Messages in this thread | | | Date | Tue, 11 Sep 2018 09:13:31 +0800 | From | Chao Fan <> | Subject | Re: [PATCH v6 0/3] x86/boot/KASLR: Parse ACPI table and limit kaslr in immovable memory. |
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sorry, the cover letter forwand to rafael.
Thanks, Chao Fan
On Mon, Sep 10, 2018 at 08:40:12PM +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 movable memory chosen by KASLR 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 hot-remove, 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 new 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. >I think ACPI code is an independent part, so copy the codes >and functions to 'compressed/' directory, so that kaslr won't >influence the initialization of ACPI. > >PATCH 1/3 Add acpitb.c to provide functions to parse ACPI code. >PATCH 2/3 If CONFIG_MEMORY_HOTREMOVE enabled, walk all nodes and > store the information of immovable memory regions. >PATCH 3/3 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. > >v4->v5: >Follow Dou Liyang's suggestion: > - Add more comments about some functions based on kernel code. > - Change some typo in comments. > - Clean useless variable. > - Add check for the boundary of array. > - Add check for 'movable_node' parameter > >v5->v6: >Follow Baoquan He's suggestion: > - Change some log. > - Add the check for acpi_rsdp > - Change some code logical to make code clear > >Any comments will be welcome. > > >Chao Fan (3): > 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 | 382 ++++++++++++++++++++++++++++++ > arch/x86/boot/compressed/kaslr.c | 76 +++++- > arch/x86/boot/compressed/misc.h | 8 + > 4 files changed, 459 insertions(+), 11 deletions(-) > create mode 100644 arch/x86/boot/compressed/acpitb.c > >-- >2.17.1 >
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