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.ca...@perches.com/
Suggested-by: Joe Perches <j...@perches.com>
Signed-off-by: Dwaipayan Ray <dwaipayanr...@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

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