Remove trailing white space with:

 for f in *.{h,c}; do sed -i .sed 's/[[:blank:]]*$//' $f; done
(Thanks to Nicolás Wolovick)

bio.c

@@ -4,18 +4,18 @@
 // cached copies of disk block contents.  Caching disk blocks
 // in memory reduces the number of disk reads and also provides
 // a synchronization point for disk blocks used by multiple processes.
-// 
+//
 // Interface:
 // * To get a buffer for a particular disk block, call bread.
 // * After changing buffer data, call bwrite to write it to disk.
 // * When done with the buffer, call brelse.
 // * Do not use the buffer after calling brelse.
 // * Only one process at a time can use a buffer,
 //     so do not keep them longer than necessary.
-// 
+//
 // The implementation uses three state flags internally:
 // * B_BUSY: the block has been returned from bread
-//     and has not been passed back to brelse.  
+//     and has not been passed back to brelse.
 // * B_VALID: the buffer data has been read from the disk.
 // * B_DIRTY: the buffer data has been modified
 //     and needs to be written to disk.

bootmain.c

@@ -1,5 +1,5 @@
 // Boot loader.
-// 
+//
 // Part of the boot block, along with bootasm.S, which calls bootmain().
 // bootasm.S has put the processor into protected 32-bit mode.
 // bootmain() loads an ELF kernel image from the disk starting at

console.c

@@ -107,7 +107,7 @@ panic(char *s)
 {
   int i;
   uint pcs[10];
-  
+
   cli();
   cons.locking = 0;
   cprintf("cpu%d: panic: ", cpu->id);
@@ -130,7 +130,7 @@ static void
 cgaputc(int c)
 {
   int pos;
-  
+
   // Cursor position: col + 80*row.
   outb(CRTPORT, 14);
   pos = inb(CRTPORT+1) << 8;
@@ -146,13 +146,13 @@ cgaputc(int c)
 
   if(pos < 0 || pos > 25*80)
     panic("pos under/overflow");
-  
+
   if((pos/80) >= 24){  // Scroll up.
     memmove(crt, crt+80, sizeof(crt[0])*23*80);
     pos -= 80;
     memset(crt+pos, 0, sizeof(crt[0])*(24*80 - pos));
   }
-  
+
   outb(CRTPORT, 14);
   outb(CRTPORT+1, pos>>8);
   outb(CRTPORT, 15);

file.c

@@ -68,7 +68,7 @@ fileclose(struct file *f)
   f->ref = 0;
   f->type = FD_NONE;
   release(&ftable.lock);
-  
+
   if(ff.type == FD_PIPE)
     pipeclose(ff.pipe, ff.writable);
   else if(ff.type == FD_INODE){

forktest.c

@@ -27,24 +27,24 @@ forktest(void)
     if(pid == 0)
       exit();
   }
-  
+
   if(n == N){
     printf(1, "fork claimed to work N times!\n", N);
     exit();
   }
-  
+
   for(; n > 0; n--){
     if(wait() < 0){
       printf(1, "wait stopped early\n");
       exit();
     }
   }
-  
+
   if(wait() != -1){
     printf(1, "wait got too many\n");
     exit();
   }
-  
+
   printf(1, "fork test OK\n");
 }
 

fs.c

@@ -5,7 +5,7 @@
 //   + Directories: inode with special contents (list of other inodes!)
 //   + Names: paths like /usr/rtm/xv6/fs.c for convenient naming.
 //
-// This file contains the low-level file system manipulation 
+// This file contains the low-level file system manipulation
 // routines.  The (higher-level) system call implementations
 // are in sysfile.c.
 
@@ -29,7 +29,7 @@ void
 readsb(int dev, struct superblock *sb)
 {
   struct buf *bp;
-  
+
   bp = bread(dev, 1);
   memmove(sb, bp->data, sizeof(*sb));
   brelse(bp);
@@ -40,14 +40,14 @@ static void
 bzero(int dev, int bno)
 {
   struct buf *bp;
-  
+
   bp = bread(dev, bno);
   memset(bp->data, 0, BSIZE);
   log_write(bp);
   brelse(bp);
 }
 
-// Blocks. 
+// Blocks.
 
 // Allocate a zeroed disk block.
 static uint
@@ -348,7 +348,7 @@ iunlockput(struct inode *ip)
 //
 // The content (data) associated with each inode is stored
 // in blocks on the disk. The first NDIRECT block numbers
-// are listed in ip->addrs[].  The next NINDIRECT blocks are 
+// are listed in ip->addrs[].  The next NINDIRECT blocks are
 // listed in block ip->addrs[NDIRECT].
 
 // Return the disk block address of the nth block in inode ip.
@@ -401,7 +401,7 @@ itrunc(struct inode *ip)
       ip->addrs[i] = 0;
     }
   }
-  
+
   if(ip->addrs[NDIRECT]){
     bp = bread(ip->dev, ip->addrs[NDIRECT]);
     a = (uint*)bp->data;
@@ -554,7 +554,7 @@ dirlink(struct inode *dp, char *name, uint inum)
   de.inum = inum;
   if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
     panic("dirlink");
-  
+
   return 0;
 }
 

fs.h

@@ -1,4 +1,4 @@
-// On-disk file system format. 
+// On-disk file system format.
 // Both the kernel and user programs use this header file.
 
 

grep.c

@@ -12,7 +12,7 @@ grep(char *pattern, int fd)
 {
   int n, m;
   char *p, *q;
-  
+
   m = 0;
   while((n = read(fd, buf+m, sizeof(buf)-m-1)) > 0){
     m += n;
@@ -40,13 +40,13 @@ main(int argc, char *argv[])
 {
   int fd, i;
   char *pattern;
-  
+
   if(argc <= 1){
     printf(2, "usage: grep pattern [file ...]\n");
     exit();
   }
   pattern = argv[1];
-  
+
   if(argc <= 2){
     grep(pattern, 0);
     exit();

ide.c

@@ -39,7 +39,7 @@ idewait(int checkerr)
 {
   int r;
 
-  while(((r = inb(0x1f7)) & (IDE_BSY|IDE_DRDY)) != IDE_DRDY) 
+  while(((r = inb(0x1f7)) & (IDE_BSY|IDE_DRDY)) != IDE_DRDY)
     ;
   if(checkerr && (r & (IDE_DF|IDE_ERR)) != 0)
     return -1;
@@ -50,12 +50,12 @@ void
 ideinit(void)
 {
   int i;
-  
+
   initlock(&idelock, "ide");
   picenable(IRQ_IDE);
   ioapicenable(IRQ_IDE, ncpu - 1);
   idewait(0);
-  
+
   // Check if disk 1 is present
   outb(0x1f6, 0xe0 | (1<<4));
   for(i=0; i<1000; i++){
@@ -64,7 +64,7 @@ ideinit(void)
       break;
     }
   }
-  
+
   // Switch back to disk 0.
   outb(0x1f6, 0xe0 | (0<<4));
 }
@@ -81,9 +81,9 @@ idestart(struct buf *b)
   int sector = b->blockno * sector_per_block;
   int read_cmd = (sector_per_block == 1) ? IDE_CMD_READ :  IDE_CMD_RDMUL;
   int write_cmd = (sector_per_block == 1) ? IDE_CMD_WRITE : IDE_CMD_WRMUL;
- 
+
   if (sector_per_block > 7) panic("idestart");
-  
+
   idewait(0);
   outb(0x3f6, 0);  // generate interrupt
   outb(0x1f2, sector_per_block);  // number of sectors
@@ -117,12 +117,12 @@ ideintr(void)
   // Read data if needed.
   if(!(b->flags & B_DIRTY) && idewait(1) >= 0)
     insl(0x1f0, b->data, BSIZE/4);
-  
+
   // Wake process waiting for this buf.
   b->flags |= B_VALID;
   b->flags &= ~B_DIRTY;
   wakeup(b);
-  
+
   // Start disk on next buf in queue.
   if(idequeue != 0)
     idestart(idequeue);
@@ -131,7 +131,7 @@ ideintr(void)
 }
 
 //PAGEBREAK!
-// Sync buf with disk. 
+// Sync buf with disk.
 // If B_DIRTY is set, write buf to disk, clear B_DIRTY, set B_VALID.
 // Else if B_VALID is not set, read buf from disk, set B_VALID.
 void
@@ -153,11 +153,11 @@ iderw(struct buf *b)
   for(pp=&idequeue; *pp; pp=&(*pp)->qnext)  //DOC:insert-queue
     ;
   *pp = b;
-  
+
   // Start disk if necessary.
   if(idequeue == b)
     idestart(b);
-  
+
   // Wait for request to finish.
   while((b->flags & (B_VALID|B_DIRTY)) != B_VALID){
     sleep(b, &idelock);

ioapic.c

@@ -13,7 +13,7 @@
 #define REG_TABLE  0x10  // Redirection table base
 
 // The redirection table starts at REG_TABLE and uses
-// two registers to configure each interrupt.  
+// two registers to configure each interrupt.
 // The first (low) register in a pair contains configuration bits.
 // The second (high) register contains a bitmask telling which
 // CPUs can serve that interrupt.

log.c

@@ -31,7 +31,7 @@
 // Contents of the header block, used for both the on-disk header block
 // and to keep track in memory of logged block# before commit.
 struct logheader {
-  int n;   
+  int n;
   int block[LOGSIZE];
 };
 
@@ -65,7 +65,7 @@ initlog(int dev)
 }
 
 // Copy committed blocks from log to their home location
-static void 
+static void
 install_trans(void)
 {
   int tail;
@@ -75,7 +75,7 @@ install_trans(void)
     struct buf *dbuf = bread(log.dev, log.lh.block[tail]); // read dst
     memmove(dbuf->data, lbuf->data, BSIZE);  // copy block to dst
     bwrite(dbuf);  // write dst to disk
-    brelse(lbuf); 
+    brelse(lbuf);
     brelse(dbuf);
   }
 }
@@ -114,7 +114,7 @@ write_head(void)
 static void
 recover_from_log(void)
 {
-  read_head();      
+  read_head();
   install_trans(); // if committed, copy from log to disk
   log.lh.n = 0;
   write_head(); // clear the log
@@ -171,7 +171,7 @@ end_op(void)
 }
 
 // Copy modified blocks from cache to log.
-static void 
+static void
 write_log(void)
 {
   int tail;
@@ -181,7 +181,7 @@ write_log(void)
     struct buf *from = bread(log.dev, log.lh.block[tail]); // cache block
     memmove(to->data, from->data, BSIZE);
     bwrite(to);  // write the log
-    brelse(from); 
+    brelse(from);
     brelse(to);
   }
 }
@@ -193,7 +193,7 @@ commit()
     write_log();     // Write modified blocks from cache to log
     write_head();    // Write header to disk -- the real commit
     install_trans(); // Now install writes to home locations
-    log.lh.n = 0; 
+    log.lh.n = 0;
     write_head();    // Erase the transaction from the log
   }
 }

ls.c

@@ -8,12 +8,12 @@ fmtname(char *path)
 {
   static char buf[DIRSIZ+1];
   char *p;
-  
+
   // Find first character after last slash.
   for(p=path+strlen(path); p >= path && *p != '/'; p--)
     ;
   p++;
-  
+
   // Return blank-padded name.
   if(strlen(p) >= DIRSIZ)
     return p;
@@ -29,23 +29,23 @@ ls(char *path)
   int fd;
   struct dirent de;
   struct stat st;
-  
+
   if((fd = open(path, 0)) < 0){
     printf(2, "ls: cannot open %s\n", path);
     return;
   }
-  
+
   if(fstat(fd, &st) < 0){
     printf(2, "ls: cannot stat %s\n", path);
     close(fd);
     return;
   }
-  
+
   switch(st.type){
   case T_FILE:
     printf(1, "%s %d %d %d\n", fmtname(path), st.type, st.ino, st.size);
     break;
-  
+
   case T_DIR:
     if(strlen(path) + 1 + DIRSIZ + 1 > sizeof buf){
       printf(1, "ls: path too long\n");