Xen devel - Nov 2010 - [PATCH] xen: fix section mismatch in reference from the function xen_hvm_init_shared_info()

From: Stefan Assmann <sassmann@redhat.com>

The following warning shows up when building the kernel with
make CONFIG_DEBUG_SECTION_MISMATCH=y.

WARNING: arch/x86/built-in.o(.text+0x475): Section mismatch in reference from
the function xen_hvm_init_shared_info() to the function .init.text:extend_brk()
The function xen_hvm_init_shared_info() references
the function __init extend_brk().
This is often because xen_hvm_init_shared_info lacks a __init
annotation or the annotation of extend_brk is wrong.

The problem is that xen_hvm_init_shared_info() calls extend_brk() which is
an __init function. However xen_hvm_init_shared_info() cannot be an
__init function as it''s called on system resume as well. Easy fix by
moving extend_brk() out of the function.

Signed-off-by: Stefan Assmann <sassmann@redhat.com>
---
 arch/x86/xen/enlighten.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 02c710b..13b11fd 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -83,6 +83,7 @@ EXPORT_SYMBOL(machine_to_phys_order);
 struct start_info *xen_start_info;
 EXPORT_SYMBOL_GPL(xen_start_info);

+struct shared_info *shared_info_page;
 struct shared_info xen_dummy_shared_info;

 void *xen_initial_gdt;
@@ -1310,11 +1311,7 @@ void xen_hvm_init_shared_info(void)
 {
 	int cpu;
 	struct xen_add_to_physmap xatp;
-	static struct shared_info *shared_info_page = 0;

-	if (!shared_info_page)
-		shared_info_page = (struct shared_info *)
-			extend_brk(PAGE_SIZE, PAGE_SIZE);
 	xatp.domid = DOMID_SELF;
 	xatp.idx = 0;
 	xatp.space = XENMAPSPACE_shared_info;
@@ -1365,6 +1362,9 @@ static void __init xen_hvm_guest_init(void)
 	if (r < 0)
 		return;

+	shared_info_page = (struct shared_info *)
+		extend_brk(PAGE_SIZE, PAGE_SIZE);
+
 	xen_hvm_init_shared_info();

 	if (xen_feature(XENFEAT_hvm_callback_vector))
-- 
1.7.3.2


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On Tue, 30 Nov 2010, Stefan Assmann wrote:
> From: Stefan Assmann <sassmann@redhat.com>
> 
> The following warning shows up when building the kernel with
> make CONFIG_DEBUG_SECTION_MISMATCH=y.
> 
> WARNING: arch/x86/built-in.o(.text+0x475): Section mismatch in reference
from the function xen_hvm_init_shared_info() to the function
.init.text:extend_brk()
> The function xen_hvm_init_shared_info() references
> the function __init extend_brk().
> This is often because xen_hvm_init_shared_info lacks a __init
> annotation or the annotation of extend_brk is wrong.
> 
> The problem is that xen_hvm_init_shared_info() calls extend_brk() which is
> an __init function. However xen_hvm_init_shared_info() cannot be an
> __init function as it''s called on system resume as well. Easy fix
by
> moving extend_brk() out of the function.
> 
> Signed-off-by: Stefan Assmann <sassmann@redhat.com>
> ---
>  arch/x86/xen/enlighten.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 02c710b..13b11fd 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -83,6 +83,7 @@ EXPORT_SYMBOL(machine_to_phys_order);
>  struct start_info *xen_start_info;
>  EXPORT_SYMBOL_GPL(xen_start_info);
> 
> +struct shared_info *shared_info_page;
>  struct shared_info xen_dummy_shared_info;
> 
>  void *xen_initial_gdt;
why not static?

> @@ -1310,11 +1311,7 @@ void xen_hvm_init_shared_info(void)
>  {
>  	int cpu;
>  	struct xen_add_to_physmap xatp;
> -	static struct shared_info *shared_info_page = 0;
> 
> -	if (!shared_info_page)
> -		shared_info_page = (struct shared_info *)
> -			extend_brk(PAGE_SIZE, PAGE_SIZE);
>  	xatp.domid = DOMID_SELF;
>  	xatp.idx = 0;
>  	xatp.space = XENMAPSPACE_shared_info;
> @@ -1365,6 +1362,9 @@ static void __init xen_hvm_guest_init(void)
>  	if (r < 0)
>  		return;
> 
> +	shared_info_page = (struct shared_info *)
> +		extend_brk(PAGE_SIZE, PAGE_SIZE);
> +
>  	xen_hvm_init_shared_info();
> 
>  	if (xen_feature(XENFEAT_hvm_callback_vector))
> -- 
> 1.7.3.2
> 
thanks for the patch,

Stefano

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On 01.12.2010 12:26, Stefano Stabellini wrote:
> On Tue, 30 Nov 2010, Stefan Assmann wrote:
>> From: Stefan Assmann <sassmann@redhat.com>
>>
>> The following warning shows up when building the kernel with
>> make CONFIG_DEBUG_SECTION_MISMATCH=y.
>>
>> WARNING: arch/x86/built-in.o(.text+0x475): Section mismatch in
reference from the function xen_hvm_init_shared_info() to the function
.init.text:extend_brk()
>> The function xen_hvm_init_shared_info() references
>> the function __init extend_brk().
>> This is often because xen_hvm_init_shared_info lacks a __init
>> annotation or the annotation of extend_brk is wrong.
>>
>> The problem is that xen_hvm_init_shared_info() calls extend_brk() which
is
>> an __init function. However xen_hvm_init_shared_info() cannot be an
>> __init function as it''s called on system resume as well. Easy
fix by
>> moving extend_brk() out of the function.
>>
>> Signed-off-by: Stefan Assmann <sassmann@redhat.com>
>> ---
>>  arch/x86/xen/enlighten.c |    8 ++++----
>>  1 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
>> index 02c710b..13b11fd 100644
>> --- a/arch/x86/xen/enlighten.c
>> +++ b/arch/x86/xen/enlighten.c
>> @@ -83,6 +83,7 @@ EXPORT_SYMBOL(machine_to_phys_order);
>>  struct start_info *xen_start_info;
>>  EXPORT_SYMBOL_GPL(xen_start_info);
>>
>> +struct shared_info *shared_info_page;
>>  struct shared_info xen_dummy_shared_info;
>>
>>  void *xen_initial_gdt;
> 
> why not static?
No particular reason, feel free to make it static. Thx for the review!

  Stefan
--
Stefan Assmann         | Red Hat GmbH
Software Engineer      | Otto-Hahn-Strasse 20, 85609 Dornach
                       | HR: Amtsgericht Muenchen HRB 153243
                       | GF: Brendan Lane, Charlie Peters,
sassmann at redhat.com |     Michael Cunningham, Charles Cachera

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