kernel/linux.git/arch/um/include/shared/os.h, branch v6.12.92

um: remove copy_from_kernel_nofault_allowed

2025-04-10T12:39:25+00:00

[ Upstream commit 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 Link: https://patch.msgid.link/20250210160926.420133-3-benjamin@sipsolutions.net Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: simplify and consolidate TLB updates

2024-07-03T15:09:50+00:00

The HVC update was mostly used to compress consecutive calls into one. This is mostly relevant for userspace where it is already handled by the syscall stub code. Simplify the whole logic and consolidate it for both kernel and userspace. This does remove the sequential syscall compression for the kernel, however that shouldn't be the main factor in most runs. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-12-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Delay flushing syscalls until the thread is restarted

2024-07-03T15:09:49+00:00

As running the syscalls is expensive due to context switches, we should do so as late as possible in case more syscalls need to be queued later on. This will also benefit a later move to a SECCOMP enabled userspace as in that case the need for extra context switches is removed entirely. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-9-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: remove copy_context_skas0

2024-07-03T15:09:49+00:00

The kernel flushes the memory ranges anyway for CoW and does not assume that the userspace process has anything set up already. So, start with a fresh process for the new mm context. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-8-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Rework syscall handling

2024-07-03T15:09:49+00:00

Rework syscall handling to be platform independent. Also create a clean split between queueing of syscalls and flushing them out, removing the need to keep state in the code that triggers the syscalls. The code adds syscall_data_len to the global mm_id structure. This will be used later to allow surrounding code to track whether syscalls still need to run and if errors occurred. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20240703134536.1161108-5-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: add mmap/mremap OS calls

2024-07-03T10:24:48+00:00

For the upcoming shared-memory time-travel external optimisations, we need to be able to mmap/mremap. Add the necessary OS calls. Link: https://patch.msgid.link/20240702192118.ca4472963638.Ic2da1d3a983fe57340c1b693badfa9c5bd2d8c61@changeid Signed-off-by: Johannes Berg

um: generalize os_rcv_fd

2024-07-03T10:24:25+00:00

Change os_rcv_fd() to os_rcv_fd_msg() that can more generally receive any number of FDs in any kind of message. Link: https://patch.msgid.link/20240702192118.40b78b2bfe4e.Ic6ec12d72630e5bcae1e597d6bd5c6f29f441563@changeid Signed-off-by: Johannes Berg

um: chan: use blocking IO for console output for time-travel

2024-07-03T10:18:02+00:00

When in time-travel mode (infinite-cpu or external) time should not pass for writing to the console. As such, it makes sense to put the FD for the output side into blocking mode and simply let any write to it hang. If we did not do this, then time could pass waiting for the console to become writable again. This is not desirable as it has random effects on the clock between runs. Implement this by duplicating the FD if output is active in a relevant mode and setting the duplicate to be blocking. This avoids changing the input channel to be blocking should it exists. After this, use the blocking FD for all write operations and do not allocate an IRQ it is set. Without time-travel mode fd_out will always match fd_in and IRQs are registered. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20231018123643.1255813-4-benjamin@sipsolutions.net Signed-off-by: Johannes Berg

um: Rely on PTRACE_SETREGSET to set FS/GS base registers

2024-01-05T15:28:56+00:00

These registers are saved/restored together with the other general registers using ptrace. In arch_set_tls we then just need to set the register and it will be synced back normally. Most of this logic was introduced in commit f355559cf7845 ("[PATCH] uml: x86_64 thread fixes"). However, at least today we can rely on ptrace to restore the base registers for us. As such, only the part of the patch that tracks the FS register for use as thread local storage is actually needed. Signed-off-by: Benjamin Berg Signed-off-by: Richard Weinberger

um: seed rng using host OS rng

2022-07-18T13:04:04+00:00

UML generally does not provide access to special CPU instructions like RDRAND, and execution tends to be rather deterministic, with no real hardware interrupts, making good randomness really very hard, if not all together impossible. Not only is this a security eyebrow raiser, but it's also quite annoying when trying to do various pieces of UML-based automation that takes a long time to boot, if ever. Fix this by trivially calling getrandom() in the host and using that seed as "bootloader randomness", which initializes the rng immediately at UML boot. The old behavior can be restored the same way as on any other arch, by way of CONFIG_TRUST_BOOTLOADER_RANDOMNESS=n or random.trust_bootloader=0. So seen from that perspective, this just makes UML act like other archs, which is positive in its own right. Additionally, wire up arch_get_random_{int,long}() in the same way, so that reseeds can also make use of the host RNG, controllable by CONFIG_TRUST_CPU_RANDOMNESS and random.trust_cpu, per usual. Cc: stable@vger.kernel.org Acked-by: Johannes Berg Acked-By: Anton Ivanov Signed-off-by: Jason A. Donenfeld