On 12/05/13 10:18, Paolo Bonzini wrote:
Il 04/12/2013 02:32, Don Slutz ha scritto:
Any hints or pointers about the bug in RHEL5 binutils? I can try and
make a patch to auto detect this.
Actually it's RHEL5 GCC:
$ cat f.c
void *
f(unsigned char *buf, int len)
{
return (void*)0L;
}
void *
g(unsigned char *buf, int len)
{
return f(buf, len);
}
$ gcc -shared -o f.so f.c -fPIE -fPIC
/usr/bin/ld: /tmp/ccQc9els.o: relocation R_X86_64_PC32 against `f' can not be
used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: ld returned 1 exit status
The bug is simply that "-fPIE -fPIC" counts as -fPIE rather than -fPIC:
$ gcc -S -o - f.c -fPIE |grep call
call f # PC32 relocation
$ gcc -S -o - f.c -fPIC |grep call
call f@PLT # PLT32 relocation
On RHEL5:
$ gcc -S -o - f.c -fPIE -fPIC |grep call
call f
On RHEL6:
$ gcc -S -o - f.c -fPIE -fPIC |grep call
call f@PLT
Paolo
RHEL5 also "works" if you add -pie:
dcs-xen-53:~/tmp>gcc -shared -o f.so f.c -fPIE -fPIC
/usr/bin/ld: /tmp/cc6pp1n2.o: relocation R_X86_64_PC32 against `f' can
not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: ld returned 1 exit status
dcs-xen-53:~/tmp>gcc -shared -o f.so f.c -fPIE -fPIC -pie
dcs-xen-53:~/tmp>gcc -S -o - f.c -fPIE -pie|grep call
call f
I have not figured out a way to take advantage of this.
I just checked and Fedora 17 has the same issue with gcc:
FC17:
dcs-xen-52:~/tmp>gcc -S -o - f.c -fPIE -fPIC |grep call
call f
dcs-xen-52:~/tmp>gcc -shared -o f.so f.c -fPIE -fPIC
/usr/bin/ld: /tmp/ccUlVgMP.o: relocation R_X86_64_PC32 against symbol
`f' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status
However QEMU builds just fine. So it is looking like libtool is also
part of the problem.
-Don Slutz
