scripts/decode_stacktrace.sh: support old bash version

Old bash version don't support associative array variables.  Avoid to use
associative array variables to avoid error.

Without this, old bash version will report error as fellowing
[   15.954042] Kernel panic - not syncing: sysrq triggered crash
[   15.955252] CPU: 1 PID: 167 Comm: sh Not tainted 5.18.0-rc1-00208-gb7d075db2fd5 #4
[   15.956472] Hardware name: Hobot J5 Virtual development board (DT)
[   15.957856] Call trace:
./scripts/decode_stacktrace.sh: line 128: ,dump_backtrace: syntax error: operand expected (error token is ",dump_backtrace")

Link: https://lkml.kernel.org/r/20220409180331.24047-1-schspa@gmail.com
Signed-off-by: Schspa Shi <schspa@gmail.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

scripts/decode_stacktrace.sh

@@ -45,8 +45,13 @@ else
 	fi
 fi
 
-declare -A cache
-declare -A modcache
+declare aarray_support=true
+declare -A cache 2>/dev/null
+if [[ $? != 0 ]]; then
+	aarray_support=false
+else
+	declare -A modcache
+fi
 
 find_module() {
 	if [[ -n $debuginfod ]] ; then
@@ -97,7 +102,7 @@ parse_symbol() {
 
 	if [[ $module == "" ]] ; then
 		local objfile=$vmlinux
-	elif [[ "${modcache[$module]+isset}" == "isset" ]]; then
+	elif [[ $aarray_support == true && "${modcache[$module]+isset}" == "isset" ]]; then
 		local objfile=${modcache[$module]}
 	else
 		local objfile=$(find_module)
@@ -105,7 +110,9 @@ parse_symbol() {
 			echo "WARNING! Modules path isn't set, but is needed to parse this symbol" >&2
 			return
 		fi
-		modcache[$module]=$objfile
+		if [[ $aarray_support == true ]]; then
+			modcache[$module]=$objfile
+		fi
 	fi
 
 	# Remove the englobing parenthesis
@@ -125,7 +132,7 @@ parse_symbol() {
 	# Use 'nm vmlinux' to figure out the base address of said symbol.
 	# It's actually faster to call it every time than to load it
 	# all into bash.
-	if [[ "${cache[$module,$name]+isset}" == "isset" ]]; then
+	if [[ $aarray_support == true && "${cache[$module,$name]+isset}" == "isset" ]]; then
 		local base_addr=${cache[$module,$name]}
 	else
 		local base_addr=$(nm "$objfile" 2>/dev/null | awk '$3 == "'$name'" && ($2 == "t" || $2 == "T") {print $1; exit}')
@@ -133,7 +140,9 @@ parse_symbol() {
 			# address not found
 			return
 		fi
-		cache[$module,$name]="$base_addr"
+		if [[ $aarray_support == true ]]; then
+			cache[$module,$name]="$base_addr"
+		fi
 	fi
 	# Let's start doing the math to get the exact address into the
 	# symbol. First, strip out the symbol total length.
@@ -149,11 +158,13 @@ parse_symbol() {
 
 	# Pass it to addr2line to get filename and line number
 	# Could get more than one result
-	if [[ "${cache[$module,$address]+isset}" == "isset" ]]; then
+	if [[ $aarray_support == true && "${cache[$module,$address]+isset}" == "isset" ]]; then
 		local code=${cache[$module,$address]}
 	else
 		local code=$(${CROSS_COMPILE}addr2line -i -e "$objfile" "$address" 2>/dev/null)
-		cache[$module,$address]=$code
+		if [[ $aarray_support == true ]]; then
+			cache[$module,$address]=$code
+		fi
 	fi
 
 	# addr2line doesn't return a proper error code if it fails, so