2015-11-12 21:40:04

by Laura Abbott

[permalink] [raw]
Subject: Section mismatches in arch/powerpc/kernel/head_64.S

Hi,

There seem to be section mismatches coming from head_64.S

WARNING: vmlinux.o(.text+0x8994): Section mismatch in reference from the
variable __boot_from_prom to the function .init.text:prom_init()
The function __boot_from_prom() references
the function __init prom_init().
This is often because __boot_from_prom lacks a __init
annotation or the annotation of prom_init is wrong.

WARNING: vmlinux.o(.text+0x8c30): Section mismatch in reference from the
variable start_here_multiplatform to the function .init.text:early_setup()
The function start_here_multiplatform() references
the function __init early_setup().
This is often because start_here_multiplatform lacks a __init
annotation or the annotation of early_setup is wrong.

WARNING: vmlinux.o(.text+0x8c54): Section mismatch in reference from the
variable start_here_common to the function .init.text:setup_system()
The function start_here_common() references
the function __init setup_system().
This is often because start_here_common lacks a __init
annotation or the annotation of setup_system is wrong.

WARNING: vmlinux.o(.text+0x8c68): Section mismatch in reference from the
variable start_here_common to the function .init.text:start_kernel()
The function start_here_common() references
the function __init start_kernel().
This is often because start_here_common lacks a __init
annotation or the annotation of start_kernel is wrong.

FATAL: modpost: Section mismatches detected.
Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.
scripts/Makefile.modpost:97: recipe for target 'vmlinux.o' failed

These were noticed when I accidentally turned off CONFIG_SECTION_MISMATCH_WARN_ONLY
(see https://bugzilla.redhat.com/show_bug.cgi?id=1281446) which now
makes them a compilation failure. Config attached. Currently just working
around this by keeping that option on.

Thanks,
Laura


Attachments:
kernel-4.4.0-ppc64le.config (140.08 kB)

2015-11-16 00:50:50

by Michael Ellerman

[permalink] [raw]
Subject: Re: Section mismatches in arch/powerpc/kernel/head_64.S

Hi Laura,

On Thu, 2015-11-12 at 13:39 -0800, Laura Abbott wrote:
> Hi,

> There seem to be section mismatches coming from head_64.S
>
> WARNING: vmlinux.o(.text+0x8994): Section mismatch in reference from the
> variable __boot_from_prom to the function .init.text:prom_init()
> The function __boot_from_prom() references
> the function __init prom_init().
> This is often because __boot_from_prom lacks a __init
> annotation or the annotation of prom_init is wrong.
>
> WARNING: vmlinux.o(.text+0x8c30): Section mismatch in reference from the
> variable start_here_multiplatform to the function .init.text:early_setup()
> The function start_here_multiplatform() references
> the function __init early_setup().
> This is often because start_here_multiplatform lacks a __init
> annotation or the annotation of early_setup is wrong.
>
> WARNING: vmlinux.o(.text+0x8c54): Section mismatch in reference from the
> variable start_here_common to the function .init.text:setup_system()
> The function start_here_common() references
> the function __init setup_system().
> This is often because start_here_common lacks a __init
> annotation or the annotation of setup_system is wrong.
>
> WARNING: vmlinux.o(.text+0x8c68): Section mismatch in reference from the
> variable start_here_common to the function .init.text:start_kernel()
> The function start_here_common() references
> the function __init start_kernel().
> This is often because start_here_common lacks a __init
> annotation or the annotation of start_kernel is wrong.

These all look correct, ie. they are references from non-init code to init
code. I don't think any of them are real bugs, because that is all early boot
code anyway which should never run after boot, or if it did that would be a big
anyway.

I'm not sure how we fix them. Some of that code might be able to be moved out
of head_64.S and made __init, but then you just have the same problem again.

It looks like x86 calls through a pointer and marks that as __REFDATA, but
that's kind of gross just to avoid a section mismatch warning.

So I'm not sure what the solution is here.

cheers

2015-11-16 11:42:38

by Denis Kirjanov

[permalink] [raw]
Subject: Re: Section mismatches in arch/powerpc/kernel/head_64.S

On 11/13/15, Laura Abbott <[email protected]> wrote:
> Hi,
>
> There seem to be section mismatches coming from head_64.S
>
> WARNING: vmlinux.o(.text+0x8994): Section mismatch in reference from the
> variable __boot_from_prom to the function .init.text:prom_init()
> The function __boot_from_prom() references
> the function __init prom_init().
> This is often because __boot_from_prom lacks a __init
> annotation or the annotation of prom_init is wrong.
>
> WARNING: vmlinux.o(.text+0x8c30): Section mismatch in reference from the
> variable start_here_multiplatform to the function .init.text:early_setup()
> The function start_here_multiplatform() references
> the function __init early_setup().
> This is often because start_here_multiplatform lacks a __init
> annotation or the annotation of early_setup is wrong.
>
> WARNING: vmlinux.o(.text+0x8c54): Section mismatch in reference from the
> variable start_here_common to the function .init.text:setup_system()
> The function start_here_common() references
> the function __init setup_system().
> This is often because start_here_common lacks a __init
> annotation or the annotation of setup_system is wrong.
>
> WARNING: vmlinux.o(.text+0x8c68): Section mismatch in reference from the
> variable start_here_common to the function .init.text:start_kernel()
> The function start_here_common() references
> the function __init start_kernel().
> This is often because start_here_common lacks a __init
> annotation or the annotation of start_kernel is wrong.
>
> FATAL: modpost: Section mismatches detected.
> Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.
> scripts/Makefile.modpost:97: recipe for target 'vmlinux.o' failed
>
> These were noticed when I accidentally turned off
> CONFIG_SECTION_MISMATCH_WARN_ONLY
> (see https://bugzilla.redhat.com/show_bug.cgi?id=1281446) which now
> makes them a compilation failure. Config attached. Currently just working
> around this by keeping that option on.

Looks like something new because I haven't seen these warnings. I'll
check what can be done here...

Thanks!
>
> Thanks,
> Laura
>