Hi, Sorry for disturbance, no reply for a week, any comments?
Thanks, Chao Fan On Mon, Jul 23, 2018 at 05:29:04PM +0800, Chao Fan wrote: >***Background: >People reported that kaslr may randomly chooses some positions >which are located in movable memory regions. This will break memory >hotplug feature and make the memory can't be removed. > >***Solutions: >There should be a method to limit kaslr to choosing immovable memory >regions, so there are 2 solutions: >1) Add a kernel parameter to specify the memory regions. >2) Get the information of memory hotremove, then kaslr will know the > right regions. >In method 2, information about memory hot remove is in ACPI >tables, which will be parsed after 'start_kernel', kaslr can't get >the information. >In method 1, users should know the regions address and specify in >kernel parameter. > >In the earliest time, I tried to dig ACPI tabls to solve this problem. >But I didn't splite the code in 'compressed/' and ACPI code, so the patch >is hard to follow so refused by community. >Somebody suggest to add a kernel parameter to specify the >immovable memory so that limit kaslr in these regions. Then I make >a patchset. After several versions, Ingo gave a suggestion: >https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1634024.html >Follow Ingo's suggestion, imitate the ACPI code to parse the acpi >tables, so that the kaslr can get necessary memory information in >ACPI tables. >Since I think ACPI code is independent part, so copy the codes >and functions to 'compressed/' directory, so that kaslr won't >influence the initialization of ACPI. > >PATCH 1/4 Reuse the head file of linux/acpi.h, and copy a fcuntion from > ACPI code. >PATCH 2/4 Functions to parse ACPI code. >PATCH 3/4 If 'CONFIG_MEMORY_HOTREMOVE' specified, walk all nodes and > store the information of immovable memory regions. >PATCH 4/4 According to the immovable memory regions, filter the > immovable regions which KASLR can choose. > >***Test results: > - I did a very simple test, and it can get the memory information in > bios and efi KVM guest machine, and put it by early printk. But no > more tests, so it's with RFC tag. > >v1->v2: > - Simplify some code. >Follow Baoquan He's suggestion: > - Reuse the head file of acpi code. > >v2->v3: > - Test in more conditions, so remove the 'RFC' tag. > - Change some comments. > >v3->v4: >Follow Thomas Gleixner's suggetsion: > - Put the whole efi related function into #define CONFIG_EFI and return > false in the other stub. > - Simplify two functions in head file. > >Any comments will be welcome. > > >Chao Fan (4): > x86/boot: Add acpitb.h to help parse acpi tables > x86/boot: Add acpitb.c to parse acpi tables > x86/boot/KASLR: Walk srat tables to filter immovable memory > x86/boot/KASLR: Limit kaslr to choosing the immovable memory > > arch/x86/boot/compressed/Makefile | 4 + > arch/x86/boot/compressed/acpitb.c | 251 ++++++++++++++++++++++++++++++ > arch/x86/boot/compressed/acpitb.h | 7 + > arch/x86/boot/compressed/kaslr.c | 121 ++++++++++++-- > 4 files changed, 372 insertions(+), 11 deletions(-) > create mode 100644 arch/x86/boot/compressed/acpitb.c > create mode 100644 arch/x86/boot/compressed/acpitb.h > >-- >2.17.1 >
