[patch] Nios II build_id fix

[patch] Nios II build_id fix

[Cesar Philippidis]

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LD isn't able to insert the build_id hash into the .note.gnu.build-id
section because write_build_id () relies on asection.size, which is set
to zero inside nios2_elf32_build_stubs () when that function allocates
memory for linker stubs. The fix is to have nios2_elf32_build_stubs ()
ignore non-stub sections, as done for the ARM targets. Other targets,
AVR specifically, may have a similar problem. However, I don't have
access to those targets, so I'm unable to test a patch for them.

This error manifests itself in gdb.base/sepdebug.exp, so it shouldn't
require a new test case. I've tested it on a nios2-elf target. Is it OK?
If so, please commit since I don't have an SVN account.

Thanks,
Cesar

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2014-04-04  Cesar Philippidis  <cesar@codesourcery.com>

	* bfd/elf32-nios2.c (nios2_elf32_build_stubs): Ignore non-stub
	sections when allocating memory for the linker stubs. 

Index: bfd/elf32-nios2.c
===================================================================
--- bfd/elf32-nios2.c	(revision 430086)
+++ bfd/elf32-nios2.c	(working copy)
@@ -2016,6 +2016,10 @@ nios2_elf32_build_stubs (struct bfd_link
     {
       bfd_size_type size;
 
+      /* Ignore non-stub sections.  */
+      if (!strstr (stub_sec->name, STUB_SUFFIX))
+	continue;
+      
       /* Allocate memory to hold the linker stubs.  */
       size = stub_sec->size;
       stub_sec->contents = bfd_zalloc (htab->stub_bfd, size);

Re: [patch] Nios II build_id fix

[Alan Modra]

On Fri, Apr 04, 2014 at 10:52:22AM -0700, Cesar Philippidis wrote:
> @@ -2016,6 +2016,10 @@ nios2_elf32_build_stubs (struct bfd_link
>      {
>        bfd_size_type size;
>  
> +      /* Ignore non-stub sections.  */
> +      if (!strstr (stub_sec->name, STUB_SUFFIX))
> +	continue;

Um, how do you manage to get non-stub sections in the stub bfd?  Hmm,
via dynobj being set to the stub bfd, I expect.  If so, you could
probably test (stub_sec->flags & SEC_LINKER_CREATED) == 0 instead.

-- 
Alan Modra
Australia Development Lab, IBM

Re: [patch] Nios II build_id fix

[Sandra Loosemore]

On 04/04/2014 07:31 PM, Alan Modra wrote:
> On Fri, Apr 04, 2014 at 10:52:22AM -0700, Cesar Philippidis wrote:
>> @@ -2016,6 +2016,10 @@ nios2_elf32_build_stubs (struct bfd_link
>>       {
>>         bfd_size_type size;
>>
>> +      /* Ignore non-stub sections.  */
>> +      if (!strstr (stub_sec->name, STUB_SUFFIX))
>> +	continue;
>
> Um, how do you manage to get non-stub sections in the stub bfd?  Hmm,
> via dynobj being set to the stub bfd, I expect.  If so, you could
> probably test (stub_sec->flags & SEC_LINKER_CREATED) == 0 instead.

I had the same question when looking at this code.  I think this also 
suffers from the same bug (PR 13049) mentioned in the comment on 
STUB_SUFFIX in elf32-arm.c.

Hmmmm.  I see that stub sections are being created without 
SEC_LINKER_CREATED (ld/emultempl/nios2elf.em), while dynamic sections 
created in dynobj do have that flag by default (from 
ELF_DYNAMIC_SEC_FLAGS).  Other sections that end up in dynobj maybe do, 
maybe don't -- it doesn't seem like a reliable way to distinguish stub 
sections from anything else, at least.

Maybe we could define a new section flag for actual stub sections? 
That's a target-independent change (bfd/section.c) and I couldn't 
approve it.  Alan, WDYT?

Otherwise, I suppose we're stuck with the same band-aid in the ARM 
backend....

-Sandra

Re: [patch] Nios II build_id fix

[Alan Modra]

On Sat, Apr 05, 2014 at 09:16:10PM -0600, Sandra Loosemore wrote:
> On 04/04/2014 07:31 PM, Alan Modra wrote:
> >On Fri, Apr 04, 2014 at 10:52:22AM -0700, Cesar Philippidis wrote:
> >>@@ -2016,6 +2016,10 @@ nios2_elf32_build_stubs (struct bfd_link
> >>      {
> >>        bfd_size_type size;
> >>
> >>+      /* Ignore non-stub sections.  */
> >>+      if (!strstr (stub_sec->name, STUB_SUFFIX))
> >>+	continue;
> >
> >Um, how do you manage to get non-stub sections in the stub bfd?  Hmm,
> >via dynobj being set to the stub bfd, I expect.  If so, you could
> >probably test (stub_sec->flags & SEC_LINKER_CREATED) == 0 instead.
> 
> I had the same question when looking at this code.  I think this
> also suffers from the same bug (PR 13049) mentioned in the comment
> on STUB_SUFFIX in elf32-arm.c.
> 
> Hmmmm.  I see that stub sections are being created without
> SEC_LINKER_CREATED (ld/emultempl/nios2elf.em), while dynamic
> sections created in dynobj do have that flag by default (from
> ELF_DYNAMIC_SEC_FLAGS).  Other sections that end up in dynobj maybe
> do, maybe don't

What other sections?  I don't think there will be any.  You'll either
have stub sections or dynobj sections.  The latter all have
SEC_LINKER_CREATED, the former doesn't.

I handle exactly the same situation in elf64-ppc.c, where dynobj is
forced to be the stub bfd, without resorting to testing for
STUB_SUFFIX in the name.

Note that elf32-arm.c only needs to test for the stub name because the
ARM backend does create other sections (glue, veneer) in the stub bfd
besides stub sections.  nios2 doesn't, as far as I can see.

-- 
Alan Modra
Australia Development Lab, IBM

Re: [patch] Nios II build_id fix

[Cesar Philippidis]

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On 4/5/14, 10:12 PM, Alan Modra wrote:
> On Sat, Apr 05, 2014 at 09:16:10PM -0600, Sandra Loosemore wrote:
>> On 04/04/2014 07:31 PM, Alan Modra wrote:
>>> On Fri, Apr 04, 2014 at 10:52:22AM -0700, Cesar Philippidis wrote:
>>>> @@ -2016,6 +2016,10 @@ nios2_elf32_build_stubs (struct bfd_link
>>>>      {
>>>>        bfd_size_type size;
>>>>
>>>> +      /* Ignore non-stub sections.  */
>>>> +      if (!strstr (stub_sec->name, STUB_SUFFIX))
>>>> +	continue;
>>>
>>> Um, how do you manage to get non-stub sections in the stub bfd?  Hmm,
>>> via dynobj being set to the stub bfd, I expect.  If so, you could
>>> probably test (stub_sec->flags & SEC_LINKER_CREATED) == 0 instead.
>>
>> I had the same question when looking at this code.  I think this
>> also suffers from the same bug (PR 13049) mentioned in the comment
>> on STUB_SUFFIX in elf32-arm.c.
>>
>> Hmmmm.  I see that stub sections are being created without
>> SEC_LINKER_CREATED (ld/emultempl/nios2elf.em), while dynamic
>> sections created in dynobj do have that flag by default (from
>> ELF_DYNAMIC_SEC_FLAGS).  Other sections that end up in dynobj maybe
>> do, maybe don't
> 
> What other sections?  I don't think there will be any.  You'll either
> have stub sections or dynobj sections.  The latter all have
> SEC_LINKER_CREATED, the former doesn't.
> 
> I handle exactly the same situation in elf64-ppc.c, where dynobj is
> forced to be the stub bfd, without resorting to testing for
> STUB_SUFFIX in the name.
> 
> Note that elf32-arm.c only needs to test for the stub name because the
> ARM backend does create other sections (glue, veneer) in the stub bfd
> besides stub sections.  nios2 doesn't, as far as I can see.

Checking for dynobjs seemed to work out. I've tested this patch on both
ELF and Linux Nios II targets. Is it OK?

Thanks,
Cesar


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2014-04-08  Cesar Philippidis  <cesar@codesourcery.com>

	bfd/
	* elf32-nios2.c (nios2_elf32_build_stubs): Ignore dynobjs
	when building function stubs.
	

Index: bfd/elf32-nios2.c
===================================================================
--- bfd/elf32-nios2.c	(revision 430290)
+++ bfd/elf32-nios2.c	(working copy)
@@ -2013,16 +2013,18 @@ nios2_elf32_build_stubs (struct bfd_link
   for (stub_sec = htab->stub_bfd->sections;
        stub_sec != NULL;
        stub_sec = stub_sec->next)
-    {
-      bfd_size_type size;
-
-      /* Allocate memory to hold the linker stubs.  */
-      size = stub_sec->size;
-      stub_sec->contents = bfd_zalloc (htab->stub_bfd, size);
-      if (stub_sec->contents == NULL && size != 0)
-	return FALSE;
-      stub_sec->size = 0;
-    }
+    /* A dynobj may be forced to be a stub bfd, so ignore it here.  */
+    if ((stub_sec->flags & SEC_LINKER_CREATED) == 0)
+      {  
+	bfd_size_type size;
+
+	/* Allocate memory to hold the linker stubs.  */
+	size = stub_sec->size;
+	stub_sec->contents = bfd_zalloc (htab->stub_bfd, size);
+	if (stub_sec->contents == NULL && size != 0)
+	  return FALSE;
+	stub_sec->size = 0;
+      }
 
   /* Build the stubs as directed by the stub hash table.  */
   table = &htab->bstab;

Re: [patch] Nios II build_id fix

[Sandra Loosemore]

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On 04/08/2014 06:15 PM, Cesar Philippidis wrote:
>
> Checking for dynobjs seemed to work out. I've tested this patch on both
> ELF and Linux Nios II targets. Is it OK?

Thanks.  I've checked in this version, with expanded comments to better 
explain what is going on.

-Sandra


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2014-04-10  Cesar Philippidis  <cesar@codesourcery.com>

	bfd/
	* elf32-nios2.c (nios2_elf32_build_stubs): Ignore dynobjs
	when building function stubs.

[-- Attachment #3: binutils-buildid.patch --]
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diff --git a/bfd/elf32-nios2.c b/bfd/elf32-nios2.c
index 3a44f1d..678f2e3 100644
--- a/bfd/elf32-nios2.c
+++ b/bfd/elf32-nios2.c
@@ -2013,16 +2013,21 @@ nios2_elf32_build_stubs (struct bfd_link_info *info)
   for (stub_sec = htab->stub_bfd->sections;
        stub_sec != NULL;
        stub_sec = stub_sec->next)
-    {
-      bfd_size_type size;
-
-      /* Allocate memory to hold the linker stubs.  */
-      size = stub_sec->size;
-      stub_sec->contents = bfd_zalloc (htab->stub_bfd, size);
-      if (stub_sec->contents == NULL && size != 0)
-	return FALSE;
-      stub_sec->size = 0;
-    }
+    /* The stub_bfd may contain non-stub sections if it is also the
+       dynobj.  Any such non-stub sections are created with the
+       SEC_LINKER_CREATED flag set, while stub sections do not
+       have that flag.  Ignore any non-stub sections here.  */
+    if ((stub_sec->flags & SEC_LINKER_CREATED) == 0)
+      {  
+	bfd_size_type size;
+
+	/* Allocate memory to hold the linker stubs.  */
+	size = stub_sec->size;
+	stub_sec->contents = bfd_zalloc (htab->stub_bfd, size);
+	if (stub_sec->contents == NULL && size != 0)
+	  return FALSE;
+	stub_sec->size = 0;
+      }
 
   /* Build the stubs as directed by the stub hash table.  */
   table = &htab->bstab;