A linux stat64 call is supposed to end up calling xstat64 with a static version of stat64 generated that passes a version along with the call.
We are seeing a condition where a C linked (gcc) version of code that calls stat64, when linked against an older version of a (C++ linked) shared library (libdb2.so.1, that uses stat64, but isn't supposed to provide it), is not ending up with a the "proper" static version of this stat64 call. The C++ linked app has what we expect:
00000000004007c8 <__xstat64@plt>:
4007c8: jmpq *1051250(%rip) # 501240 <_GLOBAL_OFFSET_TABLE_+0x20>
4007ce: pushq $0x1
4007d3: jmpq 4007a8 <_init+0x18>
0000000000400ac0 <stat64>:
400ac0: push %rbp
400ac1: mov %rsp,%rbp
400ac4: sub $0x10,%rsp
400ac8: mov %rdi,0xfffffffffffffff8(%rbp)
400acc: mov %rsi,0xfffffffffffffff0(%rbp)
400ad0: mov 0xfffffffffffffff0(%rbp),%rdx
400ad4: mov 0xfffffffffffffff8(%rbp),%rsi
400ad8: mov $0x1,%edi
400add: callq 4007c8 <__xstat64@plt>
400ae2: leaveq
400ae3: retq
whereas the gcc linked code (that also links to our libdb2 shared lib) ends up with a global reference to stat64 instead of the "static" version that it is suppose to have:
0000000000400618 <stat64@plt>:
400618: jmpq *1050146(%rip) # 500c40 <_GLOBAL_OFFSET_TABLE_+0x20>
40061e: pushq $0x1
400623: jmpq 4005f8 <_init+0x18>
The same code, also when linked with gcc, when not linked to our libdb2 library, ends up with the expected "static" stat64 function:
0000000000400550 <__xstat64@plt>:
400550: jmpq *1050170(%rip) # 500b90 <_GLOBAL_OFFSET_TABLE_+0x20>
400556: pushq $0x1
40055b: jmpq 400530 <_init+0x18>
00000000004007b0 <stat64>:
4007b0: mov %rsi,%rdx
4007b3: mov %rdi,%rsi
4007b6: mov $0x1,%edi
4007bb: jmpq 400550 <__xstat64@plt>
EDIT: more info obtained from a linker map (-Wl,--print-map)
When the gcc linked exe doesn't link to our (libdb2) shared lib, we see that it gets it's stat64 from libc_nonshared.a:
/usr/lib64/libc_nonshared.a(stat64.oS)
/home/hotellnx94/peeterj/tmp/cc2f7ETx.o (stat64)
...
.plt 0x0000000000400530 0x70
*(.plt)
.plt 0x0000000000400530 0x70 /usr/lib64/gcc/x86_64-suse-linux/4.1.2/../../../../lib64/crt1.o
0x0000000000400540 __libc_start_main@@GLIBC_2.2.5
0x0000000000400550 __xstat64@@GLIBC_2.2.5
0x0000000000400560 printf@@GLIBC_2.2.5
0x0000000000400570 memset@@GLIBC_2.2.5
0x0000000000400580 strerror@@GLIBC_2.2.5
0x0000000000400590 __errno_location@@GLIBC_2.2.5
.text 0x00000000004007b0 0x10 /usr/lib64/libc_nonshared.a(stat64.oS)
0x00000000004007b0 stat64
whereas, once we link to our shared lib (libdb2), the symbols are picked up from crt1.o instead of lib_nonshared.a:
.plt 0x00000000004005f8 0x70
*(.plt)
.plt 0x00000000004005f8 0x70 /usr/lib64/gcc/x86_64-suse-linux/4.1.2/../../../../lib64/crt1.o
0x0000000000400608 __libc_start_main@@GLIBC_2.2.5
0x0000000000400618 stat64
0x0000000000400628 printf@@GLIBC_2.2.5
0x0000000000400638 memset@@GLIBC_2.2.5
0x0000000000400648 strerror@@GLIBC_2.2.5
0x0000000000400658 __errno_location@@GLIBC_2.2.5
What could we be doing (or would have been doing since we don't see this in new versions of our library), that would cause lib_nonshared.a to no longer be shared once the consumer links to our library?
