[PATCH v2 2/2] tools/bootconfig: Recognize underscores in histogram variables

[Eduardo Mucelli Rezende Oliveira <edumucelli@gmail.com>]

The variable dependency resolver in ftrace2bconf.sh only recognizes
letters and digits in histogram variable names. A reference such as
$start_ts is read as $start, and the start_ts definition is missed.
The consumer is repeatedly deferred and eventually omitted from the
export with an undefined-variable diagnostic.

Include underscores when matching both definitions and references so
that valid histogram variables are resolved and their consumers are
exported after the providers.

Fixes: 2b86062a34a8 ("tools/bootconfig: Add a script to generates bootconfig from ftrace")
Signed-off-by: Eduardo Mucelli Rezende Oliveira <edumucelli@gmail.com>
---
The histogram-variable documentation even uses names such as wakeup_lat
and us_per_sec [1]. These are valid in tracefs, but the exporter cannot
resolve references to them and leaves out the dependent histogram.

I tested this in a temporary tracefs instance on my Ubuntu machine,
running kernel 7.0.0-38-generic, with recording disabled. I created a
provider histogram defining start_ts and a consumer using $start_ts.
The original exporter reported an undefined variable and left out the
consumer. With the fix, both were exported and restored correctly.
A separate pair using ts0 worked in both versions.

[1] https://docs.kernel.org/trace/histogram.html#histogram-variables

 tools/bootconfig/scripts/ftrace2bconf.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/bootconfig/scripts/ftrace2bconf.sh b/tools/bootconfig/scripts/ftrace2bconf.sh
index 032ac5b10a4a..b01297217cf3 100755
--- a/tools/bootconfig/scripts/ftrace2bconf.sh
+++ b/tools/bootconfig/scripts/ftrace2bconf.sh
@@ -88,10 +88,10 @@ DEFINED_VARS=
 UNRESOLVED_EVENTS=
 
 defined_vars() { # event-dir
-	grep "^hist" $1/trigger | grep -o ':[a-zA-Z0-9]*='
+	grep "^hist" $1/trigger | grep -o ':[a-zA-Z0-9_]*='
 }
 referred_vars() {
-	grep "^hist" $1/trigger | grep -o '$[a-zA-Z0-9]*'
+	grep "^hist" $1/trigger | grep -o '$[a-zA-Z0-9_]*'
 }
 
 event_is_enabled() { # enable-file
-- 
2.53.0