linux

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Alexander Gordeev 2f0e8aae26 s390/mm: rework memcpy_real() to avoid DAT-off mode

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 <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

2022-09-14 16:46:01 +02:00

cmm.c

s390/cmm: add missing virt_to_phys() conversion

2021-12-10 16:14:25 +01:00

dump_pagetables.c

s390/smp,ptdump: add absolute lowcore markers

2022-09-14 16:46:00 +02:00

extable.c

s390/uaccess: use exception handler to zero result on get_user() failure

2022-06-01 12:03:17 +02:00

extmem.c

s390/extmem: remove stale -ENOSPC comment and handling