linux-toradex.git/arch/um/kernel/um_arch.c, branch v6.7

x86/alternative: Rename apply_ibt_endbr()

2023-07-10T07:52:23+00:00

The current name doesn't reflect what it does very well.

Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Kees Cook 
Reviewed-by: Sami Tolvanen 
Link: https://lkml.kernel.org/r/20230622144321.427441595%40infradead.org

um/cpu: Switch to arch_cpu_finalize_init()

2023-06-16T08:16:00+00:00

check_bugs() is about to be phased out. Switch over to the new
arch_cpu_finalize_init() implementation.

No functional change.

Signed-off-by: Thomas Gleixner 
Acked-by: Richard Weinberger 
Link: https://lore.kernel.org/r/20230613224545.493148694@linutronix.de

um: make stub data pages size tweakable

2023-04-20T21:08:43+00:00

There's a lot of code here that hard-codes that the
data is a single page, and right now that seems to
be sufficient, but to make it easier to change this
in the future, add a new STUB_DATA_PAGES constant
and use it throughout the code.

Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger

um: Make the definition of cpu_data more compatible

2023-02-10T20:36:58+00:00

Match the x86 implementation to improve build errors.
Noticed when building allyesconfig.

e.g.
../arch/um/include/asm/processor-generic.h:94:19: error: called object is not a function or function pointer
   94 | #define cpu_data (&boot_cpu_data)
      |                  ~^~~~~~~~~~~~~~~
../drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c:2157:16: note: in expansion of macro ‘cpu_data’
 2157 |         return cpu_data(first_cpu_of_numa_node).apicid;

Signed-off-by: Peter Foley 
Signed-off-by: Richard Weinberger

x86/ibt: Implement FineIBT

2022-11-01T12:44:10+00:00

Implement an alternative CFI scheme that merges both the fine-grained
nature of kCFI but also takes full advantage of the coarse grained
hardware CFI as provided by IBT.

To contrast:

  kCFI is a pure software CFI scheme and relies on being able to read
text -- specifically the instruction *before* the target symbol, and
does the hash validation *before* doing the call (otherwise control
flow is compromised already).

  FineIBT is a software and hardware hybrid scheme; by ensuring every
branch target starts with a hash validation it is possible to place
the hash validation after the branch. This has several advantages:

   o the (hash) load is avoided; no memop; no RX requirement.

   o IBT WAIT-FOR-ENDBR state is a speculation stop; by placing
     the hash validation in the immediate instruction after
     the branch target there is a minimal speculation window
     and the whole is a viable defence against SpectreBHB.

   o Kees feels obliged to mention it is slightly more vulnerable
     when the attacker can write code.

Obviously this patch relies on kCFI, but additionally it also relies
on the padding from the call-depth-tracking patches. It uses this
padding to place the hash-validation while the call-sites are
re-written to modify the indirect target to be 16 bytes in front of
the original target, thus hitting this new preamble.

Notably, there is no hardware that needs call-depth-tracking (Skylake)
and supports IBT (Tigerlake and onwards).

Suggested-by: Joao Moreira (Intel) 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Kees Cook 
Link: https://lore.kernel.org/r/20221027092842.634714496@infradead.org

Merge tag 'for-linus-6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

2022-10-15T01:14:48+00:00

Pull UML updates from Richard Weinberger:

 - Move to strscpy()

 - Improve panic notifiers

 - Fix NR_CPUS usage

 - Fixes for various comments

 - Fixes for virtio driver

* tag 'for-linus-6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux:
  uml: Remove the initialization of statics to 0
  um: Do not initialise statics to 0.
  um: Fix comment typo
  um: Improve panic notifiers consistency and ordering
  um: remove unused reactivate_chan() declaration
  um: mmaper: add __exit annotations to module exit funcs
  um: virt-pci: add __init/__exit annotations to module init/exit funcs
  hostfs: move from strlcpy with unused retval to strscpy
  um: move from strlcpy with unused retval to strscpy
  um: increase default virtual physical memory to 64 MiB
  UM: cpuinfo: Fix a warning for CONFIG_CPUMASK_OFFSTACK
  um: read multiple msg from virtio slave request fd

um: Improve panic notifiers consistency and ordering

2022-09-19T21:04:54+00:00

Currently the panic notifiers from user mode linux don't follow
the convention for most of the other notifiers present in the
kernel (indentation, priority setting, numeric return).
More important, the priorities could be improved, since it's a
special case (userspace), hence we could run the notifiers earlier;
user mode linux shouldn't care much with other panic notifiers but
the ordering among the mconsole and arch notifier is important,
given that the arch one effectively triggers a core dump.

Fix that by running the mconsole notifier as the first panic
notifier, followed by the architecture one (that coredumps).

Cc: Anton Ivanov 
Cc: Johannes Berg 
Cc: Richard Weinberger 
Signed-off-by: Guilherme G. Piccoli 

V3:
- No changes.

V2:
- Kept the notifier header to avoid implicit usage - thanks
Johannes for the suggestion!

Signed-off-by: Richard Weinberger

um: move from strlcpy with unused retval to strscpy

2022-09-19T20:45:24+00:00

Follow the advice of the below link and prefer 'strscpy' in this
subsystem. Conversion is 1:1 because the return value is not used.
Generated by a coccinelle script.

Link: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/
Signed-off-by: Wolfram Sang 
Signed-off-by: Richard Weinberger

um: increase default virtual physical memory to 64 MiB

2022-09-19T20:40:24+00:00

The current 32 MiB of RAM causes OOMs to appear shortly after
booting in a minimal OpenWrt 22.03 configuration with a
5.10.134 kernel.

Of course, passing a "mem=64M" (from the --help text) parameter
works too, but it produces the following (info) message:

| [    0.000000] Unknown kernel command line parameters "mem=64M", will be passed to user space.

That's why, I think it would be nicer, if this is working out
of the box again :).

Signed-off-by: Christian Lamparter 
Signed-off-by: Richard Weinberger

um: fix default console kernel parameter

2022-09-19T20:38:44+00:00

OpenWrt's UML with 5.15 was producing odd errors/warnings during preinit
part of the early userspace portion:

|[    0.000000] Kernel command line: ubd0=root.img root=98:0 console=tty
|[...]
|[    0.440000] random: jshn: uninitialized urandom read (4 bytes read)
|[    0.460000] random: jshn: uninitialized urandom read (4 bytes read)
|/etc/preinit: line 47: can't create /dev/tty: No such device or address
|/etc/preinit: line 48: can't create /dev/tty: No such device or address
|/etc/preinit: line 58: can't open /dev/tty: No such device or address
|[...] repeated many times

That "/dev/tty" came from the command line (which is automatically
added if no console= parameter was specified for the uml binary).

The TLDP project tells the following about the /dev/tty:

| /dev/tty stands for the controlling terminal (if any) for the current
| process.[...]
| /dev/tty is something like a link to the actually terminal device[..]

The "(if any)" is important here, since it's possible for processes to
not have a controlling terminal.

I think this was a simple typo and the author wanted tty0 there.

CC: Thomas Meyer 
Fixes: d7ffac33631b ("um: stdio_console: Make preferred console")
Signed-off-by: Christian Lamparter 
Signed-off-by: Richard Weinberger