linux-kernel - Re: [PATCH v10 0/7] x86/boot/KASLR: Parse ACPI table and limit kaslr in immovable memory

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Message-ID: <20181031074234.GB6609@localhost.localdomain>
Date:   Wed, 31 Oct 2018 15:42:34 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <linux-efi@...r.kernel.org>, <linux-acpi@...r.kernel.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>
Subject: Re: [PATCH v10 0/7] x86/boot/KASLR: Parse ACPI table and limit kaslr
 in immovable memory

Hi all,

Sorry for disturbance.
No reply to this version for more than one week,
any comments?

Thanks,
Chao Fan

On Mon, Oct 22, 2018 at 05:37:13PM +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 imitate the codes
>and functions to 'compressed/' directory, so that kaslr won't
>influence the initialization of ACPI.
>
>PATCH 1/7 Introduce cmdline_find_option_arg() to detect if option=arg
>          in cmdline
>PATCH 2/7 Copy kstrtoull() to compressed period, used to convert memory
>          address from string to unsigned long long.
>PATCH 3/7 Add efi_get_rsdp_addr() to dig out RSDP from EFI table when
>          booting from EFI.
>PATCH 4/7 Add bios_get_rsdp_addr() to search RSDP in memory when EFI
>          table not found.
>PATCH 5/7 Add get_acpi_rsdp() to parse RSDP in cmdline from kexec
>PATCH 6/7 Dig out SRAT table from RSDP and walk SRAT table to store
>          the immovable memory regions.
>PATCH 7/7 Calculate the intersection between memory regions from e820/efi
>          memory table and immovable memory regions. Limit KASLR choose
>          these regions for randomization.
>
>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.
>
>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
>
>v9->v10:
>Follow Baoquan's suggestion:
> - Change some log
> - Merge last two patch together.
>
>Any comments will be welcome.
>
>Chao Fan (7):
>  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: Limit kaslr to choosing the immovable memory
>
> arch/x86/boot/compressed/Makefile  |   4 +
> arch/x86/boot/compressed/acpitb.c  | 352 +++++++++++++++++++++++++++++
> arch/x86/boot/compressed/cmdline.c |  15 ++
> arch/x86/boot/compressed/kaslr.c   |  81 +++++--
> arch/x86/boot/compressed/misc.c    |  88 ++++++++
> arch/x86/boot/compressed/misc.h    |  20 ++
> 6 files changed, 545 insertions(+), 15 deletions(-)
> create mode 100644 arch/x86/boot/compressed/acpitb.c
>
>-- 
>2.17.2
>