s390/mm: uninline copy_oldmem_kernel() function

2022-09-14T14:46:01Z

Uninline copy_oldmem_kernel() function and make it consistent with a very similar memcpy_real() implementation, by moving to code to crash_dump.c, where it actually belongs. Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Vasily Gorbik

s390/mm: rework memcpy_real() to avoid DAT-off mode

2022-09-14T14:46:01Z

Function memcpy_real() is an univeral data mover that does not require DAT mode to be able reading from a physical address. Its advantage is an ability to read from any address, even those for which no kernel virtual mapping exists. Although memcpy_real() is interrupt-safe, there are no handlers that make use of this function. The compiler instrumentation have to be disabled and separate no-DAT stack used to allow execution of the function once DAT mode is disabled. Rework memcpy_real() to overcome these shortcomings. As result, data copying (which is primarily reading out a crashed system memory by a user process) is executed on a regular stack with enabled interrupts. Also, use of memcpy_real_buf swap buffer becomes unnecessary and the swapping is eliminated. The above is achieved by using a fixed virtual address range that spans a single page and remaps that page repeatedly when memcpy_real() is called for a particular physical address. Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Vasily Gorbik

kernel/arch/s390/include/asm/maccess.h, branch linux-6.2.y

s390/mm: uninline copy_oldmem_kernel() function

s390/mm: rework memcpy_real() to avoid DAT-off mode