[PATCH 3/3] checkpatch: add ethtool_sprintf rules

[Justin Stitt <justinstitt@google.com>]

Add some warnings for using ethtool_sprintf() where a simple
ethtool_puts() would suffice.

The two cases are:

1) Use ethtool_sprintf() with just two arguments:
|       ethtool_sprintf(&data, driver[i].name);
or
2) Use ethtool_sprintf() with a standalone "%s" fmt string:
|       ethtool_sprintf(&data, "%s", driver[i].name);

The former may cause -Wformat-security warnings while the latter is just
not preferred. Both are safely in the category of warnings, not errors.

Signed-off-by: Justin Stitt <justinstitt@google.com>
---
 scripts/checkpatch.pl | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7d16f863edf1..1ba9ce778746 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -7020,6 +7020,19 @@ sub process {
 			     "Prefer strscpy, strscpy_pad, or __nonstring over strncpy - see: https://github.com/KSPP/linux/issues/90\n" . $herecurr);
 		}
 
+# ethtool_sprintf uses that should likely be ethtool_puts
+		if (   $line =~ /\bethtool_sprintf\s*\(\s*$FuncArg\s*,\s*$FuncArg\s*\)/   ) {
+			WARN("ETHTOOL_SPRINTF",
+			     "Prefer ethtool_puts over ethtool_sprintf with only two arguments" . $herecurr);
+		}
+
+		# use $rawline because $line loses %s via sanitization and thus we can't match against it.
+		if (   $rawline =~ /\bethtool_sprintf\s*\(\s*$FuncArg\s*,\s*\"\%s\"\s*,\s*$FuncArg\s*\)/   ) {
+			WARN("ETHTOOL_SPRINTF2",
+			     "Prefer ethtool_puts over ethtool_sprintf with standalone \"%s\" specifier" . $herecurr);
+		}
+
+
 # typecasts on min/max could be min_t/max_t
 		if ($perl_version_ok &&
 		    defined $stat &&

-- 
2.42.0.758.gaed0368e0e-goog