linux-stable.git/arch/s390/include/asm/processor.h, branch linux-5.4.y

s390: Mark psw in __load_psw_mask() as __unitialized

2024-07-18T09:40:54+00:00

[ Upstream commit 7278a8fb8d032dfdc03d9b5d17e0bc451cdc1492 ]

Without __unitialized, the following code is generated when
INIT_STACK_ALL_ZERO is enabled:

86: d7 0f f0 a0 f0 a0     xc      160(16,%r15), 160(%r15)
8c: e3 40 f0 a0 00 24     stg     %r4, 160(%r15)
92: c0 10 00 00 00 08     larl    %r1, 0xa2
98: e3 10 f0 a8 00 24     stg     %r1, 168(%r15)
9e: b2 b2 f0 a0           lpswe   160(%r15)

The xc is not adding any security because psw is fully initialized
with the following instructions. Add __unitialized to the psw
definitiation to avoid the superfluous clearing of psw.

Reviewed-by: Heiko Carstens 
Signed-off-by: Sven Schnelle 
Signed-off-by: Alexander Gordeev 
Signed-off-by: Sasha Levin

s390/processor: always inline stap() and __load_psw_mask()

2021-07-20T14:10:44+00:00

[ Upstream commit 9c9a915afd90f7534c16a71d1cd44b58596fddf3 ]

s390 is the only architecture which makes use of the __no_kasan_or_inline
attribute for two functions. Given that both stap() and __load_psw_mask()
are very small functions they can and should be always inlined anyway.

Therefore get rid of __no_kasan_or_inline and always inline these
functions.

Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik 
Signed-off-by: Sasha Levin

s390: prevent leaking kernel address in BEAR

2020-04-13T08:48:06+00:00

commit 0b38b5e1d0e2f361e418e05c179db05bb688bbd6 upstream.

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 
Signed-off-by: Greg Kroah-Hartman

s390/base: remove unused s390_base_mcck_handler

2019-09-03T11:53:56+00:00

s390_base_mcck_handler was used during system reset if diag308 set was
not available. But after commit d485235b0054 ("s390: assume diag308 set
always works") is a dead code and could be removed.

Acked-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

arch: replace _BITUL() in kernel-space headers with BIT()

2019-07-17T02:23:22+00:00

Now that BIT() can be used from assembly code, we can safely replace
_BITUL() with equivalent BIT().

UAPI headers are still required to use _BITUL(), but there is no more
reason to use it in kernel headers.  BIT() is shorter.

Link: http://lkml.kernel.org/r/20190609153941.17249-2-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Christian Borntraeger 
Cc: Vineet Gupta 
Cc: Catalin Marinas 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

processor: get rid of cpu_relax_yield

2019-06-15T10:25:55+00:00

stop_machine is the only user left of cpu_relax_yield. Given that it
now has special semantics which are tied to stop_machine introduce a
weak stop_machine_yield function which architectures can override, and
get rid of the generic cpu_relax_yield implementation.

Acked-by: Peter Zijlstra (Intel) 
Acked-by: Thomas Gleixner 
Signed-off-by: Heiko Carstens

s390: improve wait logic of stop_machine

2019-06-15T10:25:52+00:00

The stop_machine loop to advance the state machine and to wait for all
affected CPUs to check-in calls cpu_relax_yield in a tight loop until
the last missing CPUs acknowledged the state transition.

On a virtual system where not all logical CPUs are backed by real CPUs
all the time it can take a while for all CPUs to check-in. With the
current definition of cpu_relax_yield a diagnose 0x44 is done which
tells the hypervisor to schedule *some* other CPU. That can be any
CPU and not necessarily one of the CPUs that need to run in order to
advance the state machine. This can lead to a pretty bad diagnose 0x44
storm until the last missing CPU finally checked-in.

Replace the undirected cpu_relax_yield based on diagnose 0x44 with a
directed yield. Each CPU in the wait loop will pick up the next CPU
in the cpumask of stop_machine. The diagnose 0x9c is used to tell the
hypervisor to run this next CPU instead of the current one. If there
is only a limited number of real CPUs backing the virtual CPUs we
end up with the real CPUs passed around in a round-robin fashion.

[heiko.carstens@de.ibm.com]:
    Use cpumask_next_wrap as suggested by Peter Zijlstra.

Signed-off-by: Martin Schwidefsky 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Thomas Gleixner 
Signed-off-by: Heiko Carstens

s390: simplify disabled_wait

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

The disabled_wait() function uses its argument as the PSW address when
it stops the CPU with a wait PSW that is disabled for interrupts.
The different callers sometimes use a specific number like 0xdeadbeef
to indicate a specific failure, the early boot code uses 0 and some
other calls sites use __builtin_return_address(0).

At the time a dump is created the current PSW and the registers of a
CPU are written to lowcore to make them avaiable to the dump analysis
tool. For a CPU stopped with disabled_wait the PSW and the registers
do not really make sense together, the PSW address does not point to
the function the registers belong to.

Simplify disabled_wait() by using _THIS_IP_ for the PSW address and
drop the argument to the function.

Signed-off-by: Martin Schwidefsky

s390/unwind: introduce stack unwind API

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

Rework the dump_trace() stack unwinder interface to support different
unwinding algorithms. The new interface looks like this:

	struct unwind_state state;
	unwind_for_each_frame(&state, task, regs, start_stack)
		do_something(state.sp, state.ip, state.reliable);

The unwind_bc.c file contains the implementation for the classic
back-chain unwinder.

One positive side effect of the new code is it now handles ftraced
functions gracefully. It prints the real name of the return function
instead of 'return_to_handler'.

Signed-off-by: Martin Schwidefsky

s390: make __load_psw_mask work with clang

2019-04-11T11:36:52+00:00

clang fails to use the %O and %R inline assembly modifiers
the same way as gcc, leading to build failures with every use
of __load_psw_mask():

/tmp/nmi-4a9f80.s: Assembler messages:
/tmp/nmi-4a9f80.s:571: Error: junk at end of line: `+8(160(%r11))'
/tmp/nmi-4a9f80.s:626: Error: junk at end of line: `+8(160(%r11))'

Replace these with a more conventional way of passing the addresses
that should work with both clang and gcc.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Martin Schwidefsky