Fix layout issues for printed version

entryother.S

@@ -12,11 +12,10 @@
 # at an address in the low 2^16 bytes.
 #
 # Bootothers (in main.c) sends the STARTUPs one at a time.
-# It copies this code (start) at 0x7000.
+# It copies this code (start) at 0x7000.  It puts the address of
-# It puts the address of a newly allocated per-core stack in start-4,
+# a newly allocated per-core stack in start-4,the address of the
-# the address of the place to jump to (mpenter) in start-8, and the physical
+# place to jump to (mpenter) in start-8, and the physical address
-# address of enterpgdir in start-12.
+# of enterpgdir in start-12.
-#
 #
 # This code is identical to bootasm.S except:
 #   - it does not need to enable A20

log.c

@@ -76,11 +76,10 @@ install_trans(void)
   //if (log.lh.n > 0)
   //  cprintf("install_trans %d\n", log.lh.n);
   for (tail = 0; tail < log.lh.n; tail++) {
-    // cprintf("put entry %d to disk block %d\n", tail, log.lh.sector[tail]);
+    struct buf *lbuf = bread(log.dev, log.start+tail+1); // read log block
-    struct buf *lbuf = bread(log.dev, log.start+tail+1);   // read i'th block from log
+    struct buf *dbuf = bread(log.dev, log.lh.sector[tail]); // read dst
-    struct buf *dbuf = bread(log.dev, log.lh.sector[tail]);  // read dst block
+    memmove(dbuf->data, lbuf->data, BSIZE);  // copy block to dst
-    memmove(dbuf->data, lbuf->data, BSIZE);
+    bwrite(dbuf);  // flush dst to disk
-    bwrite(dbuf);
     brelse(lbuf); 
     brelse(dbuf);
   }
@@ -102,7 +101,7 @@ read_head(void)
   //  cprintf("read_head: %d\n", log.lh.n);
 }
 
-// Write the in-memory log header to disk, committing log entries till head
+// Write in-memory log header to disk, committing log entries till head
 static void
 write_head(void)
 {
@@ -144,7 +143,7 @@ void
 commit_trans(void)
 {
   if (log.lh.n > 0) {
-    write_head();        // This causes all blocks till log.head to be commited
+    write_head();    // Causes all blocks till log.head to be commited
     install_trans(); // Install all the transactions till head
     log.lh.n = 0; 
     write_head();    // Reclaim log

main.c

@@ -33,7 +33,7 @@ main(void)
   ideinit();       // disk
   if(!ismp)
     timerinit();   // uniprocessor timer
-  startothers();    // start other processors (must come before kinit; must use enter_alloc)
+  startothers();    // start other processors (must come before kinit)
   kinit();         // initialize memory allocator
   userinit();      // first user process  (must come after kinit)
   // Finish setting up this processor in mpmain.
@@ -81,13 +81,14 @@ startothers(void)
     if(c == cpus+cpunum())  // We've started already.
       continue;
 
-    // Tell entryother.S what stack to use, the address of mpenter and pgdir;
+    // Tell entryother.S what stack to use, where to enter, and what 
-    // We cannot use kpgdir yet, because the AP processor is running in low 
+    // pgdir to use. We cannot use kpgdir yet, because the AP processor
-    // memory, so we use entrypgdir for the APs too.  kalloc can return addresses
+    // is running in low  memory, so we use entrypgdir for the APs too.
-    // above 4Mbyte (the machine may have much more physical memory than 4Mbyte), which 
+    // kalloc can return addresses above 4Mbyte (the machine may have 
-    // aren't mapped by entrypgdir, so we must allocate a stack using enter_alloc();
+    // much more physical memory than 4Mbyte), which aren't mapped by
-    // This introduces the constraint that xv6 cannot use kalloc until after these 
+    // entrypgdir, so we must allocate a stack using enter_alloc(); 
-    // last enter_alloc invocations.
+    // this introduces the constraint that xv6 cannot use kalloc until 
+    // after these last enter_alloc invocations.
     stack = enter_alloc();
     *(void**)(code-4) = stack + KSTACKSIZE;
     *(void**)(code-8) = mpenter;

memlayout.h

@@ -1,10 +1,10 @@
 // Memory layout
 
 #define EXTMEM  0x100000            // Start of extended memory
-#define PHYSTOP 0xE000000           // Top physical memory (too hard to get from E820)
+#define PHYSTOP 0xE000000           // Top physical memory
 #define DEVSPACE 0xFE000000         // Other devices are at high addresses
 
-// Key addresses for address space layout (see kmap in vm.c for the layout)
+// Key addresses for address space layout (see kmap in vm.c for layout)
 #define KERNBASE 0x80000000         // First kernel virtual address
 #define KERNLINK (KERNBASE+EXTMEM)  // Address where kernel is linked
 

mmu.h

@@ -118,8 +118,8 @@ struct segdesc {
 #define PGADDR(d, t, o) ((uint)((d) << PDXSHIFT | (t) << PTXSHIFT | (o)))
 
 // Page directory and page table constants.
-#define NPDENTRIES      1024            // page directory entries per page directory
+#define NPDENTRIES      1024    // # directory entries per page directory
-#define NPTENTRIES      1024            // page table entries per page table
+#define NPTENTRIES      1024    // # PTEs per page table
 #define PGSIZE          4096    // bytes mapped by a page
 
 #define PGSHIFT         12      // log2(PGSIZE)

runoff.list

@@ -8,10 +8,6 @@ asm.h
 mmu.h
 elf.h
 
-# bootloader
-bootasm.S
-bootmain.c
-
 # entering xv6
 entry.S
 entryother.S
@@ -22,12 +18,13 @@ spinlock.h
 spinlock.c
 
 # processes
+vm.c
 proc.h
 proc.c
 swtch.S
 kalloc.c
 data.S
-vm.c
+
 # system calls
 traps.h
 vectors.pl
@@ -45,8 +42,8 @@ fs.h
 file.h
 ide.c
 bio.c
-fs.c
 log.c
+fs.c
 file.c
 sysfile.c
 exec.c
@@ -54,7 +51,6 @@ exec.c
 # pipes
 pipe.c
 
-
 # string operations
 string.c
 
@@ -76,7 +72,7 @@ usys.S
 init.c
 sh.c
 
-
+# bootloader
-
+bootasm.S
-
+bootmain.c
 

vm.c

@@ -68,7 +68,8 @@ walkpgdir(pde_t *pgdir, const void *va, char* (*alloc)(void))
 // physical addresses starting at pa. va and size might not
 // be page-aligned.
 static int
-mappages(pde_t *pgdir, void *va, uint size, uint pa, int perm, char* (*alloc)(void))
+mappages(pde_t *pgdir, void *va, uint size, uint pa, int perm, 
+         char* (*alloc)(void))
 {
   char *a, *last;
   pte_t *pte;
@@ -91,18 +92,20 @@ mappages(pde_t *pgdir, void *va, uint size, uint pa, int perm, char* (*alloc)(vo
 }
 
 // The mappings from logical to virtual are one to one (i.e.,
-// segmentation doesn't do anything).
+// segmentation doesn't do anything). There is one page table per
-// There is one page table per process, plus one that's used
+// process, plus one that's used when a CPU is not running any
-// when a CPU is not running any process (kpgdir).
+// process (kpgdir). A user process uses the same page table as
-// A user process uses the same page table as the kernel; the
+// the kernel; the page protection bits prevent it from using
-// page protection bits prevent it from using anything other
+// anything other than its memory.
-// than its memory.
 // 
 // setupkvm() and exec() set up every page table like this:
-//   0..KERNBASE      : user memory (text, data, stack, heap), mapped to some unused phys mem
+//   0..KERNBASE: user memory (text+data+stack+heap), mapped to some free
-//   KERNBASE..KERNBASE+EXTMEM: mapped to 0..EXTMEM  (below extended memory)
+//                phys memory
-//   KERNBASE+EXTMEM..KERNBASE+end : mapped to EXTMEM..end (mapped without write permission)
+//   KERNBASE..KERNBASE+EXTMEM: mapped to 0..EXTMEM (for I/O space)
-//   KERNBASE+end..KERBASE+PHYSTOP     : mapped to end..PHYSTOP (rw data + free memory)
+//   KERNBASE+EXTMEM..KERNBASE+end: mapped to EXTMEM..end  kernel,
+//                                  w. no write permission
+//   KERNBASE+end..KERBASE+PHYSTOP: mapped to end..PHYSTOP, 
+//                                  rw data + free memory
 //   0xfe000000..0: mapped direct (devices such as ioapic)
 //
 // The kernel allocates memory for its heap and for user memory
@@ -116,8 +119,8 @@ static struct kmap {
   uint phys_end;
   int perm;
 } kmap[] = {
-  { P2V(0), 0, 1024*1024, PTE_W},  // First 1Mbyte contains BIOS and some IO devices
+  { P2V(0), 0, 1024*1024, PTE_W},  // I/O space
-  { (void *)KERNLINK, V2P(KERNLINK), V2P(data),  0},  // kernel text, rodata
+  { (void *)KERNLINK, V2P(KERNLINK), V2P(data),  0}, // kernel text+rodata
   { data, V2P(data), PHYSTOP,  PTE_W},  // kernel data, memory
   { (void*)DEVSPACE, DEVSPACE, 0, PTE_W},  // more devices
 };
@@ -136,8 +139,8 @@ setupkvm(char* (*alloc)(void))
   if (p2v(PHYSTOP) > (void *) DEVSPACE)
     panic("PHYSTOP too high");
   for(k = kmap; k < &kmap[NELEM(kmap)]; k++)
-    if(mappages(pgdir, k->virt, k->phys_end - k->phys_start, (uint)k->phys_start, 
+    if(mappages(pgdir, k->virt, k->phys_end - k->phys_start, 
-                k->perm, alloc) < 0)
+                (uint)k->phys_start, k->perm, alloc) < 0)
       return 0;
 
   return pgdir;