[PATCH v2 5/9] add mem_min_overlap to find the first avoid region within a memory region

[Baoquan He <bhe@redhat.com>]

Given a memory region mem_min_overlap will iterate all avoid region
to find the first one which overlap with it. This function will be
used later.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/boot/compressed/aslr.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index 26610a2..ded3959 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -213,6 +213,38 @@ static bool mem_avoid_overlap(struct mem_vector *img)
 	return false;
 }
 
+static unsigned long mem_min_overlap(struct mem_vector *img, struct mem_vector *out)
+{
+	int i;
+	struct setup_data *ptr;
+	unsigned long min = img->start + img->size;
+
+	for (i = 0; i < MEM_AVOID_MAX; i++) {
+		if (mem_overlaps(img, &mem_avoid[i]) && (mem_avoid[i].start < min) ) {
+			*out = mem_avoid[i];
+			min = mem_avoid[i].start;
+		}
+	}
+
+	/* Check all entries in the setup_data linked list. */
+	ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data;
+	while (ptr) {
+		struct mem_vector avoid;
+
+		avoid.start = (unsigned long)ptr;
+		avoid.size = sizeof(*ptr) + ptr->len;
+
+		if (mem_overlaps(img, &avoid) && (avoid.start < min) ) {
+			*out = avoid;
+			min = avoid.start;
+		}
+
+		ptr = (struct setup_data *)(unsigned long)ptr->next;
+	}
+
+	return min;
+}
+
 static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
 			   CONFIG_PHYSICAL_ALIGN];
 
-- 
1.9.3