Attachment 174075 Details for Bug 212139 – Thought experiment alternative patch

[patch] Thought experiment alternative patch

p (text/plain), 986 bytes, created by Peter Wemm on 2016-08-25 20:18:39 UTC

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Creator: Peter Wemm

Created: 2016-08-25 20:18:39 UTC

Size: 986 bytes

patch

obsolete

>Index: i386/libi386/biosdisk.c
>===================================================================
>--- i386/libi386/biosdisk.c	(revision 304792)
>+++ i386/libi386/biosdisk.c	(working copy)
>@@ -511,21 +511,21 @@
>     DEBUG("open_disk %p", dev);
>     blks = size / BD(dev).bd_sectorsize;
>     if (rsize)
> 	*rsize = 0;
> 
>-    if (dblk >= BD(dev).bd_sectors) {
>-	DEBUG("IO past disk end %llu", (unsigned long long)dblk);
>-	return (EIO);
>-    }
>-
>-    if (dblk + blks > BD(dev).bd_sectors) {
>-	/* perform partial read */
>-	blks = BD(dev).bd_sectors - dblk;
>+#define clip(x) ((x) & 0xffffffff)
>+    if (clip(dblk + blks) > clip(BD(dev).bd_sectors)) {
>+	/*
>+	 * perform partial read to prevent readahead crossing
>+	 * any 32 bit aliases of the end of disk.
>+	 */
>+	blks = clip(BD(dev).bd_sectors) - clip(dblk);
> 	size = blks * BD(dev).bd_sectorsize;
> 	DEBUG("short read %d", blks);
>     }
>+#undef clip
> 
>     switch(rw){
>     case F_READ:
> 	DEBUG("read %d from %lld to %p", blks, dblk, buf);
>

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Attachments on bug 212139: 174052 | 174075 | 174080