checkpatch: attempt to find unnecessary 'out of memory' messages
Logging messages that show some type of "out of memory" error are
generally unnecessary as there is a generic message and a stack dump
done by the memory subsystem.
These messages generally increase kernel size without much added value.
Emit a warning on these types of messages.
This test looks for any inserted message function, then looks at the
previous line for an "if (!foo)" or "if (foo == NULL)" test and then
looks at the preceding statement for an allocation function like "foo =
kmalloc()"
ie: this code matches:
foo = kmalloc();
if (foo == NULL) {
printk("Out of memory\n");
return -ENOMEM;
}
This test is very crude and incomplete.
This test can miss quite a lot of of OOM messages that do not have this
specific form.
ie: this code does not match:
foo = kmalloc();
if (!foo) {
rtn = -ENOMEM;
printk("Out of memory!\n");
goto out;
}
This test could also be a false positive when the logging message itself
does not specify anything about memory, but I did not find any false
positives in my limited testing.
spatch could be a better solution but correctness seems non-trivial for
that tool too.
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 182be0f..ac1d6b0 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4014,6 +4014,23 @@
}
}
+# check for unnecessary "Out of Memory" messages
+ if ($line =~ /^\+.*\b$logFunctions\s*\(/ &&
+ $prevline =~ /^[ \+]\s*if\s*\(\s*(\!\s*|NULL\s*==\s*)?($Lval)(\s*==\s*NULL\s*)?\s*\)/ &&
+ (defined $1 || defined $3) &&
+ $linenr > 3) {
+ my $testval = $2;
+ my $testline = $lines[$linenr - 3];
+
+ my ($s, $c) = ctx_statement_block($linenr - 3, $realcnt, 0);
+# print("line: <$line>\nprevline: <$prevline>\ns: <$s>\nc: <$c>\n\n\n");
+
+ if ($c =~ /(?:^|\n)[ \+]\s*(?:$Type\s*)?\Q$testval\E\s*=\s*(?:\([^\)]*\)\s*)?\s*(?:devm_)?(?:[kv][czm]alloc(?:_node|_array)?\b|kstrdup|(?:dev_)?alloc_skb)/) {
+ WARN("OOM_MESSAGE",
+ "Possible unnecessary 'out of memory' message\n" . $hereprev);
+ }
+ }
+
# check for bad placement of section $InitAttribute (e.g.: __initdata)
if ($line =~ /(\b$InitAttribute\b)/) {
my $attr = $1;