Merge branch 'master' of git+ssh://amsterdam.csail.mit.edu/home/am0/6.828/xv6

Conflicts:
	vm.c

1 files changed, 17 insertions, 15 deletions

diff --git a/vm.c b/vm.c
index 7bda3dd..247fede 100644
--- a/vm.c
+++ b/vm.c
@@ -92,19 +92,21 @@ mappages(pde_t *pgdir, void *va, uint size, uint pa,
 }
 
 // The mappings from logical to virtual are one to one (i.e.,
-// segmentation doesn't do anything).
-// There is one page table per process, plus one that's used
-// when a CPU is not running any process (kpgdir).
-// A user process uses the same page table as the kernel; the
-// page protection bits prevent it from using anything other
-// than its memory.
+// segmentation doesn't do anything). There is one page table per
+// process, plus one that's used when a CPU is not running any
+// process (kpgdir). A user process uses the same page table as
+// the kernel; the page protection bits prevent it from using
+// anything other 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
-//   KERNBASE..KERNBASE+EXTMEM: mapped to 0..EXTMEM  (below extended memory)
-//   KERNBASE+EXTMEM..KERNBASE+end : mapped to EXTMEM..end (mapped without write permission)
-//   KERNBASE+end..KERBASE+PHYSTOP     : mapped to end..PHYSTOP (rw data + free memory)
-//   0xfe000000..0    : mapped direct (devices such as ioapic)
+//   0..KERNBASE: user memory (text+data+stack+heap), mapped to some free
+//                phys memory
+//   KERNBASE..KERNBASE+EXTMEM: mapped to 0..EXTMEM (for I/O space)
+//   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
 // between kernend and the end of physical memory (PHYSTOP).
@@ -117,8 +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
-  { (void *)KERNLINK, V2P(KERNLINK), V2P(data),  0},  // kernel text, rodata
+  { P2V(0), 0, 1024*1024, PTE_W},  // I/O space
+  { (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
 };
@@ -137,8 +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, 
-                k->perm, alloc) < 0)
+    if(mappages(pgdir, k->virt, k->phys_end - k->phys_start, 
+                (uint)k->phys_start, k->perm, alloc) < 0)
       return 0;
 
   return pgdir;