[PATCH 1/4] scripts/decode_stacktrace: skip missing symbols

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

For now script turns missing symbols into '0' and make bogus decode.
Skip them instead. Also simplify parsing output of 'nm'.

Before:

$ echo 'xxx+0x0/0x0' | ./scripts/decode_stacktrace.sh vmlinux ""
xxx (home/khlebnikov/src/linux/./arch/x86/include/asm/processor.h:398)

After:

$ echo 'xxx+0x0/0x0' | ./scripts/decode_stacktrace.sh vmlinux ""
xxx+0x0/0x0

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
 scripts/decode_stacktrace.sh |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/scripts/decode_stacktrace.sh b/scripts/decode_stacktrace.sh
index 66a6d511b524..6ec8d6dff86c 100755
--- a/scripts/decode_stacktrace.sh
+++ b/scripts/decode_stacktrace.sh
@@ -56,7 +56,11 @@ parse_symbol() {
 	if [[ "${cache[$module,$name]+isset}" == "isset" ]]; then
 		local base_addr=${cache[$module,$name]}
 	else
-		local base_addr=$(nm "$objfile" | grep -i ' t ' | awk "/ $name\$/ {print \$1}" | head -n1)
+		local base_addr=$(nm "$objfile" | awk '$3 == "'$name'" && ($2 == "t" || $2 == "T") {print $1; exit}')
+		if [[ $base_addr == "" ]] ; then
+			# address not found
+			return
+		fi
 		cache[$module,$name]="$base_addr"
 	fi
 	# Let's start doing the math to get the exact address into the