From 81fbd74a4b598c52957b491896ec839316ceeec3 Mon Sep 17 00:00:00 2001
From: Warner Losh <imp@FreeBSD.org>
Date: Fri, 3 Feb 2023 08:38:22 -0700
Subject: [PATCH] kboot: space_avail -- how much space exists from 'start' to
 end of segment

Sponsored by:		Netflix
Reviewed by:		tsoome
Differential Revision:	https://reviews.freebsd.org/D38313
---
 stand/kboot/kboot.h |  1 +
 stand/kboot/seg.c   | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/stand/kboot/kboot.h b/stand/kboot/kboot.h
index dcf1487ce40..4a8fe497339 100644
--- a/stand/kboot/kboot.h
+++ b/stand/kboot/kboot.h
@@ -44,6 +44,7 @@ void remove_avail(uint64_t start, uint64_t end, uint64_t type);
 uint64_t first_avail(uint64_t align, uint64_t min_size, uint64_t type);
 void print_avail(void);
 bool populate_avail_from_iomem(void);
+uint64_t space_avail(uint64_t start);
 
 /* util.c */
 bool file2str(const char *fn, char *buffer, size_t buflen);
diff --git a/stand/kboot/seg.c b/stand/kboot/seg.c
index 8cf3b833c9d..947aa0a2a7a 100644
--- a/stand/kboot/seg.c
+++ b/stand/kboot/seg.c
@@ -344,3 +344,22 @@ out:
 	close(fd);
 	return true;
 }
+
+/*
+ * Return the amount of space available in the segment that @start@ lives in,
+ * from @start@ to the end of the segment.
+ */
+uint64_t
+space_avail(uint64_t start)
+{
+	for (int i = 0; i < nr_seg; i++) {
+		if (start >= segs[i].start && start <= segs[i].end)
+			return segs[i].end - start;
+	}
+
+	/*
+	 * Properly used, we should never get here. Unsure if this should be a
+	 * panic or not.
+	 */
+	return 0;
+}