linux.git/arch/um/kernel/process.c, branch v5.11

Revert "um: allocate a guard page to helper threads"

2021-01-26T21:11:38+00:00

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 
Fixes: ef4459a6da09 ("um: allocate a guard page to helper threads")
Signed-off-by: Johannes Berg 
Signed-off-by: Richard Weinberger

um: allocate a guard page to helper threads

2020-12-13T21:38:06+00:00

We've been running into stack overflows in helper threads
corrupting memory (e.g. because somebody put printf() or
os_info() there), so to avoid those causing hard-to-debug
issues later on, allocate a guard page for helper thread
stacks and mark it read-only.

Unfortunately, the crash dump at that point is useless as
the stack tracer will try to backtrace the *kernel* thread,
not the helper thread, but at least we don't survive to a
random issue caused by corruption.

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

um: Support suspend to RAM

2020-12-13T21:22:49+00:00

With all the previous bits in place, we can now also support
suspend to RAM, in the sense that everything is suspended,
not just most, including userspace, processes like in s2idle.

Since um_idle_sleep() now waits forever, we can simply call
that to "suspend" the system.

As before, you can wake it up using SIGUSR1 since we're just
in a pause() call that only needs to return.

In order to implement selective resume from certain devices,
and not have any arbitrary device interrupt wake up, suspend
interrupts by removing SIGIO notification (O_ASYNC) from all
the FDs that are not supposed to wake up the system. However,
swap out the handler so we don't actually handle the SIGIO as
an interrupt.

Since we're in pause(), the mere act of receiving SIGIO wakes
us up, and then after things have been restored enough, re-set
O_ASYNC for all previously suspended FDs, reinstall the proper
SIGIO handler, and send SIGIO to self to process anything that
might now be pending.

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

um: Simplify os_idle_sleep() and sleep longer

2020-12-13T21:22:37+00:00

There really is no reason to pass the amount of time we should
sleep, especially since it's just hard-coded to one second.

Additionally, one second isn't really all that long, and as we
are expecting to be woken up by a signal, we can sleep longer
and avoid doing some work every second, so replace the current
clock_nanosleep() with just an empty select() that can _only_
be woken up by a signal.

We can also remove the deliver_alarm() since we don't need to
do that when we got e.g. SIGIO that woke us up, and if we got
SIGALRM the signal handler will actually (have) run, so it's
just unnecessary extra work.

Similarly, in time-travel mode, just program the wakeup event
from idle to be S64_MAX, which is basically the most you could
ever simulate to. Of course, you should already have an event
in the list that's earlier and will cause a wakeup, normally
that's the regular timer interrupt, though in suspend it may
(later) also be an RTC event. Since actually getting to this
point would be a bug and you can't ever get out again, panic()
on it in the time control code.

Signed-off-by: Johannes Berg 
Acked-By: Anton Ivanov 
Signed-off-by: Richard Weinberger

um: Add support for TIF_NOTIFY_SIGNAL

2020-12-13T21:21:02+00:00

Wire up TIF_NOTIFY_SIGNAL handling for um.

Cc: linux-um@lists.infradead.org
Signed-off-by: Jens Axboe 
Acked-By: Anton Ivanov 
Signed-off-by: Richard Weinberger

sched/idle: Fix arch_cpu_idle() vs tracing

2020-11-24T15:47:35+00:00

We call arch_cpu_idle() with RCU disabled, but then use
local_irq_{en,dis}able(), which invokes tracing, which relies on RCU.

Switch all arch_cpu_idle() implementations to use
raw_local_irq_{en,dis}able() and carefully manage the
lockdep,rcu,tracing state like we do in entry.

(XXX: we really should change arch_cpu_idle() to not return with
interrupts enabled)

Reported-by: Sven Schnelle 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Mark Rutland 
Tested-by: Mark Rutland 
Link: https://lkml.kernel.org/r/20201120114925.594122626@infradead.org

tracehook: clear TIF_NOTIFY_RESUME in tracehook_notify_resume()

2020-10-17T21:04:36+00:00

All the callers currently do this, clean it up and move the clearing
into tracehook_notify_resume() instead.

Reviewed-by: Oleg Nesterov 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Jens Axboe

arch: rename copy_thread_tls() back to copy_thread()

2020-07-04T21:41:37+00:00

Now that HAVE_COPY_THREAD_TLS has been removed, rename copy_thread_tls()
back simply copy_thread(). It's a simpler name, and doesn't imply that only
tls is copied here. This finishes an outstanding chunk of internal process
creation work since we've added clone3().

Cc: linux-arch@vger.kernel.org
Acked-by: Thomas Bogendoerfer A
Acked-by: Stafford Horne 
Acked-by: Greentime Hu 
Acked-by: Geert Uytterhoeven A
Reviewed-by: Kees Cook 
Signed-off-by: Christian Brauner

mm: don't include asm/pgtable.h if linux/mm.h is already included

2020-06-09T16:39:13+00:00

Patch series "mm: consolidate definitions of page table accessors", v2.

The low level page table accessors (pXY_index(), pXY_offset()) are
duplicated across all architectures and sometimes more than once.  For
instance, we have 31 definition of pgd_offset() for 25 supported
architectures.

Most of these definitions are actually identical and typically it boils
down to, e.g.

static inline unsigned long pmd_index(unsigned long address)
{
        return (address >> PMD_SHIFT) & (PTRS_PER_PMD - 1);
}

static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
{
        return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address);
}

These definitions can be shared among 90% of the arches provided
XYZ_SHIFT, PTRS_PER_XYZ and xyz_page_vaddr() are defined.

For architectures that really need a custom version there is always
possibility to override the generic version with the usual ifdefs magic.

These patches introduce include/linux/pgtable.h that replaces
include/asm-generic/pgtable.h and add the definitions of the page table
accessors to the new header.

This patch (of 12):

The linux/mm.h header includes  to allow inlining of the
functions involving page table manipulations, e.g.  pte_alloc() and
pmd_alloc().  So, there is no point to explicitly include 
in the files that include .

The include statements in such cases are remove with a simple loop:

	for f in $(git grep -l "include ") ; do
		sed -i -e '/include / d' $f
	done

Signed-off-by: Mike Rapoport 
Signed-off-by: Andrew Morton 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Brian Cain 
Cc: Catalin Marinas 
Cc: Chris Zankel 
Cc: "David S. Miller" 
Cc: Geert Uytterhoeven 
Cc: Greentime Hu 
Cc: Greg Ungerer 
Cc: Guan Xuetao 
Cc: Guo Ren 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Ley Foon Tan 
Cc: Mark Salter 
Cc: Matthew Wilcox 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Mike Rapoport 
Cc: Nick Hu 
Cc: Paul Walmsley 
Cc: Richard Weinberger 
Cc: Rich Felker 
Cc: Russell King 
Cc: Stafford Horne 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Tony Luck 
Cc: Vincent Chen 
Cc: Vineet Gupta 
Cc: Will Deacon 
Cc: Yoshinori Sato 
Link: http://lkml.kernel.org/r/20200514170327.31389-1-rppt@kernel.org
Link: http://lkml.kernel.org/r/20200514170327.31389-2-rppt@kernel.org
Signed-off-by: Linus Torvalds

um: time-travel: Rewrite as an event scheduler

2020-03-29T21:28:51+00:00

Instead of tracking all the various timer configurations,
modify the time-travel mode to have an event scheduler and
use a timer event on the scheduler to handle the different
timer configurations.

This doesn't change the function right now, but it prepares
the code for having different kinds of events in the future
(i.e. interrupts coming from other devices that are part of
co-simulation.)

While at it, also move time_travel_sleep() to time.c to
reduce the externally visible API surface.

Also, we really should mark time-travel as incompatible with
SMP, even if UML doesn't support SMP yet.

Finally, I noticed a bug while developing this - if we move
time forward due to consuming time while reading the clock,
we might move across the next event and that would cause us
to go backward in time when we then handle that event. Fix
that by invoking the whole event machine in this case, but
in order to simplify this, make reading the clock only cost
something when interrupts are not disabled. Otherwise, we'd
have to hook into the interrupt delivery machinery etc. and
that's somewhat intrusive.

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