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Diffstat (limited to 'c/src/lib/libbsp/i386/pc386/start/start16.S')
| -rw-r--r-- | c/src/lib/libbsp/i386/pc386/start/start16.S | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/c/src/lib/libbsp/i386/pc386/start/start16.S b/c/src/lib/libbsp/i386/pc386/start/start16.S new file mode 100644 index 0000000000..4b12408cd6 --- /dev/null +++ b/c/src/lib/libbsp/i386/pc386/start/start16.S @@ -0,0 +1,183 @@ +/*-------------------------------------------------------------------------+ +| start16.s v1.0 - PC386 BSP - 1998/04/13 ++--------------------------------------------------------------------------+ +| This file contains the entry point for the application. +| The name of this entry point is compiler dependent. +| It jumps to the BSP which is responsible for performing all initialization. ++--------------------------------------------------------------------------+ +| (C) Copyright 1997 - +| - NavIST Group - Real-Time Distributed Systems and Industrial Automation +| +| http://pandora.ist.utl.pt +| +| Instituto Superior Tecnico * Lisboa * PORTUGAL ++--------------------------------------------------------------------------+ +| Disclaimer: +| +| This file is provided "AS IS" without warranty of any kind, either +| expressed or implied. ++--------------------------------------------------------------------------+ +| This code is partly based on (from the Linux source tree): +| video.S - Copyright (C) 1995, 1996 Martin Mares <mj@k332.feld.cvut.cz> ++--------------------------------------------------------------------------*/ + + +/*----------------------------------------------------------------------------+ +| Constants ++----------------------------------------------------------------------------*/ + +.set PROT_CODE_SEG, 0x08 # offset of code segment descriptor into GDT +.set PROT_DATA_SEG, 0x10 # offset of code segment descriptor into GDT +.set CR0_PE, 1 # protected mode flag on CR0 register +.set HDRSTART, HEADERADDR # address of start of bin2boot header +.set HDROFF, 0x24 # offset into bin2boot header of start32 addr +.set STACKOFF, 0x200-0x10 # offset to load into %esp, from start of image + + /* #define NEW_GAS */ +/*----------------------------------------------------------------------------+ +| CODE section ++----------------------------------------------------------------------------*/ + +.text + + .globl _start16 # entry point + .globl start16 +start16: +_start16: + +.code16 + + cli # DISABLE INTERRUPTS!!! + + movw %cs, %ax # + movw %ax, %ds # set the rest of real mode registers + movw %ax, %es # + movw %ax, %ss # + +#if defined(RTEMS_VIDEO_80x50) + + /*---------------------------------------------------------------------+ + | Switch VGA video to 80 lines x 50 columns mode. Has to be done before + | turning protected mode on since it uses BIOS int 10h (video) services. + +---------------------------------------------------------------------*/ + + movw $0x0003, %ax # forced set + int $0x10 + movw $0x1112, %ax # use 8x8 font + xorb %bl, %bl + int $0x10 + movw $0x1201, %ax # turn off cursor emulation + movb $0x34, %bl + int $0x10 + movb $0x01, %ah # define cursor (scan lines 0 to 7) + movw $0x0007, %cx + int $0x10 + +#endif /* RTEMS_VIDEO_80x50 */ + + /*---------------------------------------------------------------------+ + | Bare PC machines boot in real mode! We have to turn protected mode on. + +---------------------------------------------------------------------*/ +#ifdef NEW_GAS + data32 + addr32 +#endif + lgdt gdtptr - start16 # load Global Descriptor Table + movl %cr0, %eax + orl $CR0_PE, %eax + movl %eax, %cr0 # turn on protected mode + +#ifdef NEW_GAS + ljmpl $PROT_CODE_SEG, $1f # flush prefetch queue, and reload %cs +#else + ljmp $PROT_CODE_SEG, $1f # flush prefetch queue, and reload %cs +#endif +.code32 +1: + /*---------------------------------------------------------------------+ + | load the other segment registers + +---------------------------------------------------------------------*/ + movl $PROT_DATA_SEG, %eax + movl %ax, %ds + movl %ax, %es + movl %ax, %ss + movl $start16 + STACKOFF, %esp # set up stack pointer + addl $start16 + STACKOFF, %ebp # set up stack pointer + + /*---------------------------------------------------------------------+ + | we have to enable A20 in order to access memory above 1MByte + +---------------------------------------------------------------------*/ + call empty_8042 + movb $0xD1, %al # command write + outb %al, $0x64 + call empty_8042 + movb $0xDF, %al # A20 on + outb %al, $0x60 + call empty_8042 + + movl %cs:HDRSTART + HDROFF, %eax # + pushl %eax # jump to start of 32 bit code + ret # + +/*----------------------------------------------------------------------------+ +| delay ++------------------------------------------------------------------------------ +| Delay is needed after doing I/O. We do it by writing to a non-existent port. ++----------------------------------------------------------------------------*/ + .globl _delay + .globl delay +delay: +_delay: + outb %al, $0xED # about 1uS delay + ret + +/*----------------------------------------------------------------------------+ +| empty_8042 ++------------------------------------------------------------------------------ +| This routine checks that the keyboard command queue is empty (after emptying +| the output buffers). +| No timeout is used - if this hangs there is something wrong with the machine, +| and we probably couldn't proceed anyway. ++----------------------------------------------------------------------------*/ + .globl _empty_8042 + .globl empty_8042 +empty_8042: +_empty_8042: + call delay + inb $0x64, %al # 8042 status port + testb $0x01, %al # output buffer? + jz no_output + call delay + in $0x60, %al # read it + jmp empty_8042 +no_output: + test $0x02, %al # is input buffer full? + jnz empty_8042 # yes - loop + ret + +/*----------------------------------------------------------------------------+ +| DATA section ++----------------------------------------------------------------------------*/ + +/************************** +* GLOBAL DESCRIPTOR TABLE * +**************************/ + + .p2align 4 +gdtptr: + /* we use the NULL descriptor to store the GDT pointer - a trick quite + nifty due to: Robert Collins (rcollins@x86.org) */ + .word gdtlen - 1 + .long gdtptr + .word 0x0000 + + /* code segment */ + .word 0xffff, 0 + .byte 0, 0x9f, 0xcf, 0 + + /* data segment */ + .word 0xffff, 0 + .byte 0, 0x93, 0xcf, 0 + + .set gdtlen, . - gdtptr # length of GDT + |