http://sourceware.org/bugzilla/show_bug.cgi?id=13178
Bug #: 13178
Summary: Unnecessary GOT relocation created for IFUNC
Product: binutils
Version: 2.21
Status: NEW
Severity: normal
Priority: P2
Component: ld
AssignedTo: [email protected]
ReportedBy: [email protected]
Classification: Unclassified
Host: x86_64-linux
Created attachment 5926
--> http://sourceware.org/bugzilla/attachment.cgi?id=5926
Test program to show unnecessary IFUNC relocation
When compiling the attached code using
gcc -shared -o u.so -fpic u.so
on an x86-64 system you will see the following relocations:
Relocation section [ 7] '.rela.dyn' for section [ 0] '' at offset 0x3e8
contains 5 entries:
Offset Type Value Addend Name
0x0000000000200760 X86_64_RELATIVE 000000000000000000 +2099040
0x00000000002008e8 X86_64_GLOB_DAT 000000000000000000 +0 __gmon_start__
0x00000000002008f0 X86_64_GLOB_DAT 000000000000000000 +0
_Jv_RegisterClasses
0x00000000002008f8 X86_64_GLOB_DAT 000000000000000000 +0 __cxa_finalize
0x0000000000200900 X86_64_GLOB_DAT 0x00000000000005d8 +0 f
Relocation section [ 8] '.rela.plt' for section [10] '.plt' at offset 0x460
contains 3 entries:
Offset Type Value Addend Name
0x0000000000200920 X86_64_JUMP_SLOT 000000000000000000 +0
__cxa_finalize
0x0000000000200928 X86_64_JUMP_SLOT 0x00000000000005d8 +0 f
0x0000000000200930 X86_64_JUMP_SLOT 0x00000000000005e5 +0 g
There are two relocations against f. Since there is no reference to f other
than through a call there is no need for a GOT relocation. The PLT relocation
is all that's needed. It works fine for normal symbols (there is only one
relocation for g) and IFUNCs should be handled just like that.
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