linux-toradex.git/arch/s390/kernel/traps.c, branch v6.16

Merge tag 's390-6.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2025-03-29T18:59:43+00:00

Pull s390 updates from Vasily Gorbik:

 - Add sorting of mcount locations at build time

 - Rework uaccess functions with C exception handling to shorten inline
   assembly size and enable full inlining. This yields near-optimal code
   for small constant copies with a ~40kb kernel size increase

 - Add support for a configurable STRICT_MM_TYPECHECKS which allows to
   generate better code, but also allows to have type checking for debug
   builds

 - Optimize get_lowcore() for common callers with alternatives that
   nearly revert to the pre-relocated lowcore code, while also slightly
   reducing syscall entry and exit time

 - Convert MACHINE_HAS_* checks for single facility tests into cpu_has_*
   style macros that call test_facility(), and for features with
   additional conditions, add a new ALT_TYPE_FEATURE alternative to
   provide a static branch via alternative patching. Also, move machine
   feature detection to the decompressor for early patching and add
   debugging functionality to easily show which alternatives are patched

 - Add exception table support to early boot / startup code to get rid
   of the open coded exception handling

 - Use asm_inline for all inline assemblies with EX_TABLE or ALTERNATIVE
   to ensure correct inlining and unrolling decisions

 - Remove 2k page table leftovers now that s390 has been switched to
   always allocate 4k page tables

 - Split kfence pool into 4k mappings in arch_kfence_init_pool() and
   remove the architecture-specific kfence_split_mapping()

 - Use READ_ONCE_NOCHECK() in regs_get_kernel_stack_nth() to silence
   spurious KASAN warnings from opportunistic ftrace argument tracing

 - Force __atomic_add_const() variants on s390 to always return void,
   ensuring compile errors for improper usage

 - Remove s390's ioremap_wt() and pgprot_writethrough() due to
   mismatched semantics and lack of known users, relying on asm-generic
   fallbacks

 - Signal eventfd in vfio-ap to notify userspace when the guest AP
   configuration changes, including during mdev removal

 - Convert mdev_types from an array to a pointer in vfio-ccw and vfio-ap
   drivers to avoid fake flex array confusion

 - Cleanup trap code

 - Remove references to the outdated linux390@de.ibm.com address

 - Other various small fixes and improvements all over the code

* tag 's390-6.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (78 commits)
  s390: Use inline qualifier for all EX_TABLE and ALTERNATIVE inline assemblies
  s390/kfence: Split kfence pool into 4k mappings in arch_kfence_init_pool()
  s390/ptrace: Avoid KASAN false positives in regs_get_kernel_stack_nth()
  s390/boot: Ignore vmlinux.map
  s390/sysctl: Remove "vm/allocate_pgste" sysctl
  s390: Remove 2k vs 4k page table leftovers
  s390/tlb: Use mm_has_pgste() instead of mm_alloc_pgste()
  s390/lowcore: Use lghi instead llilh to clear register
  s390/syscall: Merge __do_syscall() and do_syscall()
  s390/spinlock: Implement SPINLOCK_LOCKVAL with inline assembly
  s390/smp: Implement raw_smp_processor_id() with inline assembly
  s390/current: Implement current with inline assembly
  s390/lowcore: Use inline qualifier for get_lowcore() inline assembly
  s390: Move s390 sysctls into their own file under arch/s390
  s390/syscall: Simplify syscall_get_arguments()
  s390/vfio-ap: Notify userspace that guest's AP config changed when mdev removed
  s390: Remove ioremap_wt() and pgprot_writethrough()
  s390/mm: Add configurable STRICT_MM_TYPECHECKS
  s390/mm: Convert pgste_val() into function
  s390/mm: Convert pgprot_val() into function
  ...

s390: Use inline qualifier for all EX_TABLE and ALTERNATIVE inline assemblies

2025-03-18T16:13:51+00:00

Use asm_inline for all inline assemblies which make use of the EX_TABLE or
ALTERNATIVE macros.

These macros expand to many lines and the compiler assumes the number of
lines within an inline assembly is the same as the number of instructions
within an inline assembly. This has an effect on inlining and loop
unrolling decisions.

In order to avoid incorrect assumptions use asm_inline, which tells the
compiler that an inline assembly has the smallest possible size.

In order to avoid confusion when asm_inline should be used or not, since a
couple of inline assemblies are quite large: the rule is to always use
asm_inline whenever the EX_TABLE or ALTERNATIVE macro is used. In specific
cases there may be reasons to not follow this guideline, but that should
be documented with the corresponding code.

Using the inline qualifier everywhere has only a small effect on the kernel
image size:

add/remove: 0/10 grow/shrink: 19/8 up/down: 1492/-1858 (-366)

The only location where this seems to matter is load_unaligned_zeropad()
from word-at-a-time.h where the compiler inlines more functions within the
dcache code, which is indeed code where performance matters.

Suggested-by: Juergen Christ 
Reviewed-by: Juergen Christ 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/traps: Change stack overflow message

2025-03-04T16:34:03+00:00

When the kernel stack pointer is pointing to invalid memory,
a 'Kernel stack overflow' message is printed, which is misleading.
Change the message to actually say that the stack pointer is invalid
instead.

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

s390/traps: Cleanup coding style

2025-03-04T16:34:03+00:00

Just some trivial whitespace and coding style changes.

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

s390/traps: Get rid of superfluous cpu_has_vx() check

2025-03-04T16:34:03+00:00

If the vector facility is installed cpu_has_vx() is always true, if it is
not installed the result is always false, and no vector exception can
happen. Therefore remove the superfluous check.

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

s390/traps: Use pr_emerg() instead of printk()

2025-03-04T16:34:03+00:00

Use pr_emerg() instead of printk() in case of a stack overflow,
providing the emergency printk level. Also slightly adjust the
printed text for pr_emerg() and panic().

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

s390/traps: Cleanup get_user() handling in illegal_op()

2025-03-04T16:34:03+00:00

The usage of get_user() in illegal_op() is quite unusual. Make the code
more readable and get rid of unnecessary casts. The generated code is
identical before/after this change.

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

s390: Use system header file variant of include directive

2025-03-04T16:18:08+00:00

A few include directives use the local search variant even though the files
to be included aren't local. Therefore use the normal system header file
variant of the include directive.

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

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

2025-03-04T16:18:07+00:00

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

s390/traps: Fix test_monitor_call() inline assembly

2025-03-04T16:15:18+00:00

The test_monitor_call() inline assembly uses the xgr instruction, which
also modifies the condition code, to clear a register. However the clobber
list of the inline assembly does not specify that the condition code is
modified, which may lead to incorrect code generation.

Use the lhi instruction instead to clear the register without that the
condition code is modified. Furthermore this limits clearing to the lower
32 bits of val, since its type is int.

Fixes: 17248ea03674 ("s390: fix __EMIT_BUG() macro")
Cc: stable@vger.kernel.org
Reviewed-by: Juergen Christ 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik