Linker misaligns section in 16-bit RAW

[chibicitiberiu]

Hello,
I am trying to create a raw binary which is basically the 2nd stage of a bootloader. I am using the following linker script:

FORMAT RAW BIN 
OPTION QUIET,
       NODEFAULTLIBS,
       START=entry, 
       VERBOSE,
       OFFSET=0,
       STACK=0x200
ORDER
    CLNAME CODE
        SEGMENT _ENTRY
        SEGMENT _TEXT
    CLNAME DATA

The C files are compiled with wcc -3 -d3 -s -wx -ms -zl -zq, and the assembly code with NASM. I am using the 2.0 release from the sourceforge page, and compiling from latest 64-bit Ubuntu.

The problem I'm having is this:

Segment                Class          Group          Address         Size
=======                =====          =====          =======         ====

_ENTRY                 CODE           AUTO           00000000        00000013
_TEXT                  CODE           AUTO           00000013        00000b8c
CONST                  DATA           DGROUP         00000ba0        00000134
CONST2                 DATA           DGROUP         00000cd4        00000004
_DATA                  DATA           DGROUP         00000cd8        00000000
_BSS                   BSS            DGROUP         00000cd8        00000005

The address where the CONST section begins is wrong, 0x13 + 0xb8c = 0xb9f, not 0xba0. In the emitted binary, the beginning address of the CONST section is indeed 0xb9f, but all the references to the constants are shifted by 1 byte.

For example, when calling puts("Hello world"), I get the output ello world. Adding 1 byte to the '_ENTRY' section (which is coded in assembly), seems to temporarily 'fix' the problem. Also, making small changes in code does that, such as adding a variable, or making a variable from int8 to int16.

[jmalak]

Thanks for problem report.
Could you check with latest build version linker from Latest build.
could you add here all *.objects file with linker command to be able analyse where problem is.

[jmalak]

I think that 0x0ba0 could be OK because it is start of DGROUP and if some segments in dgroup is of type WORD or higher then dgroup is align to appropriate value.
Anyway what is strange is wrong offset as you reported.

[chibicitiberiu]

I tested using latest build, and the problem still appears.

I added everything, including the wlink command args in the zip:
stage2.zip

If you open the output binary (stage2.bin) in a hex editor, you can actually see that the CONST section as mentioned in the "map" file begins with a 1 byte offset (the first constant should be the "012345679ABCDEF" string, but according to the map file, the CONST section begins at the '1' character)

[jmalak]

Thanks. I will analyse a problem.

[jmalak]

DGROUP is WORD aligned that linker map is OK
It is mised emiting of padding byte after CODE class.
I will fix it.

[jmalak]

it is fixed by commit dcd360a
try new version after building, it can take about 1 hour.

[chibicitiberiu]

I tested, and I can confirm it is fixed 👍
Thank you very much for the help.

[jmalak]

You are welcome