Merged mcb30-realmode-redesign back to HEAD

3 files changed, 178 insertions, 95 deletions

diff --git a/src/arch/i386/prefix/floppyprefix.S b/src/arch/i386/prefix/dskprefix.S
index 18bed4c8f..d1f64e7ae 100644
--- a/src/arch/i386/prefix/floppyprefix.S
+++ b/src/arch/i386/prefix/dskprefix.S
@@ -1,3 +1,5 @@
+#include "compiler.h"
+
 /* NOTE: this boot sector contains instructions that need at least an 80186.
  * Yes, as86 has a bug somewhere in the valid instruction set checks.
  *
@@ -115,7 +117,6 @@ got_sectors:
 
 /* ok, we've written the Loading... message, now we want to load the system */
 
-	pushw	%es			/* = ds */
 	movw	$SYSSEG, %ax
 	movw	%ax,%es			/* segment of SYSSEG<<4 */
 	pushw	%es
@@ -130,8 +131,6 @@ got_sectors:
 
 	call	print_nl
 	pop	%es			/* = SYSSEG */
-	pop	%es			/* balance push/pop es */
-sigok: 
 
 /* Restore original disk parameters */
 	movw	$0x78, %bx
@@ -142,20 +141,47 @@ sigok:
 	movw	%di,(%bx)
 	movw	%si,2(%bx)
 
-/* after that (everything loaded), we call to the .ROM file loaded. */
-
-	pushl	$0		/* No parameters to preserve for exit path */
-	pushw	$0		/* Use prefix exit path mechanism */
-	ljmp	$SYSSEG, $_start
-
-	.section ".text16", "ax", @progbits
-	.globl	prefix_exit
-prefix_exit:
-	xchgw	%bx, %bx
-	int	$0x19		/* should try to boot machine */
-	.globl	prefix_exit_end
-prefix_exit_end:
-	.previous
+	/* Everything now loaded.  %es = SYSSEG, so %es:0000 points to
+	 * start of loaded image.
+	 */
+
+start_runtime:
+
+#ifdef	COMPRESS
+	/* Decompress runtime image.  %es:0000 points to decompressed
+	 * image on exit.
+	 */
+	lcall	$SYSSEG, $decompress16
+#endif
+	
+	/* Set up internal environment.  Address of entry-point
+	 * function is returned in %es:di.
+	 */
+	pushw	%es		/* setup16 says %ds:0000 must point to image */
+	popw	%ds
+	movw	$setup16, %di
+	pushw	%cs
+	call	ljmp_to_es_di
+
+	/* Call initialisation routine.  Relocation may be done.  New
+	 * address of entry-point function is returned in %es:di.
+	 */
+	pushl	$arch_rm_initialise
+	pushw	%cs		/* == lcall %es:di */
+	call	ljmp_to_es_di
+	
+	/* Call to arch_rm_main.  Register INT19 as an exit path.  This
+	 * call will never return.
+	 */
+	movl	$exit_via_int19, %eax
+	pushl	$arch_rm_main
+	pushl	%eax		/* Dummy return address */
+
+	/* Do the equivalent of ljmp *%es:di */
+ljmp_to_es_di:	
+	pushw	%es
+	pushw	%di
+	lret
 
 /* This routine loads the system at address SYSSEG<<4, making sure no 64kB
  * boundaries are crossed. We try to load it as fast as possible, loading whole
@@ -164,7 +190,7 @@ prefix_exit_end:
  * in:	es - starting address segment (normally SYSSEG)
  */
 read_it: 
-	movw	$0,sread		/* read whole image incl boot sector */
+	movw	$1,sread		/* don't reload the prefix */
 	movw	%es,%ax
 	testw	$0x0fff, %ax
 die:	jne	die			/* es must be at 64kB boundary */
diff --git a/src/arch/i386/prefix/int19exit.c b/src/arch/i386/prefix/int19exit.c
new file mode 100644
index 000000000..e7be06244
--- /dev/null
+++ b/src/arch/i386/prefix/int19exit.c
@@ -0,0 +1,13 @@
+#include "bochs.h"
+#include "realmode.h"
+
+/*
+ * The "exit via INT 19" exit path.  INT 19 is the old (pre-BBS) "boot
+ * system" interrupt.
+ *
+ */
+
+void exit_via_int19 ( struct real_mode_regs *rm_regs ) {
+	bochsbp();
+	/* Placeholder */
+}
diff --git a/src/arch/i386/prefix/unnrv2b.S b/src/arch/i386/prefix/unnrv2b.S
index 1836fa715..50776dc93 100644
--- a/src/arch/i386/prefix/unnrv2b.S
+++ b/src/arch/i386/prefix/unnrv2b.S
@@ -15,115 +15,159 @@
  * - Structure modified to be a subroutine call rather than an
  *   executable prefix.
  *   Michael Brown 30 Mar 2004
+ *
+ * - Modified to be compilable as either 16-bit or 32-bit code.
+ *   Michael Brown 9 Mar 2005
  */
 
+/****************************************************************************
+ * This file provides the decompress_block() and decompress_block16()
+ * functions which can be called in order to decompress an image
+ * compressed with the nrv2b utility in src/util.
+ *
+ * These functions are designed to be called by the prefix.  They are
+ * position-independent code.
+ *
+ * The same basic assembly code is used to compile both
+ * decompress_block() and decompress_block16().
+ ****************************************************************************
+ */
 
 	.text
 	.arch i386
 	.section ".prefix", "ax", @progbits
-	.code32
-	
-	.globl decompress
-decompress:
-	/* Save the initial register values */
-	pushal
 
-	/*
-	 * See where I am running, and compute %ebp
-	 * %ebp holds delta between physical and virtual addresses.
-	 */
-	call	1f
-1:	popl	%ebp
-	subl	$1b, %ebp
+#ifdef CODE16
+/****************************************************************************
+ * decompress_block16 (real-mode near call, position independent)
+ *
+ * Parameters (passed via registers):
+ *   %ds:%si - Pointer to compressed input data
+ *   %es:%di - Pointer to output buffer
+ * Returns:
+ *   All registers are preserved
+ *
+ * NOTE: The compressed data size must be in the range [1,65533-%si]
+ * and the uncompressed data size must be in the range [1,65536-%di]
+ * (where %si and %di are the input values for those registers).  Note
+ * particularly that the lower limit is 1, not 0, and that the upper
+ * limit on the input (compressed) data really is 65533, since the
+ * algorithm may read up to three bytes beyond the end of the input
+ * data, since it reads dwords.
+ *
+ * Although splitting up the data into (almost) 64kB chunks for
+ * compression is awkward and worsens the compression ratio, it has
+ * little to no practical effect since our image size is currently
+ * <64kB for all single drivers.  Having a decompression routine that
+ * can run in real-mode avoids the need to duplicate RM-to-PM
+ * transition code from librm (or have part of librm kept
+ * uncompressed, which is itself awkward) and means that we don't need
+ * to set up the PM stack until we hit the setup routine itself.
+ ****************************************************************************
+ */
+
+#define REG(x) x
 
-	/* "compressed" and "decompress_to" defined by linker script */
-	/* move compressed image up to temporary area before decompressing */
-	std
-	movl	$_compressed_size, %ecx
-	leal	_compressed+4-1(%ebp, %ecx), %esi
-	leal	_compressed_copy-1(%ebp, %ecx), %edi
-	rep movsb
-	/* Setup to run the decompressor */
-	cld
-	leal	_compressed_copy(%ebp), %esi
-	leal	decompress_to(%ebp), %edi
-	movl	$-1, %ebp	/* last_m_off = -1 */
-	jmp	dcl1_n2b
+	.code16
+	.globl	decompress_block16
+decompress_block16:
+	
+#else /* CODE16 */
 
-/* ------------- DECOMPRESSION -------------
+/****************************************************************************
+ * decompress_block (32-bit protected-mode near call, position independent)
+ *
+ * Parameters (passed via registers):
+ *   %ds:%esi - Pointer to compressed input data
+ *   %es:%edi - Pointer to output buffer
+ * Returns:
+ *   All registers are preserved
+ ****************************************************************************
+ */
 
- Input:
-   %esi - source
-   %edi - dest
-   %ebp - -1
-   cld
+#define REG(x) e ## x
+	
+	.code32
+	.globl	decompress_block
+decompress_block:
 
- Output:
-   %eax - 0
-   %ecx - 0
-*/
+#endif /* CODE16 */
 
-.macro getbit bits
-.if	\bits == 1
-	addl	%ebx, %ebx
-	jnz	1f
-.endif
-	movl	(%esi), %ebx
-	subl	$-4, %esi	/* sets carry flag */
-	adcl	%ebx, %ebx
-1:
-.endm
+#define xAX	REG(ax)
+#define xCX	REG(cx)
+#define xBP	REG(bp)
+#define xSI	REG(si)
+#define xDI	REG(di)
 
+	/* Save registers */
+	pushal
+	/* Do the decompression */
+	cld
+	xor	%xBP, %xBP
+	dec	%xBP		/* last_m_off = -1 */
+	jmp	dcl1_n2b
+	
 decompr_literals_n2b:
 	movsb
-
 decompr_loop_n2b:
 	addl	%ebx, %ebx
 	jnz	dcl2_n2b
 dcl1_n2b:
-	getbit	32
+	call	getbit32
 dcl2_n2b:
 	jc	decompr_literals_n2b
-	xorl	%eax, %eax
-	incl	%eax		/* m_off = 1 */
+	xor	%xAX, %xAX
+	inc	%xAX		/* m_off = 1 */
 loop1_n2b:
-	getbit	1
-	adcl	%eax, %eax	/* m_off = m_off*2 + getbit() */
-	getbit	1
+	call	getbit1
+	adc	%xAX, %xAX	/* m_off = m_off*2 + getbit() */
+	call	getbit1
 	jnc	loop1_n2b	/* while(!getbit()) */
-	xorl	%ecx, %ecx
-	subl	$3, %eax
+	sub	$3, %xAX
 	jb	decompr_ebpeax_n2b	/* if (m_off == 2) goto decompr_ebpeax_n2b ? */
-	shll	$8, %eax	
-	movb	(%esi), %al	/* m_off = (m_off - 3)*256 + src[ilen++] */
-	incl	%esi
-	xorl	$-1, %eax	
+	shl	$8, %xAX	
+	movb	(%xSI), %al	/* m_off = (m_off - 3)*256 + src[ilen++] */
+	inc	%xSI
+	not	%xAX	
 	jz	decompr_end_n2b	/* if (m_off == 0xffffffff) goto decomp_end_n2b */
-	movl	%eax, %ebp	/* last_m_off = m_off ?*/
+	mov	%xAX, %xBP	/* last_m_off = m_off ?*/
 decompr_ebpeax_n2b:
-	getbit	1		
-	adcl	%ecx, %ecx	/* m_len = getbit() */
-	getbit	1
-	adcl	%ecx, %ecx	/* m_len = m_len*2 + getbit()) */
+	xor	%xCX, %xCX
+	call	getbit1
+	adc	%xCX, %xCX	/* m_len = getbit() */
+	call	getbit1
+	adc	%xCX, %xCX	/* m_len = m_len*2 + getbit()) */
 	jnz	decompr_got_mlen_n2b	/* if (m_len == 0) goto decompr_got_mlen_n2b */
-	incl	%ecx		/* m_len++ */
+	inc	%xCX		/* m_len++ */
 loop2_n2b:
-	getbit	1	
-	adcl	%ecx, %ecx	/* m_len = m_len*2 + getbit() */
-	getbit	1
+	call	getbit1	
+	adc	%xCX, %xCX	/* m_len = m_len*2 + getbit() */
+	call	getbit1
 	jnc	loop2_n2b	/* while(!getbit()) */
-	incl	%ecx
-	incl	%ecx		/* m_len += 2 */
+	inc	%xCX
+	inc	%xCX		/* m_len += 2 */
 decompr_got_mlen_n2b:
-	cmpl	$-0xd00, %ebp
-	adcl	$1, %ecx	/* m_len = m_len + 1 + (last_m_off > 0xd00) */
-	pushl	%esi
-	leal	(%edi,%ebp), %esi	/* m_pos = dst + olen + -m_off  */
+	cmp	$-0xd00, %xBP
+	adc	$1, %xCX	/* m_len = m_len + 1 + (last_m_off > 0xd00) */
+	push	%xSI
+	lea	(%xBP,%xDI), %xSI	/* m_pos = dst + olen + -m_off  */
 	rep
-	movsb			/* dst[olen++] = *m_pos++ while(m_len > 0) */
-	popl	%esi
+	es movsb		/* dst[olen++] = *m_pos++ while(m_len > 0) */
+	pop	%xSI
 	jmp	decompr_loop_n2b
+
+
+getbit1:
+	addl	%ebx, %ebx
+	jnz	1f
+getbit32:
+	movl	(%xSI), %ebx
+	sub	$-4, %xSI	/* sets carry flag */
+	adcl	%ebx, %ebx
+1:
+	ret
+
 decompr_end_n2b:
-	/* Restore the initial register values */
+	/* Restore registers and return */
 	popal
 	ret