checkpatch: add rules to check init attribute and const defects

People get this regularly wrong and it breaks the LTO builds, as it causes
a section attribute conflict.

Add --fix capability too.

Based on a patch from Andi Kleen.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -241,8 +241,11 @@ sub hash_show_words {
 			__ref|
 			__rcu
 		}x;
-
-our $InitAttribute = qr{__(?:mem|cpu|dev|net_|)(?:initdata|initconst|init\b)};
+our $InitAttributePrefix = qr{__(?:mem|cpu|dev|net_|)};
+our $InitAttributeData = qr{$InitAttributePrefix(?:initdata\b)};
+our $InitAttributeConst = qr{$InitAttributePrefix(?:initconst\b)};
+our $InitAttributeInit = qr{$InitAttributePrefix(?:init\b)};
+our $InitAttribute = qr{$InitAttributeData|$InitAttributeConst|$InitAttributeInit};
 
 # Notes to $Attribute:
 # We need \b after 'init' otherwise 'initconst' will cause a false positive in a check
@@ -3759,6 +3762,35 @@ sub process {
 			}
 		}
 
+# check for $InitAttributeData (ie: __initdata) with const
+		if ($line =~ /\bconst\b/ && $line =~ /($InitAttributeData)/) {
+			my $attr = $1;
+			$attr =~ /($InitAttributePrefix)(.*)/;
+			my $attr_prefix = $1;
+			my $attr_type = $2;
+			if (ERROR("INIT_ATTRIBUTE",
+				  "Use of const init definition must use ${attr_prefix}initconst\n" . $herecurr) &&
+			    $fix) {
+				$fixed[$linenr - 1] =~
+				    s/$InitAttributeData/${attr_prefix}initconst/;
+			}
+		}
+
+# check for $InitAttributeConst (ie: __initconst) without const
+		if ($line !~ /\bconst\b/ && $line =~ /($InitAttributeConst)/) {
+			my $attr = $1;
+			if (ERROR("INIT_ATTRIBUTE",
+				  "Use of $attr requires a separate use of const\n" . $herecurr) &&
+			    $fix) {
+				my $lead = $fixed[$linenr - 1] =~
+				    /(^\+\s*(?:static\s+))/;
+				$lead = rtrim($1);
+				$lead = "$lead " if ($lead !~ /^\+$/);
+				$lead = "${lead}const ";
+				$fixed[$linenr - 1] =~ s/(^\+\s*(?:static\s+))/$lead/;
+			}
+		}
+
 # prefer usleep_range over udelay
 		if ($line =~ /\budelay\s*\(\s*(\d+)\s*\)/) {
 			# ignore udelay's < 10, however