kernel.git/arch/um/include/shared/os.h, branch linux-6.15.y

um: Rewrite the sigio workaround based on epoll and tgkill

2025-03-20T08:28:44Z

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

2025-03-20T08:26:38Z

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

2025-03-18T10:03:29Z

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

2024-11-07T16:36:31Z

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

2024-11-07T16:36:30Z

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

2024-10-25T09:34:54Z

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

2024-10-23T07:52:49Z

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

um: Discover host_task_size from envp

2024-10-10T11:37:22Z

When loading the UML binary, the host kernel will place the stack at the highest possible address. It will then map the program name and environment variables onto the start of the stack. As such, an easy way to figure out the host_task_size is to use the highest pointer to an environment variable as a reference. Ensure that this works by disabling address layout randomization and re-executing UML in case it was enabled. This increases the available TASK_SIZE for 64 bit UML considerably. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240919124511.282088-9-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: remove auxiliary FP registers

2024-10-10T10:10:30Z

We do not need the extra save/restore of the FP registers when getting the fault information. This was originally added in commit 2f56debd77a8 ("uml: fix FP register corruption") but at that time the code was not saving/restoring the FP registers when switching to userspace. This was fixed in commit fbfe9c847edf ("um: Save FPU registers between task switches") and since then the auxiliary registers have not been useful. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20241004233821.2130874-1-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Remove unused os_getpgrp function

2024-10-10T10:02:04Z

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