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.
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| @@ -4014,6 +4014,23 @@ sub process { · 4013 unmodified lines | ||
| 4014 | 4014 | } |
| 4015 | 4015 | } |
| 4016 | 4016 | |
| 4017 | +# check for unnecessary "Out of Memory" messages | |
| 4018 | + if ($line =~ /^\+.*\b$logFunctions\s*\(/ && | |
| 4019 | + $prevline =~ /^[ \+]\s*if\s*\(\s*(\!\s*|NULL\s*==\s*)?($Lval)(\s*==\s*NULL\s*)?\s*\)/ && | |
| 4020 | + (defined $1 || defined $3) && | |
| 4021 | + $linenr > 3) { | |
| 4022 | + my $testval = $2; | |
| 4023 | + my $testline = $lines[$linenr - 3]; | |
| 4024 | + | |
| 4025 | + my ($s, $c) = ctx_statement_block($linenr - 3, $realcnt, 0); | |
| 4026 | +# print("line: <$line>\nprevline: <$prevline>\ns: <$s>\nc: <$c>\n\n\n"); | |
| 4027 | + | |
| 4028 | + if ($c =~ /(?:^|\n)[ \+]\s*(?:$Type\s*)?\Q$testval\E\s*=\s*(?:\([^\)]*\)\s*)?\s*(?:devm_)?(?:[kv][czm]alloc(?:_node|_array)?\b|kstrdup|(?:dev_)?alloc_skb)/) { | |
| 4029 | + WARN("OOM_MESSAGE", | |
| 4030 | + "Possible unnecessary 'out of memory' message\n" . $hereprev); | |
| 4031 | + } | |
| 4032 | + } | |
| 4033 | + | |
| 4017 | 4034 | # check for bad placement of section $InitAttribute (e.g.: __initdata) |
| 4018 | 4035 | if ($line =~ /(\b$InitAttribute\b)/) { |
| 4019 | 4036 | my $attr = $1; |