linux-kernel - Re: [ 76/94] x86, realmode: 16-bit real-mode code support for relocs tool

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Message-ID: <1338136652.20487.95.camel@deadeye>
Date:	Sun, 27 May 2012 17:37:32 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Jarkko Sakkinen <jarkko.sakkinen@....fi>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Jarkko Sakkinen <jarkko.sakkinen@...el.com>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [ 76/94] x86, realmode: 16-bit real-mode code support for
 relocs tool

On Sun, 2012-05-27 at 10:05 +0900, Greg KH wrote:
> 3.3-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: "H. Peter Anvin" <hpa@...ux.intel.com>
> 
> commit 6520fe5564acf07ade7b18a1272db1184835c487 upstream.
> 
> A new option is added to the relocs tool called '--realmode'.
> This option causes the generation of 16-bit segment relocations
> and 32-bit linear relocations for the real-mode code. When
> the real-mode code is moved to the low-memory during kernel
> initialization, these relocation entries can be used to
> relocate the code properly.
> 
> In the assembly code 16-bit segment relocations must be relative
> to the 'real_mode_seg' absolute symbol. Linear relocations must be
> relative to a symbol prefixed with 'pa_'.
> 
> 16-bit segment relocation is used to load cs:ip in 16-bit code.
> Linear relocations are used in the 32-bit code for relocatable
> data references. They are declared in the linker script of the
> real-mode code.
> 
> The relocs tool is moved to arch/x86/tools/relocs.c, and added new
> target archscripts that can be used to build scripts needed building
> an architecture.  be compiled before building the arch/x86 tree.
> 
> [ hpa: accelerating this because it detects invalid absolute
>   relocations, a serious bug in binutils 2.22.52.0.x which currently
>   produces bad kernels. ]
>
> [ jsakkine: applied against 3.3.7 ]
[...]

Are these relocs patches worth applying to 3.2.y as well?  This one
needs backporting (see attached).  The following 5 can be cleanly
cherry-picked after that.

Ben.

-- 
Ben Hutchings
The obvious mathematical breakthrough [to break modern encryption] would be
development of an easy way to factor large prime numbers. - Bill Gates

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