djgpp problems

[mztan]

hey all,

i'm having some problems loading libraries in djgpp... i'm getting undefined reference errors all over the place.

ld -e _main -Map map.txt -Ttext 0x1000 -o kernel.o main.o video.o ports.o init.o util.o fdc.o -lc

i figure this should work, except i get wacky errors like:
c:/djgpp/bin/../lib/libc.a(dpmiexcp.o)(.text+0x162):dpmiexcp.c: undefined reference to `_stklen'
c:/djgpp/bin/../lib/libc.a(dpmiexcp.o)(.text+0x16b):dpmiexcp.c: undefined reference to `__djgpp_selector_limit'
c:/djgpp/bin/../lib/libc.a(dpmiexcp.o)(.text+0x5da):dpmiexcp.c: undefined reference to `__djgpp_selector_limit'
c:/djgpp/bin/../lib/libc.a(dpmiexcp.o)(.text+0x83d):dpmiexcp.c: undefined reference to `_stklen'
c:/djgpp/bin/../lib/libc.a(dpmiexcp.o)(.text+0x843):dpmiexcp.c: undefined reference to `__djgpp_stack_limit'

i guess i need to include more libraries or something, but i dont know which ones to include.

can a brother get a little help in hurr? thanks heh.

[Solar]

c:/djgpp/bin/../lib/libc.a...

You're trying to mix a flat kernel binary with the C runtime of your host system... doesn't work.

I'm not familiar with DJGCC, but you should look into the flags -nostdlib, -nostartfiles, and -nodefaultlibs.

[mztan]

Well i need the libraries because otherwise, i get other undefined reference errors... like
util.o(.text+0x2e):util.c: undefined reference to `_go32_info_block'
util.o(.text+0x41):util.c: undefined reference to `_go32_info_block'
util.o(.text+0x49):util.c: undefined reference to `__dpmi_get_and_disable_virtual_interrupt_state'
util.o(.text+0x64):util.c: undefined reference to `_go32_dpmi_get_protected_mode_interrupt_vector'
util.o(.text+0x8b):util.c: undefined reference to `_go32_dpmi_allocate_iret_wrapper'
util.o(.text+0xa4):util.c: undefined reference to `_go32_dpmi_set_protected_mode_interrupt_vector'
util.o(.text+0xbb):util.c: undefined reference to `_go32_dpmi_set_protected_mode_interrupt_vector'
util.o(.text+0xcd):util.c: undefined reference to `_go32_dpmi_free_iret_wrapper'
util.o(.text+0xdb):util.c: undefined reference to `__dpmi_get_and_set_virtual_interrupt_state'
util.o(.text+0x160):util.c: undefined reference to `_go32_dpmi_allocate_dos_memory'

[Pype.Clicker]

well, if there are so much dependencies to Dos Protected Mode Interface in your code, chances that you're heading the wrong way.

probably you're expecting too much (and #include<...>d too much header files). When writing an OS, you're pretty much on your own, including whatever concerns interrupts, memory allocation and the like.

[mztan]

Well I'm simply using a FDC driver I got from another post. fdc.c, fdc.h... They include a whole bunch of stuff... a lot of system-level functions, etc, I guess.

[Solar]

So they probably already have implemented those parts of the standard library.

You don't have a standard library available to you when you start writing a kernel. You have to either port one or write your own. When you're starting with your kernel, "#include" is basically a mistake.

[mztan]

Uhh... I have not done any #includes... the drivers include things like dos.h, go32.h, assert.h, etc. etc.

[AR]

There's your problem then, if this is ment to be an OS you'll have to remove those includes and modify the code to not use the DOS functions and write your own replacement code to take the place of the DOS functions.

[mztan]

So... if util.c is calling stuff like "_go32_dpmi_allocate_dos_memory", which is located in libc.a... how would I remove those types of functions and write my own substitutes? I don't really understand..

Here is a function located in util.c that calls a lot of library functions. Any suggestions as to how I can rewrite this?

Code: Select all

void set_irq_handler(int irq,void (*handler)(void),IrqSave *irqsave)
{
   int picbase,irqstate;
   
   if (irq == 0x1c) {
      /* kludge to allow use of int 1ch in DOS */
      picbase = 0;
   } else {
      /* get INT base of IRQ's */
      if (irq < 8) {
    picbase = _go32_info_block.master_interrupt_controller_base;
      } else {
    irq -= 8;
    picbase = _go32_info_block.slave_interrupt_controller_base;
      }
   }
   
   /* disable interrupts */
   irqstate = __dpmi_get_and_disable_virtual_interrupt_state();
   
   if (handler) {
      /* setting new handler */
      _go32_dpmi_get_protected_mode_interrupt_vector(picbase + irq,
                       &irqsave->oldhdlr);
      irqsave->newhdlr.pm_offset = (unsigned long)handler;
      irqsave->newhdlr.pm_selector = _go32_my_cs();
      _go32_dpmi_allocate_iret_wrapper(&irqsave->newhdlr);
      _go32_dpmi_set_protected_mode_interrupt_vector(picbase + irq,
                       &irqsave->newhdlr);
   } else {
      /* restoring old handler */
      _go32_dpmi_set_protected_mode_interrupt_vector(picbase + irq,
                       &irqsave->oldhdlr);
      _go32_dpmi_free_iret_wrapper(&irqsave->newhdlr);
   }

   /* re-enable interrupts if necessary */
   __dpmi_get_and_set_virtual_interrupt_state(irqstate);
}

[Pype.Clicker]

So... if util.c is calling stuff like "_go32_dpmi_allocate_dos_memory", which is located in libc.a... how would I remove those types of functions and write my own substitutes? I don't really understand..

Well, it may require you to write new code for the functions in util.c that will only require things you provide ... and ultimately write system code (well, code that access intel-defined data structures, processor registers, I/O space and the like

DPMI cannot access those resources (they may be under the control of windows, for instance)... so the DPMI programmer has to use klumsy DPMI interface to access these stuff ...

Code: Select all

void set_irq_handler(int irq,void (*handler)(void),IrqSave *irqsave)
{
   int picbase,irqstate;

Code: Select all

   if (irq == 0x1c) {
      /* kludge to allow use of int 1ch in DOS */
      picbase = 0;
   } else {

chances that you want to keep RBIL:int1C are low. Drop this

Code: Select all

      /* get INT base of IRQ's */
      if (irq < 8) {
    picbase = _go32_info_block.master_interrupt_controller_base;
      } else {
    irq -= 8;
    picbase = _go32_info_block.slave_interrupt_controller_base;
      }

Check out our wikiFAQ ... it has informations about "how to remap the PIC" that will let you know why this could work (with proper remapping)

Code: Select all

     picbase = 20+irq

Code: Select all

   
   /* disable interrupts */
   irqstate = __dpmi_get_and_disable_virtual_interrupt_state();

just asm("CLI") for this one (see FAQ >> Inline Assembly >> disable())

Code: Select all

   if (handler) {
      /* setting new handler */
      _go32_dpmi_get_protected_mode_interrupt_vector(picbase + irq,
                       &irqsave->oldhdlr);
      irqsave->newhdlr.pm_offset = (unsigned long)handler;
      irqsave->newhdlr.pm_selector = _go32_my_cs();
      _go32_dpmi_allocate_iret_wrapper(&irqsave->newhdlr);
      _go32_dpmi_set_protected_mode_interrupt_vector(picbase + irq,
                       &irqsave->newhdlr);

and i hesitated for the word "klumsy" ... probably you'll have to write code for "wrappers" yourself (in ASM) the FAQ will help you at it, again ...

Code: Select all

      /* restoring old handler */
      _go32_dpmi_set_protected_mode_interrupt_vector(picbase + irq,
                       &irqsave->oldhdlr);
      _go32_dpmi_free_iret_wrapper(&irqsave->newhdlr);
   }

i'm not sure you need that one...

Code: Select all

   /* re-enable interrupts if necessary */
   __dpmi_get_and_set_virtual_interrupt_state(irqstate);
}

asm("sti");



btw, just by curiosity, where did you get that "util.c" from ?

[Candy]

Another note for this thread, you can't just take code from somewhere else and expect it to work. Everything has to be hand-made or customized for your OS.

[mztan]

Ahh... thanks Pype... I posted a request for some sample fdc driver code earlier... ashley04 (something along those lines) told me to try this code.

Thanks.

[mztan]

Hrmm... so how would I go about rewriting _go32_dpmi_get_protected_mode_interrupt_vector()? I guess I understand what it does now. I read the FAQ on ISRs, but that is different, isn't it? "_go32_dpmi_get_protected_mode_interrupt_vector()" and "_go32_dpmi_set_protected_mode_interrupt_vector()" change the ISRs, right?, as opposed to the stuff on the FAQ that add ISRs... I don't really know how to phrase my question.

[jonathanmcdougall]

> Hrmm... so how would I go about rewriting
> _go32_dpmi_get_protected_mode_interrupt_vector()? I guess
> I understand what it does now. I read the FAQ on ISRs, but
>`that is different, isn't it?
<snip>

Have a look at http://k101.f2g.net, chapter 10. This will get you started with interrupts.

I think I already saw that floppy driver somewhere. It is usable, but you must adapt it. First, you will need to setup your interrupts (chapter 10 is your friend). Next, you'll want to setup dma (that's for transfering data from/to the floppy). This might be more difficult since I haven't seen a complete tutorial on that (but my website will have one pretty soon). Finally, you'll have to modify the driver to use your functions.

You cannot expect to take some arbitrary code out there and make it work with your OS out of the box. Virtually all the code you will find will be specific to an implementation. Some may be easy to port but most won't be.


Jonathan