scripts/decode_stacktrace.sh: guess path to vmlinux by release name

Add option decode_stacktrace -r <release> to specify only release name.
This is enough to guess standard paths to vmlinux and modules:

$ echo -e 'schedule+0x0/0x0
tap_open+0x0/0x0 [tap]' |
	./scripts/decode_stacktrace.sh -r 5.4.0-37-generic
schedule (kernel/sched/core.c:4138)
tap_open (drivers/net/tap.c:502) tap
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Sasha Levin <sashal@kernel.org>
Link: http://lkml.kernel.org/r/159282923334.248444.2399153100007347838.stgit@buzzSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/decode_stacktrace.sh

@@ -5,14 +5,33 @@
 
 if [[ $# < 1 ]]; then
 	echo "Usage:"
-	echo "	$0 <vmlinux> [base path] [modules path]"
+	echo "	$0 -r <release> | <vmlinux> [base path] [modules path]"
 	exit 1
 fi
 
-vmlinux=$1
-basepath=${2-auto}
-modpath=$3
-release=""
+if [[ $1 == "-r" ]] ; then
+	vmlinux=""
+	basepath="auto"
+	modpath=""
+	release=$2
+
+	for fn in {,/usr/lib/debug}/boot/vmlinux-$release{,.debug} /lib/modules/$release{,/build}/vmlinux ; do
+		if [ -e "$fn" ] ; then
+			vmlinux=$fn
+			break
+		fi
+	done
+
+	if [[ $vmlinux == "" ]] ; then
+		echo "ERROR! vmlinux image for release $release is not found" >&2
+		exit 2
+	fi
+else
+	vmlinux=$1
+	basepath=${2-auto}
+	modpath=$3
+	release=""
+fi
 
 declare -A cache
 declare -A modcache