protect-my-balls_mod.patch

diff --git a/Makefile b/Makefile
index 09d790c..963585c 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@ OBJS = \
 	vm.o\
 
 # Cross-compiling (e.g., on Mac OS X)
-# TOOLPREFIX = i386-jos-elf
+TOOLPREFIX = i386-elf-
 
 # Using native tools (e.g., on X86 Linux)
 #TOOLPREFIX = 
@@ -72,11 +72,11 @@ QEMU = $(shell if which qemu > /dev/null; \
 endif
 
 CC = $(TOOLPREFIX)gcc
-AS = $(TOOLPREFIX)gas
+AS = $(TOOLPREFIX)as
 LD = $(TOOLPREFIX)ld
 OBJCOPY = $(TOOLPREFIX)objcopy
 OBJDUMP = $(TOOLPREFIX)objdump
-CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
+CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -fno-omit-frame-pointer
 CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
 ASFLAGS = -m32 -gdwarf-2 -Wa,-divide
 # FreeBSD ld wants ``elf_i386_fbsd''
@@ -146,7 +146,7 @@ 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
 
@@ -217,7 +217,7 @@ QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
 	then echo "-gdb tcp::$(GDBPORT)"; \
 	else echo "-s -p $(GDBPORT)"; fi)
 ifndef CPUS
-CPUS := 2
+CPUS := 1
 endif
 QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)
 
diff --git a/defs.h b/defs.h
index 82fb982..c07e9c8 100644
--- a/defs.h
+++ b/defs.h
@@ -185,6 +185,8 @@ void            switchuvm(struct proc*);
 void            switchkvm(void);
 int             copyout(pde_t*, uint, void*, uint);
 void            clearpteu(pde_t *pgdir, char *uva);
+int             mprotect(void *, int);
+int             munprotect(void *, int);
 
 // number of elements in fixed-size array
 #define NELEM(x) (sizeof(x)/sizeof((x)[0]))
diff --git a/exec.c b/exec.c
index b40134f..dc64a25 100644
--- a/exec.c
+++ b/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;
diff --git a/syscall.c b/syscall.c
index ee85261..ddf09de 100644
--- a/syscall.c
+++ b/syscall.c
@@ -63,7 +63,7 @@ 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 || (uint)i >= curproc->sz || (uint)i+size > curproc->sz || (uint)i < PGSIZE)
     return -1;
   *pp = (char*)i;
   return 0;
@@ -103,6 +103,8 @@ 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 +128,8 @@ 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
diff --git a/syscall.h b/syscall.h
index bc5f356..ef11022 100644
--- a/syscall.h
+++ b/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
diff --git a/sysproc.c b/sysproc.c
index 0686d29..a6f6ea3 100644
--- a/sysproc.c
+++ b/sysproc.c
@@ -89,3 +89,27 @@ sys_uptime(void)
   release(&tickslock);
   return xticks;
 }
+
+int sys_mprotect(void) {
+  void *addr;
+  int len;
+
+  if (argptr(0, (char **)&addr, sizeof(void *)) || argint(1, &len) < 0)
+    return -1;
+  if ((uint)addr % PGSIZE != 0 || len <= 0 || (uint)addr < PGSIZE)
+    return -1;
+
+  return mprotect(addr, len);
+}
+
+int sys_munprotect(void) {
+  void *addr;
+  int len;
+
+  if (argptr(0, (char **)&addr, sizeof(void *)) || argint(1, &len) < 0)
+    return -1;
+  if ((uint)addr % PGSIZE != 0 || len <= 0 || (uint)addr < PGSIZE)
+    return -1;
+
+  return munprotect(addr, len);
+}
diff --git a/user.h b/user.h
index 4f99c52..f5aea04 100644
--- a/user.h
+++ b/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*);
diff --git a/usys.S b/usys.S
index 8bfd8a1..42f7a42 100644
--- a/usys.S
+++ b/usys.S
@@ -29,3 +29,5 @@ SYSCALL(getpid)
 SYSCALL(sbrk)
 SYSCALL(sleep)
 SYSCALL(uptime)
+SYSCALL(mprotect)
+SYSCALL(munprotect)
diff --git a/vm.c b/vm.c
index 7134cff..c7e8ff5 100644
--- a/vm.c
+++ b/vm.c
@@ -322,7 +322,7 @@ copyuvm(pde_t *pgdir, uint sz)
 
   if((d = setupkvm()) == 0)
     return 0;
-  for(i = 0; i < sz; i += PGSIZE){
+  for(i = PGSIZE; i < sz; i += PGSIZE){
     if((pte = walkpgdir(pgdir, (void *) i, 0)) == 0)
       panic("copyuvm: pte should exist");
     if(!(*pte & PTE_P))
@@ -392,3 +392,43 @@ copyout(pde_t *pgdir, uint va, void *p, uint len)
 //PAGEBREAK!
 // Blank page.
 
+int mprotect(void *addr, int len) {
+  struct proc *curproc = myproc();
+  if ((uint)addr >= curproc->sz || (uint)addr + len >= curproc->sz)
+    return -1;
+
+  char *a, *last;
+  pte_t *pte;
+  a = (char *)PGROUNDDOWN((uint)addr);
+  last = (char *)PGROUNDDOWN(((uint)addr) + len - 1);
+  for (;;) {
+    if ((pte = walkpgdir(curproc->pgdir, a, 0)) == 0)
+      return -1;
+    *pte &= ~PTE_W;
+    if (a >= last)
+      break;
+    a += PGSIZE;
+  }
+  lcr3(V2P(curproc->pgdir)); // update page flag
+  return 0;
+}
+int munprotect(void *addr, int len) {
+  struct proc *curproc = myproc();
+  if ((uint)addr >= curproc->sz || (uint)addr + len >= curproc->sz)
+    return -1;
+
+  char *a, *last;
+  pte_t *pte;
+  a = (char *)PGROUNDDOWN((uint)addr);
+  last = (char *)PGROUNDDOWN(((uint)addr) + len - 1);
+  for (;;) {
+    if ((pte = walkpgdir(curproc->pgdir, a, 0)) == 0)
+      return -1;
+    *pte |= PTE_W;
+    if (a >= last)
+      break;
+    a += PGSIZE;
+  }
+  lcr3(V2P(curproc->pgdir)); // update page flag
+  return 0;
+}