[PATCH v3] checkpatch: extend attributes check to handle more patterns

[Dwaipayan Ray <dwaipayanray1@gmail.com>]

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, 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.

New attributes which are now handled are:

__alias__(#symbol)
__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__
__fallthrough__
__noinline__
__nonstring__
__noreturn__
__pure__
__unused__
__used__

Link: https://lore.kernel.org/linux-kernel-mentees/3ec15b41754b01666d94b76ce51b9832c2dd577a.camel@perches.com/
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Dwaipayan Ray <dwaipayanray1@gmail.com>
---
 scripts/checkpatch.pl | 105 +++++++++++++++++++++++++++---------------
 1 file changed, 69 insertions(+), 36 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7e505688257a..01d83d345b4c 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);
-		}
+		    $line =~ /__attribute__\s*\(\s*($balanced_parens)\s*\)/) {
+			my $attr = $1;
+			$attr =~ s/\s*\(\s*(.*)\)\s*/$1/;
+
+			my %attr_list = (
+				"alias"				=> "__alias",
+				"aligned"			=> "__aligned",
+				"always_inline"			=> "__always_inline",
+				"assume_aligned"		=> "__assume_aligned",
+				"cold"				=> "__cold",
+				"const"				=> "__const",
+				"copy"				=> "__copy",
+				"designated_init"		=> "__designated_init",
+				"externally_visible"		=> "__visible",
+				"fallthrough"			=> "fallthrough",
+				"gnu_inline"			=> "__gnu_inline",
+				"malloc"			=> "__malloc",
+				"mode"				=> "__mode",
+				"no_caller_saved_registers"	=> "__no_caller_saved_registers",
+				"noclone"			=> "__noclone",
+				"noinline"			=> "noinline",
+				"nonstring"			=> "__nonstring",
+				"noreturn"			=> "__noreturn",
+				"packed"			=> "__packed",
+				"pure"				=> "__pure",
+				"used"				=> "__used"
+			);
+
+			if ($attr =~ /^(\w+)\s*(${balanced_parens})?/) {
+				my $curr_attr = $1;
+				my $params = '';
+				$params = $2 if defined($2);
+				$curr_attr =~ s/^[\s_]+|[\s_]+$//g;
+
+				if (exists($attr_list{$curr_attr})) {
+					my $new = $attr_list{$curr_attr};
+					WARN("PREFER_DEFINED_ATTRIBUTE_MACRO",
+					     "$new$params is preffered over __attribute__(($attr))\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" . $herecurr);
-		}
+			# Check for __attribute__ format(printf, prefer __printf
+			if ($attr =~ /^_*format_*\s*\(\s*printf/) {
+				if (WARN("PREFER_DEFINED_ATTRIBUTE_MACRO",
+				         "__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;
 
-# 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)/;
+				}
 			}
-		}
 
-# 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($1) . ")"/ex;
+			# Check for __attribute__ format(scanf, prefer __scanf
+			if ($attr =~ /^_*format_*\s*\(\s*scanf\b/) {
+				if (WARN("PREFER_DEFINED_ATTRIBUTE_MACRO",
+				         "__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__ section, prefer __section
+			if ($attr =~ /^_*section_*\s*\(\s*("[^"]*")/) {
+				my $old = substr($rawline, $-[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