99 lines
3.3 KiB
HTML
99 lines
3.3 KiB
HTML
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The President and Fellows of Harvard College.
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<html>
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<head>
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<title>poisondisk</title>
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<link rel="stylesheet" type="text/css" media="all" href="../man.css">
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</head>
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<body bgcolor=#ffffff>
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<h2 align=center>poisondisk</h2>
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<h4 align=center>OS/161 Reference Manual</h4>
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<h3>Name</h3>
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<p>
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poisondisk - write known "poison" values to a disk image
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</p>
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<h3>Synopsis</h3>
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<p>
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<tt>/testbin/poisondisk</tt> <em>disk-device</em><br>
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<tt>hostbin/host-poisondisk</tt> <em>disk-image</em>
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</p>
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<h3>Description</h3>
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<p>
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<tt>poisondisk</tt> writes known poison values to a disk image.
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This allows (mostly) reliable detection of reads from uninitialized
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disk blocks: they produce the poison value.
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(Otherwise, uninitialized disk blocks tend to be zeroed; this is much
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harder to detect and much harder to distinguish from an intentional
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condition.)
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</p>
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<p>
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<tt>poisondisk</tt> will overwrite any data already on the disk, so
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run it prior to running <A HREF=../sbin/mksfs.html>mksfs</A> when
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creating a new volume.
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</p>
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<p>
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A host version of poisondisk is build (like with the SFS tools) so it
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can be run outside OS/161.
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This version understands System/161 disk image headers and will only
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overwrite System/161 disk images.
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</p>
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<p>
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The poison value is 0xa9.
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</p>
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<h3>Requirements</h3>
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<p>
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<tt>poisondisk</tt> uses the following system calls:
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<ul>
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<li><A HREF=../syscall/open.html>open</A></li>
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<li><A HREF=../syscall/fstat.html>fstat</A></li>
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<li><A HREF=../syscall/lseek.html>lseek</A></li>
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<li><A HREF=../syscall/read.html>read</A></li>
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<li><A HREF=../syscall/write.html>write</A></li>
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<li><A HREF=../syscall/close.html>close</A></li>
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<li><A HREF=../syscall/_exit.html>_exit</A></li>
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</ul>
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</p>
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<p>
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<tt>poisondisk</tt> will work once you have implemented the system
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calls it uses (including fstat, which is typically not part of the
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basic system calls assignment), but is only really useful for working
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on the file system.
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</p>
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</body>
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</html>
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