Archivo en el núcleo de Linux

[Caster]

Antes de todo, no tengo ni **** idea de programación. Estos dias voy a instalarme Ubuntu en mi PC y navegando por internert se me dio por buscar el nucleo de Linux 0.01, los descargue y lo estuve viendo, y encontré unos archivos llamados 'boot.s' y 'head.s' a parte de los archivos '.c' los heads y algunos mas, lo '.c' y los heads se que tipo de archivos son, abri los archivos 'boot.s' y 'head.s' para ver que tenian, pero no me entero de nada, supongo que seran los archivos que cargan el kernel o algo de eso, y viendo el codigo aun me entero menos porque no se que lenguaje es, supongo que será ensamblador, aqui os dejo el codigo de uno de los archivos:

Código (asm) [Seleccionar] Expandir

/*
*  head.s contains the 32-bit startup code.
*
* NOTE!!! Startup happens at absolute address 0x00000000, which is also where
* the page directory will exist. The startup code will be overwritten by
* the page directory.
*/
.text
.globl _idt,_gdt,_pg_dir
_pg_dir:
startup_32:
movl $0x10,%eax
mov %ax,%ds
mov %ax,%es
mov %ax,%fs
mov %ax,%gs
lss _stack_start,%esp
call setup_idt
call setup_gdt
movl $0x10,%eax # reload all the segment registers
mov %ax,%ds # after changing gdt. CS was already
mov %ax,%es # reloaded in 'setup_gdt'
mov %ax,%fs
mov %ax,%gs
lss _stack_start,%esp
xorl %eax,%eax
1: incl %eax # check that A20 really IS enabled
movl %eax,0x000000
cmpl %eax,0x100000
je 1b
movl %cr0,%eax # check math chip
andl $0x80000011,%eax # Save PG,ET,PE
testl $0x10,%eax
jne 1f # ET is set - 387 is present
orl $4,%eax # else set emulate bit
1: movl %eax,%cr0
jmp after_page_tables

/*
*  setup_idt
*
*  sets up a idt with 256 entries pointing to
*  ignore_int, interrupt gates. It then loads
*  idt. Everything that wants to install itself
*  in the idt-table may do so themselves. Interrupts
*  are enabled elsewhere, when we can be relatively
*  sure everything is ok. This routine will be over-
*  written by the page tables.
*/
setup_idt:
lea ignore_int,%edx
movl $0x00080000,%eax
movw %dx,%ax /* selector = 0x0008 = cs */
movw $0x8E00,%dx /* interrupt gate - dpl=0, present */

lea _idt,%edi
mov $256,%ecx
rp_sidt:
movl %eax,(%edi)
movl %edx,4(%edi)
addl $8,%edi
dec %ecx
jne rp_sidt
lidt idt_descr
ret

/*
*  setup_gdt
*
*  This routines sets up a new gdt and loads it.
*  Only two entries are currently built, the same
*  ones that were built in init.s. The routine
*  is VERY complicated at two whole lines, so this
*  rather long comment is certainly needed :-).
*  This routine will beoverwritten by the page tables.
*/
setup_gdt:
lgdt gdt_descr
ret

.org 0x1000
pg0:

.org 0x2000
pg1:

.org 0x3000
pg2: # This is not used yet, but if you
# want to expand past 8 Mb, you'll have
# to use it.

.org 0x4000
after_page_tables:
pushl $0 # These are the parameters to main :-)
pushl $0
pushl $0
pushl $L6 # return address for main, if it decides to.
pushl $_main
jmp setup_paging
L6:
jmp L6 # main should never return here, but
# just in case, we know what happens.

/* This is the default interrupt "handler" :-) */
.align 2
ignore_int:
incb 0xb8000+160 # put something on the screen
movb $2,0xb8000+161 # so that we know something
iret # happened


/*
* Setup_paging
*
* This routine sets up paging by setting the page bit
* in cr0. The page tables are set up, identity-mapping
* the first 8MB. The pager assumes that no illegal
* addresses are produced (ie >4Mb on a 4Mb machine).
*
* NOTE! Although all physical memory should be identity
* mapped by this routine, only the kernel page functions
* use the >1Mb addresses directly. All "normal" functions
* use just the lower 1Mb, or the local data space, which
* will be mapped to some other place - mm keeps track of
* that.
*
* For those with more memory than 8 Mb - tough luck. I've
* not got it, why should you :-) The source is here. Change
* it. (Seriously - it shouldn't be too difficult. Mostly
* change some constants etc. I left it at 8Mb, as my machine
* even cannot be extended past that (ok, but it was cheap :-)
* I've tried to show which constants to change by having
* some kind of marker at them (search for "8Mb"), but I
* won't guarantee that's all :-( )
*/
.align 2
setup_paging:
movl $1024*3,%ecx
xorl %eax,%eax
xorl %edi,%edi /* pg_dir is at 0x000 */
cld;rep;stosl
movl $pg0+7,_pg_dir /* set present bit/user r/w */
movl $pg1+7,_pg_dir+4 /*  --------- " " --------- */
movl $pg1+4092,%edi
movl $0x7ff007,%eax /*  8Mb - 4096 + 7 (r/w user,p) */
std
1: stosl /* fill pages backwards - more efficient :-) */
subl $0x1000,%eax
jge 1b
xorl %eax,%eax /* pg_dir is at 0x0000 */
movl %eax,%cr3 /* cr3 - page directory start */
movl %cr0,%eax
orl $0x80000000,%eax
movl %eax,%cr0 /* set paging (PG) bit */
ret /* this also flushes prefetch-queue */

.align 2
.word 0
idt_descr:
.word 256*8-1 # idt contains 256 entries
.long _idt
.align 2
.word 0
gdt_descr:
.word 256*8-1 # so does gdt (not that that's any
.long _gdt # magic number, but it works for me :^)

.align 3
_idt: .fill 256,8,0 # idt is uninitialized

_gdt: .quad 0x0000000000000000 /* NULL descriptor */
.quad 0x00c09a00000007ff /* 8Mb */
.quad 0x00c09200000007ff /* 8Mb */
.quad 0x0000000000000000 /* TEMPORARY - don't use */
.fill 252,8,0 /* space for LDT's and TSS's etc */

Alguien me podia aclarar que tipo de archivos son estos, cual es su funcion y que lenguaje es el que estan escritos, es solo curiosidad.

Muchas gracias

[dac]

Es codigo en ensamblador, y el "boot" es el codigo encargado de iniciar el SO.

Pues eso es.. asi muy a la lijera..

Saludos!

[Caster]

Lo que yo pensaba mas o menos, muchas gracias!

Saludos, Caster.