linux-kernel - Re: [PATCH v26 26/30] ELF: Introduce arch_setup_elf

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Message-ID: <d04259f1-a869-ec1c-aa74-93cd6c2c2d7b@intel.com>
Date:   Thu, 20 May 2021 10:18:10 -0700
From:   "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>,
        Mark Brown <broonie@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v26 26/30] ELF: Introduce arch_setup_elf_property()

On 5/20/2021 2:26 AM, Borislav Petkov wrote:
> On Wed, May 19, 2021 at 03:14:58PM -0700, Yu, Yu-cheng wrote:
>> However, those parsing functions take (struct arch_elf_state *) as an input.
> 
> Exactly.
> 
>> It probably makes sense to have ARCH_USE_GNU_PROPERTY dependent on
>> ARCH_BINFMT_ELF_STATE.  It would be ok as-is too.  ARM people might have
>> other plans in mind.
> 
> Well, let's look at ARM, ARM64 in particular. They have defined struct
> arch_elf_state without the ifdeffery in
> 
> arch/arm64/include/asm/elf.h
> 
> and are using that struct in arch_parse_elf_property().
> 
> And they have selected ARCH_BINFMT_ELF_STATE just so that they disable
> those dummy accessors in fs/binfmt_elf.c
> 
> And you're practically glueing together ARCH_BINFMT_ELF_STATE and
> ARCH_USE_GNU_PROPERTY. However, all the functionality is for adding
> the gnu property note so I think you should select both but only use
> ARCH_USE_GNU_PROPERTY in all the ifdeffery in your patch to at least
> have this as simple as possible.
> 

ARM64 has ARCH_USE_GNU_PROPERTY and ARCH_BINFMT_ELF_STATE selected 
unconditionally.  We will do the same for X86_64 and remove the ifdeffery.

>> I just looked at the ABI document.
> 
> Which document is that? Link?
> 
>> ARM has GNU_PROPERTY_AARCH64_FEATURE_1_AND 0xc0000000
>>
>> X86 has:
>> 	GNU_PROPERTY_X86_ISA_1_USED	0xc0000000
>> 	GNU_PROPERTY_X86_ISA_1_NEEDED	0xc0000001
>> 	GNU_PROPERTY_X86_FEATURE_1_AND	0xc0000002
> 
> Our defines should at least have a comment pointing to that document.
> 
> Thx.
> 

The latest pdf's are posted here.

https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/x86-64-psABI

Thanks,
Yu-cheng