Date:   Fri, 30 Nov 2018 14:39:31 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Masayoshi Mizuma <msys.mizuma@...il.com>
CC:     <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>,
        <indou.takao@...fujitsu.com>, <caoj.fnst@...fujitsu.com>
Subject: Re: [PATCH v12 0/5] x86/boot/KASLR: Parse ACPI table and limit KASLR
 to choosing immovable memory

On Fri, Nov 30, 2018 at 09:15:13AM +0800, Chao Fan wrote:
>On Thu, Nov 29, 2018 at 12:32:46PM -0500, Masayoshi Mizuma wrote:
>>Hi Chao,
>>
>>Thank you for your continued working.
>
>Thanks for your test.
>
>>
>>Could you please build your patches before sending?
>
>Sorry for the mistake, I build it with the whole patches.
>I found there are some problems with the method to splite patch.
>I will rework on it and build every commit.
>
>Thanks,
>Chao Fan
>
>>Your patches depend on the following kconfig,
>>so please build them under the config combination.
>>
>>RANDOMIZE_BASE
>>MEMORY_HOTREMOVE
>>EARLY_PARSE_RSDP
>>KEXEC
>>EFI

Hi Masa,

After retest, I make clean and make again.
I met the problem is the useless #endif issue you mentioned.
But I found both:

#ifndef BOOT_STRING
EXPORT_SYMBOL(kstrtoull);

and

EXPORT_SYMBOL(kstrtoull);
#ifndef BOOT_STRING

work for me. So I don't know the key problem, cause the config you
mentioned are y.

Thanks,
Chao Fan

>>
>>Thanks,
>>Masa
>>
>>On Thu, Nov 29, 2018 at 04:16:26PM +0800, Chao Fan wrote:
>>> ***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 will know the
>>> right regions. Information about memory hot-remove is in ACPI
>>> tables, which will be parsed after start_kernel(), so that 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 table from RSDP and walk SRAT table 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.
>>> 
>>> 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' 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
>>> 
>>> v9->v10:
>>> Follow Baoquan's suggestion:
>>>  - Change some log
>>>  - Merge last two patch together.
>>> 
>>> v10->v11:
>>> Follow Boris' suggestion:
>>>  - Link kstrtoull() instead of copying it.
>>>  - Drop the useless wrapped function.
>>> 
>>> 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()
>>> 
>>> Any comments will be welcome.
>>> 
>>> 
>>> Chao Fan (5):
>>>   x86/boot: Add get_acpi_rsdp() to parse RSDP in cmdline from KEXEC
>>>   x86/boot: Add efi_get_rsdp_addr() to find RSDP from EFI table
>>>   x86/boot: Add bios_get_rsdp_addr() to search RSDP in memory
>>>   x86/boot: Parse SRAT table from RSDP and store immovable memory
>>>   x86/boot/KASLR: Limit KASLR to extracting kernel in immovable memory
>>> 
>>>  arch/x86/Kconfig                  |  10 +
>>>  arch/x86/boot/compressed/Makefile |   2 +
>>>  arch/x86/boot/compressed/acpitb.c | 322 ++++++++++++++++++++++++++++++
>>>  arch/x86/boot/compressed/kaslr.c  |  79 ++++++--
>>>  arch/x86/boot/compressed/misc.c   |   5 +
>>>  arch/x86/boot/compressed/misc.h   |  24 +++
>>>  lib/kstrtox.c                     |   5 +
>>>  7 files changed, 432 insertions(+), 15 deletions(-)
>>>  create mode 100644 arch/x86/boot/compressed/acpitb.c
>>> 
>>> -- 
>>> 2.19.1
>>> 
>>> 
>>> 
>>
>>

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