From a3ca27c405faad584af6e8e38cdafe5be73230a1 Mon Sep 17 00:00:00 2001 From: Alexander Gordeev Date: Fri, 9 Aug 2024 08:47:15 +0200 Subject: s390/mm: Prevent lowcore vs identity mapping overlap 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 Signed-off-by: Alexander Gordeev Signed-off-by: Vasily Gorbik --- 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 4ec99f73fa27..a3fea683b227 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) { @@ -918,6 +934,7 @@ 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(); -- cgit