.

Makefile

@@ -96,7 +96,7 @@ LINKC	= $(LINK.c) $< $(LOADLIBES) $(LDLIBS) -o $@
 # tests without instrumentation
 test.t	: $(TESTS:%=%.trun)
 %.trun	: %.t
-	$(XRUN<)
+	gdb -q -ex run -ex backtrace -ex quit $(XRUN<)
 
 %.t	: %.c $(ccan_config)
 	$(LINKC)

bigfile/virtmem.c

@@ -223,6 +223,8 @@ int fileh_mmap(VMA *vma, BigFileH *fileh, pgoff_t pgoffset, pgoff_t pglen)
     void *addr;
     size_t len = pglen * fileh->ramh->ram->pagesize;
     int err = 0;
+    BigFile *file = fileh->file;
+    const bigfile_ops *fops = file->file_ops;
     sigset_t save_sigset;
 
     sigsegv_block(&save_sigset);
@@ -235,11 +237,22 @@ int fileh_mmap(VMA *vma, BigFileH *fileh, pgoff_t pgoffset, pgoff_t pglen)
     if (!vma->page_ismappedv)
         goto fail;
 
+    // XXX hardcoded - allow user choise?
+    vma->mmap_overlay = (fops->mmap_setup_read != NULL);
+
+    if (vma->mmap_overlay) {
+        TODO (file->blksize != fileh->ramh->ram->pagesize);
+        addr = fops->mmap_setup_read(file, pgoffset, pglen, vma);
+        if (!addr)
+            goto fail;
+        // XXX + mmap(fileh->dirty_pages)
+    } else {
         /* allocate address space somewhere */
-    // XXX overlay: -> mmap(base, READ) + mmap(fileh->dirty_pages)
         addr = mem_valloc(NULL, len);
         if (!addr)
             goto fail;
+    }
+
 
     /* everything allocated - link it up */
     vma->addr_start  = (uintptr_t)addr;

include/wendelin/bigfile/file.h

@@ -96,6 +96,6 @@ struct bigfile_ops {
      */
     void (*release)  (BigFile *file);
 };
-
+typedef struct bigfile_ops bigfile_ops;
 
 #endif

include/wendelin/bigfile/virtmem.h

@@ -137,6 +137,9 @@ struct VMA {
 
     /* whether corresponding to pgoffset-f_offset page is mapped in this VMA */
     bitmap      *page_ismappedv;    /* len ~ Δaddr / pagesize */
+
+    // XXX name
+    unsigned    mmap_overlay : 1;   /* whether base data are taken as file mmap XXX */
 };