https://llvm.org/bugs/show_bug.cgi?id=26818
Bug ID: 26818
Summary: lld incorrectly resolves function pointer relocation
in dso
Product: lld
Version: unspecified
Hardware: PC
OS: FreeBSD
Status: NEW
Severity: normal
Priority: P
Component: All Bugs
Assignee: unassignedb...@nondot.org
Reporter: ema...@freebsd.org
CC: llvm-bugs@lists.llvm.org
Blocks: 23214
Classification: Unclassified
Consider this test program:
% cat lib.c
#include <stdio.h>
int(*fp)(const char *, ...) = printf;
void
fn(void)
{
fp("hello %s\n", "world");
}
% cat main.c
void fn(void);
int
main(int argc, char *argv[])
{
fn();
}
Linking with ld.bfd:
% cc -fPIC -shared -o lib.so lib.c
% cc -fPIC -Wl,-rpath=. lib.so main.c
% ./a.out
hello world
And there's a relocation for 'fp' for printf:
% readelf -s lib.so | grep fp
7: 0000000000200808 8 OBJECT GLOBAL DEFAULT 22 fp
47: 0000000000200808 8 OBJECT GLOBAL DEFAULT 22 fp
% readelf -r lib.so | grep 200808
0000002007c8 000700000006 R_X86_64_GLOB_DAT 0000000000200808 fp + 0
000000200808 000400000001 R_X86_64_64 0000000000000000 printf + 0
Linking with ld.lld:
% cc -fuse-ld=lld -fPIC -shared -o lib.so lib.c
% cc -fuse-ld=lld -fPIC -Wl,-rpath=. lib.so main.c
% ./a.out
zsh: segmentation fault (core dumped) ./a.out
And no relocation for the function pointer:
% readelf -s lib.so | grep fp
6: 0000000000003018 8 OBJECT GLOBAL DEFAULT 19 fp
21: 0000000000003018 8 OBJECT GLOBAL DEFAULT 19 fp
% readelf -r lib.so
Relocation section '.rela.dyn' at offset 0x438 contains 5 entries:
Offset Info Type Sym. Value Sym. Name +
Addend
000000002138 000300000006 R_X86_64_GLOB_DAT 0000000000000000 __cxa_finalize +
0
000000002140 000200000006 R_X86_64_GLOB_DAT 0000000000000000
_Jv_RegisterClasses + 0
000000003008 000000000008 R_X86_64_RELATIVE
0000000000003008
000000003010 000000000008 R_X86_64_RELATIVE
0000000000002018
000000002148 000600000006 R_X86_64_GLOB_DAT 0000000000003018 fp + 0
Relocation section '.rela.plt' at offset 0x4b0 contains 2 entries:
Offset Info Type Sym. Value Sym. Name +
Addend
000000003038 000300000007 R_X86_64_JUMP_SLO 0000000000000000 __cxa_finalize +
0
000000003040 000700000007 R_X86_64_JUMP_SLO 0000000000001150 printf + 0
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