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Ensure that empty e820 regions are skipped even at the end of the

memory map.  (We achieve this by setting CF on the last entry if it is
zero-length; this avoids the need to look ahead to see at each entry
if the *next* entry would be both the last entry and zero-length).

This fixes the "0kB base memory" error message upon starting Windows
2003 on a SunFire X2100.
tags/v0.9.3
Michael Brown 17 years ago
parent
commit
35ee7e4479
1 changed files with 18 additions and 11 deletions
  1. 18
    11
      src/arch/i386/firmware/pcbios/e820mangler.S

+ 18
- 11
src/arch/i386/firmware/pcbios/e820mangler.S View File

361
 	pushl	%edx	
361
 	pushl	%edx	
362
 	call	split_e820
362
 	call	split_e820
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 	pushfw
363
 	pushfw
364
-	/* Skip empty region checking if we've reached the end of the
365
-	 * map or hit an error, to avoid a potential endless loop.
366
-	 */
367
-	jc	1f
368
-	testl	%ebx, %ebx
369
-	jz	1f
370
-	/* Check for an empty region */
364
+	/* If we've hit an error, exit immediately */
365
+	jc	99f
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+	/* If region is non-empty, return this region */
371
 	pushl	%eax
367
 	pushl	%eax
372
 	movl	%es:8(%di), %eax
368
 	movl	%es:8(%di), %eax
373
 	orl	%es:12(%di), %eax
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 	orl	%es:12(%di), %eax
374
 	popl	%eax
370
 	popl	%eax
375
-	jnz	1f
376
-	/* Strip empty regions out of the returned map */
371
+	jnz	99f
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+	/* Region is empty.  If this is not the end of the map,
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+	 * skip over this region.
374
+	 */
375
+	testl	%ebx, %ebx
376
+	jz	1f
377
 	popfw
377
 	popfw
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 	popl	%edx
378
 	popl	%edx
379
 	popl	%ecx
379
 	popl	%ecx
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 	popl	%eax
380
 	popl	%eax
381
 	jmp	int15_e820
381
 	jmp	int15_e820
382
-	/* Restore flags from original INT 15,e820 call and return */
383
-1:	popfw
382
+1:	/* Region is empty and this is the end of the map.  Return
383
+	 * with CF set to avoid placing an empty region at the end of
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+	 * the map.
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+	 */
386
+	popfw
387
+	stc
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+	pushfw
389
+99:	/* Restore flags from original INT 15,e820 call and return */
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+	popfw
384
 	addr32 leal	12(%esp), %esp /* avoid changing flags */
391
 	addr32 leal	12(%esp), %esp /* avoid changing flags */
385
 	lret	$2
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 	lret	$2
386
 	.size int15_e820, . - int15_e820
393
 	.size int15_e820, . - int15_e820

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