https://sourceware.org/bugzilla/show_bug.cgi?id=26936
Michael Matz <matz at suse dot de> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |matz at suse dot de
--- Comment #14 from Michael Matz <matz at suse dot de> ---
So, it's a bit involved. As far as I can determine it needs a linkonce section
(not just a comdat group!) and three input files. Reproducer:
% cat crt.s
.file "crt.s"
.section .gnu.linkonce.t.__x86.get_pc_thunk.bx,"ax",@progbits
.globl __x86.get_pc_thunk.bx
.hidden __x86.get_pc_thunk.bx
.type __x86.get_pc_thunk.bx, @function
__x86.get_pc_thunk.bx:
.cfi_startproc
movl (%esp), %ebx
ret
.cfi_endproc
% cat split-1.s
.file "split-1.c"
.text
.Ltext0:
.globl _start
_start:
.globl main
.type main, @function
main:
ret
.size main, .-main
.section
.text.__x86.get_pc_thunk.bx,"axG",@progbits,__x86.get_pc_thunk.bx,comdat
.globl __x86.get_pc_thunk.bx
.hidden __x86.get_pc_thunk.bx
.type __x86.get_pc_thunk.bx, @function
__x86.get_pc_thunk.bx:
.cfi_startproc
movl (%esp), %ebx
ret
.cfi_endproc
% cat morestack.S
.section
.text.__x86.get_pc_thunk.bx,"axG",@progbits,__x86.get_pc_thunk.bx,comdat
.globl __x86.get_pc_thunk.bx
.hidden __x86.get_pc_thunk.bx
.type __x86.get_pc_thunk.bx, @function
__x86.get_pc_thunk.bx:
.cfi_startproc
movl (%esp), %ebx
ret
.cfi_endproc
.size __x86.get_pc_thunk.bx, . - __x86.get_pc_thunk.bx
Note how crt.s uses a traditional linkonce section while the others use comdat
groups. Also note that all three define the symbol in question. Now, compile
with -g and observe relocations and lineinfo:
% gcc -m32 -g -c crt.s split-1.s morestack.S
% readelf -W -wl -r morestack.o
...
Relocation section '.rel.debug_line' at offset 0x238 contains 1 entry:
Offset Info Type Sym.Value Sym. Name
0000002f 00000401 R_386_32 00000000
.text.__x86.get_pc_thunk.bx
...
Line Number Statements:
[0x0000002c] Extended opcode 2: set Address to 0x0
[0x00000033] Advance Line by 9 to 10
Observe how the line number address should be relocated to the final address of
the .text.__x86.get_pc_thunk.bx symbol. Now link and observe line number info
again:
% /matz/git/binutils/dev/ld/ld-new -m elf_i386 crt.o split-1.o morestack.o
% readelf -W -s -wl -r a.out
...
12: 08049000 0 FUNC GLOBAL HIDDEN 1 __x86.get_pc_thunk.bx
...
The File Name Table (offset 0x97):
Entry Dir Time Size Name
1 0 0 0 morestack.S
Line Number Statements:
[0x000000a7] Extended opcode 2: set Address to 0x0
[0x000000ae] Advance Line by 9 to 10
Address is still zero, the relocation wasn't applied. (PIE doesn't seem to
matter in this reduced case anymore).
Note that the equivalent relocation from split-1.s _is_ applied:
...
The File Name Table (offset 0x50):
Entry Dir Time Size Name
1 0 0 0 split-1.s
Line Number Statements:
...
[0x0000006b] Extended opcode 2: set Address to 0x8049000
[0x00000072] Advance Line by 19 to 20
It's also resolved in the line number section of crt.s. If I use a comdat
group in crt.s (not a link once section) the problem goes away. If I remove
split-1.o
from the link (and accept the warning about missing _start), the relocation in
morestack.o is correctly resolved.
So, there's definitely something fishy with the discarded sections and
relocations referring to them.
--
You are receiving this mail because:
You are on the CC list for the bug.
