+++ This bug was initially created as a clone of Bug #12570 +++

[hjl@gnu-6 pr12570]$ cat x.c
void foo (void);

void
bar ()
{
  foo ();
}
[hjl@gnu-6 pr12570]$ cat dummy.S 
[hjl@gnu-6 pr12570]$ make
gcc -O2 -fpic   -c -o x.o x.c
./ld -shared -o x.so x.o
gcc -c -O2 -fpic -o dummy.o dummy.S
./ld -shared -o y.so dummy.o x.o
readelf -wf x.so
Contents of the .eh_frame section:

00000000 00000014 00000000 CIE
  Version:               1
  Augmentation:          "zR"
  Code alignment factor: 1
  Data alignment factor: -8
  Return address column: 16
  Augmentation data:     1b

  DW_CFA_def_cfa: r7 (rsp) ofs 8
  DW_CFA_offset: r16 (rip) at cfa-8
  DW_CFA_nop
  DW_CFA_nop

00000018 00000014 0000001c FDE cie=00000000 pc=00000260..00000265
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop

readelf -wf y.so
Contents of the .eh_frame section:

00000000 00000014 00000000 CIE
  Version:               1
  Augmentation:          "zR"
  Code alignment factor: 1
  Data alignment factor: -8
  Return address column: 16
  Augmentation data:     1b

  DW_CFA_def_cfa: r7 (rsp) ofs 8
  DW_CFA_offset: r16 (rip) at cfa-8
  DW_CFA_nop
  DW_CFA_nop

00000018 00000024 0000001c FDE cie=00000000 pc=00000240..00000260
  DW_CFA_def_cfa_offset: 16
  DW_CFA_advance_loc: 6 to 00000246
  DW_CFA_def_cfa_offset: 24
  DW_CFA_advance_loc: 10 to 00000250
  DW_CFA_def_cfa_expression (DW_OP_breg7 (rsp): 8; DW_OP_breg16 (rip): 0; DW_OP_lit15; DW_OP_and; DW_OP_lit11; DW_OP_ge; DW_OP_lit3; DW_OP_shl; DW_OP_plus)
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop

00000040 00000014 00000044 FDE cie=00000000 pc=00000260..00000265
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop
  DW_CFA_nop

[hjl@gnu-6 pr12570]$ 

Linker doesn't always generate unwind info for PLT.