From 5859628dbdbf542ac65538c755dd37301afe7007 Mon Sep 17 00:00:00 2001
From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Date: Wed, 18 Jan 2023 19:26:14 -0300
Subject: [PATCH] kdump-load: Parse the biggest RAM buffer for pstore

The way kdump-load parses /proc/iomem currently expects it has only
a single RAM buffer - but what if we have more, how to choose?

This commit enables multi RAM buffers parsing, and the tool now
copes with various available buffers, selecting the biggest one.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
---
 kdump-load.sh.in | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/kdump-load.sh.in b/kdump-load.sh.in
index b61df85..f343bba 100644
--- a/kdump-load.sh.in
+++ b/kdump-load.sh.in
@@ -74,6 +74,27 @@ clear_all_initrds() {
 	rm -f "${MOUNT_FOLDER}"/kdump-initrd-*
 }
 
+#  Next routine parses /proc/iomem to obtain the biggest RAM buffer
+#  available. Saves the results in 2 global variables: MEM_{SIZE,START}.
+parse_ram_buffers() {
+	BUFFERS="$(grep "RAM buffer" /proc/iomem)"
+	while read -r line
+	do
+		RANGE=$(echo "$line" | cut -f1 -d\ )
+
+		MEM_END=$(echo "$RANGE" | cut -f2 -d-)
+		MSTART=$(echo "$RANGE" | cut -f1 -d-)
+		MSIZE=$(( 16#${MEM_END} - 16#${MSTART} ))
+
+		if [ ${MSIZE} -gt "${MEM_SIZE}" ]; then
+			MEM_SIZE="${MSIZE}"
+			MEM_START="${MSTART}"
+		fi
+	done <<< "${BUFFERS}"
+	#  Trick to preserve global variables modifications inside loops
+	#  using here-strings got from https://stackoverflow.com/a/16854326 .
+}
+
 #  Function to display basic help about how to use this tool.
 usage() {
     cat <<EOF
@@ -132,13 +153,11 @@ preamble
 if [ "${USE_PSTORE_RAM}" -eq 1 ]; then
 	MEM_REQUIRED="${PSTORE_MEM_AMOUNT}"
 	RECORD_SIZE="${PSTORE_RECORD_SZ}"
-	RANGE=$(grep "RAM buffer" /proc/iomem | head -n1 | cut -f1 -d\ )
+	MEM_SIZE=0
 
-	MEM_END=$(echo "$RANGE" | cut -f2 -d-)
-	MEM_START=$(echo "$RANGE" | cut -f1 -d-)
-	MEM_SIZE=$(( 16#${MEM_END} - 16#${MEM_START} ))
+	parse_ram_buffers
 
-	if [ ${MEM_SIZE} -ge "${MEM_REQUIRED}" ]; then
+	if [ "${MEM_SIZE}" -gt 0 ]; then
 		if modprobe ramoops mem_address=0x"${MEM_START}" mem_size="${MEM_REQUIRED}" record_size="${RECORD_SIZE}"; then
 			#  If Pstore is set, update grub.cfg to avoid reserving crashkernel memory.
 			logger "kdump: pstore-RAM was loaded successfully"