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[bzimage] Align initrd images to page boundary

Some versions of Linux apparently complain if initrds are not aligned
to a page boundary.  Fix by changing INITRD_ALIGN from 4 bytes to 4096
bytes.

The amount of padding at the end of each initrd will now often be
sufficient to allow the cpio header to be prepended without crossing
an alignment boundary.  The final location of the initrd may therefore
end up being slightly higher than the post-shuffle location.
bzimage_load_initrd() must therefore now copy the initrd body prior to
copying the cpio header, otherwise the start of the initrd body may be
overwritten by the cpio header.  (Note that the guarantee that an
initrd will never need to overwrite an initrd at a higher location
still holds, since the overall length of each initrd cannot decrease
as a result of adding a cpio header.)

Reported-by: Dave Hansen <dave@sr71.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
tags/v1.20.1
Michael Brown 11 år sedan
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2 ändrade filer med 16 tillägg och 19 borttagningar
  1. 13
    17
      src/arch/i386/image/bzimage.c
  2. 3
    2
      src/arch/i386/include/initrd.h

+ 13
- 17
src/arch/i386/image/bzimage.c Visa fil

@@ -360,7 +360,7 @@ static size_t bzimage_load_initrd ( struct image *image,
360 360
 	char *filename = initrd->cmdline;
361 361
 	char *cmdline;
362 362
 	struct cpio_header cpio;
363
-        size_t offset = 0;
363
+	size_t offset;
364 364
 	size_t name_len;
365 365
 	size_t pad_len;
366 366
 
@@ -368,7 +368,7 @@ static size_t bzimage_load_initrd ( struct image *image,
368 368
 	if ( initrd == image )
369 369
 		return 0;
370 370
 
371
-	/* Create cpio header before non-prebuilt images */
371
+	/* Create cpio header for non-prebuilt images */
372 372
 	if ( filename && filename[0] ) {
373 373
 		cmdline = strchr ( filename, ' ' );
374 374
 		name_len = ( ( cmdline ? ( ( size_t ) ( cmdline - filename ) )
@@ -383,24 +383,20 @@ static size_t bzimage_load_initrd ( struct image *image,
383 383
 			bzimage_parse_cpio_cmdline ( image, &cpio,
384 384
 						     ( cmdline + 1 /* ' ' */ ));
385 385
 		}
386
-		if ( address ) {
387
-			copy_to_user ( address, offset, &cpio,
388
-				       sizeof ( cpio ) );
389
-		}
390
-		offset += sizeof ( cpio );
391
-		if ( address ) {
392
-			memset_user ( address, offset, 0, name_len );
393
-			copy_to_user ( address, offset, filename,
394
-				       ( name_len - 1 /* NUL (or space) */ ) );
395
-		}
396
-		offset += name_len;
397
-		offset = ( ( offset + 0x03 ) & ~0x03 );
386
+		offset = ( ( sizeof ( cpio ) + name_len + 0x03 ) & ~0x03 );
387
+	} else {
388
+		offset = 0;
398 389
 	}
399 390
 
400
-	/* Copy in initrd image body */
401
-	if ( address )
402
-		memmove_user ( address, offset, initrd->data, 0, initrd->len );
391
+	/* Copy in initrd image body (and cpio header if applicable) */
403 392
 	if ( address ) {
393
+		memmove_user ( address, offset, initrd->data, 0, initrd->len );
394
+		if ( offset ) {
395
+			memset_user ( address, 0, 0, offset );
396
+			copy_to_user ( address, 0, &cpio, sizeof ( cpio ) );
397
+			copy_to_user ( address, sizeof ( cpio ), filename,
398
+				       ( name_len - 1 /* NUL (or space) */ ) );
399
+		}
404 400
 		DBGC ( image, "bzImage %p initrd %p [%#08lx,%#08lx,%#08lx)"
405 401
 		       "%s%s\n", image, initrd, user_to_phys ( address, 0 ),
406 402
 		       user_to_phys ( address, offset ),

+ 3
- 2
src/arch/i386/include/initrd.h Visa fil

@@ -13,9 +13,10 @@ FILE_LICENCE ( GPL2_OR_LATER );
13 13
 
14 14
 /** Minimum alignment for initrds
15 15
  *
16
- * Chosen to maximise memcpy() speeds
16
+ * Some versions of Linux complain about initrds that are not
17
+ * page-aligned.
17 18
  */
18
-#define INITRD_ALIGN 4
19
+#define INITRD_ALIGN 4096
19 20
 
20 21
 /** Minimum free space required to reshuffle initrds
21 22
  *

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