linux-kernel - Re: [PATCH v7 22/27] binfmt_elf: Extract .note.gnu.property from an ELF file

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Date:   Tue, 18 Jun 2019 18:05:24 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     Dave Martin <Dave.Martin@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, 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@...capital.net>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...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>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>
Subject: Re: [PATCH v7 22/27] binfmt_elf: Extract .note.gnu.property from an ELF file

* Yu-cheng Yu:

>> I assumed that it would also parse the main executable and make
>> adjustments based on that.
>
> Yes, Linux also looks at the main executable's header, but not its
> NT_GNU_PROPERTY_TYPE_0 if there is a loader.
>
>> 
>> ld.so can certainly provide whatever the kernel needs.  We need to tweak
>> the existing loader anyway.
>> 
>> No valid statically-linked binaries exist today, so this is not a
>> consideration at this point.
>
> So from kernel, we look at only PT_GNU_PROPERTY?

If you don't parse notes/segments in the executable for CET, then yes.
We can put PT_GNU_PROPERTY into the loader.

Thanks,
Florian