printString function not printing strings!

[Benjamin1996]

Hi guys!
I have a problem that's seriously starting to get on my nerves. For some reason I can't get my printString(char* message) function working. And by working I mean it doesn't print out anything, what so ever. First I tried with my own printString(char* message) function, but I then thought that I had just done something wrong. Then I instead decided to c+p a function from a tutorial, yet, no reactions from VMWare player. My first consideration was that the memory map might look different on my MacBook than on a PC. But I scratched that idea as I can easily clear the screen by writing to 0xb8000.
Here's some links to pastebin.com where I have uploaded the code:
main.c: http://pastebin.com/gi7CvS8Y
video.c: http://pastebin.com/8X2MjiAH
video.h: http://pastebin.com/9BVBHBys
And finally here's compile.bat:

Code: Select all

@echo off
"C:\Mingw\bin\gcc.exe" -ffreestanding -c main.c -o main.o
"C:\Mingw\bin\gcc.exe" -c video.c -o video.o
"C:\Mingw\bin\gcc.exe" -c hal.c -o hal.o
ld -e _kernelEntry -Map memorymap.map -Ttext 0x1000 -o kernel.o main.o video.o hal.o
objcopy -O binary kernel.o kernel.bin
makeboot cyborgosx.img "C:\Users\Benjamin\Desktop\CyborgOSX\output\bootloader.bin" kernel.bin
copy "C:\Users\Benjamin\Desktop\CyborgOSX\core\*.img" "C:\Users\Benjamin\Desktop\CyborgOSX\core\src\*.img"
del *.img
"C:\Users\Benjamin\Downloads\cdrtools-latest\mkisofs.exe" -o cyborgosx.iso -A CyborgOSX -b cyborgosx.img src
copy "C:\Users\Benjamin\Desktop\CyborgOSX\core\*.o" "C:\Users\Benjamin\Desktop\CyborgOSX\output\*.o"
copy "C:\Users\Benjamin\Desktop\CyborgOSX\core\*.bin" "C:\Users\Benjamin\Desktop\CyborgOSX\output\*.bin"
copy "C:\Users\Benjamin\Desktop\CyborgOSX\core\*.iso" "C:\Users\Benjamin\Desktop\CyborgOSX\output\*.iso"
del *.o
del *.bin
del *.iso
pause

And in VMWare player, the screen is cleared with cyan background, magenta text, and the cursor is reset to 0,0. But no string is displayed, what so ever.
I would really like some help!

[Solar]

Check if your kernel binary actually contains the string you are trying to print. If it doesn't, you need a linker script that links .rodata into the kernel binary.

[Benjamin1996]

Check if your kernel binary actually contains the string you are trying to print. If it doesn't, you need a linker script that links .rodata into the kernel binary.

Both kernel.bin and cyborgosx.iso contains the "Welcome to CyborgOSX!" string..

[Velko]

Is offset calculated correctly? Try to print without adding offset to videoMemory.

If this works, there's probably something wrong with your in() function.

[Benjamin1996]

Is offset calculated correctly? Try to print without adding offset to videoMemory.

If this works, there's probably something wrong with your in() function.

Nope. I commented out "videoMemory += offset * 2;", yet, nothing happens .

[neon]

char* videoMemory = (char*)0xb8000;

This should be unsigned.

If you verified the string is in the binary; verify that the address passed to the routine actually points to the correct offset in the binary. Also, make sure a valid stack is set up.

[Benjamin1996]

char* videoMemory = (char*)0xb8000;

This should be unsigned.

If you verified the string is in the binary; verify that the address passed to the routine actually points to the correct offset in the binary. Also, make sure a valid stack is set up.

How, exactly, would I find out if the addresses match, and if the stack is valid?

[jal]

How, exactly, would I find out if the addresses match, and if the stack is valid?

On a different note, do you have a working printChar function or the like? If so, try making a printString function that uses printChar. Also, try a sequence of printChar-s to see whether that works. If it does, it is likely a linking problem.


JAL

[Benjamin1996]

How, exactly, would I find out if the addresses match, and if the stack is valid?

On a different note, do you have a working printChar function or the like? If so, try making a printString function that uses printChar. Also, try a sequence of printChar-s to see whether that works. If it does, it is likely a linking problem.


JAL

I think it's a linking problem then, because adding

Code: Select all

	*videoMemory = 'A';
	videoMemory++;
	*videoMemory = 0x0035;
	videoMemory++;

to the "kernelEntry()" function in main.c, does print out an A in the upper left-most corner of the screen .

[jal]

I think it's a linking problem then, because adding

Code: Select all

	*videoMemory = 'A';
	videoMemory++;
	*videoMemory = 0x0035;
	videoMemory++;

to the "kernelEntry()" function in main.c, does print out an A in the upper left-most corner of the screen :).

It could of course still be a bug in the printString routine. Try something like this:

Code: Select all

char someString[] = "Hello world";

for (int i = 0; someString[i] != 0; i++)
{
     videoMemory[i*2] = someString[i];
     videoMemory[i*2+1] = 0x35;                  // or whatever you like
}

If this doesn't work, it is definitely a linking problem.


JAL

[Benjamin1996]

I think it's a linking problem then, because adding

Code: Select all

	*videoMemory = 'A';
	videoMemory++;
	*videoMemory = 0x0035;
	videoMemory++;

to the "kernelEntry()" function in main.c, does print out an A in the upper left-most corner of the screen .

It could of course still be a bug in the printString routine. Try something like this:

Code: Select all

char someString[] = "Hello world";

for (int i = 0; someString[i] != 0; i++)
{
     videoMemory[i*2] = someString[i];
     videoMemory[i*2+1] = 0x35;                  // or whatever you like
}

If this doesn't work, it is definitely a linking problem.


JAL

I tried to replace my while loop with your for loop, but still no effect, so it's probably a linking problem.. so far, so good .

[jal]

I tried to replace my while loop with your for loop, but still no effect, so it's probably a linking problem.. so far, so good :).

Indeed. Linking problems should not be too hard to solve (although I have unfortunately no experience with mingw or Windows development).


JAL

[Benjamin1996]

Hmm.. I just tried to add the following directly into my kernelEntry function, but still nothing is displayed:

Code: Select all

    unsigned char* videoMemory = (unsigned char*)0xb8000;
    char welcome[] = {"Welcome to CyborgOSX!"};
    int i = 0;
	
    while(welcome[i] != 0){
        *videoMemory = welcome[i++];
	videoMemory++;
	*videoMemory = 0x0009;
	videoMemory++;
    }

I don't know if this is of any help, but at least you know now .

[Solar]

Linking problems should not be too hard to solve (although I have unfortunately no experience with mingw or Windows development).

*cough*crosscompiler*cough*...

[Benjamin1996]

I just remembered something about having to add the -i option to ld.exe in the line where I link all the kernel files into kernel.o. However, doing this causes the OS to triple fault trying to jump to 0x0008:0x01000. This might not be helpful at all, if so, sorry about that. - It was just something that came to my mind (also, I've got no clue what the -i option does, what so ever).