[PATCH v6] checkpatch: extend attributes check to handle more patterns

[Dwaipayan Ray]

It is generally preferred that the macros from
include/linux/compiler_attributes.h are used, unless there
is a reason not to.

checkpatch currently checks __attribute__ for each of
packed, aligned, section, printf, scanf, and weak. Other
declarations in compiler_attributes.h are not handled.

Add a generic test to check the presence of such attributes.
Some attributes require more specific handling and are kept
separate.

Also add fixes to the generic attributes check to substitute
the correct conversions.

New attributes which are now handled are:

__always_inline__
__assume_aligned__(a, ## __VA_ARGS__)
__cold__
__const__
__copy__(symbol)
__designated_init__
__externally_visible__
__gnu_inline__
__malloc__
__mode__(x)
__no_caller_saved_registers__
__noclone__
__noinline__
__nonstring__
__noreturn__
__pure__
__unused__
__used__

Declarations which contain multiple attributes like
__attribute__((__packed__, __cold__)) are also handled except
when proper conversions for one or more attributes of the list
cannot be determined.

Link: https://lore.kernel.org/linux-kernel-mentees/3ec15b41754b01666d94b76ce51b9832c2dd577a.camel@xxxxxxxxxxx/
Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
Signed-off-by: Dwaipayan Ray <dwaipayanray1@xxxxxxxxx>
---
 scripts/checkpatch.pl | 109 +++++++++++++++++++++++++++---------------
 1 file changed, 71 insertions(+), 38 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7e505688257a..eeebd8149be9 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6155,50 +6155,83 @@ sub process {
 			}
 		}
 
-# Check for __attribute__ packed, prefer __packed
+# Check for compiler attributes
 		if ($realfile !~ m@\binclude/uapi/@ &&
-		    $line =~ /\b__attribute__\s*\(\s*\(.*\bpacked\b/) {
-			WARN("PREFER_PACKED",
-			     "__packed is preferred over __attribute__((packed))\n" . $herecurr);
-		}
-
-# Check for __attribute__ aligned, prefer __aligned
-		if ($realfile !~ m@\binclude/uapi/@ &&
-		    $line =~ /\b__attribute__\s*\(\s*\(.*aligned/) {
-			WARN("PREFER_ALIGNED",
-			     "__aligned(size) is preferred over __attribute__((aligned(size)))\n" . $herecurr);
-		}
-
-# Check for __attribute__ section, prefer __section
-		if ($realfile !~ m@\binclude/uapi/@ &&
-		    $line =~ /\b__attribute__\s*\(\s*\(.*_*section_*\s*\(\s*("[^"]*")/) {
-			my $old = substr($rawline, $-[1], $+[1] - $-[1]);
-			my $new = substr($old, 1, -1);
-			if (WARN("PREFER_SECTION",
-				 "__section($new) is preferred over __attribute__((section($old)))\n" . $herecurr) &&
-			    $fix) {
-				$fixed[$fixlinenr] =~ s/\b__attribute__\s*\(\s*\(\s*_*section_*\s*\(\s*\Q$old\E\s*\)\s*\)\s*\)/__section($new)/;
+		    $rawline =~ /\b__attribute__\s*\(\s*($balanced_parens)\s*\)/) {
+			my $attr = $1;
+			$attr =~ s/\s*\(\s*(.*)\)\s*/$1/;
+
+			my %attr_list = (
+				"aligned"			=> "__aligned",
+				"always_inline"			=> "__always_inline",
+				"assume_aligned"		=> "__assume_aligned",
+				"cold"				=> "__cold",
+				"const"				=> "__attribute_const__",
+				"copy"				=> "__copy",
+				"designated_init"		=> "__designated_init",
+				"externally_visible"		=> "__visible",
+				"format"			=> "printf|scanf",
+				"gnu_inline"			=> "__gnu_inline",
+				"malloc"			=> "__malloc",
+				"mode"				=> "__mode",
+				"no_caller_saved_registers"	=> "__no_caller_saved_registers",
+				"noclone"			=> "__noclone",
+				"noinline"			=> "noinline",
+				"nonstring"			=> "__nonstring",
+				"noreturn"			=> "__noreturn",
+				"packed"			=> "__packed",
+				"pure"				=> "__pure",
+				"used"				=> "__used"
+			);
+
+			my @conv_array = ();
+			my $conv_possible = 1;
+
+			while ($attr =~ /\s*(\w+)\s*(${balanced_parens})?/g) {
+				my $curr_attr = $1;
+				my $params = '';
+				$params = $2 if defined($2);
+				$curr_attr =~ s/^[\s_]+|[\s_]+$//g;
+
+				if (exists($attr_list{$curr_attr})) {
+					if ($curr_attr eq "format" && $params) {
+						$params =~ /^\s*\(\s*(\w+)\s*,\s*(.*)/;
+						push(@conv_array, "__$1\($2");
+					} else {
+						my $new = $attr_list{$curr_attr};
+						push(@conv_array, "$new$params");
+					}
+				} else {
+					$conv_possible = 0;
+					last;
+				}
 			}
-		}
 
-# Check for __attribute__ format(printf, prefer __printf
-		if ($realfile !~ m@\binclude/uapi/@ &&
-		    $line =~ /\b__attribute__\s*\(\s*\(\s*format\s*\(\s*printf/) {
-			if (WARN("PREFER_PRINTF",
-				 "__printf(string-index, first-to-check) is preferred over __attribute__((format(printf, string-index, first-to-check)))\n" . $herecurr) &&
-			    $fix) {
-				$fixed[$fixlinenr] =~ s/\b__attribute__\s*\(\s*\(\s*format\s*\(\s*printf\s*,\s*(.*)\)\s*\)\s*\)/"__printf(" . trim($1) . ")"/ex;
+			if (scalar @conv_array > 0 && $conv_possible == 1) {
+				my $replace = join(' ', @conv_array);
+				if (WARN("PREFER_DEFINED_ATTRIBUTE_MACRO",
+				         "$replace is preferred over __attribute__(($attr))\n" . $herecurr) &&
+					$fix) {
+					$fixed[$fixlinenr] =~ s/\b__attribute__\s*\(\s*\(\s*\Q$attr\E\s*\)\s*\)/$replace/;
+					$fixed[$fixlinenr] =~ s/\}\Q$replace\E/} $replace/;
+				}
+			}
 
+			# Check for __attribute__ section, prefer __section
+			if ($attr =~ /^_*section_*\s*\(\s*("[^"]*")/) {
+				my $old = substr($attr, $-[1], $+[1] - $-[1]);
+				my $new = substr($old, 1, -1);
+				if (WARN("PREFER_DEFINED_ATTRIBUTE_MACRO",
+				         "__section($new) is preferred over __attribute__((section($old)))\n" . $herecurr) &&
+					$fix) {
+					$fixed[$fixlinenr] =~ s/\b__attribute__\s*\(\s*\(\s*_*section_*\s*\(\s*\Q$old\E\s*\)\s*\)\s*\)/__section($new)/;
+				}
 			}
-		}
 
-# Check for __attribute__ format(scanf, prefer __scanf
-		if ($realfile !~ m@\binclude/uapi/@ &&
-		    $line =~ /\b__attribute__\s*\(\s*\(\s*format\s*\(\s*scanf\b/) {
-			if (WARN("PREFER_SCANF",
-				 "__scanf(string-index, first-to-check) is preferred over __attribute__((format(scanf, string-index, first-to-check)))\n" . $herecurr) &&
-			    $fix) {
-				$fixed[$fixlinenr] =~ s/\b__attribute__\s*\(\s*\(\s*format\s*\(\s*scanf\s*,\s*(.*)\)\s*\)\s*\)/"__scanf(" . trim($1) . ")"/ex;
+			# Check for __attribute__ unused, prefer __always_unused or __maybe_unused
+			if ($attr =~ /^_*unused/) {
+				WARN("PREFER_DEFINED_ATTRIBUTE_MACRO",
+				     "__always_unused or __maybe_unused is preferred over __attribute__((__unused__))\n" . $herecurr);
 			}
 		}
 
-- 
2.27.0