Re: Problem loading a multiboot kernel

[Vincent Girard-Reydet]

Hi,

The reboot occures only when I specify a VMA different from the LMA in the 
linker script.
In fact, it seems that Grub always follows the ELF header when ther's one, 
even if a a.out kludge is provided. The header of my file lokks like this :

1b ad b0 02  // magic
00 01 00 02 // flags, including the A.OUT kludge bit
e4 51 4f fc    // checksum
00 01 00 04 // header address
00 01 00 00 /load start
00 01 8c 68  // load end
00 11 be d4 // bss end
00 01 00 24 // entry point

So normally I should be loaded and started to about 0x100000. But when I try 
booting, Grub tells me

[Multiboot-elf, <0xc0000000:0x8c68:0x1326c>
Error 28: Selected item cannot fit into memory.




Le Mercredi 30 Juillet 2003 08:44, Vincent Girard-Reydet a écrit :
> Le Mercredi 30 Juillet 2003 02:47, Jeff Sheinberg a écrit :
> > Vincent Girard-Reydet writes:
> >  > Hope this is the rightplace to post my question. I'm currently
> >  > working on a kernel that I made multiboot compliant.
> >  >
> >  > This kernel is linked as an ELF program, section .text starting
> >  > at 0xc0000000.  As I need to configure the paged memory before
> >  > switching to high addresses, I must load my kernel at a much
> >  > lower address. So I ask in my Multiboot header to be loaded at
> >  > 0x100000, and I use translation tricks (leal and co) to get my
> >  > code working untill the pagination is activated.
> >  >
> >  > But Grub won't load my kernel. I checked the addresses in the
> >  > Multiboot header with objdump, they are correct. I put an
> >  > instruction that prints a character on the screen and loops at
> >  > the cery end of my kernel, to only check if I'm booted. But the
> >  > machine reboots when Grub loads the kernel.
> >
> > Have you tried "mbchk YOUR_KERNEL", try "info mbchk" for details.
>
> Here is the output of mbchk :
>
> The Multiboot header is found at the offset 4100.
> /mnt/tmp/kernel.bin: Page alignment is turned off.
> /mnt/tmp/kernel.bin: Memory information is turned on.
> /mnt/tmp/kernel.bin: Address fields is turned on.
> /mnt/tmp/kernel.bin: All checks passed.
>
> For info, here are the ELF headers of my file :
>
> bash-2.05b$ objdump -ph /mnt/tmp/kernel.bin
>
> /mnt/tmp/kernel.bin:     file format elf32-i386
>
> Program Header:
>     LOAD off    0x00001000 vaddr 0xc0000000 paddr 0xc0000000 align 2**12
>          filesz 0x00008c68 memsz 0x0001bed4 flags rwx
>
> Sections:
> Idx Name          Size      VMA       LMA       File off  Algn
>   0 .text         000050f7  c0000000  c0000000  00001000  2**2
>                   CONTENTS, ALLOC, LOAD, READONLY, CODE
>   1 .data         00003b68  c0005100  c0005100  00006100  2**5
>                   CONTENTS, ALLOC, LOAD, DATA
>   2 .bss          00012ed4  c0009000  c0009000  0000a000  2**12
>                   ALLOC
>   3 .debug_line   00003a3a  00000000  00000000  0000a000  2**0
>                   CONTENTS, READONLY, DEBUGGING
>   4 .debug_info   00009b3d  00000000  00000000  0000da3a  2**0
>                   CONTENTS, READONLY, DEBUGGING
>   5 .debug_abbrev 000020b7  00000000  00000000  00017577  2**0
>                   CONTENTS, READONLY, DEBUGGING
>   6 .debug_aranges 00000470  00000000  00000000  00019630  2**3
>                   CONTENTS, READONLY, DEBUGGING
>   7 .debug_frame  0000124c  00000000  00000000  00019aa0  2**2
>                   CONTENTS, READONLY, DEBUGGING
>   8 .debug_pubnames 0000060c  00000000  00000000  0001acec  2**0
>                   CONTENTS, READONLY, DEBUGGING
>   9 .debug_str    0000168c  00000000  00000000  0001b2f8  2**0
>                   CONTENTS, READONLY, DEBUGGING
>  10 .comment      00000640  00000000  00000000  0001c984  2**0
>                   CONTENTS, READONLY