copyout() copies data to a va in a pagetable, for exec() &c

usertest that passes too many arguments, break exec

1 files changed, 28 insertions, 4 deletions

diff --git a/vm.c b/vm.c
index cd6b255..551efbf 100644
--- a/vm.c
+++ b/vm.c
@@ -6,8 +6,6 @@
 #include "proc.h"
 #include "elf.h"
 
-#define USERTOP  0xA0000
-
 static pde_t *kpgdir;  // for use in scheduler()
 
 // Set up CPU's kernel segment descriptors.
@@ -126,7 +124,7 @@ setupkvm(void)
 {
   pde_t *pgdir;
   extern char etext[];
-  char *rwstart = PGROUNDDOWN(etext) - PGSIZE;
+  char *rwstart = PGROUNDDOWN(etext);
   uint rwlen = (uint)rwstart - 0x100000;
 
   // Allocate page directory
@@ -193,7 +191,10 @@ char*
 uva2ka(pde_t *pgdir, char *uva)
 {    
   pte_t *pte = walkpgdir(pgdir, uva, 0);
-  if(pte == 0) return 0;
+  if((*pte & PTE_P) == 0)
+    return 0;
+  if((*pte & PTE_U) == 0)
+    return 0;
   uint pa = PTE_ADDR(*pte);
   return (char *)pa;
 }
@@ -326,3 +327,26 @@ bad:
   return 0;
 }
 
+// copy some data to user address va in page table pgdir.
+// most useful when pgdir is not the current page table.
+// returns 1 if everthing OK, 0 on error.
+// uva2ka ensures this only works for PTE_U pages.
+int
+copyout(pde_t *pgdir, uint va, void *xbuf, uint len)
+{
+  char *buf = (char *) xbuf;
+  while(len > 0){
+    uint va0 = (uint)PGROUNDDOWN(va);
+    char *pa0 = uva2ka(pgdir, (char*) va0);
+    if(pa0 == 0)
+      return 0;
+    uint n = PGSIZE - (va - va0);
+    if(n > len)
+      n = len;
+    memmove(pa0 + (va - va0), buf, n);
+    len -= n;
+    buf += n;
+    va = va0 + PGSIZE;
+  }
+  return 1;
+}