Bug 23937

Summary:	powerpc64le local ifunc IRELATIVE relocs are wrong
Product:	binutils	Reporter:	Alan Modra <amodra>
Component:	ld	Assignee:	Alan Modra <amodra>
Status:	RESOLVED FIXED
Severity:	normal	CC:	fweimer
Priority:	P2
Version:	2.32
Target Milestone:	2.32
See Also:	https://bugzilla.redhat.com/show_bug.cgi?id=1679074
Host:		Target:	powerpc64le-linux
Build:		Last reconfirmed:

Description Alan Modra 2018-11-30 03:33:19 UTC

With a brand new binutils and gcc, when I compile gcc/testsuite/gcc.dg/attr-ifunc-4.c I see the call to magic() in main() going via a plt stub.  There's an IRELATIVE reloc on the .iplt entry used by the stub.  That's all as expected but
the IRELATIVE reloc points at resolver+8.  It should point at resolver+0.

As it is, when ld.so calls the resolver func r2 will have ld.so's TOC pointer value and thus calculate the wrong offset to implementation().

Comment 1 Sourceware Commits 2018-11-30 05:50:37 UTC

The master branch has been updated by Alan Modra <amodra@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ba85c15dabe144e4bcee5a1b388b32bee10729e1

commit ba85c15dabe144e4bcee5a1b388b32bee10729e1
Author: Alan Modra <amodra@gmail.com>
Date:   Fri Nov 30 15:34:11 2018 +1030

    PR23937, powerpc64le local ifunc IRELATIVE relocs are wrong
    
    IFUNC resolvers must always be called via their global entry point.
    They will be called from ld.so rather than from the local executable.
    
    	PR 23937
    bfd/
    	* elf64-ppc.c (write_plt_relocs_for_local_syms): Don't add local
    	entry offset for ifuncs.
    ld/
    	* testsuite/ld-powerpc/pr23937.d,
    	* testsuite/ld-powerpc/pr23937.s: New test.
    	* testsuite/ld-powerpc/powerpc.exp: Run it.

Comment 2 Sourceware Commits 2018-11-30 05:55:00 UTC

The binutils-2_31-branch branch has been updated by Alan Modra <amodra@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0f494b01431de53959dd72ccfed06a01d5172e3f

commit 0f494b01431de53959dd72ccfed06a01d5172e3f
Author: Alan Modra <amodra@gmail.com>
Date:   Fri Nov 30 15:34:11 2018 +1030

    PR23937, powerpc64le local ifunc IRELATIVE relocs are wrong
    
    IFUNC resolvers must always be called via their global entry point.
    They will be called from ld.so rather than from the local executable.
    
    	PR 23937
    bfd/
    	* elf64-ppc.c (write_plt_relocs_for_local_syms): Don't add local
    	entry offset for ifuncs.
    ld/
    	* testsuite/ld-powerpc/pr23937.d,
    	* testsuite/ld-powerpc/pr23937.s: New test.
    	* testsuite/ld-powerpc/powerpc.exp: Run it.
    
    (cherry picked from commit ba85c15dabe144e4bcee5a1b388b32bee10729e1)

Comment 3 Alan Modra 2018-11-30 05:57:41 UTC

Fixed.