s390: Remove 2k vs 4k page table leftovers

Since commit d08d4e7cd6bf ("s390/mm: use full 4KB page for 2KB PTE") always
4k page tables are allocated, however there is still some (now) obsolete
code l

s390: Remove 2k vs 4k page table leftovers

Since commit d08d4e7cd6bf ("s390/mm: use full 4KB page for 2KB PTE") always
4k page tables are allocated, however there is still some (now) obsolete
code left which deals with switching from 2k to 4k page tables for qemu/kvm
processes.

Reviewed-by: Alexander Gordeev <[email protected]>
Remove the not needed code.

Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390/syscall: Merge __do_syscall() and do_syscall()

The compiler inlines do_syscall() into __do_syscall(). Therefore do this in
C code as well, since this makes the code easier to understand.

Also

s390/syscall: Merge __do_syscall() and do_syscall()

The compiler inlines do_syscall() into __do_syscall(). Therefore do this in
C code as well, since this makes the code easier to understand.

Also adjust and add various unlikely() and likely() annotations.

Furthermore this allows to replace the separate exit_to_user_mode() and
syscall_exit_to_user_mode_work() calls with a combined
syscall_exit_to_user_mode() call which results in slightly better code.

Acked-by: Vasily Gorbik <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390/bear: Convert cpu_has_bear() to cpu feature function

Get rid of the cpu_has_bear jump label and convert cpu_has_bear() to a cpu
feature function using test_facility() and with that use a static

s390/bear: Convert cpu_has_bear() to cpu feature function

Get rid of the cpu_has_bear jump label and convert cpu_has_bear() to a cpu
feature function using test_facility() and with that use a static branch.

Reviewed-by: Vasily Gorbik <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390: remove native mmap2() syscall

The mmap2() syscall has never been used on 64-bit s390x and should
have been removed as part of 5a79859ae0f3 ("s390: remove 31 bit
support").

Remove it now.

Ack

s390: remove native mmap2() syscall

The mmap2() syscall has never been used on 64-bit s390x and should
have been removed as part of 5a79859ae0f3 ("s390: remove 31 bit
support").

Remove it now.

Acked-by: Heiko Carstens <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>

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s390: Replace S390_lowcore by get_lowcore()

Replace all S390_lowcore usages in arch/s390/ by get_lowcore().

Acked-by: Heiko Carstens <[email protected]>
Signed-off-by: Sven Schnelle <[email protected]

s390: Replace S390_lowcore by get_lowcore()

Replace all S390_lowcore usages in arch/s390/ by get_lowcore().

Acked-by: Heiko Carstens <[email protected]>
Signed-off-by: Sven Schnelle <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390: add support for BEAR enhancement facility

The Breaking-Event-Address-Register (BEAR) stores the address of the
last breaking event instruction. Breaking events are usually instructions
that ch

s390: add support for BEAR enhancement facility

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 <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390: rename PIF_SYSCALL_RESTART to PIF_EXECVE_PGSTE_RESTART

PIF_SYSCALL_RESTART is now only used to restart execve when loading
PGSTE binaries. Rename the flag to reflect that, and avoid people
thi

s390: rename PIF_SYSCALL_RESTART to PIF_EXECVE_PGSTE_RESTART

PIF_SYSCALL_RESTART is now only used to restart execve when loading
PGSTE binaries. Rename the flag to reflect that, and avoid people
thinking that this bit has anything to do with generic syscall
restarting.

Signed-off-by: Sven Schnelle <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390: move restart of execve() syscall

On s390, execve might have to be restarted for PGSTE binaries
like kvm. In the past this was done via the PIF_SYSCALL_RESTART
bit. However, with the recent cha

s390: move restart of execve() syscall

On s390, execve might have to be restarted for PGSTE binaries
like kvm. In the past this was done via the PIF_SYSCALL_RESTART
bit. However, with the recent changes, syscalls are now restarted
differently. Now that execve() is the only call that might get
restarted via PIF_SYSCALL_RESTART, move the loop to do_syscall().
This also has the advantage that the restart is no longer visible
to userspace.

Signed-off-by: Sven Schnelle <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390/signal: remove sigreturn on stack

{rt_}sigreturn is now called from the vdso, so we no longer
need the svc on the stack, and therefore no hack to support that
mechanism on machines with non-exe

s390/signal: remove sigreturn on stack

{rt_}sigreturn is now called from the vdso, so we no longer
need the svc on the stack, and therefore no hack to support that
mechanism on machines with non-executable stack.

Signed-off-by: Sven Schnelle <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390/signal: switch to using vdso for sigreturn and syscall restart

with generic entry, there's a bug when it comes to restarting of signals.
The failing sequence is:

a) a signal is coming in, and

s390/signal: switch to using vdso for sigreturn and syscall restart

with generic entry, there's a bug when it comes to restarting of signals.
The failing sequence is:

a) a signal is coming in, and no handler is registered, so the lower
part of arch_do_signal_or_restart() in arch/s390/kernel/signal.c
sets PIF_SYSCALL_RESTART.

b) a second signal gets pending while the kernel is still in the exit
loop, and for that one, a handler exists.

c) The first part of arch_do_signal_or_restart() is called. That part
calls handle_signal(), which sets up stack + registers for handling
the signal.

d) __do_syscall() in arch/s390/kernel/syscall.c checks for
PIF_SYSCALL_RESTART right before leaving to userspace. If it is set,
it restart's the syscall. However, the registers are already setup
for handling a signal from c). The syscall is now restarted with the
wrong arguments.

Change the code to:

- use vdso for syscall_restart() instead of PIF_SYSCALL_RESTART because
we cannot rewind and go back to userspace on s390 because the system call
number might be encoded in the svc instruction.
- for all other syscalls we rewind the PSW and return to userspace.

Cc: <[email protected]> # v5.12+ d57778feb987: s390/vdso: always enable vdso
Cc: <[email protected]> # v5.12+ 686341f2548b: s390/vdso64: add sigreturn,rt_sigreturn and restart_syscall
Cc: <[email protected]> # v5.12+ 43e1f76b0b69: s390/vdso: rename VDSO64_LBASE to VDSO_LBASE
Cc: <[email protected]> # v5.12+ 779df2248739: s390/vdso: add minimal compat vdso
Cc: <[email protected]> # v5.12+
Signed-off-by: Sven Schnelle <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390/entry: use assignment to read intcode / asm to copy gprs

arch/s390/kernel/syscall.c: In function __do_syscall:
arch/s390/kernel/syscall.c:147:9: warning: memcpy reading 64 bytes from a region o

s390/entry: use assignment to read intcode / asm to copy gprs

arch/s390/kernel/syscall.c: In function __do_syscall:
arch/s390/kernel/syscall.c:147:9: warning: memcpy reading 64 bytes from a region of size 0 [-Wstringop-overread]
147 | memcpy(&regs->gprs[8], S390_lowcore.save_area_sync, 8 * sizeof(unsigned long));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/s390/kernel/syscall.c:148:9: warning: memcpy reading 4 bytes from a region of size 0 [-Wstringop-overread]
148 | memcpy(&regs->int_code, &S390_lowcore.svc_ilc, sizeof(regs->int_code));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by moving the gprs restore from C to assembly, and use a assignment
for int_code instead of memcpy.

Signed-off-by: Sven Schnelle <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390/entry: add support for syscall stack randomization

This adds support for adding a random offset to the stack while handling
syscalls. The patch uses get_tod_clock_fast() as this is considered g

s390/entry: add support for syscall stack randomization

This adds support for adding a random offset to the stack while handling
syscalls. The patch uses get_tod_clock_fast() as this is considered good
enough and has much less performance penalty compared to using
get_random_int(). The patch also adds randomization in pgm_check_handler()
as the sigreturn/rt_sigreturn system calls might be called from there.

Signed-off-by: Sven Schnelle <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Heiko Carstens <[email protected]>

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s390: pass struct pt_regs instead of registers to syscalls

Instead of fetching all registers from struct pt_regs and passing
them to the syscall wrappers, let the system call wrappers only
fetch the

s390: pass struct pt_regs instead of registers to syscalls

Instead of fetching all registers from struct pt_regs and passing
them to the syscall wrappers, let the system call wrappers only
fetch the values really required.

Signed-off-by: Sven Schnelle <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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s390: convert to generic entry

This patch converts s390 to use the generic entry infrastructure from
kernel/entry/*.

There are a few special things on s390:

- PIF_PER_TRAP is moved to TIF_PER_TRAP

s390: convert to generic entry

This patch converts s390 to use the generic entry infrastructure from
kernel/entry/*.

There are a few special things on s390:

- PIF_PER_TRAP is moved to TIF_PER_TRAP as the generic code doesn't
know about our PIF flags in exit_to_user_mode_loop().

- The old code had several ways to restart syscalls:

a) PIF_SYSCALL_RESTART, which was only set during execve to force a
restart after upgrading a process (usually qemu-kvm) to pgste page
table extensions.

b) PIF_SYSCALL, which is set by do_signal() to indicate that the
current syscall should be restarted. This is changed so that
do_signal() now also uses PIF_SYSCALL_RESTART. Continuing to use
PIF_SYSCALL doesn't work with the generic code, and changing it
to PIF_SYSCALL_RESTART makes PIF_SYSCALL and PIF_SYSCALL_RESTART
more unique.

- On s390 calling sys_sigreturn or sys_rt_sigreturn is implemented by
executing a svc instruction on the process stack which causes a fault.
While handling that fault the fault code sets PIF_SYSCALL to hand over
processing to the syscall code on exit to usermode.

The patch introduces PIF_SYSCALL_RET_SET, which is set if ptrace sets
a return value for a syscall. The s390x ptrace ABI uses r2 both for the
syscall number and return value, so ptrace cannot set the syscall number +
return value at the same time. The flag makes handling that a bit easier.
do_syscall() will just skip executing the syscall if PIF_SYSCALL_RET_SET
is set.

CONFIG_DEBUG_ASCE was removd in favour of the generic CONFIG_DEBUG_ENTRY.
CR1/7/13 will be checked both on kernel entry and exit to contain the
correct asces.

Signed-off-by: Sven Schnelle <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

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