Never free the lower 1Mbyte of physical memory.

We use it for the AP boot code and stack and could free it after that, but it's easier not to.

Never free the lower 1Mbyte of physical memory.
8797a898 · Silas Boyd-Wickizer · 7737297d · 8797a898
--- a/kernel/kalloc.cc
+++ b/kernel/kalloc.cc
@@ -87,7 +87,7 @@ initmem(u64 mbaddr)
  while (p < ep) {
    mbmem = (Mbmem *)(p+4);
    p += 4 + *(u32*)p;
-    if (mbmem->type == 1) {
+    if (mbmem->type == 1 && mbmem->base >= 0x100000) {
      membytes += mbmem->length;
      mem[nmem] = *mbmem;
      nmem++;