simplify kernel mapping calls

1 files changed, 26 insertions, 33 deletions

diff --git a/kernel/vm.c b/kernel/vm.c
index 7dc84ba..b327b94 100644
--- a/kernel/vm.c
+++ b/kernel/vm.c
@@ -27,33 +27,26 @@ kvminit()
   memset(kernel_pagetable, 0, PGSIZE);
 
   // uart registers
-  mappages(kernel_pagetable, UART0, PGSIZE,
-           UART0, PTE_R | PTE_W);
+  kmap(UART0, UART0, PGSIZE, PTE_R | PTE_W);
 
   // virtio mmio disk interface
-  mappages(kernel_pagetable, VIRTIO0, PGSIZE,
-           VIRTIO0, PTE_R | PTE_W);
+  kmap(VIRTIO0, VIRTIO0, PGSIZE, PTE_R | PTE_W);
 
   // CLINT
-  mappages(kernel_pagetable, CLINT, 0x10000,
-           CLINT, PTE_R | PTE_W);
+  kmap(CLINT, CLINT, 0x10000, PTE_R | PTE_W);
 
   // PLIC
-  mappages(kernel_pagetable, PLIC, 0x4000000,
-           PLIC, PTE_R | PTE_W);
+  kmap(PLIC, PLIC, 0x400000, PTE_R | PTE_W);
 
   // map kernel text executable and read-only.
-  mappages(kernel_pagetable, KERNBASE, (uint64)etext-KERNBASE,
-           KERNBASE, PTE_R | PTE_X);
+  kmap(KERNBASE, KERNBASE, (uint64)etext-KERNBASE, PTE_R | PTE_X);
 
   // map kernel data and the physical RAM we'll make use of.
-  mappages(kernel_pagetable, (uint64)etext, PHYSTOP-(uint64)etext,
-           (uint64)etext, PTE_R | PTE_W);
+  kmap((uint64)etext, (uint64)etext, PHYSTOP-(uint64)etext, PTE_R | PTE_W);
 
   // map the trampoline for trap entry/exit to
   // the highest virtual address in the kernel.
-  mappages(kernel_pagetable, TRAMPOLINE, PGSIZE,
-           (uint64)trampout, PTE_R | PTE_X);
+  kmap(TRAMPOLINE, (uint64)trampout, PGSIZE, PTE_R | PTE_X);
 }
 
 // Switch h/w page table register to the kernel's page table,
@@ -117,6 +110,15 @@ walkaddr(pagetable_t pagetable, uint64 va)
   return pa;
 }
 
+// add a mapping to the kernel page table.
+// only used when booting.
+// does not flush TLB or enable paging.
+void
+kmap(uint64 va, uint64 pa, uint64 sz, int perm)
+{
+  if(mappages(kernel_pagetable, va, sz, pa, perm) != 0)
+    panic("kmap");
+}
 
 // Create PTEs for virtual addresses starting at va that refer to
 // physical addresses starting at pa. va and size might not
@@ -405,25 +407,13 @@ copyinstr(pagetable_t pagetable, char *dst, uint64 srcva, uint64 max)
   }
 }
 
-char *
-mapkstack(uint64 kstack)
-{
-  char *k = kalloc();
-  if(k == 0) {
-    return 0;
-  }
-  if (mappages(kernel_pagetable, kstack, PGSIZE,
-               (uint64) k, PTE_R | PTE_W) == 0) {
-    kvminithart();
-    return (char *) kstack;
-  }
-  kfree(k);
-  return 0;
-}
-
-// assumes va is page aligned
+// translate a kernel virtual address to
+// a physical address. only needed for
+// addresses on the stack.
+// assumes va is page aligned.
 uint64
-kernelpa(uint64 va) {
+kernelpa(uint64 va)
+{
   uint64 off = va % PGSIZE;
   pte_t *pte;
   uint64 pa;
@@ -437,8 +427,11 @@ kernelpa(uint64 va) {
   return pa+off;
 }
 
+// mark a PTE invalid for user access.
+// used by exec for the user stack guard page.
 void
-clearpteu(pagetable_t pagetable, uint64 va) {
+clearpteu(pagetable_t pagetable, uint64 va)
+{
   pte_t *pte;
   
   pte = walk(pagetable, va, 0);