6.10-stable review patch. If anyone has any objections, please let me know.
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From: Alexander Gordeev agordeev@linux.ibm.com
[ Upstream commit a3ca27c405faad584af6e8e38cdafe5be73230a1 ]
The identity mapping position in virtual memory is randomized together with the kernel mapping. That position can never overlap with the lowcore even when the lowcore is relocated.
Prevent overlapping with the lowcore to allow independent positioning of the identity mapping. With the current value of the alternative lowcore address of 0x70000 the overlap could happen in case the identity mapping is placed at zero.
This is a prerequisite for uncoupling of randomization base of kernel image and identity mapping in virtual memory.
Acked-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Alexander Gordeev agordeev@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kernel/setup.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index 610e6f794511..4b1afd8ac3ee 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -734,7 +734,23 @@ static void __init memblock_add_physmem_info(void) }
/* - * Reserve memory used for lowcore/command line/kernel image. + * Reserve memory used for lowcore. + */ +static void __init reserve_lowcore(void) +{ + void *lowcore_start = get_lowcore(); + void *lowcore_end = lowcore_start + sizeof(struct lowcore); + void *start, *end; + + if ((void *)__identity_base < lowcore_end) { + start = max(lowcore_start, (void *)__identity_base); + end = min(lowcore_end, (void *)(__identity_base + ident_map_size)); + memblock_reserve(__pa(start), __pa(end)); + } +} + +/* + * Reserve memory used for absolute lowcore/command line/kernel image. */ static void __init reserve_kernel(void) { @@ -915,6 +931,7 @@ void __init setup_arch(char **cmdline_p)
/* Do some memory reservations *before* memory is added to memblock */ reserve_pgtables(); + reserve_lowcore(); reserve_kernel(); reserve_initrd(); reserve_certificate_list();