From ebfdc40969f24fc0cdd1349835d36e8ebae05374 Mon Sep 17 00:00:00 2001 From: Joe Perches Date: Wed, 6 Aug 2014 16:10:27 -0700 Subject: [PATCH] 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 Acked-by: Dan Carpenter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- scripts/checkpatch.pl | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 182be0f12407..ac1d6b0a6f09 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -4014,6 +4014,23 @@ sub process { } } +# 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; -- 2.20.1