Date:   Fri, 14 Dec 2018 17:30:08 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <bp@...en8.de>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
        <keescook@...omium.org>, <bhe@...hat.com>, <msys.mizuma@...il.com>
CC:     <indou.takao@...fujitsu.com>, <caoj.fnst@...fujitsu.com>,
        <fanc.fnst@...fujitsu.com>
Subject: [PATCH v14 0/5] x86/boot/KASLR: Parse ACPI table and limit KASLR to choosing immovable memory

***Background:
People reported that KASLR may randomly choose 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:
Get the information of memory hot-remove, then KASLR knows the
right regions. Information about memory hot-remove is in ACPI
SRAT, which will be parsed after start_kernel(), so KASLR
can't get the information.

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.
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 1/5 Add get_acpi_rsdp() to parse RSDP in cmdline from KEXEC
PATCH 2/5 Add efi_get_rsdp_addr() to find RSDP from EFI table when
          booting from EFI.
PATCH 3/5 Add bios_get_rsdp_addr() to search RSDP in memory when EFI
          table not found.
PATCH 4/5 Compute SRAT from RSDP and walk SRAT to store the immovable
          memory regions.
PATCH 5/5 Calculate the intersection between memory regions from e820/efi
          memory table and immovable memory regions. Limit KASLR to
          choosing these regions for randomization.

v13->v14:
Follow Baoquan's suggestion:
 - Use simple_strtoull() for now.
Follow Boris' suggestion:
 - Put 'return 0' out of 'ifdef' to make sure function return.
Follow Masa's suggestion:
 - Change the end of string as '\0'

v12->v13:
Follow Boris' suggestion:
 - Copy kstrtoull() to boot/string.c
Follow Masa's suggestion:
 - Change some code logical
Follow Baoquan's suggestion:
 - Add tag to disable export symbol

v11->v12:
Follow Boris' suggestion:
 - Change patch log and code comments.
 - Add 'CONFIG_EARLY_PARSE_RSDP' to make code easy to read
 - Put strtoull() to misc.c
Follow Masa's suggestion:
 - Remove the detection for 'movable_node'
 - Change the code logical about cmdline_find_option()

v10->v11:
Follow Boris' suggestion:
 - Link kstrtoull() instead of copying it.
 - Drop the useless wrapped function.

v9->v10:
Follow Baoquan's suggestion:
 - Change some log
 - Merge last two patch together.

v8-v9:
Follow Boris' suggestion:
 - 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

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

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

v5->v6:
Follow Baoquan He's suggestion:
 - Change some log.
 - Add the check for acpi_rsdp
 - Change some code logical to make code clear

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

v3->v4:
Follow Thomas Gleixner's suggestion:
 - Put the whole efi related function into #define CONFIG_EFI and return
   false in the other stub.

v2->v3:
 - Test in more conditions, so remove the 'RFC' tag.
 - Change some comments.

v1->v2:
 -  Simplify some code.
Follow Baoquan He's suggestion:
 - Reuse the head file of acpi code.

Any comments will be welcome.


Chao Fan (5):
  x86/boot: Introduce get_acpi_rsdp() to parse RSDP in cmdline from
    KEXEC
  x86/boot: Introduce efi_get_rsdp_addr() to find RSDP from EFI table
  x86/boot: Introduce bios_get_rsdp_addr() to search RSDP in memory
  x86/boot: Parse SRAT address from RSDP and store immovable memory
  x86/boot/KASLR: Limit KASLR to extracting kernel in immovable memory

 arch/x86/Kconfig                  |  12 ++
 arch/x86/boot/compressed/Makefile |   2 +
 arch/x86/boot/compressed/acpi.c   | 323 ++++++++++++++++++++++++++++++
 arch/x86/boot/compressed/kaslr.c  |  79 ++++++--
 arch/x86/boot/compressed/misc.h   |  19 ++
 5 files changed, 420 insertions(+), 15 deletions(-)
 create mode 100644 arch/x86/boot/compressed/acpi.c

-- 
2.19.2

Powered by blists - more mailing lists