diff options
Diffstat (limited to 'c/src/lib/libbsp/i386/pc386/start/start16.s')
| -rw-r--r-- | c/src/lib/libbsp/i386/pc386/start/start16.s | 52 |
1 files changed, 38 insertions, 14 deletions
diff --git a/c/src/lib/libbsp/i386/pc386/start/start16.s b/c/src/lib/libbsp/i386/pc386/start/start16.s index 0e715368ba..c5febfda92 100644 --- a/c/src/lib/libbsp/i386/pc386/start/start16.s +++ b/c/src/lib/libbsp/i386/pc386/start/start16.s @@ -1,5 +1,5 @@ /*-------------------------------------------------------------------------+ -| start16hi.s v1.0 - PC386 BSP - 1998/04/13 +| 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. @@ -27,8 +27,11 @@ +----------------------------------------------------------------------------*/ .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 START32, START32ADDR # address of protected mode code +.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 /*----------------------------------------------------------------------------+ | A Descriptor table register has the following format: @@ -51,6 +54,20 @@ _start16: .code16 + cli # DISABLE INTERRUPTS!!! + + movw %cs, %ax # + movw %ax, %ds # set the rest of real mode registers + movw %ax, %es # + movw %ax, %ss # + +.code32 + + movl $STACKOFF, %esp # set stack pointer + movl $STACKOFF, %ebp # + +.code16 + #if defined(RTEMS_VIDEO_80x50) /*---------------------------------------------------------------------+ @@ -72,29 +89,34 @@ _start16: #endif /* RTEMS_VIDEO_80x50 */ - cli # DISABLE INTERRUPTS!!! - /*---------------------------------------------------------------------+ | Bare PC machines boot in real mode! We have to turn protected mode on. +---------------------------------------------------------------------*/ - movl $gdtptr, %eax - andl $0x0000ffff, %eax # get offset into segment - lgdt %cs:(%eax) # load Global Descriptor Table - movl $idtptr, %eax - andl $0x0000ffff, %eax # get offset into segment - lidt %cs:(%eax) # load Interrupt Descriptor Table + lgdt gdtptr - start16 # load Global Descriptor Table + lidt idtptr - start16 # load Interrupt Descriptor Table movl %cr0, %eax orl $CR0_PE, %eax movl %eax, %cr0 # turn on protected mode - - ljmp $PROT_CODE_SEG, $1f # flush prefetch queue + + ljmp $PROT_CODE_SEG, $1f # flush prefetch queue, and reload %cs 1: .code32 - /*---------------------------------------------------------------------+ | we have to enable A20 in order to access memory above 1MByte + /*---------------------------------------------------------------------+ + | load the other segment registers + +---------------------------------------------------------------------*/ + movl $PROT_DATA_SEG, %eax + movl %ax, %ds + movl %ax, %es + movl %ax, %ss + addl $start16, %esp # fix up stack pointer + addl $start16, %ebp # fix up stack pointer + + /*---------------------------------------------------------------------+ + | we have to enable A20 in order to access memory above 1MByte +---------------------------------------------------------------------*/ call empty_8042 movb $0xD1, %al # command write @@ -104,7 +126,9 @@ _start16: outb %al, $0x60 call empty_8042 - ljmp $PROT_CODE_SEG, $START32 # jump to start of 32 bit code + movl %cs:HDRSTART + HDROFF, %eax # + pushl %eax # jump to start of 32 bit code + ret # /*----------------------------------------------------------------------------+ | delay |