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| author | Alexander Gordeev <agordeev@linux.ibm.com> | 2022-07-24 16:02:16 +0300 |
|---|---|---|
| committer | Vasily Gorbik <gor@linux.ibm.com> | 2022-09-14 17:46:01 +0300 |
| commit | 2f0e8aae26a27fe73d033788f8e92188e7584f41 (patch) | |
| tree | 07c8abbd98e7b51142126c6c5880eaeea65ccaf9 /arch/s390/boot | |
| parent | 14a3a2624285d36624966935ec12f228d876c028 (diff) | |
| download | linux-2f0e8aae26a27fe73d033788f8e92188e7584f41.tar.xz | |
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>
Diffstat (limited to 'arch/s390/boot')
| -rw-r--r-- | arch/s390/boot/startup.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c index 41b7af7a9365..6e7f01ca53e6 100644 --- a/arch/s390/boot/startup.c +++ b/arch/s390/boot/startup.c @@ -17,6 +17,7 @@ unsigned long __bootdata_preserved(__kaslr_offset); unsigned long __bootdata_preserved(__abs_lowcore); +unsigned long __bootdata_preserved(__memcpy_real_area); unsigned long __bootdata(__amode31_base); unsigned long __bootdata_preserved(VMALLOC_START); unsigned long __bootdata_preserved(VMALLOC_END); @@ -182,7 +183,9 @@ static void setup_kernel_memory_layout(void) /* force vmalloc and modules below kasan shadow */ vmax = min(vmax, KASAN_SHADOW_START); #endif - __abs_lowcore = round_down(vmax - ABS_LOWCORE_MAP_SIZE, sizeof(struct lowcore)); + __memcpy_real_area = round_down(vmax - PAGE_SIZE, PAGE_SIZE); + __abs_lowcore = round_down(__memcpy_real_area - ABS_LOWCORE_MAP_SIZE, + sizeof(struct lowcore)); MODULES_END = round_down(__abs_lowcore, _SEGMENT_SIZE); MODULES_VADDR = MODULES_END - MODULES_LEN; VMALLOC_END = MODULES_VADDR; |