linux-kernel - Re: bug: kernel 3.0-rc3 not relocatable on i386?

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Message-ID: <4DF87D2B.7090201@gmail.com>
Date:	Wed, 15 Jun 2011 11:36:43 +0200
From:	Maarten Lankhorst <m.b.lankhorst@...il.com>
To:	Petr Tesarik <ptesarik@...e.cz>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: bug: kernel 3.0-rc3 not relocatable on i386?

Hi Petr,

Op 15-06-11 10:12, Petr Tesarik schreef:
> Hi all,
>
> it seems that the 3.0-rc3 kernel is not relocatable on i386. I get
> warnings about jiffies being an absolute symbol, and indeed, when GRUB
> loads the kernel at a non-default address, jiffies is not relocated.
>
> In my example the kernel is configured with
> CONFIG_PHYSICAL_START=0x1000000
> CONFIG_PHYSICAL_ALIGN=0x200000
> CONFIG_RELOCATABLE=y
> and loaded at 0x200000 by GRUB.
>
> Booting fails when checking whether the timer works, because do_timer()
> increments jiffies_64, but timer_irq_works() checks jiffies. The code
> looks like this:
>
> c13daab7:       8b 3d 40 7a 39 c1       mov    0xc1397a40,%edi
>
> but arch/x86/boot/compressed/vmlinux.relocs does not contain c13daaba.
> Consequently, timer_irq_works() reads the wrong memory location and
> fails, causing a panic:
>
> kernel panic: IO-APIC + timer doesn't work! Boot with apic=debug and
> send a report.  Then try booting with the 'noapic' option.
>
> Needless to say, the kernel freezes a few initcalls later when booted
> with noapic, because IO-APIC worked fine, in fact. I verified that by
> inserting a debugging printk() in do_timer(), and I also verified with
> that printk() that the address of jiffies_64 and the address of jiffies
> differ at run time.

Can you try this patch?

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 89aed99..49e666e 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -34,12 +34,11 @@ OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT)
 #ifdef CONFIG_X86_32
 OUTPUT_ARCH(i386)
 ENTRY(phys_startup_32)
-jiffies = jiffies_64;
 #else
 OUTPUT_ARCH(i386:x86-64)
 ENTRY(phys_startup_64)
-jiffies_64 = jiffies;
 #endif
+jiffies_64 = jiffies;
 
 #if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
 /*
--
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