linux-toradex.git/arch/x86/um/shared, branch master

um: move asm-offsets generation into a single file

2025-10-27T14:07:44+00:00

There's nothing subarch dependent here, and it's odd
that includes need to be done in the subarch, and then
entries defined in the common file.

Simplify the whole thing from three files into one.

Link: https://patch.msgid.link/20251007071452.367989-4-johannes@sipsolutions.net
Signed-off-by: Johannes Berg

um/hostfs: define HOSTFS_ATTR_* via asm-offsets

2025-10-27T14:07:43+00:00

The HOSTFS_ATTR_* values were meant to be standalone for
communication between hostfs's kernel and user code parts.
However, it's easy to forget that HOSTFS_ATTR_* should be
used even on the kernel side, and that wasn't consistently
done. As a result, the values need to match ATTR_* values,
which is not useful to maintain by hand. Instead, generate
them via asm-offsets like other constants that UML needs
in user-side code that aren't otherwise available in any
header files that can be included there.

Signed-off-by: Johannes Berg 
Reviewed-by: Hongbo Li 
Link: https://patch.msgid.link/20251007071452.367989-3-johannes@sipsolutions.net
Signed-off-by: Johannes Berg

um: Centralize stub size calculations

2025-09-10T12:23:52+00:00

Currently, the stub size is calculated in multiple places. Define
a macro that performs the calculation so that the code is easier
to read and maintain.

Signed-off-by: Tiwei Bie 
Signed-off-by: Johannes Berg

um: simplify syscall header files

2025-07-11T06:49:02+00:00

Since Thomas's recent commit 2af10530639b ("um/x86: Add
system call table to header file") , we now have two
extern declarations of the syscall table, one internal
and one external, and they don't even match on 32-bit.
Clean this up and remove all the extra code.

Reviewed-by: Thomas Weißschuh 
Link: https://patch.msgid.link/20250704141243.a68366f6acc3.If8587a4aafdb90644fc6d0b2f5e31a2d1887915f@changeid
Signed-off-by: Johannes Berg

Merge tag 'uml-for-linux-6.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

2025-06-05T18:45:33+00:00

Pull UML updates from Johannes Berg:
 "The only really new thing is the long-standing seccomp work
  (originally from 2021!). Wven if it still isn't enabled by default due
  to security concerns it can still be used e.g. for tests.

   - remove obsolete network transports

   - remove PCI IO port support

   - start adding seccomp-based process handling instead of ptrace"

* tag 'uml-for-linux-6.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux: (29 commits)
  um: remove "extern" from implementation of sigchld_handler
  um: fix unused variable warning
  um: fix SECCOMP 32bit xstate register restore
  um: pass FD for memory operations when needed
  um: Add SECCOMP support detection and initialization
  um: Implement kernel side of SECCOMP based process handling
  um: Track userspace children dying in SECCOMP mode
  um: Add helper functions to get/set state for SECCOMP
  um: Add stub side of SECCOMP/futex based process handling
  um: Move faultinfo extraction into userspace routine
  um: vector: Use mac_pton() for MAC address parsing
  um: vector: Clean up and modernize log messages
  um: chan_kern: use raw spinlock for irqs_to_free_lock
  MAINTAINERS: remove obsolete file entry in TUN/TAP DRIVER
  um: Fix tgkill compile error on old host OSes
  um: stop using PCI port I/O
  um: Remove legacy network transport infrastructure
  um: vector: Eliminate the dependency on uml_net
  um: Remove obsolete legacy network transports
  um/asm: Replace "REP; NOP" with PAUSE mnemonic
  ...

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: Add helper functions to get/set state for SECCOMP

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

When not using ptrace, we need to both save and restore registers
through the mcontext as provided by the host kernel to our signal
handlers.

Add corresponding functions to store the state to an mcontext and
helpers to access the mcontext of the subprocess through the stub data.

Signed-off-by: Benjamin Berg 
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250602130052.545733-4-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: Add stub side of SECCOMP/futex based process handling

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

This adds the stub side for the new seccomp process management code. In
this case we do register save/restore through the signal handler
mcontext.

Add special code for handling TLS, which for x86_64 means setting the
FS_BASE/GS_BASE registers while for i386 it means calling the
set_thread_area syscall.

Co-authored-by: Johannes Berg 
Signed-off-by: Benjamin Berg 
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250602130052.545733-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg

um: fix _nofault accesses

2025-05-05T08:06:51+00:00

Nathan reported [1] that when built with clang, the um kernel
crashes pretty much immediately. This turned out to be an issue
with the inline assembly I had added, when clang used %rax/%eax
for both operands. Reorder it so current->thread.segv_continue
is written first, and then the lifetime of _faulted won't have
overlap with the lifetime of segv_continue.

In the email thread Benjamin also pointed out that current->mm
is only NULL for true kernel tasks, but we could do this for a
userspace task, so the current->thread.segv_continue logic must
be lifted out of the mm==NULL check.

Finally, while looking at this, put a barrier() so the NULL
assignment to thread.segv_continue cannot be reorder before
the possibly faulting operation.

Reported-by: Nathan Chancellor 
Closes: https://lore.kernel.org/r/20250402221254.GA384@ax162 [1]
Fixes: d1d7f01f7cd3 ("um: mark rodata read-only and implement _nofault accesses")
Tested-by: Nathan Chancellor 
Signed-off-by: Johannes Berg

um: mark rodata read-only and implement _nofault accesses

2025-03-18T10:03:14+00:00

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 
Co-developed-by: Benjamin Berg 
Signed-off-by: Benjamin Berg 
Link: https://patch.msgid.link/20250210160926.420133-2-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg