hwrng: virtio - Rename driver object to remove section mismatch warning
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Message ID 20091211153658.GA1207@gondor.apana.org.au
State New, archived
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Series
  • hwrng: virtio - Rename driver object to remove section mismatch warning
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Commit Message

Herbert Xu Dec. 11, 2009, 3:36 p.m. UTC 
Hi:

Finally found the cause of the section mismatch warning in hwrng.
Apparently in addition to __devexit_p we now have to name the
variable in a certain way.

I'll add this patch.

commit 8afb602bb676ed7da3cba154f2f5edf3971a582b
Author: Herbert Xu <herbert@gondor.apana.org.au>
Date:   Fri Dec 11 23:35:06 2009 +0800

    hwrng: virtio - Rename driver object to remove section mismatch warning
    
    The section mismatch warning shows up unless the __devexit referencing
    variable is named in a certain way.
    
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Comments

Matt Mackall Dec. 11, 2009, 7:25 p.m. UTC | #1 
On Fri, 2009-12-11 at 23:36 +0800, Herbert Xu wrote:
> Hi:
> 
> Finally found the cause of the section mismatch warning in hwrng.
> Apparently in addition to __devexit_p we now have to name the
> variable in a certain way.

That's fairly appalling. Any idea why?
Randy Dunlap Dec. 11, 2009, 8:08 p.m. UTC | #2 
On Fri, 11 Dec 2009 13:25:57 -0600 Matt Mackall wrote:

> On Fri, 2009-12-11 at 23:36 +0800, Herbert Xu wrote:
> > Hi:
> > 
> > Finally found the cause of the section mismatch warning in hwrng.
> > Apparently in addition to __devexit_p we now have to name the
> > variable in a certain way.
> 
> That's fairly appalling. Any idea why?

(I haven't read the rest of this thread..)

scripts/mod/modpost.c looks for certain variable names to identify
variables that can have references to other (non-data) sections.
It's mostly explained there.

(added cc: Sam)

---
~Randy
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Sam Ravnborg Dec. 12, 2009, 12:21 a.m. UTC | #3 
On Fri, Dec 11, 2009 at 12:08:49PM -0800, Randy Dunlap wrote:
> On Fri, 11 Dec 2009 13:25:57 -0600 Matt Mackall wrote:
> 
> > On Fri, 2009-12-11 at 23:36 +0800, Herbert Xu wrote:
> > > Hi:
> > > 
> > > Finally found the cause of the section mismatch warning in hwrng.
> > > Apparently in addition to __devexit_p we now have to name the
> > > variable in a certain way.
> > 
> > That's fairly appalling. Any idea why?
> 
> (I haven't read the rest of this thread..)
> 
> scripts/mod/modpost.c looks for certain variable names to identify
> variables that can have references to other (non-data) sections.
> It's mostly explained there.

Another option is to annotate the relevant variable.

>From init.h:
/* modpost check for section mismatches during the kernel build.
 * A section mismatch happens when there are references from a
 * code or data section to an init section (both code or data).
 * The init sections are (for most archs) discarded by the kernel
 * when early init has completed so all such references are potential bugs.
 * For exit sections the same issue exists.
 * The following markers are used for the cases where the reference to
 * the *init / *exit section (code or data) is valid and will teach
 * modpost not to issue a warning.
 * The markers follow same syntax rules as __init / __initdata. */
#define __ref            __section(.ref.text) noinline
#define __refdata        __section(.ref.data)
#define __refconst       __section(.ref.rodata)

	Sam
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Matt Mackall Dec. 12, 2009, 12:33 a.m. UTC | #4 
On Sat, 2009-12-12 at 01:21 +0100, Sam Ravnborg wrote:
> On Fri, Dec 11, 2009 at 12:08:49PM -0800, Randy Dunlap wrote:
> > On Fri, 11 Dec 2009 13:25:57 -0600 Matt Mackall wrote:
> > 
> > > On Fri, 2009-12-11 at 23:36 +0800, Herbert Xu wrote:
> > > > Hi:
> > > > 
> > > > Finally found the cause of the section mismatch warning in hwrng.
> > > > Apparently in addition to __devexit_p we now have to name the
> > > > variable in a certain way.
> > > 
> > > That's fairly appalling. Any idea why?
> > 
> > (I haven't read the rest of this thread..)
> > 
> > scripts/mod/modpost.c looks for certain variable names to identify
> > variables that can have references to other (non-data) sections.
> > It's mostly explained there.
> 
> Another option is to annotate the relevant variable.

Ok, I guess I knew about the annotations. So I take it the name magic
exists just for convenience or to hit the common cases?
Sam Ravnborg Dec. 12, 2009, 7:21 a.m. UTC | #5 
On Fri, Dec 11, 2009 at 06:33:17PM -0600, Matt Mackall wrote:
> On Sat, 2009-12-12 at 01:21 +0100, Sam Ravnborg wrote:
> > On Fri, Dec 11, 2009 at 12:08:49PM -0800, Randy Dunlap wrote:
> > > On Fri, 11 Dec 2009 13:25:57 -0600 Matt Mackall wrote:
> > > 
> > > > On Fri, 2009-12-11 at 23:36 +0800, Herbert Xu wrote:
> > > > > Hi:
> > > > > 
> > > > > Finally found the cause of the section mismatch warning in hwrng.
> > > > > Apparently in addition to __devexit_p we now have to name the
> > > > > variable in a certain way.
> > > > 
> > > > That's fairly appalling. Any idea why?
> > > 
> > > (I haven't read the rest of this thread..)
> > > 
> > > scripts/mod/modpost.c looks for certain variable names to identify
> > > variables that can have references to other (non-data) sections.
> > > It's mostly explained there.
> > 
> > Another option is to annotate the relevant variable.
> 
> Ok, I guess I knew about the annotations. So I take it the name magic
> exists just for convenience or to hit the common cases?

The name magic was introduced first - and by this we covered a
lot of common cases.
But we could not rename everything and thus we invented
the annotation.

The annotation ar preferable to the name magic becuse they
1) follow the usual way to tell that something is special
2) that it documents that this data structure have deliberate
  access to *init/*exit sections

So the preference should be to use annotations over name magic.
[Maybe text from modpost needs an update to reflect this...]

	Sam
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Patch
diff mbox series 

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index bdaef8e..64fe0a7 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -114,7 +114,7 @@  static struct virtio_device_id id_table[] = {
 	{ 0 },
 };
 
-static struct virtio_driver virtio_rng = {
+static struct virtio_driver virtio_rng_driver = {
 	.driver.name =	KBUILD_MODNAME,
 	.driver.owner =	THIS_MODULE,
 	.id_table =	id_table,
@@ -124,12 +124,12 @@  static struct virtio_driver virtio_rng = {
 
 static int __init init(void)
 {
-	return register_virtio_driver(&virtio_rng);
+	return register_virtio_driver(&virtio_rng_driver);
 }
 
 static void __exit fini(void)
 {
-	unregister_virtio_driver(&virtio_rng);
+	unregister_virtio_driver(&virtio_rng_driver);
 }
 module_init(init);
 module_exit(fini);