Bug 3132

Summary:	Incorrect 16-bit relocations in ELF
Product:	binutils	Reporter:	Markus Gyger <markus+sw>
Component:	gas	Assignee:	unassigned
Status:	NEW ---
Severity:	normal	CC:	bug-binutils
Priority:	P2
Version:	2.17
Target Milestone:	---
Host:	i386-pc-solaris2.10	Target:	h8300-elf
Build:	i386-pc-solaris2.10	Last reconfirmed:
Attachments:	Assembler example to show incorrect 16-bit ELF relocation

Description Markus Gyger 2006-08-25 15:28:16 UTC

ELF on ld 2.17 incorrectly calculates 8- and 16-bit relocations that worked with
COFF on ld 2.16.2.

  h8300-coff-as -oreloc.o reloc.s
  h8300-coff-ld -mh8300s --oformat binary reloc.o
  od -tx1 a.out
correctly yields:
  0000000 6a 08 e0 02 00 02

while

  h8300-elf-as -oreloc.o reloc.s
  h8300-elf-ld -mh8300self --oformat binary reloc.o
yields:
  reloc.o:(.text+0x2): relocation truncated to fit: R_H8_DIR16A8 against `addr'

and

  h8300-elf-as -oreloc.o reloc.s
  h8300-elf-ld -mh8300self reloc.o
  h8300-elf-objdump -d a.out
  h8300-elf-objcopy -Obinary a.out
  od -tx1 a.out
yields:
  0000000 6a 08 e0 02 01 06


Content of reloc.s:
.h8300s
_start = 0
.global _start

mov @addr + 2 :16, r0l
addr = 0xffe000

.word label - .
label:

Comment 1 Markus Gyger 2006-08-25 15:30:47 UTC

Created attachment 1250 [details]
Assembler example to show incorrect 16-bit ELF relocation

Comment 2 Alan Modra 2022-08-24 13:59:57 UTC

This is a gas problem.  gas is generating R_H8_DIR16 for the .word expression, which is wrong.  The expression needs a 16 bit pc-relative reloc instead, or gas should be resolving the "label-." expression itself.  It doesn't resolve the expression because h8300 sets linkrelax and there is no logic to detect that the expression is pc-relative and does not cross a region that could change size.