linux.git/arch/um/os-Linux, branch v6.15 Linux kernel source tree um: Rewrite the sigio workaround based on epoll and tgkill 2025-03-20T08:28:44+00:00 Tiwei Bie tiwei.btw@antgroup.com 2025-03-15T16:19:08+00:00 33c9da5dfb18c2ff5a88d01aca2cf253cd0ac3bc 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 <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20250315161910.4082396-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
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 <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250315161910.4082396-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Prohibit the VM_CLONE flag in run_helper_thread() 2025-03-20T08:26:38+00:00 Tiwei Bie tiwei.btw@antgroup.com 2025-03-19T13:55:23+00:00 69f52573c24de9d2919f83e3b3b396a09118b7c4 Directly creating helper threads with VM_CLONE using clone can compromise the thread safety of errno. Since all these helper threads have been converted to use os_run_helper_thread(), let's prevent using this flag in run_helper_thread(). Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20250319135523.97050-5-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
Directly creating helper threads with VM_CLONE using clone can
compromise the thread safety of errno. Since all these helper
threads have been converted to use os_run_helper_thread(), let's
prevent using this flag in run_helper_thread().

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250319135523.97050-5-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Switch to the pthread-based helper in sigio workaround 2025-03-20T08:26:38+00:00 Tiwei Bie tiwei.btw@antgroup.com 2025-03-19T13:55:22+00:00 d295beeed2552a987796d627ba7d0985b1e2d72f The write_sigio thread and UML kernel thread share the same errno, which can lead to conflicts when both call syscalls concurrently. Switch to the pthread-based helper to address this issue. Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20250319135523.97050-4-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
The write_sigio thread and UML kernel thread share the same errno,
which can lead to conflicts when both call syscalls concurrently.
Switch to the pthread-based helper to address this issue.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250319135523.97050-4-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Add pthread-based helper support 2025-03-20T08:26:38+00:00 Tiwei Bie tiwei.btw@antgroup.com 2025-03-19T13:55:20+00:00 4f087eafdcef24b7160b097ddb9704084767b77a 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 <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20250319135523.97050-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
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 <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250319135523.97050-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: remove copy_from_kernel_nofault_allowed 2025-03-18T10:03:29+00:00 Benjamin Berg benjamin.berg@intel.com 2025-02-10T16:09:26+00:00 84a6fc378471fbeaf48f8604566a5a33a3d63c18 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 <benjamin.berg@intel.com> Link: https://patch.msgid.link/20250210160926.420133-3-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
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 <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250210160926.420133-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: mark rodata read-only and implement _nofault accesses 2025-03-18T10:03:14+00:00 Johannes Berg johannes.berg@intel.com 2025-02-10T16:09:25+00:00 d1d7f01f7cd35e16c6bcef5a0e31988b5c9980f9 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 <johannes.berg@intel.com> Co-developed-by: Benjamin Berg <benjamin.berg@intel.com> Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20250210160926.420133-2-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
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 <johannes.berg@intel.com>
Co-developed-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250210160926.420133-2-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: fix execve stub execution on old host OSs 2025-02-12T22:40:45+00:00 Benjamin Berg benjamin.berg@intel.com 2025-01-13T09:41:07+00:00 f82a9e7b9fa922bb9cccb00aae684a27b79e6df7 The stub execution uses the somewhat new close_range and execveat syscalls. Of these two, the execveat call is essential, but the close_range call is more about stub process hygiene rather than safety (and its result is ignored). Replace both calls with a raw syscall as older machines might not have a recent enough kernel for close_range (with CLOSE_RANGE_CLOEXEC) or a libc that does not yet expose both of the syscalls. Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs") Reported-by: Glenn Washburn <development@efficientek.com> Closes: https://lore.kernel.org/20250108022404.05e0de1e@crass-HP-ZBook-15-G2 Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20250113094107.674738-1-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Richard Weinberger <richard@nod.at> 
The stub execution uses the somewhat new close_range and execveat
syscalls. Of these two, the execveat call is essential, but the
close_range call is more about stub process hygiene rather than safety
(and its result is ignored).

Replace both calls with a raw syscall as older machines might not have a
recent enough kernel for close_range (with CLOSE_RANGE_CLOEXEC) or a
libc that does not yet expose both of the syscalls.

Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Reported-by: Glenn Washburn <development@efficientek.com>
Closes: https://lore.kernel.org/20250108022404.05e0de1e@crass-HP-ZBook-15-G2
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250113094107.674738-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
um: Remove unused THREAD_NAME_LEN macro 2025-01-10T12:49:57+00:00 Tiwei Bie tiwei.btw@antgroup.com 2024-11-28T08:31:36+00:00 c5e78b8d408add9d3562c7c44a727336ecb5d48b It's no longer used since commit 42fda66387da ("uml: throw out CONFIG_MODE_TT"). Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20241128083137.2219830-9-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
It's no longer used since commit 42fda66387da ("uml: throw out
CONFIG_MODE_TT").

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241128083137.2219830-9-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Remove unused PGD_BOUND macro 2025-01-10T12:49:57+00:00 Tiwei Bie tiwei.btw@antgroup.com 2024-11-28T08:31:35+00:00 3c68810e150b80b9282e854142922b39489a54a5 It's no longer used since commit 11100b1dfb6e ("uml: delete unused code"). Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20241128083137.2219830-8-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
It's no longer used since commit 11100b1dfb6e ("uml: delete
unused code").

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241128083137.2219830-8-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Mark setup_env_path as __init 2025-01-10T12:49:57+00:00 Tiwei Bie tiwei.btw@antgroup.com 2024-11-28T08:31:34+00:00 0c5258efd69b73bd12f3e68cfe72e1396fdb857c It's only invoked during boot from main(). Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20241128083137.2219830-7-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
It's only invoked during boot from main().

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241128083137.2219830-7-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>