Initial version of single-cpu xv6 with page tables

1 files changed, 40 insertions, 50 deletions

diff --git a/exec.c b/exec.c
index 17fab01..65de312 100644
--- a/exec.c
+++ b/exec.c
@@ -11,12 +11,13 @@ exec(char *path, char **argv)
 {
   char *mem, *s, *last;
   int i, argc, arglen, len, off;
-  uint sz, sp, argp;
+  uint sz, sp, spoffset, argp;
   struct elfhdr elf;
   struct inode *ip;
   struct proghdr ph;
+  pde_t *pgdir, *oldpgdir;
 
-  mem = 0;
+  pgdir = 0;
   sz = 0;
 
   if((ip = namei(path)) == 0)
@@ -29,37 +30,8 @@ exec(char *path, char **argv)
   if(elf.magic != ELF_MAGIC)
     goto bad;
 
-  // Compute memory size of new process.
-  // Program segments.
-  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;
-    if(ph.type != ELF_PROG_LOAD)
-      continue;
-    if(ph.memsz < ph.filesz)
-      goto bad;
-    sz += ph.memsz;
-  }
-  
-  // Arguments.
-  arglen = 0;
-  for(argc=0; argv[argc]; argc++)
-    arglen += strlen(argv[argc]) + 1;
-  arglen = (arglen+3) & ~3;
-  sz += arglen;
-  sz += 4*(argc+1);  // argv data
-  sz += 4;  // argv
-  sz += 4;  // argc
-
-  // Stack.
-  sz += PAGE;
-  
-  // Allocate program memory.
-  sz = (sz+PAGE-1) & ~(PAGE-1);
-  mem = kalloc(sz);
-  if(mem == 0)
+  if (!(pgdir = setupkvm()))
     goto bad;
-  memset(mem, 0, sz);
 
   // Load program into memory.
   for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
@@ -67,37 +39,48 @@ exec(char *path, char **argv)
       goto bad;
     if(ph.type != ELF_PROG_LOAD)
       continue;
-    if(ph.va + ph.memsz < ph.va || ph.va + ph.memsz > sz)
-      goto bad;
     if(ph.memsz < ph.filesz)
       goto bad;
-    if(readi(ip, mem + ph.va, ph.offset, ph.filesz) != ph.filesz)
+    if (!allocuvm(pgdir, (char *)ph.va, ph.memsz))
+      goto bad;
+    sz += PGROUNDUP(ph.memsz);
+    if (!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz))
       goto bad;
-    memset(mem + ph.va + ph.filesz, 0, ph.memsz - ph.filesz);
   }
   iunlockput(ip);
-  
-  // Initialize stack.
+
+  // Allocate and initialize stack at sz
+  if (!allocuvm(pgdir, (char *)sz, PGSIZE))
+    goto bad;
+  mem = uva2ka(pgdir, (char *)sz);
+  spoffset = sz;
+  sz += PGSIZE;
+
+  arglen = 0;
+  for(argc=0; argv[argc]; argc++)
+    arglen += strlen(argv[argc]) + 1;
+  arglen = (arglen+3) & ~3;
+
   sp = sz;
   argp = sz - arglen - 4*(argc+1);
 
   // Copy argv strings and pointers to stack.
-  *(uint*)(mem+argp + 4*argc) = 0;  // argv[argc]
+  *(uint*)(mem+argp-spoffset + 4*argc) = 0;  // argv[argc]
   for(i=argc-1; i>=0; i--){
     len = strlen(argv[i]) + 1;
     sp -= len;
-    memmove(mem+sp, argv[i], len);
-    *(uint*)(mem+argp + 4*i) = sp;  // argv[i]
+    memmove(mem+sp-spoffset, argv[i], len);
+    *(uint*)(mem+argp-spoffset + 4*i) = sp;  // argv[i]
   }
 
   // Stack frame for main(argc, argv), below arguments.
   sp = argp;
   sp -= 4;
-  *(uint*)(mem+sp) = argp;
+  *(uint*)(mem+sp-spoffset) = argp;
   sp -= 4;
-  *(uint*)(mem+sp) = argc;
+  *(uint*)(mem+sp-spoffset) = argc;
   sp -= 4;
-  *(uint*)(mem+sp) = 0xffffffff;   // fake return pc
+  *(uint*)(mem+sp-spoffset) = 0xffffffff;   // fake return pc
 
   // Save program name for debugging.
   for(last=s=path; *s; s++)
@@ -105,18 +88,25 @@ exec(char *path, char **argv)
       last = s+1;
   safestrcpy(proc->name, last, sizeof(proc->name));
 
-  // Commit to the new image.
-  kfree(proc->mem, proc->sz);
-  proc->mem = mem;
+  // Commit to the user image.
+  oldpgdir = proc->pgdir;
+  proc->pgdir = pgdir;
   proc->sz = sz;
   proc->tf->eip = elf.entry;  // main
   proc->tf->esp = sp;
-  usegment();
+
+  // printstack();
+
+  loadvm(proc);
+
+  freevm(oldpgdir);
+
+  // printstack(); 
+
   return 0;
 
  bad:
-  if(mem)
-    kfree(mem, sz);
+  freevm(pgdir);
   iunlockput(ip);
   return -1;
 }