um: Rewrite the sigio workaround based on epoll and tgkill

The existing sigio workaround implementation removes FDs from the
poll when events are triggered, requiring users to re-add them via
add_si

um: Rewrite the sigio workaround based on epoll and tgkill

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Add pthread-based helper support

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

um: Add pthread-based helper support

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: remove copy_from_kernel_nofault_allowed

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 t

um: remove copy_from_kernel_nofault_allowed

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: remove broken double fault detection

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.

Re

um: remove broken double fault detection

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: remove file sync for stub data

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-

um: remove file sync for stub data

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Add os_set_pdeathsig helper function

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 une

um: Add os_set_pdeathsig helper function

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Abandon the _PAGE_NEWPROT bit

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

um: Abandon the _PAGE_NEWPROT bit

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 <[email protected]>
Signed-off-by: Tiwei Bie <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Discover host_task_size from envp

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 o

um: Discover host_task_size from envp

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: remove auxiliary FP registers

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 registe

um: remove auxiliary FP registers

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Remove unused os_getpgrp function

The function is not used anywhere.

Signed-off-by: Benjamin Berg <[email protected]>
Link: https://patch.msgid.link/20240913134442.967599-5-benjamin@sipso

um: Remove unused os_getpgrp function

The function is not used anywhere.

Signed-off-by: Benjamin Berg <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Remove unused os_stop_process

The function is not used anywhere.

Signed-off-by: Benjamin Berg <[email protected]>
Link: https://patch.msgid.link/20240913134442.967599-4-benjamin@sipsoluti

um: Remove unused os_stop_process

The function is not used anywhere.

Signed-off-by: Benjamin Berg <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Remove unused os_process_parent

The function is not used anywhere.

Signed-off-by: Benjamin Berg <[email protected]>
Link: https://patch.msgid.link/20240913134442.967599-3-benjamin@sipsolu

um: Remove unused os_process_parent

The function is not used anywhere.

Signed-off-by: Benjamin Berg <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Remove unused os_process_pc

The function is not used anywhere in the codebase.

Signed-off-by: Benjamin Berg <[email protected]>
Link: https://patch.msgid.link/20240913134442.967599-2-benj

um: Remove unused os_process_pc

The function is not used anywhere in the codebase.

Signed-off-by: Benjamin Berg <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: simplify and consolidate TLB updates

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

um: simplify and consolidate TLB updates

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Delay flushing syscalls until the thread is restarted

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 la

um: Delay flushing syscalls until the thread is restarted

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: remove copy_context_skas0

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 n

um: remove copy_context_skas0

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: Rework syscall handling

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 c

um: Rework syscall handling

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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um: add mmap/mremap OS calls

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/2024070

um: add mmap/mremap OS calls

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 <[email protected]>

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um: generalize os_rcv_fd

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.I

um: generalize os_rcv_fd

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 <[email protected]>

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

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 F

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

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 <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

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

These registers are saved/restored together with the other general
registers using ptrace. In arch_set_tls we then just need to set the
regis

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

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 <[email protected]>
Signed-off-by: Richard Weinberger <[email protected]>

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um: seed rng using host OS rng

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

um: seed rng using host OS rng

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: [email protected]
Acked-by: Johannes Berg <[email protected]>
Acked-By: Anton Ivanov <[email protected]>
Signed-off-by: Jason A. Donenfeld <[email protected]>

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um: Fix WRITE_ZEROES in the UBD Driver

Call to fallocate with FALLOC_FL_PUNCH_HOLE on a device backed by a sparse
file can end up by missing data, zeroes data range, if the underlying file
is used w

um: Fix WRITE_ZEROES in the UBD Driver

Call to fallocate with FALLOC_FL_PUNCH_HOLE on a device backed by a sparse
file can end up by missing data, zeroes data range, if the underlying file
is used with a tool like bmaptool which will referenced only used spaces.

Signed-off-by: Frédéric Danis <[email protected]>
Acked-by: Anton Ivanov <[email protected]>
Signed-off-by: Richard Weinberger <[email protected]>

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um: header debriding - os.h

Signed-off-by: Al Viro <[email protected]>
Signed-off-by: Richard Weinberger <[email protected]>

um: rename set_signals() to um_set_signals()

Rename set_signals() as there's at least one driver that
uses the same name and can now be built on UM due to PCI
support, and thus we can get symbol con

um: rename set_signals() to um_set_signals()

Rename set_signals() as there's at least one driver that
uses the same name and can now be built on UM due to PCI
support, and thus we can get symbol conflicts.

Also rename set_signals_trace() to be consistent.

Reported-by: kernel test robot <[email protected]>
Fixes: 68f5d3f3b654 ("um: add PCI over virtio emulation driver")
Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: Richard Weinberger <[email protected]>

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