first commit

kernel/ramdisk.c

@@ -0,0 +1,45 @@
+//
+// ramdisk that uses the disk image loaded by qemu -initrd fs.img
+//
+
+#include "types.h"
+#include "riscv.h"
+#include "defs.h"
+#include "param.h"
+#include "memlayout.h"
+#include "spinlock.h"
+#include "sleeplock.h"
+#include "fs.h"
+#include "buf.h"
+
+void
+ramdiskinit(void)
+{
+}
+
+// If B_DIRTY is set, write buf to disk, clear B_DIRTY, set B_VALID.
+// Else if B_VALID is not set, read buf from disk, set B_VALID.
+void
+ramdiskrw(struct buf *b)
+{
+  if(!holdingsleep(&b->lock))
+    panic("ramdiskrw: buf not locked");
+  if((b->flags & (B_VALID|B_DIRTY)) == B_VALID)
+    panic("ramdiskrw: nothing to do");
+
+  if(b->blockno >= FSSIZE)
+    panic("ramdiskrw: blockno too big");
+
+  uint64 diskaddr = b->blockno * BSIZE;
+  char *addr = (char *)RAMDISK + diskaddr;
+
+  if(b->flags & B_DIRTY){
+    // write
+    memmove(addr, b->data, BSIZE);
+    b->flags &= ~B_DIRTY;
+  } else {
+    // read
+    memmove(b->data, addr, BSIZE);
+    b->flags |= B_VALID;
+  }
+}