[Bug binutils/25041] New: [avr-objdump] Invalid disassembly of avrtiny LDS/STS instructions

[michael.pucher.main at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25041

            Bug ID: 25041
           Summary: [avr-objdump] Invalid disassembly of avrtiny LDS/STS
                    instructions
           Product: binutils
           Version: 2.32
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: michael.pucher.main at gmail dot com
  Target Milestone: ---

Overview
------------------

This concerns the AVR version of objdump. When trying to disassemble the
LDS/STS instructions for the, e.g. ATtiny10, the address is not decoded
correctly.


Steps to reproduce
------------------


1) tiny.S:

_start:
        lds r16, 0x80
        sts 0x80, r16

2) Assemble with:

avr-as -m "attiny10" -o tiny.elf tiny.S

3) Disassemble with:

avr-objdump -Dm"avr:100" tiny.elf


Actual Results
------------------

Disassembly of section .text:

00000000 <_start>:
   0:   00 a0           lds     r16, 0x00
   2:   00 a8           sts     0x00, r16


Expected Results
------------------

Disassembly of section .text:

00000000 <_start>:
   0:   00 a0           lds     r16, 0x80
   2:   00 a8           sts     0x80, r16


Additional Information
------------------

This bug was probably introduced due to some ambiguity in the official ISA doc.
The online doc clearly says that the parameter for LDS/STS instruction ranges
from 0x40 to 0xBF. [1]

However the ISA PDF [2] says the parameter ranges from 0 - 128, but provides
details on how the address parameter is actually calculated. Given that the
parameter makes more sense ranging from 0x40-0xBF, because of the way it is
actually decoded and that avr-as (!) itself warns that 0x0 as parameter for
LDS/STS is out of range, this should be adapted in objdump as well.

[1]
https://www.microchip.com/webdoc/avrassembler/avrassembler.wb_LDS_-_Load_direct_from_SRAM.html
[2]
http://ww1.microchip.com/downloads/en/devicedoc/atmel-0856-avr-instruction-set-manual.pdf

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