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Currently the kernel crashes in Kasan instrumentation code if CONFIG_KASAN_S390_4_LEVEL_PAGING is used on protected virtualization capable machine where the ultravisor imposes addressing limitations on the host and those limitations are lower then KASAN_SHADOW_OFFSET. The problem is that Kasan has to know in advance where vmalloc/modules areas would be. With protected virtualization enabled vmalloc/modules areas are moved down to the ultravisor secure storage limit while kasan still expects them at the very end of 4-level paging address space. To fix that make Kasan recognize when protected virtualization is enabled and predefine vmalloc/modules areas position which are compliant with ultravisor secure storage limit. Kasan shadow itself stays in place and might reside above that ultravisor secure storage limit. One slight difference compaired to a kernel without Kasan enabled is that vmalloc/modules areas position is not reverted to default if ultravisor initialization fails. It would still be below the ultravisor secure storage limit. Kernel layout with kasan, 4-level paging and protected virtualization enabled (ultravisor secure storage limit is at 0x0000800000000000): ---[ vmemmap Area Start ]--- 0x0000400000000000-0x0000400080000000 ---[ vmemmap Area End ]--- ---[ vmalloc Area Start ]--- 0x00007fe000000000-0x00007fff80000000 ---[ vmalloc Area End ]--- ---[ Modules Area Start ]--- 0x00007fff80000000-0x0000800000000000 ---[ Modules Area End ]--- ---[ Kasan Shadow Start ]--- 0x0018000000000000-0x001c000000000000 ---[ Kasan Shadow End ]--- 0x001c000000000000-0x0020000000000000 1P PGD I Kernel layout with kasan, 4-level paging and protected virtualization disabled/unsupported: ---[ vmemmap Area Start ]--- 0x0000400000000000-0x0000400060000000 ---[ vmemmap Area End ]--- ---[ Kasan Shadow Start ]--- 0x0018000000000000-0x001c000000000000 ---[ Kasan Shadow End ]--- ---[ vmalloc Area Start ]--- 0x001fffe000000000-0x001fffff80000000 ---[ vmalloc Area End ]--- ---[ Modules Area Start ]--- 0x001fffff80000000-0x0020000000000000 ---[ Modules Area End ]--- Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> |
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