libipt: split pt_image_read()

Split pt_image_read() into hot and cold parts, where the hot part loops over
already mapped sections in the image's LRU cache.  When encountering an
unmapped section, we switch to the cold part where we map and unmap sections
before reading.

Change-Id: I7d818c45193afc2b5e442424a1ca80eb941cb7b3
Signed-off-by: Markus Metzger <[email protected]>

libipt/src/pt_image.c

@@ -417,22 +417,38 @@ static int pt_image_prune_cache(struct pt_image *image)
 	return status;
 }
 
-int pt_image_read(struct pt_image *image, uint8_t *buffer, uint16_t size,
-		  const struct pt_asid *asid, uint64_t addr)
+static int pt_image_read_callback(struct pt_image *image, uint8_t *buffer,
+				  uint16_t size, const struct pt_asid *asid,
+				  uint64_t addr)
 {
-	struct pt_section_list **list, **start;
 	read_memory_callback_t *callback;
-	int status;
 
-	if (!image || !asid)
+	if (!image)
+		return -pte_internal;
+
+	callback = image->readmem.callback;
+	if (!callback)
+		return -pte_nomap;
+
+	return callback(buffer, size, asid, addr, image->readmem.context);
+}
+
+static int pt_image_read_cold(struct pt_image *image,
+			      struct pt_section_list **list,
+			      uint8_t *buffer, uint16_t size,
+			      const struct pt_asid *asid, uint64_t addr)
+{
+	struct pt_section_list **start;
+
+	if (!image || !list)
 		return -pte_internal;
 
 	start = &image->sections;
-	for (list = start; *list;) {
+	while (*list) {
 		struct pt_mapped_section *msec;
 		struct pt_section_list *elem;
 		struct pt_section *sec;
-		int mapped, errcode;
+		int mapped, errcode, status;
 
 		elem = *list;
 		msec = &elem->section;
@@ -493,10 +509,44 @@ int pt_image_read(struct pt_image *image, uint8_t *buffer, uint16_t size,
 		return status;
 	}
 
-	callback = image->readmem.callback;
-	if (callback)
-		return callback(buffer, size, asid, addr,
-				image->readmem.context);
+	return pt_image_read_callback(image, buffer, size, asid, addr);
+}
+
+int pt_image_read(struct pt_image *image, uint8_t *buffer, uint16_t size,
+		  const struct pt_asid *asid, uint64_t addr)
+{
+	struct pt_section_list **list, **start;
+
+	if (!image || !asid)
+		return -pte_internal;
+
+	start = &image->sections;
+	for (list = start; *list;) {
+		struct pt_mapped_section *msec;
+		struct pt_section_list *elem;
+		int status;
+
+		elem = *list;
+		msec = &elem->section;
+
+		if (!elem->mapped)
+			break;
+
+		status = pt_msec_read_mapped(msec, buffer, size, asid, addr);
+		if (status < 0) {
+			list = &elem->next;
+			continue;
+		}
+
+		/* Move the section to the front if it isn't already. */
+		if (list != start) {
+			*list = elem->next;
+			elem->next = *start;
+			*start = elem;
+		}
+
+		return status;
+	}
 
-	return -pte_nomap;
+	return pt_image_read_cold(image, list, buffer, size, asid, addr);
 }