[PATCH v9 0/8] x86/boot/KASLR: Parse ACPI table and limit kaslr in immovable memory

Chao Fan
2018-10-17T10:20:04Z

***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 imitate 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.

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

v6->v7:
Follow Rafael's suggestion:
- Add more comments and patch log.
Follow test robot's suggestion:
- Add "static" tag for function

v7-v8:
Follow Kees Cook's suggestion:
- Use mem_overlaps() to check memory region.
- Use #ifdef in the definition of function.

v8-v9:
Follow Boris' suggetion:
- Change code style.
- Splite PATCH 1/3 to more path.
- Introduce some new function
- Use existing function to rework some code
Follow Masayoshi's suggetion:
- Make code more readable

Any comments will be welcome.

Chao Fan (8):
x86/boot: Introduce cmdline_find_option_arg()to detect if option=arg
in cmdline
x86/boot: Copy kstrtoull() to compressed period
x86/boot: Add efi_get_rsdp_addr() to dig out RSDP from EFI table
x86/boot: Add bios_get_rsdp_addr() to search RSDP in memory
x86/boot: Add get_acpi_rsdp() to parse RSDP in cmdlien from kexec
x86/boot: Dig out SRAT table from RSDP and find immovable memory
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 | 354 +++++++++++++++++++++++++++++
arch/x86/boot/compressed/cmdline.c | 15 ++
arch/x86/boot/compressed/kaslr.c | 77 ++++++-
arch/x86/boot/compressed/misc.c | 88 +++++++
arch/x86/boot/compressed/misc.h | 15 ++
6 files changed, 542 insertions(+), 11 deletions(-)
create mode 100644 arch/x86/boot/compressed/acpitb.c

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2.17.2