From e113f1c974c820f9633dc0073eda525d7575f365 Mon Sep 17 00:00:00 2001
From: Pingfan Liu <piliu@redhat.com>
Date: Mon, 20 Jan 2020 10:25:24 +0800
Subject: [PATCH 3/7] [PATCH] cope with not-present mem section

After kernel commit ba72b4c8cf60 ("mm/sparsemem: support sub-section
hotplug"), when hot-removed, section_mem_map is still encoded with section
start pfn, not NULL. This break the current makedumpfile.

  # makedumpfile -x vmlinux -l -d 31 vmcore vmcore.dump
  get_mem_section: Could not validate mem_section.
  get_mm_sparsemem: Can't get the address of mem_section.

  makedumpfile Failed.

Whatever section_mem_map coding info after hot-removed, it is reliable
just to work on SECTION_MARKED_PRESENT bit. Fixing makedumpfile by this
way.

[ This issue occurs on kernel 5.3 through 5.5, and should be fixed by
commit 1f503443e7df ("mm/sparse.c: reset section's mem_map when fully
deactivated") in 5.6-rc1, 5.5.3 and 5.4.19. ]

Signed-off-by: Pingfan Liu <piliu@redhat.com>
To: kexec@lists.infradead.org
Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qian Cai <cai@lca.pw>
---
 makedumpfile.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/makedumpfile-1.6.7/makedumpfile.c b/makedumpfile-1.6.7/makedumpfile.c
index ae7336a..607e07f 100644
--- a/makedumpfile-1.6.7/makedumpfile.c
+++ b/makedumpfile-1.6.7/makedumpfile.c
@@ -3406,8 +3406,6 @@ section_mem_map_addr(unsigned long addr, unsigned long *map_mask)
 	map = ULONG(mem_section + OFFSET(mem_section.section_mem_map));
 	mask = SECTION_MAP_MASK;
 	*map_mask = map & ~mask;
-	if (map == 0x0)
-		*map_mask |= SECTION_MARKED_PRESENT;
 	map &= mask;
 	free(mem_section);
 
@@ -3453,10 +3451,8 @@ validate_mem_section(unsigned long *mem_sec,
 			mem_map = NOT_MEMMAP_ADDR;
 		} else {
 			mem_map = section_mem_map_addr(section, &map_mask);
+			/* for either no mem_map or hot-removed */
 			if (!(map_mask & SECTION_MARKED_PRESENT)) {
-				return FALSE;
-			}
-			if (mem_map == 0) {
 				mem_map = NOT_MEMMAP_ADDR;
 			} else {
 				mem_map = sparse_decode_mem_map(mem_map,
-- 
2.7.5