linux.git/arch/s390/kernel/entry.S, branch v5.17

s390: add support for BEAR enhancement facility

2021-10-26T13:21:29+00:00

The Breaking-Event-Address-Register (BEAR) stores the address of the
last breaking event instruction. Breaking events are usually instructions
that change the program flow - for example branches, and instructions
that modify the address in the PSW like lpswe. This is useful for debugging
wild branches, because one could easily figure out where the wild branch
was originating from.

What is problematic is that lpswe is considered a breaking event, and
therefore overwrites BEAR on kernel exit. The BEAR enhancement facility
adds new instructions that allow to save/restore BEAR and also an lpswey
instruction that doesn't cause a breaking event. So we can save BEAR on
kernel entry and restore it on exit to user space.

Signed-off-by: Sven Schnelle 
Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/entry: make oklabel within CHKSTG macro local

2021-08-31T12:54:15+00:00

Make the oklabel within the CHKSTG macro local. This makes sure that
tools like objdump and the crash debugging tool still disassemble full
functions where the macro has been used instead of stopping half way
where such a global label is used and one has to guess how to
disassemble the rest of such a function:

E.g.:

0000000000cb0270 :
  cb0270:       b2 05 03 20             stck    800
  ...
  cb0354:       a7 74 00 97             jne     cb0482 

0000000000cb0358 :
  cb0358:       c0 e0 00 22 4e 8f       larl    %r14,10fa076 
  ...

Fixes: d35925b34996 ("s390/mcck: move storage error checks to assembler")
Reviewed-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens

s390/smp: enable DAT before CPU restart callback is called

2021-08-26T18:22:12+00:00

The restart interrupt is triggered whenever a secondary CPU is
brought online, a remote function call dispatched from another
CPU or a manual PSW restart is initiated and causes the system
to kdump. The handling routine is always called with DAT turned
off. It then initializes the stack frame and invokes a callback.

The existing callbacks handle DAT as follows:

  * __do_restart() and __machine_kexec() turn in on upon entry;
  * __ipl_run(), __reipl_run() and __dump_run() do not turn it
    right away, but all of them call diag308() - which turns DAT
    on, but only if kasan is enabled;

In addition to the described complexity all callbacks (and the
functions they call) should avoid kasan instrumentation while
DAT is off.

This update enables DAT in the assembler restart handler and
relieves any callbacks (which are mostly C functions) from
dealing with DAT altogether.

There are four types of CPU restart that initialize control
registers in different ways:

  1. Start of secondary CPU on boot - control registers are
     inherited from the IPL CPU;
  2. Restart of online CPU - control registers of the CPU being
     restarted are kept;
  3. Hotplug of offline CPU - control registers are inherited
     from the starting CPU;
  4. Start of offline CPU triggered by manual PSW restart -
     the control registers are read from the absolute lowcore
     and contain the boot time IPL CPU values updated with all
     follow-up calls of smp_ctl_set_bit() and smp_ctl_clear_bit()
     routines;

In first three cases contents of the control registers is the
most recent. In the latter case control registers are good
enough to facilitate successful completion of kdump operation.

Suggested-by: Heiko Carstens 
Signed-off-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens

s390/mcck: move register validation to C code

2021-07-05T10:44:23+00:00

This update partially reverts commit 3037a52f9846 ("s390/nmi:
do register validation as early as possible").

Storage error checks and control registers validation are left
in the assembler code, since correct ASCEs and page tables are
required to enable DAT - which is done before the C handler is
entered.

System damage, kernel instruction address and PSW MWP checks
are left in the assembler code as well, since there is no way
to proceed if one of these checks is failed.

The getcpu vdso syscall reads CPU number from the programmable
field of the TOD clock. Disregard the TOD programmable register
validity bit and load the CPU number into the TOD programmable
field unconditionally.

Signed-off-by: Alexander Gordeev 
Reviewed-by: Heiko Carstens 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/mcck: move storage error checks to assembler

2021-07-05T10:44:23+00:00

The current storage errors tackling is wrong - the DAT is
enabled in assembler code before the actual storage checks
in C half are executed. In case the page tables themselves
are damaged such approach is not going to work.

With this update unrecoverable storage errors are not
passed to C code for handling, but rather the machine
is stopped right away. The only exception to this flow
is when a machine check occurred in KVM guest - in this
case the errors are reinjected by the handler.

Signed-off-by: Alexander Gordeev 
Reviewed-by: Heiko Carstens 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/mcck: always enter C handler with DAT enabled

2021-07-05T10:44:23+00:00

The machine check handler must be entered with DAT disabled
in case control registers are corrupted or a storage error
happened and we can not tell if such error corresponds to a
page table.

Both of described conditions end up in stopping all CPUs and
entering the disabled wait in C half of the handler. However,
the storage errors are still checked after the DAT is enabled
and C code is entered. In case a page table is damaged such
flow is not expected to work.

This update paves the way for moving the storage error checks
from C to assembler half. All fatal errors that can only be
handled with DAT disabled are handled in assembler half also.
As result, the C half is only entered if the DAT is secured.

Signed-off-by: Alexander Gordeev 
Reviewed-by: Heiko Carstens 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/mcck: optimize user mode check in case of !CONFIG_KVM

2021-07-05T10:44:23+00:00

In case of the !CONFIG_KVM use "jz" instead of "jnz" when
detecting user mode and get rid of unnecessary jump as result.

Signed-off-by: Alexander Gordeev 
Reviewed-by: Christia Borntraeger 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/entry.S: factor out SIEEXIT macro

2021-07-05T10:44:23+00:00

Factor out SIEEXIT macro and use it instead of cleanup_sie
routine. As a side effect %r13 and %r14 are spared.

Signed-off-by: Alexander Gordeev 
Reviewed-by: Christia Borntraeger 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

Merge tag 's390-5.14-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2021-07-04T19:17:38+00:00

Pull s390 updates from Vasily Gorbik:

- Rework inline asm to get rid of error prone "register asm"
constructs, which are problematic especially when code
instrumentation is enabled.

In particular introduce and use register pair union to allocate
even/odd register pairs. Unfortunately this breaks compatibility with
older clang compilers and minimum clang version for s390 has been
raised to 13.

https://lore.kernel.org/linux-next/CAK7LNARuSmPCEy-ak0erPrPTgZdGVypBROFhtw+=3spoGoYsyw@mail.gmail.com/

- Fix gcc 11 warnings, which triggered various minor reworks all over
the code.

- Add zstd kernel image compression support.

- Rework boot CPU lowcore handling.

- De-duplicate and move kernel memory layout setup logic earlier.

- Few fixes in preparation for FORTIFY_SOURCE performing compile-time
and run-time field bounds checking for mem functions.

- Remove broken and unused power management support leftovers in s390
drivers.

- Disable stack-protector for decompressor and purgatory to fix
buildroot build.

- Fix vt220 sclp console name to match the char device name.

- Enable HAVE_IOREMAP_PROT and add zpci_set_irq()/zpci_clear_irq() in
zPCI code.

- Remove some implausible WARN_ON_ONCEs and remove arch specific
counter transaction call backs in favour of default transaction
handling in perf code.

- Extend/add new uevents for online/config/mode state changes of AP
card / queue device in zcrypt.

- Minor entry and ccwgroup code improvements.

- Other small various fixes and improvements all over the code.

* tag 's390-5.14-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (91 commits)
s390/dasd: use register pair instead of register asm
s390/qdio: get rid of register asm
s390/ioasm: use symbolic names for asm operands
s390/ioasm: get rid of register asm
s390/cmf: get rid of register asm
s390/lib,string: get rid of register asm
s390/lib,uaccess: get rid of register asm
s390/string: get rid of register asm
s390/cmpxchg: use register pair instead of register asm
s390/mm,pages-states: get rid of register asm
s390/lib,xor: get rid of register asm
s390/timex: get rid of register asm
s390/hypfs: use register pair instead of register asm
s390/zcrypt: Switch to flexible array member
s390/speculation: Use statically initialized const for instructions
virtio/s390: get rid of open-coded kvm hypercall
s390/pci: add zpci_set_irq()/zpci_clear_irq()
scripts/min-tool-version.sh: Raise minimum clang version to 13.0.0 for s390
s390/ipl: use register pair instead of register asm
s390/mem_detect: fix tprot() program check new psw handling
...

s390: clear pt_regs::flags on irq entry

2021-06-21T09:19:18+00:00

The current irq entry code doesn't initialize pt_regs::flags. On exit to
user mode arch_do_signal_or_restart() tests whether PIF_SYSCALL is set,
which might yield wrong results.

Fix this by clearing pt_regs::flags in the entry.S irq handler
code.

Reported-by: Heiko Carstens 
Signed-off-by: Sven Schnelle 
Reviewed-by: Heiko Carstens 
Fixes: 56e62a737028 ("s390: convert to generic entry")
Cc:  # 5.12
Signed-off-by: Vasily Gorbik