In time-travel mode, since my previous patch, the start time was
initialized too late, so that the system would read it before we
set it, thus always starting system time at 0 (1970-01-01). This
happens because timekeeping_init() reads the time and is called
before time_init().

Unfortunately, I didn't see this before because I was testing it
only with the RTC patch applied (and enabled), and then the time
is read again by the RTC a little - after time_init() this time.

Fix this by just doing the initialization whenever necessary.

Fixes: 2701c1bd91dd ("um: time: Fix read_persistent_clock64() in time-travel")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Changing os_idle_sleep() to use pause() (I accidentally described
it as an empty select() in the commit log because I had changed it
from that to pause() in a later revision) exposed a race condition
in the idle code. The following can happen:

 timer_settime(0, 0, {it_interval={tv_sec=0, tv_nsec=0}, it_value={tv_sec=0, tv_nsec=624017}}, NULL) = 0
 ...
 <SIGALRM is delivered but we're already on the way to idle>
 pause()

and we now hang forever. This was previously possible as well, but
it could never cause UML to hang for more than a second since we
could only sleep for that much, so at most you'd notice a "hiccup"
in the UML. Obviously, any sort of external interrupt also "saves"
it and interrupts pause().

Fix this by properly handling the race, rather than papering over
it again:

 - first, block SIGALRM, and obtain the old signal set
 - check the timer
 - suspend, waiting for any signal out of the old set, if, and only
   if, the timer will fire in the future
 - restore the old signal mask

This ensures race-free operation: as it's blocked, the signal won't
be delivered while we're looking at the timer even if it were to be
triggered right _after_ we've returned from timer_gettime() with a
non-zero value (telling us the timer will trigger). Thus, despite
getting to sigsuspend() because timer_gettime() told us we're still
waiting, we'll not hang because sigsuspend() will return immediately
due to the pending signal.

Fixes: 49da38a3ef33 ("um: Simplify os_idle_sleep() and sleep longer")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

This reverts commit 963285b0b47a ("um: support some of
ARCH_HAS_SET_MEMORY"), as it turns out that it's not only not
working (due to um never using the protection bits in the
page tables) but also corrupts the page tables if used on a
non-vmalloc page, since um never allocates proper page tables
for the 'physmem' in the first place.

Fixing all this will take more effort, so for now revert it.

Reported-by: Benjamin Berg <benjamin@sipsolutions.net>
Fixes: 963285b0b47a ("um: support some of ARCH_HAS_SET_MEMORY")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

This reverts commit ef4459a6da09 ("um: allocate a guard page to
helper threads"), it's broken in multiple ways:

 1) the free no longer matches the alloc; and

 2) more importantly, the set_memory_ro() causes allocation of
    page tables for the normal memory that doesn't have any,
    and that later causes corruption and crashes (usually but
    not always in vfree()).

We could fix the first bug and use vmalloc() to work around the
second, but set_memory_ro() actually doesn't do anything either
so I'll just revert that as well.

Reported-by: Benjamin Berg <benjamin@sipsolutions.net>
Fixes: ef4459a6da09 ("um: allocate a guard page to helper threads")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Since struct device is refcounted, we shouldn't free the vu_dev
immediately when it's removed from the platform device, but only
when the references actually all go away. Move the freeing to
the release to accomplish that.

Fixes: 5d38f324993f ("um: drivers: Add virtio vhost-user driver")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

With the addition of the ttynull console driver, the chance that a
console driver was already registerd did increase. Refine the logic when
to dump the kernel message buffer: always dump the buffer, when the UML
stdio console driver is not active and the preferred console.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

The addition of the "ttynull" console driver did break the ordering of the
UML stdio console driver.
The UML stdio console driver is added in late_initcall (7), whereby the
ttynull driver is added in device_initcall (6), which always does make the
ttynull driver the default console.

Fix it by explicitly adding the UML stdio console as the preferred console,
in case no 'console=' command line option was specified.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

Back a few years ago, ioremap() was added to UML so that we'd
not break the build for everything all the time. However, for
some reason, v1 of the patch got applied, rather than the v2
that returned NULL, which was discussed here:

https://lore.kernel.org/lkml/1495726955-27497-1-git-send-email-logang@deltatee.com/

Fix that now.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

This commit fixes a regression to handle command line parameters of ubd.
With a simple line "./linux ubd0="./disk-ext4.img", it fails at
ubd_setup_common().  The commit adds additional checks to the variables
in order to properly parse the paremeters which previously worked.

Fixes: ef3ba87cb7c9 ("um: ubd: Set device serial attribute from cmdline")
Cc: Christopher Obbard <chris.obbard@collabora.com>
Signed-off-by: Hajime Tazaki <thehajime@gmail.com>
Acked-by: Christopher Obbard <chris.obbard@collabora.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Pull UML updates from Richard Weinberger:

 - IRQ handling cleanups

 - Support for suspend

 - Various fixes for UML specific drivers: ubd, vector, xterm

* tag 'for-linus-5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml: (32 commits)
  um: Fix build w/o CONFIG_PM_SLEEP
  um: time-travel: Correct time event IRQ delivery
  um: irq/sigio: Support suspend/resume handling of workaround IRQs
  um: time-travel: Actually apply "free-until" optimisation
  um: chan_xterm: Fix fd leak
  um: tty: Fix handling of close in tty lines
  um: Monitor error events in IRQ controller
  um: allocate a guard page to helper threads
  um: support some of ARCH_HAS_SET_MEMORY
  um: time-travel: avoid multiple identical propagations
  um: Fetch registers only for signals which need them
  um: Support suspend to RAM
  um: Allow PM with suspend-to-idle
  um: time: Fix read_persistent_clock64() in time-travel
  um: Simplify os_idle_sleep() and sleep longer
  um: Simplify IRQ handling code
  um: Remove IRQ_NONE type
  um: irq: Reduce irq_reg allocation
  um: irq: Clean up and rename struct irq_fd
  um: Clean up alarm IRQ chip name
  ...