s390/uaccess: Optimize raw_copy_from_user() / raw_copy_to_user() for constant sizes

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Avoid that the compiler generates an mvcos loop for constant sizes
smaller than 4096 bytes. The mvcos instruction copies between zero and
4096 bytes (effective length) with one operation. Therefore it is not
necessary to implement a loop for sizes smaller or equal to 4096
bytes.

This reduces the kernel text size by ~50kb (defconfig, gcc 14.2.0):
add/remove: 4/5 grow/shrink: 6/471 up/down: 2294/-51700 (-49406)

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

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Heiko Carstens 2025-02-11 20:19:29 +01:00 • committed by Vasily Gorbik

parent 10a79b6fdd

commit 88e87cb7b8

1 changed files with 4 additions and 0 deletions

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arch/s390/include/asm/uaccess.h

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