On Wed, Jul 11, 2018 at 05:42:44PM +0800, Chao Fan wrote: >Hi all, > >I found there is a BUG about KASLR and ZONE_MOVABLE. > >When users use 'kernelcore=' parameter without 'movable_node', >movable memory is evenly distributed to all nodes. The size of >ZONE_MOVABLE depends on the kernel parameter 'kernelcore=' and >'movablecore='. >But sometiomes, KASLR may put the uncompressed kernel to the >tail position of a node, which will cause the kernel memory >set as ZONE_MOVABLE. This region can not be offlined. > >Here is a very simple test in my qemu-kvm machine, there is >only one node: > >The command line: >[root@localhost ~]# cat /proc/cmdline >BOOT_IMAGE=/vmlinuz-4.18.0-rc3+ root=/dev/mapper/fedora_localhost--live-root >ro resume=/dev/mapper/fedora_localhost--live-swap >rd.lvm.lv=fedora_localhost-live/root rd.lvm.lv=fedora_localhost-live/swap >console=ttyS0 earlyprintk=ttyS0,115200n8 memblock=debug kernelcore=50% > >I use 'kernelcore=50%' here. > >Here is my early print result, I print the random_addr after KASLR chooses >physical memory: >early console in extract_kernel >input_data: 0x000000000266b3b1 >input_len: 0x00000000007d8802 >output: 0x0000000001000000 >output_len: 0x0000000001e15698 >kernel_total_size: 0x0000000001a8b000 >trampoline_32bit: 0x000000000009d000 >booted via startup_32() >Physical KASLR using RDRAND RDTSC... >random_addr: 0x000000012f000000 >Virtual KASLR using RDRAND RDTSC... > >The address for kernel is 0x000000012f000000 > >Here is the log of ZONE: >[ 0.000000] Zone ranges: >[ 0.000000] DMA [mem 0x0000000000001000-0x0000000000ffffff] >[ 0.000000] DMA32 [mem 0x0000000001000000-0x00000000ffffffff] >[ 0.000000] Normal [mem 0x0000000100000000-0x00000001f57fffff] >[ 0.000000] Device empty >[ 0.000000] Movable zone start for each node >[ 0.000000] Node 0: 0x000000011b000000 >[ 0.000000] Early memory node ranges >[ 0.000000] node 0: [mem 0x0000000000001000-0x000000000009efff] >[ 0.000000] node 0: [mem 0x0000000000100000-0x00000000bffd6fff] >[ 0.000000] node 0: [mem 0x0000000100000000-0x00000001f57fffff] >[ 0.000000] Initmem setup node 0 [mem >0x0000000000001000-0x00000001f57fffff] > >Only one node in my machine, ZONE_MOVABLE begins from 0x000000011b000000, >which is lower than 0x000000012f000000. >So KASLR put the kernel to the ZONE_MOVABLE. >Try to solve this problem, I think there should be a new tactic in function >find_zone_movable_pfns_for_nodes() of mm/page_alloc.c. If kernel is >uncompressed >in a tail position, then just set the memory after the kernel as ZONE_MOVABLE, >at the same time, memory in other nodes will be set as ZONE_MOVABLE.
Sorry, mistake here. It should be: "more memory in other nodes will be set as ZONE_MOVABLE". Thanks, Chao Fan > >If there is something wrong, pleas let me know. And any comments will be >welcome. > >Thanks, >Chao Fan
