[PATCH makedumpfile] Fix incorrect PFN exclusion when LOAD segments overlap

[Ming Wang]

When iterating through LOAD segments to exclude pages in
`exclude_nodata_pages`, simply using `phys_end` to track allocated
PFNs can lead to the erroneous exclusion of valid pages from a
subsequent LOAD segment if its `phys_start` overlaps with the
previous segment's address range.

This patch addresses the issue by checking for such overlaps with the
next LOAD segment's physical address range. If an overlap is
detected, we continue including PFNs from the current segment until
reaching the end of the overlapping region.

This fix ensures that all valid pages within overlapping LOAD segments
are correctly included during PFN exclusion.

Signed-off-by: Ming Wang <wangming01 at loongson.cn>
---
 makedumpfile.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index ce0d40e..f07f831 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -5207,7 +5207,7 @@ static void
 exclude_nodata_pages(struct cycle *cycle)
 {
 	int i;
-	unsigned long long phys_start, phys_end;
+	unsigned long long phys_start, phys_end, next_phys_start, next_phys_end, overlap;
 	off_t file_size;
 
 	i = 0;
@@ -5222,7 +5222,25 @@ exclude_nodata_pages(struct cycle *cycle)
 			pfn = cycle->start_pfn;
 		if (pfn_end >= cycle->end_pfn)
 			pfn_end = cycle->end_pfn;
-		while (pfn < pfn_end) {
+
+		/**
+		 * phys_start                        phys_end
+		 * LOAD[ 0]           200000          2186200
+		 * LOAD[ 1]           200000          ee00000
+		 * LOAD[ 2]         90400000         b8a00000
+		 *
+		 * In the above example, When iterating through LOAD segments, simply excluding
+		 * already allocated Physical Frames (PFNs) based on 'phys_end' can lead to an
+		 * incorrect exclusion of valid pages within load[1], particularly in overlapping
+		 * regions between load[0] and load[1].
+		 */
+		get_pt_load_extents(i + 1, &next_phys_start, &next_phys_end, NULL, &file_size);
+		if (next_phys_start == phys_start && next_phys_end > phys_end)
+			overlap = TRUE;
+		else
+			overlap = FALSE;
+
+		while (pfn < pfn_end && !overlap) {
 			clear_bit_on_2nd_bitmap(pfn, cycle);
 			++pfn;
 		}
-- 
2.39.2