Start of a zero'd page allocator

5106ddcd · Silas Boyd-Wickizer · 78489020 · 5106ddcd · 5106ddcd · 5106ddcd
--- a/include/kernel.hh
+++ b/include/kernel.hh
@@ -238,6 +238,10 @@ void            uartintr(void);
 void            switchvm(struct proc*);
 int             pagefault(struct vmap *, uptr, u32);

+// zalloc.cc
+char*           zalloc(const char* name);
+void            zfree(char* p);
+
 // other exported/imported functions
 void cmain(u64 mbmagic, u64 mbaddr);
 void mpboot(void);

--- a/include/wq.hh
+++ b/include/wq.hh
@@ -30,7 +30,8 @@ struct cwork : public work {
 };

 struct wframe {
-  wframe(int v) : v_(v) {}
+  wframe(int v = 0) : v_(v) {}
+  void clear() { v_ = 0; }
  int inc() { return __sync_add_and_fetch(&v_, 1); }
  int dec() { return __sync_sub_and_fetch(&v_, 1); }
  bool zero() volatile { return v_ == 0; };

--- a/kernel/Makefrag
+++ b/kernel/Makefrag
@@ -49,6 +49,7 @@ OBJS = \
 	trapasm.o \
 	wq.o \
 	script.o \
+        zalloc.o \
 	incbin.o
 OBJS := $(addprefix $(O)/kernel/, $(OBJS))


--- a/kernel/uaccess.S
+++ b/kernel/uaccess.S
@@ -15,7 +15,6 @@ __fetchint64:
        mov     $0, %rax
        jmp     __fetch_end
        
-.code64
 .globl __fetchstr
 .align 8
 // rdi kernel dst
@@ -43,9 +42,16 @@ __fetchstr:
 2:      // Done
        jmp     __fetch_end

-.code64
 .globl __fetch_end
 .align 8
 __fetch_end:
        movl $0, PROC_UACCESS(%r11)
        ret
+
+.globl clear_page
+.align 8
+clear_page:
+        movl $4096/8,%ecx
+	xorl %eax,%eax
+	rep stosq
+	ret
--- a/kernel/vm.cc
+++ b/kernel/vm.cc
@@ -72,15 +72,14 @@ vmnode::allocpg()
    if (page[i])
      continue;

-    char *p = kalloc("(vmnode::allocpg)");
+    char *p = zalloc("(vmnode::allocpg)");
    if (!p) {
      cprintf("allocpg: out of memory, leaving half-filled vmnode\n");
      return -1;
    }

-    memset(p, 0, PGSIZE);
    if(!cmpxch(&page[i], (char*) 0, p))
-      kfree(p);
+      zfree(p);
  }
  return 0;
 }

--- a/kernel/zalloc.cc
+++ b/kernel/zalloc.cc
+#include "types.h"
+#include "amd64.h"
+#include "kernel.hh"
+#include "percpu.hh"
+#include "wq.hh"
+#include "kalloc.hh"
+
+extern "C" void clear_page(void*);
+
+struct zallocator {
+  run*   run;
+  wframe frame;
+};
+
+percpu<zallocator> z_;
+
+char*
+zalloc(const char* name)
+{
+  char* p = kalloc(name);
+  if (p)
+    clear_page(p);
+  return p;
+}
+
+void
+zfree(char* p)
+{
+  kfree(p);
+}
+
+void
+initz(void)
+{
+  for (int i = 0; i < NCPU; i++)
+    z_[i].frame.clear();
+}