kernel/linux.git/arch/s390/include/asm/processor.h, branch v6.6.132

s390/stackleak: Fix __stackleak_poison() inline assembly constraint

2026-03-25T10:06:01+00:00

commit 674c5ff0f440a051ebf299d29a4c013133d81a65 upstream. The __stackleak_poison() inline assembly comes with a "count" operand where the "d" constraint is used. "count" is used with the exrl instruction and "d" means that the compiler may allocate any register from 0 to 15. If the compiler would allocate register 0 then the exrl instruction would not or the value of "count" into the executed instruction - resulting in a stackframe which is only partially poisoned. Use the correct "a" constraint, which excludes register 0 from register allocation. Fixes: 2a405f6bb3a5 ("s390/stackleak: provide fast __stackleak_poison() implementation") Cc: stable@vger.kernel.org Signed-off-by: Heiko Carstens Reviewed-by: Vasily Gorbik Link: https://lore.kernel.org/r/20260302133500.1560531-4-hca@linux.ibm.com Signed-off-by: Vasily Gorbik Signed-off-by: Greg Kroah-Hartman

s390/stackleak: Use exrl instead of ex in __stackleak_poison()

2025-02-17T08:40:03+00:00

[ Upstream commit a88c26bb8e04ee5f2678225c0130a5fbc08eef85 ] exrl is present in all machines currently supported, therefore prefer it over ex. This saves one instruction and doesn't need an additional register to hold the address of the target instruction. Signed-off-by: Sven Schnelle Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Sasha Levin

s390: Mark psw in __load_psw_mask() as __unitialized

2024-07-18T11:21:15+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/stackleak: provide fast __stackleak_poison() implementation

2023-04-20T09:36:35+00:00

Provide an s390 specific __stackleak_poison() implementation which is faster than the generic variant. For the original implementation with an enforced 4kb stackframe for the getpid() system call the system call overhead increases by a factor of 3 if the stackleak feature is enabled. Using the s390 mvc based variant this is reduced to an increase of 25% instead. This is within the expected area, since the mvc based implementation is more or less a memset64() variant which comes with similar results. See commit 0b77d6701cf8 ("s390: implement memset16, memset32 & memset64"). Reviewed-by: Vasily Gorbik Signed-off-by: Heiko Carstens Link: https://lore.kernel.org/r/20230405130841.1350565-3-hca@linux.ibm.com Signed-off-by: Vasily Gorbik

s390: move on_thread_stack() to processor.h

2023-04-04T16:34:56+00:00

As preparation for the stackleak feature move on_thread_stack() to processor.h like x86. Also make it __always_inline, and slightly optimize it by reading current task's kernel stack pointer from lowcore. Reviewed-by: Vasily Gorbik Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/bp: remove __bpon()

2023-03-13T08:16:42+00:00

There is no point in changing branch prediction state of a cpu shortly before it enters stop state. Therefore remove __bpon(). Acked-by: Alexander Gordeev Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/bp: remove s390_isolate_bp_guest()

2023-03-13T08:16:42+00:00

s390_isolate_bp_guest() is unused. Remove it. Reviewed-by: Alexander Gordeev Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/bp: remove TIF_ISOLATE_BP

2023-03-13T08:16:42+00:00

TIF_ISOLATE_BP is unused since it was introduced with commit 6b73044b2b00 ("s390: run user space and KVM guests with modified branch prediction"). Given that there is no use case remove it again. Acked-by: Alexander Gordeev Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/processor: add test_and_set_cpu_flag() and test_and_clear_cpu_flag()

2023-02-15T10:07:01+00:00

Add test_and_set_cpu_flag() and test_and_clear_cpu_flag() helper functions. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390/processor: let cpu helper functions return boolean values

2023-02-15T10:07:01+00:00

Let cpu helper functions return boolean values. This also allows to make the code a bit simpler by getting rid of the "!!" construct. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens