separate flags for fork() to share vmap, filetable

296bdfb1 · Nickolai Zeldovich · 3a2a1212 · 296bdfb1 · 296bdfb1
--- a/include/fcntl.h
+++ b/include/fcntl.h
@@ -4,3 +4,7 @@
 #define O_CREATE  0x200

 #define AT_FDCWD  -100
+
+#define FORK_SHARE_VMAP   (1<<0)
+#define FORK_SHARE_FD     (1<<1)
+
--- a/kernel/proc.cc
+++ b/kernel/proc.cc
@@ -13,6 +13,7 @@
 #include "kalloc.hh"
 #include "vm.hh"
 #include "ns.hh"
+#include "fcntl.h"

 u64
 proc_hash(const u32 &p)
@@ -344,7 +345,10 @@ fork(int flags)
  if((np = proc::alloc()) == 0)
    return -1;

-  if(flags == 0) {
+  if(flags & FORK_SHARE_VMAP) {
+    np->vmap = myproc()->vmap;
+    np->vmap->ref++;
+  } else {
    // Copy process state from p.
    if((np->vmap = myproc()->vmap->copy(cow)) == 0){
      ksfree(slab_stack, np->kstack);
@@ -354,9 +358,6 @@ fork(int flags)
      freeproc(np);
      return -1;
    }
-  } else {
-    np->vmap = myproc()->vmap;
-    np->vmap->ref++;
  }

  np->parent = myproc();
@@ -366,16 +367,16 @@ fork(int flags)
  // Clear %eax so that fork returns 0 in the child.
  np->tf->rax = 0;

-  if (flags == 0) {
+  if (flags & FORK_SHARE_FD) {
+    myproc()->ftable->incref();
+    np->ftable = myproc()->ftable;
+  } else {
    np->ftable = new filetable(*myproc()->ftable);
    if (np->ftable == nullptr) {
      // XXX(sbw) leaking?
      freeproc(np);
      return -1;
    }
-  } else {
-    myproc()->ftable->incref();
-    np->ftable = myproc()->ftable;
  }

  np->cwd = idup(myproc()->cwd);