[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[amodra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

Alan Modra  changed:

   What|Removed |Added

 Resolution|--- |FIXED
 Status|NEW |RESOLVED

--- Comment #44 from Alan Modra  ---
Closing as fixed.  Yes, there are still targets that don't have all the
required support, but they tend to be targets where PIEs aren't of much
interest.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[amodra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

Alan Modra  changed:

   What|Removed |Added

 Target|aarch64, tilepro,ppc|am33,arc,bfin,frv,hppa64,ia
   ||64,m32r,m68k,metag,nds32,or
   ||1k,s390,tilepro

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #43 from cvs-commit at gcc dot gnu.org  ---
The binutils-2_35-branch branch has been updated by Hans-Peter Nilsson
:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ef6b667ead5c32c7d26fa58f1f86f70a662b

commit ef6b667ead5c32c7d26fa58f1f86f70a662b
Author: Hans-Peter Nilsson 
Date:   Tue Sep 15 03:59:06 2020 +0200

CRIS: fix PR ld/26589, a missing NULL check in fix for PR ld/22269

Not sure why there wasn't a NULL check in the ld/22269 patch
(e01c16a8) at the time, as there was one for the corresponding patch
to elf32-m68k.c (5056ba1d).

Incidentally, I had missed that in 2017, as a prerequisite for the
ld/22269 series, the check_relocs function finally were made "safe"!
(I.e. the number of references and symbol types are final, garbage
collection done, so port-specific accounting can be made sanely.)

Committed.

bfd:
PR ld/26589
* elf32-cris.c (cris_elf_check_relocs): Add missing NULL check
on argument before calling UNDEFWEAK_NO_DYNAMIC_RELOC.

ld:
PR ld/26589
* testsuite/ld-elf/pr26589.d, testsuite/ld-elf/locref3.s: New test.

(cherry picked from commit 4a8f181d196f85ca153fe51ca6bb40942e0e1ed7)

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #42 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by Hans-Peter Nilsson :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4a8f181d196f85ca153fe51ca6bb40942e0e1ed7

commit 4a8f181d196f85ca153fe51ca6bb40942e0e1ed7
Author: Hans-Peter Nilsson 
Date:   Tue Sep 15 02:57:39 2020 +0200

CRIS: fix PR ld/26589, a missing NULL check in fix for PR ld/22269

Not sure why there wasn't a NULL check in the ld/22269 patch
(e01c16a8) at the time, as there was one for the corresponding patch
to elf32-m68k.c (5056ba1d).

Incidentally, I had missed that in 2017, as a prerequisite for the
ld/22269 series, the check_relocs function finally were made "safe"!
(I.e. the number of references and symbol types are final, garbage
collection done, so port-specific accounting can be made sanely.)

Committed.

bfd:
PR ld/26589
* elf32-cris.c (cris_elf_check_relocs): Add missing NULL check
on argument before calling UNDEFWEAK_NO_DYNAMIC_RELOC.

ld:
PR ld/26589
* testsuite/ld-elf/pr26589.d, testsuite/ld-elf/locref3.s: New test.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #41 from cvs-commit at gcc dot gnu.org  ---
The binutils-2_33-branch branch has been updated by Szabolcs Nagy
:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=6fbcfe4762c3732339cffd82426d00d35382b858

commit 6fbcfe4762c3732339cffd82426d00d35382b858
Author: Szabolcs Nagy 
Date:   Thu Jan 9 17:20:56 2020 +

[PR ld/22269] arm: Avoid dynamic relocs for undefweak symbols in static PIE

With static PIE linking undefined weak symbols are resolved to 0, so no
dynamic relocation is needed for them. The UNDEFWEAK_NO_DYNAMIC_RELOC
macro was introduced so this case can be handled easily, but it was not
applied consistently in the first attempt to fix ld/22269 for arm:

  commit 95b03e4ad68e7a90f5096b47df595636344b783a
  arm: Check UNDEFWEAK_NO_DYNAMIC_RELOC

This patch fixes spurious relative relocs in static PIE binaries against
GOT entries created for undefined weak symbols on arm*-*, this fixes

FAIL: pr22269-1 (static pie undefined weak)

bfd/ChangeLog:

Backported from master
2020-01-10  Szabolcs Nagy  

PR ld/22269
* elf32-arm.c (elf32_arm_final_link_relocate): Use
UNDEFWEAK_NO_DYNAMIC_RELOC.
(allocate_dynrelocs_for_symbol): Likewise.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #40 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by Szabolcs Nagy :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=7f02673206eaef00f240b84c21069b4e5fbe09ea

commit 7f02673206eaef00f240b84c21069b4e5fbe09ea
Author: Szabolcs Nagy 
Date:   Thu Jan 9 17:20:56 2020 +

[PR ld/22269] arm: Avoid dynamic relocs for undefweak symbols in static PIE

With static PIE linking undefined weak symbols are resolved to 0, so no
dynamic relocation is needed for them. The UNDEFWEAK_NO_DYNAMIC_RELOC
macro was introduced so this case can be handled easily, but it was not
applied consistently in the first attempt to fix ld/22269 for arm:

  commit 95b03e4ad68e7a90f5096b47df595636344b783a
  arm: Check UNDEFWEAK_NO_DYNAMIC_RELOC

This patch fixes spurious relative relocs in static PIE binaries against
GOT entries created for undefined weak symbols on arm*-*, this fixes

FAIL: pr22269-1 (static pie undefined weak)

bfd/ChangeLog:

PR ld/22269
* elf32-arm.c (elf32_arm_final_link_relocate): Use
UNDEFWEAK_NO_DYNAMIC_RELOC.
(allocate_dynrelocs_for_symbol): Likewise.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[patrick.oppenlander at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

patrick.oppenlander at gmail dot com changed:

   What|Removed |Added

 CC||patrick.oppenlander at gmail 
dot c
   ||om

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[nszabolcs at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #39 from Szabolcs Nagy  ---
(In reply to Alan Modra from comment #37)
> I agree that there shouldn't be relative relocs on anything to do with foo. 
> But a pattern that matches those but not relative relocs for powerpc64 on
> the opd entry for _start is a little tricky.  Hmm, let me see what I can do.

thanks the test now does show the bug on arm,
i'll try to fix that when i get some time.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #38 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by Alan Modra :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ef0cc92e9cd7a589e441389167a8d4fb2fe46367

commit ef0cc92e9cd7a589e441389167a8d4fb2fe46367
Author: Alan Modra 
Date:   Tue Oct 22 07:42:58 2019 +1030

Don't allow RELATIVE relocs in pr22269 testcase

At least, not in the GOT.  R_PPC64_RELATIVE is fine for powerpc64 in
the .opd section.

PR 22269
* testsuite/ld-elf/pr22269-1.rd: Look for GOT section NONE and
RELATIVE relocs.
* testsuite/ld-elf/shared.exp (pr22269-1): Give test a better
name.  Use -z nocombreloc.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[amodra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #37 from Alan Modra  ---
I agree that there shouldn't be relative relocs on anything to do with foo. 
But a pattern that matches those but not relative relocs for powerpc64 on the
opd entry for _start is a little tricky.  Hmm, let me see what I can do.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[nszabolcs at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

Szabolcs Nagy  changed:

   What|Removed |Added

 CC||nszabolcs at gmail dot com

--- Comment #36 from Szabolcs Nagy  ---
on arm with -static -pie

extern int foo __attribute ((weak));

int
_start ()
{
  if ()
return foo;
}

has a R_*_RELATIVE reloc which is wrong in pie for undef weak syms.

i think the ld-elf/pr22269-1.rd test should reject relative relocs too.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #35 from cvs-commit at gcc dot gnu.org  ---
The binutils-2_31-branch branch has been updated by Max Filippov
:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=82f32155837415d3f84ceb9c9ffa36495f7211ae

commit 82f32155837415d3f84ceb9c9ffa36495f7211ae
Author: Max Filippov 
Date:   Mon Jul 2 11:12:44 2018 -0700

xtensa: don't emit dynamic relocation for weak undefined symbol

Resolved reference to a weak undefined symbol in PIE must not have
a dynamic relative relocation against itself, otherwise the value of a
reference will be changed from 0 to the base of executable, breaking
code like the following:

  void weak_function (void);
  if (weak_function)
weak_function ();

This fixes tests for PR ld/22269 and a number of PIE tests in xtensa gcc
testsuite.

bfd/
2018-07-11  Max Filippov  

* elf32-xtensa.c (elf_xtensa_allocate_dynrelocs): Don't allocate
space for dynamic relocation for undefined weak symbol.
(elf_xtensa_relocate_section): Don't emit R_XTENSA_RELATIVE
relocation for undefined weak symbols.
(shrink_dynamic_reloc_sections): Don't shrink dynamic relocation
section for relocations against undefined weak symbols.

(cherry picked from commit c451bb34ae8bd2d0669bd563366883cfbcf0de9b)

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #34 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by Max Filippov :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=c451bb34ae8bd2d0669bd563366883cfbcf0de9b

commit c451bb34ae8bd2d0669bd563366883cfbcf0de9b
Author: Max Filippov 
Date:   Mon Jul 2 11:12:44 2018 -0700

xtensa: don't emit dynamic relocation for weak undefined symbol

Resolved reference to a weak undefined symbol in PIE must not have
a dynamic relative relocation against itself, otherwise the value of a
reference will be changed from 0 to the base of executable, breaking
code like the following:

  void weak_function (void);
  if (weak_function)
weak_function ();

This fixes tests for PR ld/22269 and a number of PIE tests in xtensa gcc
testsuite.

bfd/
2018-07-06  Max Filippov  

* elf32-xtensa.c (elf_xtensa_allocate_dynrelocs): Don't allocate
space for dynamic relocation for undefined weak symbol.
(elf_xtensa_relocate_section): Don't emit R_XTENSA_RELATIVE
relocation for undefined weak symbols.
(shrink_dynamic_reloc_sections): Don't shrink dynamic relocation
section for relocations against undefined weak symbols.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #33 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by Eric Botcazou :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=185cdb8cc7c0102140d41fb6272a5ee4d72d

commit 185cdb8cc7c0102140d41fb6272a5ee4d72d
Author: Eric Botcazou 
Date:   Tue Jan 30 00:21:57 2018 +0100

 Adjust test for PR ld/22269.

 On the SPARC architecture, you need to pass a special flag to GNU as
 when you're assembling PIC/PIE code or else you get a wrong relocation
 for the GOT symbol.

ld/
* testsuite/ld-elf/shared.exp (AFLAGS_PIC): Define on SPARC.
(pr22269-1): Pass AFLAGS_PIC to the assembler.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #32 from H.J. Lu  ---
(In reply to Egeyar Bagcioglu from comment #31)
> The new test case PR22269-1 fails on sparc with the following message:
>  
> /home/egeyar/repos/binutils-obj/ld/ld-new: read-only segment has dynamic
> relocations.

Sparc linker is broken.  Someone needs to fix it.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[egeyar.bagcioglu at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

Egeyar Bagcioglu  changed:

   What|Removed |Added

 CC||egeyar.bagcioglu at oracle dot 
com

--- Comment #31 from Egeyar Bagcioglu  ---
The new test case PR22269-1 fails on sparc with the following message:

/home/egeyar/repos/binutils-obj/ld/ld-new: read-only segment has dynamic
relocations.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #30 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by Szabolcs Nagy :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a377ae2ad683d3c16ae74dba440ee441120a7d8a

commit a377ae2ad683d3c16ae74dba440ee441120a7d8a
Author: Szabolcs Nagy 
Date:   Wed Nov 15 15:56:30 2017 +

[PR ld/22269] aarch64: Handle local undefined weak symbols

With static pie linking undefined weak symbols are forced to resolve
locally
to 0, so no GOT setup is needed in elfNN_aarch64_finish_dynamic_symbol,
which previously failed for these symbols.

The failure caused the unhelpful error message:
"ld: final link failed: Nonrepresentable section on output"

bfd/
PR ld/22269
* elfnn-aarch64.c (elfNN_aarch64_finish_dynamic_symbol): Use
UNDEFWEAK_NO_DYNAMIC_RELOC to avoid dynamic GOT relocs.
(elfNN_aarch64_allocate_dynrelocs): Likewise.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #29 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by Alan Modra :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d336fa6d820f50235c271ea327fadbf4ff6e1edd

commit d336fa6d820f50235c271ea327fadbf4ff6e1edd
Author: Alan Modra 
Date:   Fri Oct 27 15:04:25 2017 +1030

Fix hppa-linux pr22269-1 fail

Adds UNDEFWEAK_NO_DYNAMIC_RELOC in the rest of places needed in this
file, reduces dynamic relocations in a number of cases, and removes
some bogus code that was attempting to handle dynamic common symbols
specially.

PR 22269
* elf32-hppa.c (elf32_hppa_check_relocs): Move SEC_ALLOC test to
ensure non_got_ref is not set due to debug references.
(elf32_hppa_adjust_dynamic_symbol): Tidy plabel handling.  Use
SYMBOL_CALLS_LOCAL and UNDEFWEAK_NO_DYNAMIC_RELOC when determining
need for a plt entry.
(allocate_dynrelocs): Similarly for got entries.  Tidy code discarding
dynamic relocs when pic.  Remove bogus code attempting to handle
commons.
(elf32_hppa_relocate_section): Similarly.  Delete resolved_to_zero
and simplify.
(elf32_hppa_finish_dynamic_symbol): Use UNDEFWEAK_NO_DYNAMIC_RELOC
and SYMBOL_REFERENCES_LOCAL in GOT handling.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #28 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f3012016f008030b48597b578a5fb1e550907374

commit f3012016f008030b48597b578a5fb1e550907374
Author: H.J. Lu 
Date:   Fri Oct 20 09:47:08 2017 -0700

Add a compile-time test for PR ld/22269

This compile-time test requires a target C compiler to run.  It fails
on many targets where ELF backend linkers fail to check undefined weak
symbol in static PIE via UNDEFWEAK_NO_DYNAMIC_RELOC.

PR ld/22269
* testsuite/ld-elf/pr22269-1.rd: New file.
* testsuite/ld-elf/pr22269-1.c: Likewise.
* testsuite/ld-elf/shared.exp: Run pr22269-1.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #27 from H.J. Lu  ---
For aarch64:

[hjl@gnu-skl-1 pr22269]$ cat x.c
extern int foo __attribute ((weak));

int
_start ()
{
  if ()
return foo;
}
[hjl@gnu-skl-1 pr22269]$ make
/export/gnu/import/git/toolchain/install/compilers/aarch64-linux-gnu/bin/aarch64-glibc-linux-gnu-gcc
-O2 -fPIE   -c -o x.o x.c
/export/gnu/import/git/toolchain/install/compilers/aarch64-linux-gnu/bin/aarch64-glibc-linux-gnu-ld
-pie --no-dynamic-linker x.o
/export/gnu/import/git/toolchain/install/compilers/aarch64-linux-gnu/bin/aarch64-glibc-linux-gnu-ld:
final link failed: Nonrepresentable section on output
make: *** [Makefile:14: x] Error 1
[hjl@gnu-skl-1 pr22269]$

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #26 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e01c16a83893b03433c8edf4ccae536d9b9f4831

commit e01c16a83893b03433c8edf4ccae536d9b9f4831
Author: H.J. Lu 
Date:   Sat Oct 14 11:09:29 2017 -0700

cris: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

bfd/

PR ld/22269
* elf32-cris.c (cris_elf_relocate_section): Don't generate
dynamic relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(cris_elf_check_relocs): Don't allocate dynamic relocation
if UNDEFWEAK_NO_DYNAMIC_RELOC is true.

ld/

PR ld/22269
* testsuite/ld-cris/weakhiddso.d: Update and remove R_CRIS_NONE.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #25 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=6ee6e05af482b356f9be4b0db877802fb47b2a12

commit 6ee6e05af482b356f9be4b0db877802fb47b2a12
Author: H.J. Lu 
Date:   Sat Oct 14 11:07:18 2017 -0700

sh: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elf32-sh.c (allocate_dynrelocs): Discard dynamic relocations
if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(sh_elf_relocate_section): Don't generate dynamic relocation if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #24 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b27bb18f45a99330600ab57892c3620343425910

commit b27bb18f45a99330600ab57892c3620343425910
Author: H.J. Lu 
Date:   Sat Oct 14 11:06:00 2017 -0700

s390: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elf32-s390.c (allocate_dynrelocs): Discard dynamic
relocations if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(elf_s390_relocate_section): Don't generate dynamic relocation
if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
* elf64-s390.c (allocate_dynrelocs): Discard dynamic
relocations if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(elf_s390_relocate_section): Don't generate dynamic relocation
if UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #23 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=31a53da5418528b9ba94bb80a97f0084f40e0c64

commit 31a53da5418528b9ba94bb80a97f0084f40e0c64
Author: H.J. Lu 
Date:   Sat Oct 14 11:04:32 2017 -0700

nios2: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elf32-nios2.c (nios2_elf32_relocate_section): Don't generate
dynamic relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(allocate_dynrelocs): Discard dynamic relocations if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #22 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=112fef4084ff0bdd6dd9aacca85f5fe62e1a5423

commit 112fef4084ff0bdd6dd9aacca85f5fe62e1a5423
Author: H.J. Lu 
Date:   Sat Oct 14 11:03:26 2017 -0700

microblaze: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elf32-microblaze.c (microblaze_elf_relocate_section): Don't
generate dynamic relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is
true.
(allocate_dynrelocs): Discard dynamic relocations if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #21 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5056ba1d4df19006b873bc8e752f85fcc712b65b

commit 5056ba1d4df19006b873bc8e752f85fcc712b65b
Author: H.J. Lu 
Date:   Sat Oct 14 11:02:20 2017 -0700

m68k: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elf32-m68k.c (elf_m68k_check_relocs): Don't allocate dynamic
relocations if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(elf_m68k_adjust_dynamic_symbol): Don't make symbol dynamic if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(elf_m68k_relocate_section): Don't generate dynamic relocation
if UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #20 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=60c1b909dfcc984f3aecb70032e90a34d71b44bc

commit 60c1b909dfcc984f3aecb70032e90a34d71b44bc
Author: H.J. Lu 
Date:   Sat Oct 14 10:54:50 2017 -0700

hppa: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elf32-hppa.c (ensure_undef_dynamic): Don't make undefined
symbol dynamic if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(allocate_dynrelocs): Discard dynamic relocations if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(elf32_hppa_relocate_section): Don't generate dynamic
relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #19 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=db41f6eb5234ea3c74c1ce4798cf9923d4a45a98

commit db41f6eb5234ea3c74c1ce4798cf9923d4a45a98
Author: H.J. Lu 
Date:   Sat Oct 14 10:53:43 2017 -0700

ia64: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elfnn-ia64.c (elfNN_ia64_check_relocs): Don't allocate
dynamic relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(allocate_fptr): Don't allocate function pointer if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(allocate_dynrel_entries): Don't allocate dynamic relocation
if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(set_got_entry): Don't set GOT entry if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(set_pltoff_entry): Don't set PLTOFF entry if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(elfNN_ia64_relocate_section): Don't install dynamic relocation
UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #18 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ad9512030937e79e28d08108fde7adf18635c58b

commit ad9512030937e79e28d08108fde7adf18635c58b
Author: H.J. Lu 
Date:   Sat Oct 14 10:52:12 2017 -0700

mips: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elfxx-mips.c (mips_elf_calculate_relocation): Don't generate
dynamic relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(allocate_dynrelocs): Don't allocate dynamic relocations if
UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #17 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=95b03e4ad68e7a90f5096b47df595636344b783a

commit 95b03e4ad68e7a90f5096b47df595636344b783a
Author: H.J. Lu 
Date:   Sat Oct 14 10:27:33 2017 -0700

arm: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elf32-arm.c (elf32_arm_final_link_relocate): Don't generate
dynamic relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(allocate_dynrelocs_for_symbol): Discard dynamic relocations
if UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #16 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a3cd202aae50abe5a571fb8c186b6b6af68edce2

commit a3cd202aae50abe5a571fb8c186b6b6af68edce2
Author: H.J. Lu 
Date:   Sat Oct 14 10:25:33 2017 -0700

tile: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elf32-tilepro.c (allocate_dynrelocs): Discard dynamic
relocations if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(tilepro_elf_relocate_section): Don't generate dynamic
relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
* elfxx-tilegx.c (allocate_dynrelocs): Discard dynamic
relocations if UNDEFWEAK_NO_DYNAMIC_RELOC is true.
(tilegx_elf_relocate_section): Don't generate dynamic
relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #15 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ddb7fd0f7b43e4c755c4b8c7752948e050363525

commit ddb7fd0f7b43e4c755c4b8c7752948e050363525
Author: H.J. Lu 
Date:   Sat Oct 14 10:23:48 2017 -0700

aarch64: Check UNDEFWEAK_NO_DYNAMIC_RELOC

Don't generate dynamic relocation against weak undefined symbol if it
is resolved to zero.  FIXME: UNDEFWEAK_NO_DYNAMIC_RELOC may need to be
checked in more places.

PR ld/22269
* elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Don't
generate dynamic relocation if UNDEFWEAK_NO_DYNAMIC_RELOC is
true.
(elfNN_aarch64_allocate_dynrelocs): Discard dynamic relocations
if UNDEFWEAK_NO_DYNAMIC_RELOC is true.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #14 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by Alan Modra :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=22b1ee183d19a92cc57859c04307d31c06792d13

commit 22b1ee183d19a92cc57859c04307d31c06792d13
Author: Alan Modra 
Date:   Thu Oct 12 13:19:10 2017 +1030

Set dynamic_undefined_weak to zero for static PIEs

I believe we should be warning if ld is given both --no-dynamic-linker
and -z dynamic-undefined-weak.  The two options are contradictory, the
first says an executable has no dynamic interpreter to resolve dynamic
symbols, while the second is asking for dynamic symbols to be emitted.
(And even if a static PIE's relocation code, which is needed to
process R_*_RELATIVE relocs, could process symbols, there are no
DT_NEEDED dynamic objects to define such symbols.)

I also think that dynamic_undefined_weak is the right flag to control
whether undefined weaks are made dynamic, whether in static PIEs or
anywhere else.  So force it to 0 for static PIEs, fixing PR 22269 for
powerpc and any other target where the backend usually defaults to
undefined weaks being made dynamic.

This patch introduces regressions.  I'd normally not do that, but
these are all in very recently added test cases, or expose bugs in the
x86 backend.  The test cases were added after I'd made it known that
this patch or one like it was imminent.

PR 22269
* emultempl/elf32.em (after_parse): Warn on --no-dynamic-linker
-z dynamic-undefined-weak combination.  Set dynamic_undefined_weak
to zero when nointerp.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #13 from H.J. Lu  ---
(In reply to Alan Modra from comment #11)
> > If there is a program bug:
> > ...
> > may lead to undesired behavior.
> 
> Quite so.
> 
> > -z dynamic-undefined-weak applies if there is a DT_NEEDED entry which
> > may provide definition for undefined weak reference at run-time.  For static
> > PIE, weak undefined should always be resolved to 0.
> 
> I agree, which is why I felt it was a good idea to default
> link_info.dynamic_undefined_weak to 0 when link_info.nointerp.

That is fine as long as "-z dynamic-undefined-weak" doesn't change
undefined weak symbol resolution in static PIE.

> Also, --no-dynamic-linker -z dynamic-undefined-weak probably ought to be an
> error, or at least warn.

Either is OK with me as long as undefined weak symbol is resolved to
0 in static PIE.

> However, making that change (or explicitly passing -z
> nodynamic-undefined-weak) results in x86 tests that fail, due to not
> generating a plt entry for the undefined weak call.  No matter how I look at

They fail because of undefined weak symbols in dynamic symbol table which
should be expected.  But undefined weak symbols are still resolved to 0 at
link-time.  I checked a few testcases to verify it.

> it, that is a bug in the x86 backend: link_info.dynamic_undefined_weak
> should not control the generation of a plt entry.  (I'm also of the opinion
> that adding a plt entry for an undefined weak without dynamic relocs is just
> bloat, but that's a separate issue and one I don't care to argue about.)

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #12 from cvs-commit at gcc dot gnu.org  ---
The master branch has been updated by H.J. Lu :

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4b97e3893ed2af7bdb9dcaa34fae1a207e2d7042

commit 4b97e3893ed2af7bdb9dcaa34fae1a207e2d7042
Author: H.J. Lu 
Date:   Sat Oct 7 03:07:36 2017 -0700

Add 2 testcases for PR ld/22269

Since undefined weak symbols in static PIE are always resolved to 0 at
run-time, linker should resolve them as 0 at link-time, regardless of
whether "-z dynamic-undefined-weak" is used.  "-z dynamic-undefined-weak"
only makes undefined weak symbols dynamic, but doesn't change undefined
weak symbol resolution in static PIE at link-time.  These tests currently
pass on x86, but fails on many other targets.

The framework to resolve weak symbols in static PE at link-time is
posted at

https://sourceware.org/ml/binutils/2017-10/msg00087.html

which requires users/hjl/check_relocs branch to call check_relocs after
opening all inputs.  I will submit backend patches for failling targets
after merging users/hjl/check_relocs branch next.

* PR ld/22269
* testsuite/ld-elf/pr22269.s: New file.
* testsuite/ld-elf/pr22269a.d: Likewise.
* testsuite/ld-elf/pr22269b.d: Likewise.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[amodra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #11 from Alan Modra  ---
> If there is a program bug:
> ...
> may lead to undesired behavior.

Quite so.

> -z dynamic-undefined-weak applies if there is a DT_NEEDED entry which
> may provide definition for undefined weak reference at run-time.  For static
> PIE, weak undefined should always be resolved to 0.

I agree, which is why I felt it was a good idea to default
link_info.dynamic_undefined_weak to 0 when link_info.nointerp.

Also, --no-dynamic-linker -z dynamic-undefined-weak probably ought to be an
error, or at least warn.

However, making that change (or explicitly passing -z nodynamic-undefined-weak)
results in x86 tests that fail, due to not generating a plt entry for the
undefined weak call.  No matter how I look at it, that is a bug in the x86
backend: link_info.dynamic_undefined_weak should not control the generation of
a plt entry.  (I'm also of the opinion that adding a plt entry for an undefined
weak without dynamic relocs is just bloat, but that's a separate issue and one
I don't care to argue about.)

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #10 from H.J. Lu  ---
(In reply to Alan Modra from comment #9)
> > Since call is PC relative, this doesn't branch to address 0.
> 
> I don't see why this matters.  A symbol that resolves to zero without
> dynamic relocs in a PIE or shared lib results in an address of zero.  If
> that zero is in a PC-relative instruction then you get zero relative to the
> shared library or PIE base.  Typical code for dealing with weakly defined
> functions like
>   if (foo)
> foo ();
> will give you a load of zero (absolute) on the condition, but a relative
> zero for the call.

If there is a program bug:

  foo ();

without if (foo) check, PC relative branch to base may not crash and may
lead to undesired behavior.

> > This doesn't work with
> > 
> > -pie --no-dynamic-linker -z dynamic-undefined-weak
> 
> Define "doesn't work".  I would have said that combination of options ought
> to result in a dynamic reloc for "func" on the original testcase.  Which is
> what powerpc will do.  It may not work in the runtime environment for static
> PIE, but that's a different issue.  By passing -z dynamic-undefined-weak you
> asked for dynamic relocs!

-z dynamic-undefined-weak applies to there is a DT_NEEDED entry which
may provide definition for undefined weak reference at run-time.  For static
PIE, weak undefined should always be resolved to 0.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[amodra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #9 from Alan Modra  ---
> Since call is PC relative, this doesn't branch to address 0.

I don't see why this matters.  A symbol that resolves to zero without dynamic
relocs in a PIE or shared lib results in an address of zero.  If that zero is
in a PC-relative instruction then you get zero relative to the shared library
or PIE base.  Typical code for dealing with weakly defined functions like
  if (foo)
foo ();
will give you a load of zero (absolute) on the condition, but a relative zero
for the call.

> This doesn't work with
> 
> -pie --no-dynamic-linker -z dynamic-undefined-weak

Define "doesn't work".  I would have said that combination of options ought to
result in a dynamic reloc for "func" on the original testcase.  Which is what
powerpc will do.  It may not work in the runtime environment for static PIE,
but that's a different issue.  By passing -z dynamic-undefined-weak you asked
for dynamic relocs!

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #8 from H.J. Lu  ---
(In reply to Alan Modra from comment #4)
> I agree that undefined weak symbols probably ought to resolve to 0 in a
> static PIE.  To do that on ppc it would be reasonable to add the following
> to elf32.em after_parse
> 
>   if (link_info.dynamic_undefined_weak == -1
>   && link_info.nointerp)
> link_info.dynamic_undefined_weak = FALSE;
> 
> or perhaps something a little more specific to static PIE..

This doesn't work with

-pie --no-dynamic-linker -z dynamic-undefined-weak

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #7 from H.J. Lu  ---
(In reply to Alan Modra from comment #6)
> Why do you think the powerpc testcase should have no dynamic relocs?  The
> one dyanmic reloc is on a GOT slot (for  in y.c).  It looks fine to me.

Oops. I was looking at the wrong bug.  But PC relative branch in x86 case
still applies.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[amodra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #6 from Alan Modra  ---
Why do you think the powerpc testcase should have no dynamic relocs?  The one
dyanmic reloc is on a GOT slot (for  in y.c).  It looks fine to me.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #5 from H.J. Lu  ---
(In reply to Alan Modra from comment #4)
> I agree that undefined weak symbols probably ought to resolve to 0 in a
> static PIE.  To do that on ppc it would be reasonable to add the following
> to elf32.em after_parse
> 
>   if (link_info.dynamic_undefined_weak == -1
>   && link_info.nointerp)
> link_info.dynamic_undefined_weak = FALSE;

For powerpc, I got

[hjl@gnu-efi-2 pr22263]$ cat x.c
__thread int * foo;

void
bar (void)
{
  *foo = 1;
}
[hjl@gnu-efi-2 pr22263]$ cat y.c
extern __thread int *foo;

static int x;

extern void bar (void);

int
_start ()
{
  foo = 
  return 0;
}
[hjl@gnu-efi-2 pr22263]$ make
/export/gnu/import/git/toolchain/install/compilers/powerpc-linux-gnu/bin/powerpc-glibc-linux-gnu-gcc
-fPIE -O2   -c -o x.o x.c
/export/gnu/import/git/toolchain/install/compilers/powerpc-linux-gnu/bin/powerpc-glibc-linux-gnu-gcc
-fPIE -O2   -c -o y.o y.c
./ld -pie -o x x.o y.o
readelf -rW x

Relocation section '.rela.dyn' at offset 0x1ac contains 1 entries:
 Offset InfoTypeSym. Value  Symbol's Name + Addend
0001ff68  0016 R_PPC_RELATIVE2
[hjl@gnu-efi-2 pr22263]$ 

There should be no dynamic relocations.

> or perhaps something a little more specific to static PIE..
> 
> However, that results in
> FAIL: ld-i386/pr19636-1d
> FAIL: ld-i386/pr19636-1e
> FAIL: ld-i386/pr19636-1f
> FAIL: ld-x86-64/pr19636-2d
> FAIL: ld-x86-64/pr19636-2e
> FAIL: ld-x86-64/pr19636-2f
> 
> So, why does x86 make undefined weak symbols dynamic in the -d tests (which
> are -pie --no-dynamic-linker)?

With your patch, I got

[hjl@gnu-efi-2 ld]$ cat
/export/gnu/import/git/sources/binutils-gdb/ld/testsuite/ld-x86-64/pr19636-2.s
.text
.weak func1
.weak func2
.weak func3
.globl _start
_start:
cmp func1@GOTPCREL(%rip),%rax
jmp *func2@GOTPCREL(%rip)
call func3@PLT
[hjl@gnu-efi-2 ld]$ cat 1
/export/build/gnu/binutils/build-x86_64-linux/ld/../gas/as-new  --64
-mrelax-relocations=no  -o tmpdir/pr19636-2.o
/export/gnu/import/git/sources/binutils-gdb/ld/testsuite/ld-x86-64/pr19636-2.s
./ld-new -z norelro 
-L/export/gnu/import/git/sources/binutils-gdb/ld/testsuite/ld-x86-64  -pie -m
elf_x86_64 --no-dynamic-linker --hash-style=sysv -o tmpdir/dump
tmpdir/pr19636-2.o 
/export/build/gnu/binutils/build-x86_64-linux/ld/../binutils/objdump  -dw
tmpdir/dump
[hjl@gnu-efi-2 ld]$ sh 1

tmpdir/dump: file format elf64-x86-64


Disassembly of section .text:

0111 <_start>:
 111:   48 3b 05 e0 00 20 00cmp0x2000e0(%rip),%rax# 2001f8
<.got>
 118:   ff 25 e2 00 20 00   jmpq   *0x2000e2(%rip)# 200200
<.got+0x8>
 11e:   e8 dd fe ff ff  callq  0 <_start-0x111>
^

Since call is PC relative, this doesn't branch to address 0.

[hjl@gnu-efi-2 ld]$ ld -z norelro 
-L/export/gnu/import/git/sources/binutils-gdb/ld/testsuite/ld-x86-64  -pie -m
elf_x86_64 --no-dynamic-linker --hash-style=sysv -o tmpdir/dump
tmpdir/pr19636-2.o 
[hjl@gnu-efi-2 ld]$ objdump  -dw tmpdir/dump

tmpdir/dump: file format elf64-x86-64


Disassembly of section .plt:

0120 <.plt>:
 120:   ff 35 2a 01 20 00   pushq  0x20012a(%rip)# 200250
<_GLOBAL_OFFSET_TABLE_+0x8>
 126:   ff 25 2c 01 20 00   jmpq   *0x20012c(%rip)# 200258
<_GLOBAL_OFFSET_TABLE_+0x10>
 12c:   0f 1f 40 00 nopl   0x0(%rax)
 130:   ff 25 2a 01 20 00   jmpq   *0x20012a(%rip)# 200260
<_GLOBAL_OFFSET_TABLE_+0x18>
 136:   68 00 00 00 00  pushq  $0x0
 13b:   e9 00 00 00 00  jmpq   140 <_start>

Disassembly of section .text:

0140 <_start>:
 140:   48 3b 05 f1 00 20 00cmp0x2000f1(%rip),%rax# 200238
<.got>
 147:   ff 25 f3 00 20 00   jmpq   *0x2000f3(%rip)# 200240
<.got+0x8>
 14d:   e8 de ff ff ff  callq  130 <.plt+0x10>
^^^

This branches to the PLT entry which branches to address 0 via indirect
GOT branch.

[hjl@gnu-efi-2 ld]$

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[amodra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #4 from Alan Modra  ---
I agree that undefined weak symbols probably ought to resolve to 0 in a static
PIE.  To do that on ppc it would be reasonable to add the following to elf32.em
after_parse

  if (link_info.dynamic_undefined_weak == -1
  && link_info.nointerp)
link_info.dynamic_undefined_weak = FALSE;

or perhaps something a little more specific to static PIE..

However, that results in
FAIL: ld-i386/pr19636-1d
FAIL: ld-i386/pr19636-1e
FAIL: ld-i386/pr19636-1f
FAIL: ld-x86-64/pr19636-2d
FAIL: ld-x86-64/pr19636-2e
FAIL: ld-x86-64/pr19636-2f

So, why does x86 make undefined weak symbols dynamic in the -d tests (which are
-pie --no-dynamic-linker)?

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

--- Comment #3 from H.J. Lu  ---
elfxx-x86.h has

/* Is a undefined weak symbol which is resolved to 0.  Reference to an
   undefined weak symbol is resolved to 0 when building executable if
   it isn't dynamic and
   1. Has non-GOT/non-PLT relocations in text section.  Or
   2. Has no GOT/PLT relocation.
   Local undefined weak symbol is always resolved to 0.
 */
#define UNDEFINED_WEAK_RESOLVED_TO_ZERO(INFO, EH) \
  ((EH)->elf.root.type == bfd_link_hash_undefweak\
   && (SYMBOL_REFERENCES_LOCAL_P ((INFO), &(EH)->elf)\
   || (bfd_link_executable (INFO)\
   && (!(EH)->has_got_reloc  \
   || (EH)->has_non_got_reloc

It may be useful for other targets.

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

H.J. Lu  changed:

   What|Removed |Added

 CC||amodra at gmail dot com

--- Comment #2 from H.J. Lu  ---
FYI, x86-64 has

[hjl@gnu-efi-2 glibc]$ gcc -c x.s
[hjl@gnu-efi-2 glibc]$ ld -pie --no-dynamic-linker x.o[hjl@gnu-efi-2 glibc]$
readelf -rl a.out 

Elf file type is DYN (Shared object file)
Entry point 0x169
There are 4 program headers, starting at offset 64

Program Headers:
  Type   Offset VirtAddr   PhysAddr
 FileSizMemSiz  Flags  Align
  LOAD   0x 0x 0x
 0x0170 0x0170  R E0x20
  LOAD   0x0f18 0x00200f18 0x00200f18
 0x00e8 0x00e8  RW 0x20
  DYNAMIC0x0f20 0x00200f20 0x00200f20
 0x00e0 0x00e0  RW 0x8
  GNU_RELRO  0x0f18 0x00200f18 0x00200f18
 0x00e8 0x00e8  R  0x1

 Section to Segment mapping:
  Segment Sections...
   00 .hash .gnu.hash .dynsym .dynstr .text 
   01 .data.rel.ro .dynamic 
   02 .dynamic 
   03 .data.rel.ro .dynamic 

There are no relocations in this file.
[hjl@gnu-efi-2 glibc]$ readelf -x .data.rel.ro a.out 

Hex dump of section '.data.rel.ro':
  0x00200f18     

[hjl@gnu-efi-2 glibc]$

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[Bug ld/22269] Undefined weak symbols isn't resolved to 0 in static PIE

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

H.J. Lu  changed:

   What|Removed |Added

 Target|aarch64 |aarch64, tilepro,ppc

--- Comment #1 from H.J. Lu  ---
For tilepro:

[hjl@gnu-efi-2 glibc]$
/export/gnu/import/git/toolchain/install/compilers/tilepro-linux-gnu/bin/tilepro-glibc-linux-gnu-gcc
-c x.s
[hjl@gnu-efi-2 glibc]$
/export/gnu/import/git/toolchain/install/compilers/tilepro-linux-gnu/bin/tilepro-glibc-linux-gnu-ld
-pie --no-dynamic-linker x.o
[hjl@gnu-efi-2 glibc]$ readelf -rl a.out 

Elf file type is DYN (Shared object file)
Entry point 0x128
There are 4 program headers, starting at offset 52

Program Headers:
  Type   Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD   0x00 0x 0x 0x00130 0x00130 R E 0x1
  LOAD   0x00ff78 0x0001ff78 0x0001ff78 0x00088 0x00088 RW  0x1
  DYNAMIC0x00ff7c 0x0001ff7c 0x0001ff7c 0x00080 0x00080 RW  0x4
  GNU_RELRO  0x00ff78 0x0001ff78 0x0001ff78 0x00088 0x00088 R   0x1

 Section to Segment mapping:
  Segment Sections...
   00 .hash .dynsym .dynstr .rela.dyn .text 
   01 .data.rel.ro .dynamic .got 
   02 .dynamic 
   03 .data.rel.ro .dynamic .got 

Relocation section '.rela.dyn' at offset 0x118 contains 1 entries:
 Offset InfoTypeSym.Value  Sym. Name + Addend
0001ff78  0301 R_TILEPRO_32     func + 0
[hjl@gnu-efi-2 glibc]$ 

For ppc,

[hjl@gnu-efi-2 glibc]$
/export/gnu/import/git/toolchain/install/compilers/powerpc-linux-gnu/bin/powerpc-glibc-linux-gnu-gcc
-c x.s
[hjl@gnu-efi-2 glibc]$
/export/gnu/import/git/toolchain/install/compilers/powerpc-linux-gnu/bin/powerpc-glibc-linux-gnu-ld
-pie --no-dynamic-linker x.o
[hjl@gnu-efi-2 glibc]$ readelf -rl a.out 

Elf file type is DYN (Shared object file)
Entry point 0x110
There are 4 program headers, starting at offset 52

Program Headers:
  Type   Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD   0x00 0x 0x 0x00114 0x00114 R E 0x1
  LOAD   0x00ff7c 0x0001ff7c 0x0001ff7c 0x00094 0x00094 RWE 0x1
  DYNAMIC0x00ff80 0x0001ff80 0x0001ff80 0x00080 0x00080 RW  0x4
  GNU_RELRO  0x00ff7c 0x0001ff7c 0x0001ff7c 0x00084 0x00084 R   0x1

 Section to Segment mapping:
  Segment Sections...
   00 .hash .dynsym .dynstr .rela.dyn .text 
   01 .data.rel.ro .dynamic .got 
   02 .dynamic 
   03 .data.rel.ro .dynamic 

Relocation section '.rela.dyn' at offset 0x104 contains 1 entries:
 Offset InfoTypeSym.Value  Sym. Name + Addend
0001ff7c  0201 R_PPC_ADDR32     func + 0
[hjl@gnu-efi-2 glibc]$

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