[PATCH RFC v2] 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, 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@xxxxxxxxxxx/
Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
Signed-off-by: Dwaipayan Ray <dwaipayanray1@xxxxxxxxx>
---
 scripts/checkpatch.pl | 130 ++++++++++++++++++++++++++++++------------
 1 file changed, 94 insertions(+), 36 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7e505688257a..69324c2e55d6 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6155,50 +6155,108 @@ 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 =~ /\b__attribute__\s*\(\s*\((.*)\)\s*\)/) {
+			my $attr = trim($1);
+
+			my $attr_list = qr {
+				__alias__|
+				__aligned__$|
+				__aligned__\(.*\)|
+				__always_inline__|
+				__assume_aligned__\(.*\)|
+				__cold__|
+				__const__|
+				__copy__\(.*\)|
+				__designated_init__|
+				__externally_visible__|
+				__fallthrough__|
+				__gnu_inline__|
+				__malloc__|
+				__mode__\(.*\)|
+				__no_caller_saved_registers__|
+				__noclone__|
+				__noinline__|
+				__nonstring__|
+				__noreturn__|
+				__packed__|
+				__pure__|
+				__used__
+			}x;
 
-# 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" . $herecurr);
-		}
+			my %attr_replace = (
+				"__alias__"			=> "__alias",
+				"__aligned__"		=> "__aligned_largest",
+				"__aligned__("		=> "__aligned",
+				"__always_inline__" 	=> "__always_inline",
+				"__assume_aligned__("	=> "__assume_aligned",
+				"__cold__"			=> "__cold",
+				"__const__"			=> "__const",
+				"__copy__("			=> "__copy",
+				"__designated_init__"		=> "__designated_init",
+				"__externally_visible__"	=> "__visible",
+				"__fallthrough__"		=> "fallthrough",
+				"__gnu_inline__"		=> "__gnu_inline",
+				"__malloc__"		=> "__malloc",
+				"__mode__("			=> "__mode",
+				"__no_caller_saved_registers__" => "__no_caller_saved_registers",
+				"__noclone__"		=> "__noclone",
+				"__noinline__"		=> "noinline",
+				"__nonstring__"		=> "__nonstring",
+				"__noreturn__"		=> "__noreturn",
+				"__packed__"		=> "__packed",
+				"__pure__"			=> "__pure",
+				"__used__"			=> "__used"
+			);
+
+			if ($attr =~/^($attr_list)/) {
+				my $old = $1;
+				if ($old =~ /^(__.+__\()(.*)\)/) {
+					my $new = $attr_replace{$1};
+					WARN("PREFER_DEFINED_ATTRIBUTE_MACRO",
+					     "$new($2) is preffered over __attribute__(($old))\n" . $herecurr);
+				} else {
+					my $new = $attr_replace{$old};
+					WARN("PREFER_DEFINED_ATTRIBUTE_MACRO",
+					     "$new is preffered over __attribute__(($old))\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($new)/;
+			# Check for __attribute__ format(printf, prefer __printf
+			if ($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__ 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