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HigherHalfWithGdt and Grub Error 28
Posted: Tue Jul 11, 2006 4:14 am
by yegor
Hello, All.
I'm trying to build a higher-half kernel with gcc 2.95.2 and gnu ld version 2.9.1. Method is one described in HigherHalfWithGdt article.
I used linker script from FAQ with no changes, assembler part has been rewritten to GAS.
The problem is when I try to launch new kernel, Grub 0.97 says: "Selected item cannot fit into memory."
Code: Select all
$ objdump -x kernel
kernel: file format elf32-i386
kernel
architecture: i386, flags 0x00000112:
EXEC_P, HAS_SYMS, D_PAGED
start address 0xc010002c
Program Header:
LOAD off 0x00000000 vaddr 0xc00ff000 paddr 0x000ff000 align 2**12
filesz 0x000038ea memsz 0x000038ea flags r-x
LOAD off 0x00004000 vaddr 0xc0103000 paddr 0x00103000 align 2**12
filesz 0x00000e88 memsz 0x0000d924 flags rw-
Sections:
Idx Name Size VMA LMA File off Algn
0 .setup 0000001e 00100000 00100000 00005000 2**0
CONTENTS, READONLY
1 .text 000028ca c0100020 00100020 00001020 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
2 .data 00000e88 c0103000 00103000 00004000 2**5
CONTENTS, ALLOC, LOAD, DATA
3 .bss 0000c924 c0104000 00104000 00005000 2**5
ALLOC
4 .note 00000104 c0110924 c0110924 0000501e 2**0
CONTENTS, READONLY
5 .comment 000001ee c0110a28 c0110a28 00005122 2**0
CONTENTS, READONLY
Even if I delete suspicious .note and .comment sections with strip, Grub reports the same error.
Any ideas?
Re:HigherHalfWithGdt and Grub Error 28
Posted: Tue Jul 11, 2006 4:47 am
by Solar
Without looking too close at the objdump, any specific reason for using a 1998 linker and a 2001 compiler? Just curious, because my first reflex would have been updating my toolchain to the latest public release...
Re:HigherHalfWithGdt and Grub Error 28
Posted: Tue Jul 11, 2006 5:04 am
by yegor
It's very simple.
I just don't know root password on that machine.
Re:HigherHalfWithGdt and Grub Error 28
Posted: Tue Jul 11, 2006 5:28 am
by Solar
You can use that 2.9x GCC to compile an up-to-date version of tools and install that to /home/yegor/bin or whereever you want. I would honestly recommend going through the
GCC Cross-Compiler tutorial using TARGET=i386-elf and PREFIX={wherever-you-have-access} to rule out some long-fixed bugs in your tools as the cause for your problems.
And now I step back to leave room for those who can help you with your
other problem (the GRUB error).
Re:HigherHalfWithGdt and Grub Error 28
Posted: Tue Jul 11, 2006 8:40 am
by yegor
Well, it's not a bad idea to build newer gcc, but it was not the point here.
Of course, I did must specify "ax" attributes for .setup section in head.S.
Re:HigherHalfWithGdt and Grub Error 28
Posted: Thu Jul 13, 2006 1:13 am
by Pype.Clicker
i'm suspicious about your "paddr 0x000ff000" part (presumably, the linker said the whole chunk had to be loaded at 0xff000 so that after the section info (one page), the code actually stands at 0x100000: quite weird).
Grub may not like to require something loaded below 1MB. Earlier versions of GRUB didn't liked physical addresses to differ from logical addresses. Checking you have a recent GRUB may help.
Re:HigherHalfWithGdt and Grub Error 28
Posted: Thu Jul 13, 2006 1:26 am
by Solar
His GRUB is 0.97, that's recent.
Re:HigherHalfWithGdt and Grub Error 28
Posted: Mon Jul 24, 2006 8:00 am
by quok
I had a similar problem when porting the HigherHalfWithGDT code to GAS, and I was using a recent toolchain (binutils 2.17 and gcc 4.1.1).
I did eventually get it to work, I'm attaching my loader.S code for review.
Code: Select all
# loader.S
.global _loader # make 'start' function global
.extern _main # our C kernel main
# Multiboot constants
.set MULTIBOOT_PAGE_ALIGN, 1<<0
.set MULTIBOOT_MEMORY_INFO, 1<<1
.set MULTIBOOT_HEADER_MAGIC, 0x1BADB002
.set MULTIBOOT_HEADER_FLAGS, MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO
.set MULTIBOOT_CHECKSUM, -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
# Multiboot header (needed to boot from GRUB)
.align 4
multiboot_header:
.long MULTIBOOT_HEADER_MAGIC
.long MULTIBOOT_HEADER_FLAGS
.long MULTIBOOT_CHECKSUM
.set STACKSIZE, 0x4000
# the kernel entry point
_loader:
# here's the trick: we load a GDT with a base address
# of 0x40000000 for the code (0x08) and data (0x10) segments
lgdt trickgdt
mov $0x10, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss
# jump to the higher half kernel
jmp $0x08, $higherhalf
higherhalf:
# from now the CPU will translate automatically every address
# by adding the base 0x40000000
mov $kernel_stack, %esp # set up a new stack for our kernel
call _main # jump to our C kernel
# just a simple protection...
jmp .
.global gdt_flush # make 'gdt_flush' accessible from C code
.extern gp # tells the assembler to look at C code for 'gp'
# this function does the same thing of the 'start' one, this time with
# the real GDT
gdt_flush:
lgdt gp
mov $0x10, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss
jmp $0x08, $flush2
flush2:
ret
.section .setup, "a" # tells the assembler to include this data in the '.setup' section
trickgdt:
.word gdt_end - gdt - 1 # size of the GDT
.long gdt # linear address of GDT
gdt:
# null gate
.long 0, 0
# code selector 0x08: base 0x40000000, limit 0xFFFFFFFF, type 0x9A, granularity 0xCF
.byte 0xFF, 0xFF, 0, 0, 0, 0B10011010, 0B11001111, 0x40
# data selector 0x10: base 0x40000000, limit 0xFFFFFFFF, type 0x92, granularity 0xCF
.byte 0xFF, 0xFF, 0, 0, 0, 0B10010010, 0B11001111, 0x40
gdt_end:
.section .bss
.align 32
.skip 0x4000 # 16K stack space, 32-bit aligned
kernel_stack:
# our kernel stack