From 4655d42e3b65f906eae8c815fb78331790f6e423 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Mon, 27 Sep 2010 16:14:33 -0400
Subject: copyout() copies data to a va in a pagetable, for exec() &c usertest
that passes too many arguments, break exec
---
vm.c | 32 ++++++++++++++++++++++++++++----
1 file changed, 28 insertions(+), 4 deletions(-)
(limited to 'vm.c')
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;
+}
--
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