linux-kernel - Re: 3.12 to 3.13 boot regression bisected

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Message-ID: <20140805141142.437ecb17@pluto>
Date:	Tue, 5 Aug 2014 14:11:42 +0200
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	P J P <ppandit@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: 3.12 to 3.13 boot regression bisected - still applies to 3.16

On Tue, 5 Aug 2014 13:51:30 +0200 Bruno Prémont wrote:

> On Tue, 5 Aug 2014 10:18:48 +0100 Matt Fleming wrote:
> > On Tue, 05 Aug, at 11:13:30AM, Bruno Prémont wrote:
> > > 
> > > I get at least to just before
> > >   status = efi_call_early(exit_boot_services, handle, key);
> > > in eboot.c on line 1310. A efi_printk inserted there is displayed.
> > 
> > This is worth pointing out in case you're unaware, but do you know that
> > it's not valid to call efi_printk() after ExitBootServices()? Doing so
> > will almost certainly cause your machine to fault.
> 
> I am aware that efi_printk() uses boot services!
> 
> 
> Now I tried out loops at many places and have gotten up to line 340 in
> 
>   arch/x86/kernel/head_64.S

oops, bad copy&paste, should have been
  arch/x86/boot/compressed/head_64.S

> System reboots within the following assembler instructions (does not
> reach line 359).
> 
> So efi_main() returns successfully but the assembler code following it
> gets something wrong.
> 
> I'm going to try further to determine which line between 340 and 359 is
> the "bad" one.

arch/x86/boot/compressed/head_64.S
341 /*
342  * Copy the compressed kernel to the end of our buffer
343  * where decompression in place becomes safe.
344  */
345         pushq   %rsi
346         leaq    (_bss-8)(%rip), %rsi
347         leaq    (_bss-8)(%rbx), %rdi
348         movq    $_bss /* - $startup_32 */, %rcx
349         shrq    $3, %rcx
350         std

code gets up to here

351         rep     movsq

this location is never reached but instead system reboots

352         cld
353         popq    %rsi
354 
355 /*      
356  * Jump to the relocated address.
357  */
 


Bruno
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