Re: [Simulavr-devel] erroneous offset in rjmp and rcall

[Theodore A. Roth]

What does `avr-objdump -h -S sos` say for the code in question?

Are you sure that the .text section is < 8 KB?

Is there any chance you could send me a simple program which demonstrates
the problem?

Ted Roth

On Thu, 19 Sep 2002, eban wrote:

:) Hello everybody!!!
:)
:) I'm new to this atmel technology and I'm trying to
:) simulate a smart card operative system called SOSSE
:) (http://www.franken.de/users/mbsks/sosse/).
:)
:) In general everything seems all right but I have
:) experienced some problems.
:)
:) The compilation seems to be all right, and i think
:) SOSSE has been used before without problems. So I
:) suspect the problem is in your simulator.
:)
:) im using simulavr version 0.1.1
:)
:) Let me show you the debug session with gdb. Running
:) simulavr alone produces the same errors:
:) ERROR: file storage.c: line 101: address out of
:) bounds: 0xffffd550
:)
:) (gdb) disassemble 0x4C 0x52
:) Dump of assembler code from 0x4c to 0x52:
:) 0x4c <.zero_bss_start+2>:    cpc     r27, r18
:) 0x4e <.zero_bss_start+4>:    brne    .-8             ; 0x48
:) 0x50 <.zero_bss_start+6>:    rjmp    .-2818          ; 0xfffff550
:) End of assembler dump.
:)
:) As you can see the rjmp goes to an invalid adress. (im
:) using at90s8515)
:) In the source code this instruction was in libc's
:) (avr-libc-20020203) gcrt1.S from Marek Michalkiewicz
:) et al:
:) ....
:) #if XRAMEND > 0x100
:)      cpc     XH, r_tmp1      ; hi8(__bss_end)
:) #endif
:)      brne    .zero_bss_loop
:)      XJMP    _U(main)
:) ....
:)
:) in the included file macros.inc is defined:
:) ....
:) #define CONCAT1(a, b) CONCAT2(a, b)
:) #define CONCAT2(a, b) a ## b
:) #define _U(x) CONCAT1(__USER_LABEL_PREFIX__, x)
:) ....
:)
:) and you can also find in this file:
:) ....
:) #if FLASHEND > 0x2000  /* ATmega */
:)   #define XJMP jmp
:)   #define XCALL call
:) #else
:)   #define XJMP rjmp
:)   #define XCALL rcall
:) #endif
:) ....
:)
:) I don't understand that a ## b notation but i think it
:) works for the assembler.
:) So instead of jumping to main (0x1550) it's jumping
:) somewere else (0xff...) or at least that's the way the
:) simulator interprets the instruction.
:)
:) I compiled a much simpler program with the same
:) compilation parameters and I didn't find this problem.
:) The problem seems to be the way you manage the rjmp
:) and rcall instructions when the offsets are large.
:)
:) If you see the binary file with hexedit you can see
:) that the instruction is well assembled:
:)      avr-objcopy -O binary sos sos.bin
:)      hexedit sos.bin
:) ....
:) 00000050   7F CA  (the bytes are reversed)
:) ....
:)
:) (0x50 is the offset of the rjmp to main)
:) (the C is part of the opcode for rjmp. Cxxx)
:)
:) the jump that should be there is of (1550h-52h)/2 =
:) A7Fh so you can see it was well assembled if the data
:) was spected to be unsigned.
:)
:) It's very likely that you have a sign conversion
:) problem or sign extension problem or something
:) similar. It makes no sense to move to that address
:) when the code words are in total 8K.
:)
:) the same problem occurs with rcall.
:)
:) best regards,
:) Alberto Escalante
:)
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