kernel/linux.git/arch/um/include/shared/os.h, branch v6.18.22

um: Implement kernel side of SECCOMP based process handling

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

This adds the kernel side of the seccomp based process handling. Co-authored-by: Johannes Berg Signed-off-by: Benjamin Berg Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20250602130052.545733-6-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

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 obsolete legacy network transports

2025-05-05T08:26:59+00:00

These legacy network transports were marked as obsolete in commit 40814b98a570 ("um: Mark non-vector net transports as obsolete"). More than five years have passed since then. Remove these network transports to reduce the maintenance burden. Suggested-by: Anton Ivanov Signed-off-by: Tiwei Bie Acked-By: Anton Ivanov Link: https://patch.msgid.link/20250503051710.3286595-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg

um: Rewrite the sigio workaround based on epoll and tgkill

2025-03-20T08:28:44+00:00

The existing sigio workaround implementation removes FDs from the poll when events are triggered, requiring users to re-add them via add_sigio_fd() after processing. This introduces a potential race condition between FD removal in write_sigio_thread() and next_poll update in __add_sigio_fd(), and is inefficient due to frequent FD removal and re-addition. Rewrite the implementation based on epoll and tgkill for improved efficiency and reliability. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20250315161910.4082396-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg

um: Add pthread-based helper support

2025-03-20T08:26:38+00:00

Introduce a new set of utility functions that can be used to create pthread-based helpers. Helper threads created in this way will ensure thread safety for errno while sharing the same memory space. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20250319135523.97050-2-tiwei.btw@antgroup.com 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: remove broken double fault detection

2024-11-07T16:36:31+00:00

The show_stack function had some code to detect double faults. However, the logic is wrong and it would e.g. trigger if a WARNING happened inside an IRQ. Remove it without trying to add a new logic. The current behaviour, which will just fault repeatedly until the IRQ stack is used up and the host kills UML, seems to be good enough. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20241103150506.1367695-5-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: remove file sync for stub data

2024-11-07T16:36:30+00:00

There is no need to sync the stub code to "disk" for the other process to see the correct memory. Drop the fsync there and remove the helper function. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20241103150506.1367695-3-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: Abandon the _PAGE_NEWPROT bit

2024-10-23T07:52:49+00:00

When a PTE is updated in the page table, the _PAGE_NEWPAGE bit will always be set. And the corresponding page will always be mapped or unmapped depending on whether the PTE is present or not. The check on the _PAGE_NEWPROT bit is not really reachable. Abandoning it will allow us to simplify the code and remove the unreachable code. Reviewed-by: Benjamin Berg Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20241011102354.1682626-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg