linux.git/arch/s390/kernel/entry.S, branch v5.9

s390: fix comment regarding interrupts in svc

2020-07-10T13:08:23+00:00

With the removal of the critical section cleanup, we now enter the svc
interrupt handler with interrupts disabled.

Fixes: 0b0ed657fe00 ("s390: remove critical section cleanup from entry.S")
Signed-off-by: Christian Borntraeger 
Signed-off-by: Heiko Carstens

s390: fix system call single stepping

2020-06-23T12:05:45+00:00

When single stepping an svc instruction on s390, the kernel is entered
with a PER program check interruption. The program check handler than
jumps to the system call handler by reloading the PSW. The code didn't
set GPR13 to the thread pointer in struct task_struct. This made the
kernel access invalid memory while trying to fetch the syscall function
address. Fix this by always assigned GPR13 after .Lsysc_per.

Fixes: 0b0ed657fe00 ("s390: remove critical section cleanup from entry.S")
Reported-and-tested-by: Christian Borntraeger 
Signed-off-by: Sven Schnelle 
Reviewed-by: Heiko Carstens 
Signed-off-by: Heiko Carstens

s390/ptrace: pass invalid syscall numbers to tracing

2020-06-16T11:44:04+00:00

tracing expects to see invalid syscalls, so pass it through.
The syscall path in entry.S checks the syscall number before
looking up the handler, so it is still safe.

Signed-off-by: Sven Schnelle 
Signed-off-by: Vasily Gorbik

s390: remove critical section cleanup from entry.S

2020-05-28T10:21:54+00:00

The current code is rather complex and caused a lot of subtle
and hard to debug bugs in the past. Simplify the code by calling
the system_call handler with interrupts disabled, save
machine state, and re-enable them later.

This requires significant changes to the machine check handling code
as well. When the machine check interrupt arrived while being in kernel
mode the new code will signal pending machine checks with a SIGP external
call. When userspace was interrupted, the handler will switch to the
kernel stack and directly execute s390_handle_mcck().

Signed-off-by: Sven Schnelle 
Signed-off-by: Vasily Gorbik

s390: prevent leaking kernel address in BEAR

2020-03-10T14:16:25+00:00

When userspace executes a syscall or gets interrupted,
BEAR contains a kernel address when returning to userspace.
This make it pretty easy to figure out where the kernel is
mapped even with KASLR enabled. To fix this, add lpswe to
lowcore and always execute it there, so userspace sees only
the lowcore address of lpswe. For this we have to extend
both critical_cleanup and the SWITCH_ASYNC macro to also check
for lpswe addresses in lowcore.

Fixes: b2d24b97b2a9 ("s390/kernel: add support for kernel address space layout randomization (KASLR)")
Cc:  # v5.2+
Reviewed-by: Gerald Schaefer 
Signed-off-by: Sven Schnelle 
Signed-off-by: Vasily Gorbik

sched/rt, s390: Use CONFIG_PREEMPTION

2019-12-08T13:37:35+00:00

CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT.
Both PREEMPT and PREEMPT_RT require the same functionality which today
depends on CONFIG_PREEMPT.

Switch the preemption and entry code over to use CONFIG_PREEMPTION. Add
PREEMPT_RT output to die().

[bigeasy: +Kconfig, dumpstack.c]

Signed-off-by: Thomas Gleixner 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Thomas Gleixner 
Cc: Christian Borntraeger 
Cc: Heiko Carstens 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Vasily Gorbik 
Cc: linux-s390@vger.kernel.org
Link: https://lore.kernel.org/r/20191015191821.11479-18-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar

s390: enforce CONFIG_SMP

2019-06-07T08:09:37+00:00

There never have been distributions that shiped with CONFIG_SMP=n for
s390. In addition the kernel currently doesn't even compile with
CONFIG_SMP=n for s390. Most likely it wouldn't even work, even if we
fix the compile error, since nobody tests it, since there is no use
case that I can think of.
Therefore simply enforce CONFIG_SMP and get rid of some more or
less unused code.

Reviewed-by: Christian Borntraeger 
Signed-off-by: Heiko Carstens

s390: add missing ENDPROC statements to assembler functions

2019-05-02T11:54:11+00:00

The assembler code in arch/s390 misses proper ENDPROC statements
to properly end functions in a few places. Add them.

Signed-off-by: Martin Schwidefsky

s390/kernel: convert SYSCALL and PGM_CHECK handlers to .quad

2019-04-29T08:47:10+00:00

With a relocatable kernel that could reside at any place in memory, the
storage size for the SYSCALL and PGM_CHECK handlers needs to be
increased from .long to .quad.

Signed-off-by: Gerald Schaefer 
Reviewed-by: Philipp Rudo 
Signed-off-by: Martin Schwidefsky

s390: autogenerate compat syscall wrappers

2019-01-18T08:33:19+00:00

Any system call that takes a pointer argument on s390 requires
a wrapper function to do a 31-to-64 zero-extension, these are
currently generated in arch/s390/kernel/compat_wrapper.c.

On arm64 and x86, we already generate similar wrappers for all
system calls in the place of their definition, just for a different
purpose (they load the arguments from pt_regs).

We can do the same thing here, by adding an asm/syscall_wrapper.h
file with a copy of all the relevant macros to override the generic
version. Besides the addition of the compat entry point, these also
rename the entry points with a __s390_ or __s390x_ prefix, similar
to what we do on arm64 and x86. This in turn requires renaming
a few things, and adding a proper ni_syscall() entry point.

In order to still compile system call definitions that pass an
loff_t argument, the __SC_COMPAT_CAST() macro checks for that
and forces an -ENOSYS error, which was the best I could come up
with. Those functions must obviously not get called from user
space, but instead require hand-written compat_sys_*() handlers,
which fortunately already exist.

Link: https://lore.kernel.org/lkml/20190116131527.2071570-5-arnd@arndb.de
Signed-off-by: Arnd Bergmann 
Reviewed-by: Heiko Carstens 
[heiko.carstens@de.ibm.com: compile fix for !CONFIG_COMPAT]
Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky