OSDev.org

Posted: **Wed Mar 11, 2009 1:12 am**

gzaloprgm wrote:However, if you use GRUB, remember it may require your OS to be GPL'd or similar.

I don't think that is true. Apart from one little structure, you don't need any other code to use Grub, so I doubt anyone would care about what license you're using...

Posted: **Wed Mar 11, 2009 2:55 pm**

Steve the Pirate wrote:
gzaloprgm wrote:However, if you use GRUB, remember it may require your OS to be GPL'd or similar.
I don't think that is true. Apart from one little structure, you don't need any other code to use Grub, so I doubt anyone would care about what license you're using...

Well, but will you include a iso / img file without a bootloader

and wait for the user to boot it with grub ?

I think you are misunderstanding GPL

The GPL is the most popular and well-known example of the type of strong copyleft license that requires derived works to be available under the same copyleft.

and

You have a GPL'ed program that I'd like to link with my code to build a proprietary program. Does the fact that I link with your program mean I have to GPL my program?
Yes.

So it's not a solution if you are making a closed-source OS

Cheers,
gzaloprgm

Posted: **Wed Mar 11, 2009 3:07 pm**

gzaloprgm wrote: I think you are misunderstanding GPL
The GPL is the most popular and well-known example of the type of strong copyleft license that requires derived works to be available under the same copyleft.
and
You have a GPL'ed program that I'd like to link with my code to build a proprietary program. Does the fact that I link with your program mean I have to GPL my program?
Yes.
So it's not a solution if you are making a closed-source OS

Unless your OS code base is actually based on Grub source code it is not a derived work.

Linking has a very specific meaning. It has nothing to do with 'including alongside'. Unless you compile your code base against Grub (similar to a library) it is not linked.

If this were not the case you'd never be able anything *but* GPL [and compatible] software on Linux.

Posted: **Wed Mar 11, 2009 10:51 pm**

ucosty wrote:Unless your OS code base is actually based on Grub source code it is not a derived work.

Linking has a very specific meaning. It has nothing to do with 'including alongside'. Unless you compile your code base against Grub (similar to a library) it is not linked.

If this were not the case you'd never be able anything *but* GPL [and compatible] software on Linux.

Precisely. Even if you distribute the GRUB binaries on you OS's disk images, you can still use any licence you want for your OS, and even keep it closed source if you really want to (but that's a really stupid idea for a hobby OS).

The only implications of using GRUB is that if sombody requests it, you will probably need to put a link (or host a copy of) the GRUB source code on your project's web page - although if you haven't modified it, you can probably just point them to the GRUB website.

Posted: **Thu Mar 12, 2009 5:51 am**

No body found a solution for my problem ?

Posted: **Thu Mar 12, 2009 5:56 am**

Erm... unless I am mistaken, we were at the point where your bootloader only loads the first 512 bytes of your kernel. Did you fix that?

You might also use objdump to make sure .text and .data are indeed the only sections from the object files that you need in your kernel binary. I'd bet money on there being a .rodata section that's not being included in the binary...

Posted: **Thu Mar 12, 2009 8:41 am**

Or there's always another idea....

Bare bones

Posted: **Thu Mar 12, 2009 4:57 pm**

Ok I have fix my bootSecteur to load 16 sector (8 kb) and this is mais kernel.o dump but what I have to do with that ?

Code: Select all

e format elf64-x86-64

Disassembly of section .text:

0000000000000000 <kernel_main>:
   0:	55                   	push   %rbp
   1:	48 89 e5             	mov    %rsp,%rbp
   4:	48 8b 05 00 00 00 00 	mov    0x0(%rip),%rax        # b <kernel_main+0xb>
   b:	c6 00 41             	movb   $0x41,(%rax)
   e:	48 83 c0 01          	add    $0x1,%rax
  12:	48 89 05 00 00 00 00 	mov    %rax,0x0(%rip)        # 19 <kernel_main+0x19>
  19:	48 8b 05 00 00 00 00 	mov    0x0(%rip),%rax        # 20 <kernel_main+0x20>
  20:	c6 00 02             	movb   $0x2,(%rax)
  23:	48 83 c0 01          	add    $0x1,%rax
  27:	48 89 05 00 00 00 00 	mov    %rax,0x0(%rip)        # 2e <kernel_main+0x2e>
  2e:	48 8b 05 00 00 00 00 	mov    0x0(%rip),%rax        # 35 <kernel_main+0x35>
  35:	c6 00 41             	movb   $0x41,(%rax)
  38:	48 83 c0 01          	add    $0x1,%rax
  3c:	48 89 05 00 00 00 00 	mov    %rax,0x0(%rip)        # 43 <kernel_main+0x43>
  43:	48 8b 05 00 00 00 00 	mov    0x0(%rip),%rax        # 4a <kernel_main+0x4a>
  4a:	c6 00 07             	movb   $0x7,(%rax)
  4d:	48 83 c0 01          	add    $0x1,%rax
  51:	48 89 05 00 00 00 00 	mov    %rax,0x0(%rip)        # 58 <kernel_main+0x58>
  58:	48 8b 05 00 00 00 00 	mov    0x0(%rip),%rax        # 5f <kernel_main+0x5f>
  5f:	c6 00 41             	movb   $0x41,(%rax)
  62:	48 83 c0 01          	add    $0x1,%rax
  66:	48 89 05 00 00 00 00 	mov    %rax,0x0(%rip)        # 6d <kernel_main+0x6d>
  6d:	48 8b 05 00 00 00 00 	mov    0x0(%rip),%rax        # 74 <kernel_main+0x74>
  74:	c6 00 02             	movb   $0x2,(%rax)
  77:	48 83 c0 01          	add    $0x1,%rax
  7b:	48 89 05 00 00 00 00 	mov    %rax,0x0(%rip)        # 82 <kernel_main+0x82>
  82:	eb fe                	jmp    82 <kernel_main+0x82>
Disassembly of section .data:

0000000000000000 <p>:
   0:	00 80 0b 00 00 00    	add    %al,0xb(%rax)
	...
Disassembly of section .eh_frame:

0000000000000000 <.eh_frame>:
   0:	14 00                	adc    $0x0,%al
   2:	00 00                	add    %al,(%rax)
   4:	00 00                	add    %al,(%rax)
   6:	00 00                	add    %al,(%rax)
   8:	01 7a 52             	add    %edi,0x52(%rdx)
   b:	00 01                	add    %al,(%rcx)
   d:	78 10                	js     1f <.eh_frame+0x1f>
   f:	01 03                	add    %eax,(%rbx)
  11:	0c 07                	or     $0x7,%al
  13:	08 90 01 00 00 24    	or     %dl,0x24000001(%rax)
  19:	00 00                	add    %al,(%rax)
  1b:	00 1c 00             	add    %bl,(%rax,%rax,1)
  1e:	00 00                	add    %al,(%rax)
  20:	00 00                	add    %al,(%rax)
  22:	00 00                	add    %al,(%rax)
  24:	84 00                	test   %al,(%rax)
  26:	00 00                	add    %al,(%rax)
  28:	00 04 01             	add    %al,(%rcx,%rax,1)
  2b:	00 00                	add    %al,(%rax)
  2d:	00 0e                	add    %cl,(%rsi)
  2f:	10 86 02 04 03 00    	adc    %al,0x30402(%rsi)
  35:	00 00                	add    %al,(%rax)
  37:	0d 06 00 00 00       	or     $0x6,%eax
  3c:	00 00                	add    %al,(%rax)
	...
Disassembly of section .comment:

0000000000000000 <.comment>:
   0:	00 47 43             	add    %al,0x43(%rdi)
   3:	43 3a 20             	rex.XB cmp    (%r8),%spl
   6:	28 47 4e             	sub    %al,0x4e(%rdi)
   9:	55                   	push   %rbp
   a:	29 20                	sub    %esp,(%rax)
   c:	34 2e                	xor    $0x2e,%al
   e:	32 2e                	xor    (%rsi),%ch
  10:	34 20                	xor    $0x20,%al
  12:	28 55 62             	sub    %dl,0x62(%rbp)
  15:	75 6e                	jne    85 <kernel_main+0x85>
  17:	74 75                	je     8e <kernel_main+0x8e>
  19:	20 34 2e             	and    %dh,(%rsi,%rbp,1)
  1c:	32 2e                	xor    (%rsi),%ch
  1e:	34 2d                	xor    $0x2d,%al
  20:	31 75 62             	xor    %esi,0x62(%rbp)
  23:	75 6e                	jne    93 <kernel_main+0x93>
  25:	74 75                	je     9c <kernel_main+0x9c>
  27:	33 29                	xor    (%rcx),%ebp
	...

Posted: **Thu Mar 12, 2009 5:02 pm**

I don't see a .data and a .rodata or .rdata section in the dump...

Posted: **Thu Mar 12, 2009 5:12 pm**

the .data is just afterthe .text
and for the .rodata how can I get it ?

Code: Select all

Disassembly of section .data:

0000000000000000 <p>:
   0:   00 80 0b 00 00 00       add    %al,0xb(%rax)

Posted: **Thu Mar 12, 2009 5:23 pm**

Are you in a 64-bit linux distribution? If so, are you linking to a 32 bit plain binary file?

I you aren't, try adding "-m 32" to the gcc compile command.

Cheers,
Gzaloprgm

Posted: **Thu Mar 12, 2009 5:40 pm**

Yes I'm on Ubuntu 64 but that does't work. I got this

ld: unrecognised emulation mode: 32
Supported emulations: elf_x86_64 elf_i386 i386linux

and i'm want a real binary

Posted: **Thu Mar 12, 2009 5:53 pm**

gzaloprgm wrote:try adding "-m 32" to the gcc compile command.

Posted: **Thu Mar 12, 2009 6:12 pm**

Ok that work thank you very much ! The problem that i got was I link with LD and not GCC. look the solution.

CFLAGS= -m32 -c -I $(INC_PATH) -ffreestanding -nostdinc -nostdlib -Wall -Werror -fno-stack-protector
LDFLAGS= -m elf_i386 -T linker.ld

I have a two other question. In many ld scipt we find ALIGN(4096) ... I know that is 64 kb but why we have to put that ???
And i'm new user under Linux ..... the elf format it is the same think of the PE format under Windows ??

Posted: **Thu Mar 12, 2009 6:19 pm**

4096 is NOT 64kb, its 4kb. You need that alignment for paging because pages a 4kb in size. You should be able to get away without it, but using at least ALIGN(16) is a good idea to speed up memory accesses.

And no, elf is not the same as PE. They are two completely different formats. You should probably use ELF for osdev because its easier to parse yourself and grub loads it easily.

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