78 lines
1.6 KiB
HTML
78 lines
1.6 KiB
HTML
<html>
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<head>
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<title>Homework: Naming</title>
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</head>
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<body>
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<h1>Homework: Naming</h1>
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<p>
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<b>Read</b>: namei in fs.c, fd.c, sysfile.c
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<p>
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This homework should be turned in at the beginning of lecture.
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<p>
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<b>Symbolic Links</b>
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<p>
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As you read namei and explore its varied uses throughout xv6,
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think about what steps would be required to add symbolic links
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to xv6.
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A symbolic link is simply a file with a special type (e.g., T_SYMLINK
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instead of T_FILE or T_DIR) whose contents contain the path being
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linked to.
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<p>
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Turn in a short writeup of how you would change xv6 to support
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symlinks. List the functions that would have to be added or changed,
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with short descriptions of the new functionality or changes.
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<p>
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<b>This completes the homework.</b>
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<p>
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The following is <i>not required</i>. If you want to try implementing
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symbolic links in xv6, here are the files that the course staff
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had to change to implement them:
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<pre>
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fs.c: 20 lines added, 4 modified
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syscall.c: 2 lines added
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syscall.h: 1 line added
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sysfile.c: 15 lines added
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user.h: 1 line added
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usys.S: 1 line added
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</pre>
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Also, here is an <i>ln</i> program:
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<pre>
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#include "types.h"
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#include "user.h"
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int
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main(int argc, char *argv[])
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{
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int (*ln)(char*, char*);
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ln = link;
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if(argc > 1 && strcmp(argv[1], "-s") == 0){
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ln = symlink;
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argc--;
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argv++;
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}
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if(argc != 3){
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printf(2, "usage: ln [-s] old new (%d)\n", argc);
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exit();
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}
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if(ln(argv[1], argv[2]) < 0){
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printf(2, "%s failed\n", ln == symlink ? "symlink" : "link");
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exit();
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}
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exit();
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}
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</pre>
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</body>
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