Subject: Re: bug#20614: Segmentation fault when building on Power8 Little Endian

From: Petr Hracek <[email-masked]>
Date: Thu, 1 Oct 2015 13:44:01 +0200

On 10/01/2015 09:43 AM, Eli Zaretskii wrote:
>> From: Petr Hracek <[email-masked]>
>> Date: Wed, 30 Sep 2015 12:39:47 +0200
>> Cc: [email-masked]
>>
>> My deep observation with emacs package and binutils:
>> 1) binutils-2.23.52.0.1-30.el7_1.2.ppc64le.rpm works completely.
>> 2) binutils-2.23.52.0.1-40.el7.ppc64le.rpm works if row
>> http://git.savannah.gnu.org/cgit/emacs.git/tree/src/unexelf.c?h=emacs-24#n869
>> is suppressed.
>>
>> With newer version of binutils I can see the same series:(
>> like:
>> Dumping under the name emacs
>> emacs: Program segment above .bss in
>> /builddir/build/BUILD/emacs-24.3/src/temacs
>> make[2]: Leaving directory `/builddir/build/BUILD/emacs-24.3/src'
>> make[2]: *** [bootstrap-emacs] Error 1
>>
>> I have collected list of commits and messages against upstream:
>> #1200138
>> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=43a8475ca01b676fb764aaed0c4ed1cc16fc3c87 #1200138
>> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=eec2f3ed9f053653ed5d629eb50e08e3ee61e9bd #1203449
>> https://bugzilla.redhat.com/attachment.cgi?id=1003499 # 1175624 .opd
>> https://sourceware.org/ml/binutils/2015-01/msg00227.html
>> # 1175624 .got which implies .sdata, .sbss, .plt .iplt and .branch_lt also have
>> to move: https://sourceware.org/ml/binutils/2015-01/msg00228.html
>> # 1175624 And .toc1: https://sourceware.org/ml/binutils/2015-01/msg00232.html
>> #1194164 func@localentry expressions, which was added to FSF binutils with git
>> commit 45965137
>> #1183838 https://bugzilla.redhat.com/attachment.cgi?id=986213
>> # 1172766 https://bugzilla.redhat.com/attachment.cgi?id=989450 I hope it helps
>> you a bit.
> I think we need help from someone who understands the Binutils part of
> this.  Can you ask some of the Binutils maintainers please join this
> discussion and analyze the problem?
Out binutils maintainers send me reference to following patch.
|# Fix incorrectly generated ELF binaries and DSOs|

diff -Nrup a/bfd/elf.c b/bfd/elf.c
--- a/bfd/elf.c	2015-07-28 10:52:10.941754850 -0600
+++ b/bfd/elf.c	2015-07-28 10:53:34.725982912 -0600
@@ -4081,11 +4081,18 @@ _bfd_elf_map_sections_to_segments (bfd *
  	      new_segment = TRUE;
  	    }
  	  else if ((last_hdr->flags & (SEC_LOAD | SEC_THREAD_LOCAL)) == 0
-		   && (hdr->flags & (SEC_LOAD | SEC_THREAD_LOCAL)) != 0)
+		   && (hdr->flags & (SEC_LOAD | SEC_THREAD_LOCAL)) != 0
+		   && ((abfd->flags & D_PAGED) == 0
+		       || (((last_hdr->lma + last_size - 1) & -maxpagesize)
+			   != (hdr->lma & -maxpagesize))))
  	    {
-	      /* We don't want to put a loadable section after a
-		 nonloadable section in the same segment.
-		 Consider .tbss sections as loadable for this purpose.  */
+	      /* We don't want to put a loaded section after a
+		 nonloaded (ie. bss style) section in the same segment
+		 as that will force the non-loaded section to be loaded.
+		 Consider .tbss sections as loaded for this purpose.
+		 However, like the writable/non-writable case below,
+		 if they are on the same page then they must be put
+		 in the same segment.  */
  	      new_segment = TRUE;
  	    }
  	  else if ((abfd->flags & D_PAGED) == 0)
diff -Nrup a/ld/testsuite/ld-powerpc/elfv2so.d b/ld/testsuite/ld-powerpc/elfv2so.d
--- a/ld/testsuite/ld-powerpc/elfv2so.d	2015-07-28 10:52:10.921755273 -0600
+++ b/ld/testsuite/ld-powerpc/elfv2so.d	2015-07-28 10:41:10.046732001 -0600
@@ -7,31 +7,31 @@
  
  Disassembly of section \.text:
  
-0+320 <.*\.plt_call\.f4>:
+0+300 <.*\.plt_call\.f4>:
  .*:	(18 00 41 f8|f8 41 00 18) 	std     r2,24\(r1\)
  .*:	(38 80 82 e9|e9 82 80 38) 	ld      r12,-32712\(r2\)
  .*:	(a6 03 89 7d|7d 89 03 a6) 	mtctr   r12
  .*:	(20 04 80 4e|4e 80 04 20) 	bctr
  
-0+330 <.*\.plt_call\.f3>:
+0+310 <.*\.plt_call\.f3>:
  .*:	(18 00 41 f8|f8 41 00 18) 	std     r2,24\(r1\)
  .*:	(28 80 82 e9|e9 82 80 28) 	ld      r12,-32728\(r2\)
  .*:	(a6 03 89 7d|7d 89 03 a6) 	mtctr   r12
  .*:	(20 04 80 4e|4e 80 04 20) 	bctr
  
-0+340 <.*\.plt_call\.f2>:
+0+320 <.*\.plt_call\.f2>:
  .*:	(18 00 41 f8|f8 41 00 18) 	std     r2,24\(r1\)
  .*:	(30 80 82 e9|e9 82 80 30) 	ld      r12,-32720\(r2\)
  .*:	(a6 03 89 7d|7d 89 03 a6) 	mtctr   r12
  .*:	(20 04 80 4e|4e 80 04 20) 	bctr
  
-0+350 <.*\.plt_call\.f1>:
+0+330 <.*\.plt_call\.f1>:
  .*:	(18 00 41 f8|f8 41 00 18) 	std     r2,24\(r1\)
  .*:	(40 80 82 e9|e9 82 80 40) 	ld      r12,-32704\(r2\)
  .*:	(a6 03 89 7d|7d 89 03 a6) 	mtctr   r12
  .*:	(20 04 80 4e|4e 80 04 20) 	bctr
  
-0+360 <f1>:
+0+340 <f1>:
  .*:	(02 00 4c 3c|3c 4c 00 02) 	addis   r2,r12,2
  .*:	(d8 81 42 38|38 42 81 d8) 	addi    r2,r2,-32296
  .*:	(a6 02 08 7c|7c 08 02 a6) 	mflr    r0
@@ -53,7 +53,7 @@ Disassembly of section \.text:
  .*:	(98 01 01 00|00 00 00 00) 	.*
  .*:	(00 00 00 00|00 01 01 98) 	.*
  
-0+3b0 <__glink_PLTresolve>:
+0+390 <__glink_PLTresolve>:
  .*:	(a6 02 08 7c|7c 08 02 a6) 	mflr    r0
  .*:	(05 00 9f 42|42 9f 00 05) 	bcl     .*
  .*:	(a6 02 68 7d|7d 68 02 a6) 	mflr    r11

-- 
Petr Hracek
Software Engineer
Developer Experience
Red Hat, Inc
Mob: +420777056169
email: [email-masked]