linux-stable.git/arch/s390/kernel/sysinfo.c, branch linux-rolling-stable

s390/sysinfo: Replace sprintf() with snprintf() for buffer safety

2025-10-21T08:17:29+00:00

Replace sprintf() with snprintf() when formatting symlink target name
to prevent potential buffer overflow. The link_to buffer is only 10
bytes, and using snprintf() ensures proper bounds checking if the
topology nesting limit value is unexpectedly large.

Signed-off-by: Josephine Pfeiffer 
Signed-off-by: Heiko Carstens

s390: Convert MACHINE_IS_[LPAR|VM|KVM], etc, machine_is_[lpar|vm|kvm]()

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

Move machine type detection to the decompressor and use static branches
to implement and use machine_is_[lpar|vm|kvm]() instead of a runtime check
via MACHINE_IS_[LPAR|VM|KVM].

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

s390/sysinfo: Move stsi() to header file

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

Move stsi() inline assembly to header file so it is possible to use it
also for the decompressor.

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

s390/sysinfo: Cleanup stsi() inline assembly

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

Merge stsi() and __stsi() and cleanup the inline assembly. This involves
making use of the flag output constraint. Semantically the result is
identical to before.

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

s390/sysinfo: Remove exception handling from __stsi()

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

The exception handling for __stsi() was added in 2001 when it still was
possible to run Linux on systems without LPAR hypervisor, and therefore
without an stsi instruction. Given that this is not supported anymore
remove the exception handling from the __stsi() inline assembly.

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

s390/cpufeature: Convert MACHINE_HAS_TOPOLOGY to cpu_has_topology()

2025-03-04T16:18:05+00:00

Convert MACHINE_HAS_... to cpu_has_...() which uses test_facility() instead
of testing the machine_flags lowcore member if the feature is present.

test_facility() generates better code since it results in a static branch
without accessing memory. The branch is patched via alternatives by the
decompressor depending on the availability of the required facility.

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

[tree-wide] finally take no_llseek out

2024-09-27T15:18:43+00:00

no_llseek had been defined to NULL two years ago, in commit 868941b14441
("fs: remove no_llseek")

To quote that commit,

  At -rc1 we'll need do a mechanical removal of no_llseek -

  git grep -l -w no_llseek | grep -v porting.rst | while read i; do
	sed -i '/\/d' $i
  done

  would do it.

Unfortunately, that hadn't been done.  Linus, could you do that now, so
that we could finally put that thing to rest? All instances are of the
form
	.llseek = no_llseek,
so it's obviously safe.

Signed-off-by: Al Viro 
Signed-off-by: Linus Torvalds

s390/sysinfo: allow response buffer in normal memory

2024-03-13T08:23:44+00:00

As provided with commit cd4386a931b63 ("s390/cpcmd,vmcp: avoid GFP_DMA
allocations") the Diagnose Code 8 response buffer does not have to be
below 2GB.

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

s390/sysinfo: convert bogomips calculation to C

2024-02-16T13:30:17+00:00

Provide several one instruction fpu inline assemebles and use them to
implement the bogomips calculation in C like style. This is more for
illustration purposes on how kernel fpu code can be written in C.

This has the advantage that the author only has to take care of the
floating point instructions, but doesn't need to take care of general
purpose register allocation (if needed), and the semantics of all other
instructions not related to fpu.

Signed-off-by: Heiko Carstens

s390/fpu: decrease stack usage for some cases

2024-02-16T13:30:16+00:00

The kernel_fpu structure has a quite large size of 520 bytes. In order to
reduce stack footprint introduce several kernel fpu structures with
different and also smaller sizes. This way every kernel fpu user must use
the correct variant. A compile time check verifies that the correct variant
is used.

There are several users which use only 16 instead of all 32 vector
registers. For those users the new kernel_fpu_16 structure with a size of
only 266 bytes can be used.

Signed-off-by: Heiko Carstens