[PATCH v3 4/6] crashdump: exclude elfcorehdr segment from digest for hotplug

[Eric DeVolder]

To allow direct modification of the elfcorehdr by the kernel, in
response to CPU and memory hot un/plug and/or online/offline events,
the buffer containing the elfcorehdr must be excluded from the
purgatory checksum/digest.

If the elfcorehdr is not excluded from the purgatory checksum/digest,
then at panic time, the checksum/digest check fails (due to the
elfcorehdr having been modified), and the kdump capture kernel does
not start.

Signed-off-by: Eric DeVolder <eric.devolder at oracle.com>
---
 kexec/kexec.c | 8 ++++++++
 kexec/kexec.h | 1 +
 2 files changed, 9 insertions(+)

diff --git a/kexec/kexec.c b/kexec/kexec.c
index 0207608..fdb4c98 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -689,6 +689,14 @@ static void update_purgatory(struct kexec_info *info)
 		if (info->segment[i].mem == (void *)info->rhdr.rel_addr) {
 			continue;
 		}
+
+		/* Don't include elfcorehdr in the checksum, if hotplug
+		 * support enabled.
+		 */
+		if (do_hotplug && (info->segment[i].mem == (void *)info->elfcorehdr)) {
+			continue;
+		}
+
 		sha256_update(&ctx, info->segment[i].buf,
 			      info->segment[i].bufsz);
 		nullsz = info->segment[i].memsz - info->segment[i].bufsz;
diff --git a/kexec/kexec.h b/kexec/kexec.h
index 487f707..1004aff 100644
--- a/kexec/kexec.h
+++ b/kexec/kexec.h
@@ -170,6 +170,7 @@ struct kexec_info {
 	int command_line_len;
 
 	int skip_checks;
+	unsigned long elfcorehdr;
 };
 
 struct arch_map_entry {
-- 
2.39.3