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From: Ingo Molnar <mingo@kernel.org>
To: Hou Wenlong <houwenlong.hwl@antgroup.com>
Cc: linux-kernel@vger.kernel.org,
	Lai Jiangshan <jiangshan.ljs@antgroup.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"maintainer:X86 ARCHITECTURE 32-BIT AND 64-BIT" <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Mike Rapoport <rppt@kernel.org>,
	Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: Re: [PATCH RFC 1/7] x86/head/64: Mark startup_gdt and startup_gdt_descr as __initdata
Date: Tue, 17 Oct 2023 15:02:27 +0200	[thread overview]
Message-ID: <ZS6F46vJfca5f6f8@gmail.com> (raw)
In-Reply-To: <20231017072311.GA46993@k08j02272.eu95sqa>


* Hou Wenlong <houwenlong.hwl@antgroup.com> wrote:

> Hi Ingo,
> 
> I have sent patch #6 separately for x86. Do you have any ideas about 
> building the head code as PIE? Should I resend the patchset for the PIE 
> feature?

So I had a brief look, and despite reading 0/43 it was unclear to me what 
the precise advantages of building as PIE are.

Ie. could you please outline:

 - *Exactly* how much PIE based KASLR randomization would gain us in terms 
   of randomization granularity and effective number of randomization bits, 
   compared to the current status quo?

 - How is code generation changed at the instruction level - how does 
   kernel size change and what are the micro-advantages/disadvantages?

 - Are there any other advantages/motivation than improving KASLR?

Ie. before asking us to apply ~50 patches and add a whole new build mode 
and the maintainance overhead to support it into infinity and beyond, could 
you please offer a better list of pros and cons?

Thanks,

	Ingo

  reply	other threads:[~2023-10-17 13:02 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-12  3:30 [PATCH RFC 0/7] x86/head/64: Build the head code as PIE Hou Wenlong
2023-07-12  3:30 ` [PATCH RFC 1/7] x86/head/64: Mark startup_gdt and startup_gdt_descr as __initdata Hou Wenlong
2023-10-16 11:57   ` Ingo Molnar
2023-10-17  7:23     ` Hou Wenlong
2023-10-17 13:02       ` Ingo Molnar [this message]
2023-10-17 16:34         ` H. Peter Anvin
2023-10-18 11:45           ` Ingo Molnar
2023-11-10  0:03             ` Josh Poimboeuf
2023-10-18  8:36         ` Hou Wenlong
2023-07-12  3:30 ` [PATCH RFC 2/7] x86/head/64: Add missing __head annotation to startup_64_load_idt() Hou Wenlong
2023-07-12  3:30 ` [PATCH RFC 3/7] x86/head/64: Move all head code from head64.c into another file Hou Wenlong
2023-07-12  3:30 ` [PATCH RFC 4/7] x86/boot/compressed: Adapt sed command if head code is built as PIE Hou Wenlong
2023-07-12  3:30 ` [PATCH RFC 5/7] x86/head/64: Build the head code " Hou Wenlong
2023-07-12  3:30 ` [PATCH RFC 6/7] x86/sme: Mark code as __head in mem_encrypt_identity.c Hou Wenlong
2023-07-12  3:30 ` [PATCH RFC 7/7] x86/sme: Build the code in mem_encrypt_identity.c as PIE Hou Wenlong

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