Clean up amd64 page table code.

36f95831 · Silas Boyd-Wickizer · ccb4db66 · 36f95831 · 36f95831 · 36f95831
--- a/mmu.h
+++ b/mmu.h
@@ -3,22 +3,8 @@
 #define PGSIZE          4096
 #define PGSHIFT		12		// log2(PGSIZE)

-#define PTXSHIFT	12		// offset of PTX in a linear address
-#define PDXSHIFT	21		// offset of PDX in a linear address
-#define PDPXSHIFT       30              // offset of PDPX in a linear address
-#define PML4XSHIFT      39              // offset of PML4X in a linear address
-
-// page table index
-#define PTX(la)		(((uptr)(la) >> PTXSHIFT) & 0x1FF)
-
-// page directory index
-#define PDX(la)		(((uptr)(la) >> PDXSHIFT) & 0x1FF)
-
-// page diretory pointer index
-#define PDPX(la)       (((uptr)(la) >> PDPXSHIFT) & 0x1FF)
-
-// page map level 4 index
-#define PML4X(la)       (((uptr)(la) >> PML4XSHIFT) & 0x1FF)
+#define PXSHIFT(n)	(PGSHIFT+(9*(n)))
+#define PX(n, la)	((((uptr) (la)) >> PXSHIFT(n)) & 0x1FF)

 // Page table/directory entry flags.
 #define PTE_P		0x001	// Present

--- a/types.h
+++ b/types.h
@@ -13,9 +13,7 @@ typedef uint64 u64;
 typedef uint64 uptr;
 typedef uptr paddr;

-typedef u64 pml4e_t;
-typedef u64 pdpe_t;
-typedef u64 pde_t;
-typedef u64 pte_t;
+typedef u64 pme_t; // Page Map Entry (refers to any entry in any level)
+typedef pme_t pml4e_t;

 #define __mpalign__ __attribute__((aligned(CACHELINE)))
--- a/vm.c
+++ b/vm.c
@@ -19,46 +19,40 @@ extern pml4e_t kpml4[];

 extern char* pgalloc(void);

+static pme_t*
+descend(pme_t *dir, void *va, u64 flags, int create, int level)
+{
+  pme_t entry;
+  pme_t *next;
+
+  dir = &dir[PX(level, va)];
+  entry = *dir;
+  if (entry == 0) {
+    if (!create)
+      return NULL;
+    next = (u64*) pgalloc();
+    if (!next)
+      return NULL;
+    *dir = v2p(next) | PTE_P | PTE_W | flags;
+  } else {
+    next = p2v(PTE_ADDR(entry));
+  }
+  
+  return next;
+}
+
 static void
 pgmap(void *va, void *last, paddr pa)
 {
-  pml4e_t *pml4;
-  pml4e_t pml4e;
-  pdpe_t *pdp;
-  pdpe_t pdpe;
-  pde_t *pd;
-  pde_t pde;
-  pte_t *pt;
+  pme_t *pdp;
+  pme_t *pd;
+  pme_t *pt;

-  for(;;){
-    pml4 = &kpml4[PML4X(va)];
-    pml4e = *pml4;
-    if (pml4e == 0) {
-      pdp = (pdpe_t *) pgalloc();
-      *pml4 = v2p(pdp) | PTE_P | PTE_W;
-    } else {
-      pdp = (pdpe_t*)p2v(PTE_ADDR(pml4e));
-    }
-
-    pdp = &pdp[PDPX(va)];
-    pdpe = *pdp;
-    if (pdpe == 0) {
-      pd = (pde_t *) pgalloc();
-      *pdp = v2p(pd) | PTE_P | PTE_W;
-    } else {
-      pd = (pde_t*)p2v(PTE_ADDR(pdpe));
-    }
-
-    pd = &pd[PDX(va)];
-    pde = *pd;
-    if (pde == 0) {
-      pt = (pte_t *) pgalloc();
-      *pd = v2p(pt) | PTE_P | PTE_W;
-    } else {
-      pt = (pde_t*)p2v(PTE_ADDR(pde));
-    }
-
-    pt = &pt[PTX(va)];
+  for (;;) {
+    pdp = descend(kpml4, va, 0, 1, 3);
+    pd = descend(pdp, va, 0, 1, 2);
+    pt = descend(pd, va, 0, 1, 1);
+    pt = &pt[PX(0,va)];
    *pt = pa | PTE_W | PTE_P;
    if(va == last)
      break;
@@ -101,7 +95,7 @@ setupkvm(void)

  if((pml4 = (pml4e_t*)kalloc()) == 0)
    return 0;
-  k = PML4X(PBASE);
+  k = PX(3, PBASE);
  memset(&pml4[0], 0, 8*k);
  memmove(&pml4[k], &kpml4[k], 8*(512-k));
  return pml4;