[PATCH] modules: don't export section names of empty sections via sysfs

[PATCH] modules: don't export section names of empty sections via sysfs

[Helge Deller]

[PATCH] modules: don't export section names of empty sections via sysfs

On the parisc architecture we face for each and every loaded kernel module
this kernel "badness warning":
  sysfs: cannot create duplicate filename '/module/ac97_bus/sections/.text'
  Badness at fs/sysfs/dir.c:487

Reason for that is, that on parisc all kernel modules do have multiple
.text sections due to the usage of the -ffunction-sections compiler flag
which is needed to reach all jump targets on this platform.

An objdump on such a kernel module gives:
Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .note.gnu.build-id 00000024  00000000  00000000  00000034  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA            
  1 .text         00000000  00000000  00000000  00000058  2**0     
                  CONTENTS, ALLOC, LOAD, READONLY, CODE            
  2 .text.ac97_bus_match 0000001c  00000000  00000000  00000058  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE              
  3 .text         00000000  00000000  00000000  000000d4  2**0       
                  CONTENTS, ALLOC, LOAD, READONLY, CODE              
...
Since the .text sections are empty (size of 0 bytes) and won't be
loaded by the kernel module loader anyway, I don't see a reason
why such sections need to be listed under 
/sys/module/<module_name>/sections/<section_name> either.

The attached patch does solve this issue by not exporting section
names which are empty.

This fixes bugzilla http://bugzilla.kernel.org/show_bug.cgi?id=14703

Signed-off-by: Helge Deller <deller@gmx.de>
CC: rusty@rustcorp.com.au
CC: akpm@linux-foundation.org
CC: James.Bottomley@HansenPartnership.com
CC: roland@redhat.com
CC: dave@hiauly1.hia.nrc.ca

diff --git a/kernel/module.c b/kernel/module.c
index 8b7d880..5842a71 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1187,7 +1187,8 @@ static void add_sect_attrs(struct module *mod, unsigned int nsect,
 
 	/* Count loaded sections and allocate structures */
 	for (i = 0; i < nsect; i++)
-		if (sechdrs[i].sh_flags & SHF_ALLOC)
+		if (sechdrs[i].sh_flags & SHF_ALLOC
+		    && sechdrs[i].sh_size)
 			nloaded++;
 	size[0] = ALIGN(sizeof(*sect_attrs)
 			+ nloaded * sizeof(sect_attrs->attrs[0]),
@@ -1207,6 +1208,8 @@ static void add_sect_attrs(struct module *mod, unsigned int nsect,
 	for (i = 0; i < nsect; i++) {
 		if (! (sechdrs[i].sh_flags & SHF_ALLOC))
 			continue;
+		if (!sechdrs[i].sh_size)
+			continue;
 		sattr->address = sechdrs[i].sh_addr;
 		sattr->name = kstrdup(secstrings + sechdrs[i].sh_name,
 					GFP_KERNEL);

Re: [PATCH] modules: don't export section names of empty sections via sysfs

[Rusty Russell]

On Thu, 3 Dec 2009 09:59:15 am Helge Deller wrote:
> [PATCH] modules: don't export section names of empty sections via sysfs

Thanks, applied.

Ah, I see Linus snuck this in before the release.  Excellent.
Rusty.

Re: [PATCH] modules: don't export section names of empty sections via sysfs

[James Bottomley]

On Thu, 2009-12-03 at 17:50 +1030, Rusty Russell wrote:
> On Thu, 3 Dec 2009 09:59:15 am Helge Deller wrote:
> > [PATCH] modules: don't export section names of empty sections via sysfs
> 
> Thanks, applied.
> 
> Ah, I see Linus snuck this in before the release.  Excellent.

That's great.  The next step is probably to find out why the toolchain
is doing this ... generating zero length allocated segments seems to be
somewhat deviant behaviour ...

James

Re: [PATCH] modules: don't export section names of empty sections via sysfs

[Kyle McMartin]

On Thu, Dec 03, 2009 at 05:50:41PM +1030, Rusty Russell wrote:
> On Thu, 3 Dec 2009 09:59:15 am Helge Deller wrote:
> > [PATCH] modules: don't export section names of empty sections via sysfs
> 
> Thanks, applied.
> 
> Ah, I see Linus snuck this in before the release.  Excellent.
> Rusty.
> 

Thanks Rusty, Helge!

cheers, Kyle