Updated

Makefile

@@ -52,7 +52,7 @@ endif
 
 # If the makefile can't find QEMU, specify its path here
 # QEMU = qemu-system-i386
-
+QEMU = /usr/libexec/qemu-kvm
 # Try to infer the correct QEMU
 ifndef QEMU
 QEMU = $(shell if which qemu > /dev/null; \
@@ -146,14 +146,14 @@ vectors.S: vectors.pl
 ULIB = ulib.o usys.o printf.o umalloc.o
 
 _%: %.o $(ULIB)
-	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $@ $^
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0x1000 -o $@ $^
 	$(OBJDUMP) -S $@ > $*.asm
 	$(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $*.sym
 
 _forktest: forktest.o $(ULIB)
 	# forktest has less library code linked in - needs to be small
 	# in order to be able to max out the proc table.
-	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _forktest forktest.o ulib.o usys.o
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0x1000 -o _forktest forktest.o ulib.o usys.o
 	$(OBJDUMP) -S _forktest > forktest.asm
 
 mkfs: mkfs.c fs.h
@@ -181,6 +181,8 @@ UPROGS=\
 	_usertests\
 	_wc\
 	_zombie\
+	_testkaccess\
+	_testnull\
 
 fs.img: mkfs README $(UPROGS)
 	./mkfs fs.img README $(UPROGS)
@@ -283,4 +285,4 @@ tar:
 	cp dist/* dist/.gdbinit.tmpl /tmp/xv6
 	(cd /tmp; tar cf - xv6) | gzip >xv6-rev10.tar.gz  # the next one will be 10 (9/17)
 
-.PHONY: dist-test dist
+.PHONY: dist-test dist

defs.h

@@ -156,6 +156,10 @@ int             fetchint(uint, int*);
 int             fetchstr(uint, char**);
 void            syscall(void);
 
+// sysproc.c
+int             sys_mprotect(void);
+int             sys_munprotect(void);
+
 // timer.c
 void            timerinit(void);
 
@@ -181,10 +185,13 @@ void            freevm(pde_t*);
 void            inituvm(pde_t*, char*, uint);
 int             loaduvm(pde_t*, char*, struct inode*, uint, uint);
 pde_t*          copyuvm(pde_t*, uint);
+pde_t*          walkpgdir(pde_t *pgdir, const void *va, int alloc);
 void            switchuvm(struct proc*);
 void            switchkvm(void);
 int             copyout(pde_t*, uint, void*, uint);
 void            clearpteu(pde_t *pgdir, char *uva);
+int             mprotectpages(void*, int);
+int             munprotectpages(void*, int);
 
 // number of elements in fixed-size array
 #define NELEM(x) (sizeof(x)/sizeof((x)[0]))

exec.c

@@ -39,7 +39,7 @@ exec(char *path, char **argv)
     goto bad;
 
   // Load program into memory.
-  sz = 0;
+  sz = PGSIZE;
   for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
     if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))
       goto bad;
@@ -111,4 +111,4 @@ exec(char *path, char **argv)
     end_op();
   }
   return -1;
-}
+}

syscall.c

@@ -19,8 +19,13 @@ fetchint(uint addr, int *ip)
 {
   struct proc *curproc = myproc();
 
-  if(addr >= curproc->sz || addr+4 > curproc->sz)
+  if(addr >= curproc->sz)
+    return -1;
+  if(addr + 4 > curproc->sz)
     return -1;
+  if(addr + 4 < addr)
+    return -1;
+
   *ip = *(int*)(addr);
   return 0;
 }
@@ -36,8 +41,10 @@ fetchstr(uint addr, char **pp)
 
   if(addr >= curproc->sz)
     return -1;
+
   *pp = (char*)addr;
   ep = (char*)curproc->sz;
+
   for(s = *pp; s < ep; s++){
     if(*s == 0)
       return s - *pp;
@@ -63,8 +70,19 @@ argptr(int n, char **pp, int size)
 
   if(argint(n, &i) < 0)
     return -1;
-  if(size < 0 || (uint)i >= curproc->sz || (uint)i+size > curproc->sz)
+
+  if(size < 0)
     return -1;
+
+  if((uint)i >= curproc->sz)
+    return -1;
+
+  if((uint)i + size > curproc->sz)
+    return -1;
+
+  if((uint)i + size < (uint)i)
+    return -1;
+
   *pp = (char*)i;
   return 0;
 }
@@ -103,6 +121,8 @@ extern int sys_unlink(void);
 extern int sys_wait(void);
 extern int sys_write(void);
 extern int sys_uptime(void);
+extern int sys_mprotect(void);
+extern int sys_munprotect(void);
 
 static int (*syscalls[])(void) = {
 [SYS_fork]    sys_fork,
@@ -126,6 +146,8 @@ static int (*syscalls[])(void) = {
 [SYS_link]    sys_link,
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
+[SYS_mprotect]    sys_mprotect,
+[SYS_munprotect]  sys_munprotect,
 };
 
 void
@@ -142,4 +164,4 @@ syscall(void)
             curproc->pid, curproc->name, num);
     curproc->tf->eax = -1;
   }
-}
+}

syscall.h

@@ -20,3 +20,5 @@
 #define SYS_link   19
 #define SYS_mkdir  20
 #define SYS_close  21
+#define SYS_mprotect  22
+#define SYS_munprotect 23

sysproc.c

@@ -89,3 +89,59 @@ sys_uptime(void)
   release(&tickslock);
   return xticks;
 }
+
+int
+sys_mprotect(void)
+{
+    char *addr;
+    int len;
+
+    if(argptr(0, &addr, sizeof(addr)) < 0)
+        return -1;
+    if(argint(1, &len) < 0)
+        return -1;
+
+    if((uint)addr % PGSIZE != 0 || len <= 0)
+        return -1;
+
+    struct proc *p = myproc();
+
+    for(int i = 0; i < len; i += PGSIZE) {
+        pte_t *pte = walkpgdir(p->pgdir, addr + i, 0);
+        if(!pte || !(*pte & PTE_P))
+            return -1;
+
+        *pte &= ~PTE_W;
+    }
+
+    return 0;
+}
+
+int
+sys_munprotect(void)
+{
+    char *addr;
+    int len;
+
+    if(argptr(0, &addr, sizeof(addr)) < 0)
+        return -1;
+    if(argint(1, &len) < 0)
+        return -1;
+
+    if((uint)addr % PGSIZE != 0 || len <= 0)
+        return -1;
+
+    struct proc *p = myproc();
+
+    for(int i = 0; i < len; i += PGSIZE) {
+        pte_t *pte = walkpgdir(p->pgdir, addr + i, 0);
+        if(!pte || !(*pte & PTE_P))
+            return -1;
+
+        *pte |= PTE_W;
+    }
+
+    lcr3(V2P(p->pgdir));
+
+    return 0;
+}

testkaccess.c

@@ -0,0 +1,11 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+int main(void){
+  printf(1, "testkaccess: illegal read attempt\n");
+  volatile int *p = (int*)0xFFFF0000;
+  volatile int x = *p;
+  printf(1, "UNEXPECTED: read=%d\n", x);
+  exit();
+}

testnull.c

@@ -0,0 +1,11 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+int main(void){
+  printf(1, "testnull: about to dereference NULL\n");
+  volatile int *p = (int*)0x0;
+  volatile int x = *p;
+  printf(1, "UNEXPECTED: read=%d\n", x);
+  exit();
+}

trap.c

@@ -79,7 +79,7 @@ trap(struct trapframe *tf)
     break;
 
   //PAGEBREAK: 13
-  default:
+  /*default:
     if(myproc() == 0 || (tf->cs&3) == 0){
       // In kernel, it must be our mistake.
       cprintf("unexpected trap %d from cpu %d eip %x (cr2=0x%x)\n",
@@ -92,6 +92,29 @@ trap(struct trapframe *tf)
             myproc()->pid, myproc()->name, tf->trapno,
             tf->err, cpuid(), tf->eip, rcr2());
     myproc()->killed = 1;
+  }*/
+
+  default:
+  if(myproc() == 0 || (tf->cs&3) == 0){
+    // Kernel mode → panic
+    cprintf("unexpected trap %d from cpu %d eip %x (cr2=0x%x)\n",
+            tf->trapno, cpuid(), tf->eip, rcr2());
+    panic("trap");
+  }
+
+  // Special handling for page fault
+  if(tf->trapno == T_PGFLT){
+    cprintf("pid %d %s: page fault at addr 0x%x, eip 0x%x\n",
+            myproc()->pid, myproc()->name, rcr2(), tf->eip);
+  } else {
+    cprintf("pid %d %s: trap %d err %d on cpu %d "
+            "eip 0x%x addr 0x%x--kill proc\n",
+            myproc()->pid, myproc()->name, tf->trapno,
+            tf->err, cpuid(), tf->eip, rcr2());
+  }
+
+  myproc()->killed = 1;
+  break;
   }
 
   // Force process exit if it has been killed and is in user space.
@@ -109,4 +132,4 @@ trap(struct trapframe *tf)
   // Check if the process has been killed since we yielded
   if(myproc() && myproc()->killed && (tf->cs&3) == DPL_USER)
     exit();
-}
+}

user.h

@@ -23,6 +23,8 @@ int getpid(void);
 char* sbrk(int);
 int sleep(int);
 int uptime(void);
+int mprotect(void*, int);
+int munprotect(void*, int);
 
 // ulib.c
 int stat(const char*, struct stat*);
@@ -36,4 +38,4 @@ uint strlen(const char*);
 void* memset(void*, int, uint);
 void* malloc(uint);
 void free(void*);
-int atoi(const char*);
+int atoi(const char*);

usys.S

@@ -29,3 +29,5 @@ SYSCALL(getpid)
 SYSCALL(sbrk)
 SYSCALL(sleep)
 SYSCALL(uptime)
+SYSCALL(mprotect)
+SYSCALL(munprotect)

vm.c

@@ -32,7 +32,7 @@ seginit(void)
 // Return the address of the PTE in page table pgdir
 // that corresponds to virtual address va.  If alloc!=0,
 // create any required page table pages.
-static pte_t *
+pte_t *
 walkpgdir(pde_t *pgdir, const void *va, int alloc)
 {
   pde_t *pde;
@@ -323,10 +323,9 @@ copyuvm(pde_t *pgdir, uint sz)
   if((d = setupkvm()) == 0)
     return 0;
   for(i = 0; i < sz; i += PGSIZE){
-    if((pte = walkpgdir(pgdir, (void *) i, 0)) == 0)
-      panic("copyuvm: pte should exist");
-    if(!(*pte & PTE_P))
-      panic("copyuvm: page not present");
+    pte = walkpgdir(pgdir, (void*)i, 0);
+    if(pte == 0 || !(*pte & PTE_P))
+      continue;
     pa = PTE_ADDR(*pte);
     flags = PTE_FLAGS(*pte);
     if((mem = kalloc()) == 0)