Bug 817645

Summary:	Receive WARNING of section mismatch in 3.3 kernel series
Product:	[Fedora] Fedora	Reporter:	stan <gryt2>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED ERRATA	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	17	CC:	gansalmon, gryt2, itamar, jonathan, kernel-maint, ketuzsezr, madhu.chinakonda
Target Milestone:	---
Target Release:	---
Hardware:	x86_64
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-07-05 18:51:53 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description stan 2012-04-30 18:06:49 UTC

Description of problem:
When compiling a kernel, the linker issues a warning.  I'm not sure I even understand the error and recommended fix.

Version-Release number of selected component (if applicable):
Any linux 3.3 series kernel.

How reproducible:
Every time.

Steps to Reproduce:
1. Configure a kernel using make menuconfig
2. Use rpmbuild to build with the custom configuration
3. Warning occurs in output.
  
Actual results:

WARNING: arch/x86/kernel/built-in.o(.data+0x500): Section mismatch in reference from the variable x86_ioapic to the function .init.text:native_ioapic_init_mappings()
The variable x86_ioapic references
the function __init native_ioapic_init_mappings()
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

Expected results:
No warning.

Additional info:  
I don't expect any resolution of this, just posting it so there is a note made of it.  The 3.3 kernels I've compiled have run fine despite the warning, but this seems like the kind of thing that could create subtle intermittent bugs.

Comment 1 Josh Boyer 2012-04-30 19:57:37 UTC

This is coming from the x86-apic_ops-Replace-apic_ops-with-x86_apic_ops.patch we're carrying.  It means the x86_ioapic global variable, which is a structure containing a pointer to various ioapic operations, has it's .init member set to native_ioapic_init_mappings.  That function is annotated as __init, which means the kernel will discard the memory that function occupies after the init portion of kernel boot is done.

It sounds really scary, but I don't think it actually causes a problem in practice as nothing will be calling x86_ioapic.init outside of the very early setup_arch code.

Still, it's a valid warning and one that might be better fixed.

Konrad, what's the status of this patch upstream and is this warning fixed in a subsequent version of the patch that we have missed?

Comment 2 stan 2012-04-30 22:37:54 UTC

Thanks for the explanation.  I didn't catch all of it, but enough to understand why the kernels worked just fine.

Comment 3 Josh Boyer 2012-07-05 18:51:53 UTC

The patches in question were committed to the 3.4 kernel (or some version of them).  Closing this out.

Comment 4 stan 2012-07-05 21:13:35 UTC

Great!  Thanks a lot.