:17:19+00:00

When in seccomp mode, we would hang forever on the futex if a child has died unexpectedly. In contrast, ptrace mode will notice it and kill the corresponding thread when it fails to run it. Fix this issue using a new IRQ that is fired after a SIGCHLD and keeping an (internal) list of all MMs. In the IRQ handler, find the affected MM and set its PID to -1 as well as the futex variable to FUTEX_IN_KERN. This, together with futex returning -EINTR after the signal is sufficient to implement a race-free detection of a child dying. Note that this also enables IRQ handling while starting a userspace process. This should be safe and SECCOMP requires the IRQ in case the process does not come up properly. Signed-off-by: Benjamin Berg Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20250602130052.545733-5-benjamin@sipsolutions.net 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: Add os_set_pdeathsig helper function

2024-10-25T09:34:54+00:00

This helper can be used to set the parent-death signal of the calling process to SIGKILL to ensure that the process will be killed if the UML kernel dies unexpectedly without proper cleanup. This helper will be used in the follow-up patches. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20241024142828.2612828-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg

um: Remove unused os_getpgrp function

2024-10-10T10:02:04+00:00

The function is not used anywhere. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240913134442.967599-5-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Remove unused os_stop_process

2024-10-10T10:02:04+00:00

The function is not used anywhere. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240913134442.967599-4-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Remove unused os_process_parent

2024-10-10T10:02:04+00:00

The function is not used anywhere. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240913134442.967599-3-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Remove unused os_process_pc

2024-10-10T10:02:04+00:00

The function is not used anywhere in the codebase. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240913134442.967599-2-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Add SPDX headers for files in arch/um/os-Linux

2019-09-15T19:37:17+00:00

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

um: Switch clocksource to hrtimers

2015-11-06T21:54:49+00:00

UML is using an obsolete itimer call for all timers and "polls" for kernel space timer firing in its userspace portion resulting in a long list of bugs and incorrect behaviour(s). It also uses ITIMER_VIRTUAL for its timer which results in the timer being dependent on it running and the cpu load. This patch fixes this by moving to posix high resolution timers firing off CLOCK_MONOTONIC and relaying the timer correctly to the UML userspace. Fixes: - crashes when hosts suspends/resumes - broken userspace timers - effecive ~40Hz instead of what they should be. Note - this modifies skas behavior by no longer setting an itimer per clone(). Timer events are relayed instead. - kernel network packet scheduling disciplines - tcp behaviour especially under load - various timer related corner cases Finally, overall responsiveness of userspace is better. Signed-off-by: Thomas Meyer Signed-off-by: Anton Ivanov [rw: massaged commit message] Signed-off-by: Richard Weinberger

um: Remove SKAS3/4 support

2015-04-13T19:00:53+00:00

Before we had SKAS0 UML had two modes of operation TT (tracing thread) and SKAS3/4 (separated kernel address space). TT was known to be insecure and got removed a long time ago. SKAS3/4 required a few (3 or 4) patches on the host side which never went mainline. The last host patch is 10 years old. With SKAS0 mode (separated kernel address space using 0 host patches), default since 2005, SKAS3/4 is obsolete and can be removed. Signed-off-by: Richard Weinberger