Re: [BUG] 4.9.0 build error on Alpha

[Helge Deller <deller@gmx.de>]

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Hi Bob,

On 30.12.2016 17:02, Maciej W. Rozycki wrote:
> On Thu, 29 Dec 2016, Bob Tracy wrote:
> 
>>> I'm guessing it's another symptom of the old "kernel too big" problem?
>>
>> How has this been worked around in the past?  I have a fairly
>> feature-full kernel, but the only built-in drivers are for the things
>> that have to be present at boot time.
> 
>  This looks like a link ordering issue to me, the failures are branches 
> between objects built from arch/alpha/lib/*.S assembly sources, which 
> must have got moved apart more with the switch of the compiler version.

Seems right.
 
>  One workaround might be making them a .o rather than .a target, which 
> will ensure they're close to each other, at the cost of a small kernel 
> size increase if some of these functions would otherwise be unused.

Possible.

>  Replacing branches with full address calculation and register jumps might 
> be another, although this would cost some run time instead, so I think the 
> former approach is a bit better.

Another possibility could be to put all the lib functions into 
a "alphalib" section into the final vmlinux.
For that add at the top of each of the .S files in lib/ 
	.section .alphalib,"ax"
and apply the attached patch for arch/alpha/kernel/vmlinux.lds.S
Patch and suggestion is completely untested.

Helge

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diff --git a/arch/alpha/kernel/vmlinux.lds.S b/arch/alpha/kernel/vmlinux.lds.S
index cebecfb..88af6bc 100644
--- a/arch/alpha/kernel/vmlinux.lds.S
+++ b/arch/alpha/kernel/vmlinux.lds.S
@@ -20,6 +20,9 @@ SECTIONS
 	_text = .;	/* Text and read-only data */
 	.text : {
 		HEAD_TEXT
+		.alphalib: {
+			*(.alphalib)
+		} :kernel
 		TEXT_TEXT
 		SCHED_TEXT
 		CPUIDLE_TEXT