zdump: Extract dfo_mem_chunk interface from DFO

The primary goal is to separate DFO code into multiple smaller modules
and make it unit testable.

This refactoring only moved the code around w/o changing any functionality.

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zdump/dfo_mem_chunk.c

@@ -0,0 +1,128 @@
+/*
+ * Copyright IBM Corp. 2001, 2017, 2021
+ *
+ * s390-tools is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#include <string.h>
+
+#include "zg.h"
+#include "dfi_mem_chunk.h"
+#include "dfo_mem_chunk.h"
+
+/*
+ * File local static data
+ */
+static struct {
+	u64			size;		/* Size of dump in bytes */
+	unsigned int		chunk_cnt;	/* Number of dump chunks */
+	struct util_list	chunk_list;	/* DFO chunk list */
+} l;
+
+/*
+ * Add dump chunk
+ */
+void dfo_chunk_add(u64 start, u64 size, void *data, dfo_chunk_read_fn read_fn)
+{
+	struct dfo_chunk *dfo_chunk;
+
+	dfo_chunk = zg_alloc(sizeof(*dfo_chunk));
+	dfo_chunk->start = start;
+	dfo_chunk->end = start + size - 1;
+	dfo_chunk->data = data;
+	dfo_chunk->read_fn = read_fn;
+	util_list_add_head(&l.chunk_list, dfo_chunk);
+	l.chunk_cnt++;
+	l.size = MAX(l.size, dfo_chunk->end + 1);
+}
+
+/*
+ * Dump chunk function: Copy zero pages for chunk
+ */
+void dfo_chunk_zero_fn(struct dfo_chunk *dfo_chunk, u64 off, void *buf, u64 cnt)
+{
+	(void) dfo_chunk;
+	(void) off;
+
+	memset(buf, 0, cnt);
+}
+
+/*
+ * Dump chunk function: Copy given buffer for chunk
+ */
+void dfo_chunk_buf_fn(struct dfo_chunk *dfo_chunk, u64 off, void *buf, u64 cnt)
+{
+	memcpy(buf, dfo_chunk->data + off, cnt);
+}
+
+/*
+ * Dump chunk function: Copy given memory range for chunk
+ */
+void dfo_chunk_mem_fn(struct dfo_chunk *dfo_chunk, u64 off, void *buf, u64 cnt)
+{
+	struct dfi_mem_chunk *mem_chunk = dfo_chunk->data;
+
+	mem_chunk->read_fn(mem_chunk, off, buf, cnt);
+}
+
+/*
+ * Find dump chunk for offset "off"
+ *
+ * This function is a bit hacky. DFO chunks can overlap. If two DFO chunks
+ * overlap, the last registered chunk wins. The dfo_chunk_find() function
+ * reflects that by returning the first memory chunk that is found in
+ * the dfo chunk list.
+ *
+ * In addition to that it calculates the "virtual end" of that chunk. An
+ * overlapping chunk can limit the "virtual end" of an underlying chunk so
+ * that the "virtual end" of that chunk is lower than the "real end".
+ *
+ * Example:
+ *
+ * chunk 1.:      |------|
+ * chunk 2.: |---------------------|
+ * off.....: ^
+ * virt end:      ^
+ * real end:                       ^
+ *
+ * In this case chunk 2 will be returned and "end" is set to the start of
+ * chunk 1.
+ */
+struct dfo_chunk *dfo_chunk_find(u64 off, u64 *end)
+{
+	struct dfo_chunk *dfo_chunk;
+
+	*end = U64_MAX;
+	dfo_chunk_iterate(dfo_chunk) {
+		if (dfo_chunk->start <= off && dfo_chunk->end >= off) {
+			*end = MIN(*end, dfo_chunk->end);
+			return dfo_chunk;
+		} else if (dfo_chunk->start > off) {
+			*end = MIN(*end, dfo_chunk->start - 1);
+		}
+	}
+	return NULL;
+}
+
+struct util_list *dfo_chunk_list(void)
+{
+	return &l.chunk_list;
+}
+
+u64 dfo_chunk_dump_size(void)
+{
+	return l.size;
+}
+
+int dfo_chunk_init(void)
+{
+	util_list_init(&l.chunk_list, struct dfo_chunk, list);
+
+	return 0;
+}
+
+void dfo_chunk_deinit(void)
+{
+	memset(&l, 0, sizeof(l));
+}