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Update from Pedro Romano <pmcnr@camoes.rnl.ist.utl.pt> with an attempt

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to fix start16.s.  It does not work locally.
This commit is contained in:
Joel Sherrill
1998-06-03 19:00:57 +00:00
parent 937a6f3cef
commit 3c7916f21c
2 changed files with 39 additions and 15 deletions
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2
c/src/lib/libbsp/i386/pc386/start/Makefile.in
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@@ -60,7 +60,7 @@ LINKCMDS=$(srcdir)/../startup/linkcmds
${ARCH}/start16.o: start16.s
sed -e 's/\/\/.*$$//' < $< | $(CPP) $(ASMFLAGS) -I. -I$(srcdir) \
-DASM -DSTART32ADDR=$(RELOCADDR) - > $*.i
-DASM -DHEADERADDR=$(HEADERADDR) - > $*.i
$(AS) $(ASFLAGS) -o $@ $*.i
${ARCH}/start16.bin: ${ARCH}/start16.o

52
c/src/lib/libbsp/i386/pc386/start/start16.s
View File

@@ -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:
@@ -49,6 +52,20 @@
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 #
.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