checkpatch.pl: new instances of ENOSYS are errors

ENOSYS means that a nonexistent system call was called.  We have a
bad habit of using it for things like invalid operations on
otherwise valid syscalls.  We should avoid this in new code.

Pervasive incorrect usage of ENOSYS came up at the kernel summit ABI
review discussion.  Let's see if checkpatch can help.

I'll submit a separate patch for include/uapi/asm-generic/errno.h.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Joe Perches <joe@perches.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 28516587babac8fbc9eb346f0a44b1aba9c39a8e..561f41ef531fd6f3d64ab4a6fcf7e278354f947d 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3396,6 +3396,14 @@ sub process {
                             "Prefer dev_$level(... to dev_printk(KERN_$orig, ...\n" . $herecurr);
                }
 
+# ENOSYS means "bad syscall nr" and nothing else.  This will have a small
+# number of false positives, but assembly files are not checked, so at
+# least the arch entry code will not trigger this warning.
+               if ($line =~ /\bENOSYS\b/) {
+                       WARN("ENOSYS",
+                            "ENOSYS means 'invalid syscall nr' and nothing else\n" . $herecurr);
+               }
+
 # function brace can't be on same line, except for #defines of do while,
 # or if closed on same line
                if (($line=~/$Type\s*$Ident\(.*\).*\s*{/) and