From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9AD8C3404D for ; Wed, 19 Feb 2020 11:20:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9ABD8206E2 for ; Wed, 19 Feb 2020 11:20:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="lqrMZzD7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727001AbgBSLU1 (ORCPT ); Wed, 19 Feb 2020 06:20:27 -0500 Received: from mail-il1-f193.google.com ([209.85.166.193]:38481 "EHLO mail-il1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726514AbgBSLU1 (ORCPT ); Wed, 19 Feb 2020 06:20:27 -0500 Received: by mail-il1-f193.google.com with SMTP id f5so20259332ilq.5; Wed, 19 Feb 2020 03:20:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=wlG3nAa6BYD+iSp33UrqkLf/yy6E18oediW8a3IHWEE=; b=lqrMZzD75cIs1XvYxtvW/PfD/BoQl24mKjNsYCd6y/97XIQT6pJHdKQvlURlGAn5ji 9Kng8T8BBQAVnuttwpOZEIB+rvcYhxrv4uUrX3xZd63KuUDvT90rqqugMLDgpHNfONVU LzTYhqlQ1dE53RZU0SAi18BpeklsaEI4VmogQl2Y+VhMaEKXnDkmDXlYMPJ9PH29lUZV WqQdiopEXJYdFpHqqHN41Q0dE6hiyh9f7I9/ssz80F0hEPTfwH+xu5orFtNJFMTSfPIV UNx0gmq06kljo9YkbVLDHDGC00zFrgpvQAi1Mc99Brv2BedjxjVa+/vjBSRKxhokYG73 1sag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=wlG3nAa6BYD+iSp33UrqkLf/yy6E18oediW8a3IHWEE=; b=fQkUud1ETtQymdXKcN8PvVl8USykAqN3/JlMvVXyOENishbfpR/yPC4gI9B1soboBf iZPpG1E4cotHyIlfKsOEBMiBnze7dyoze9rPJoI1nEV/ms2kU5MGAtnkF+4UQjjLZfe+ wAMt+yodsjkjZFdBpimoo7czyUGMRwN+2gqlICJ77Bj7Ed6EUGMt7manR82evIHiSOn7 Dp6+CQbfbZuR/tt8i1GWybEAw8UHTZq5zmau1HUloMAt1vX+ExezIpDP2Ly1j5ikGUH5 BUFG0CPMQPrCPG8mNs0uvOuzYzae9a9P6QgpnedcJ6mLSrrSLUbw/AkGv5+S0gebOgUC sDnw== X-Gm-Message-State: APjAAAWOrI/p+yuoqYjo/cgDoh2J8gxXjgqnj11xZRp61+0KfPa7W6yV P8xnf3JEhBMR8TLwhZS4aAvkej0mU6YjGOq1FYs= X-Google-Smtp-Source: APXvYqxe3KWnktEfzpmKptdMszpnXSJm8A5UxsbKU39uxO1rNDKE7wgLIqdm+nZ9iVSSMOkm7yfbWcV56Fb0MZ54YQA= X-Received: by 2002:a92:3a8d:: with SMTP id i13mr25028030ilf.112.1582111226499; Wed, 19 Feb 2020 03:20:26 -0800 (PST) MIME-Version: 1.0 References: <20200219082155.6787-1-linux@rasmusvillemoes.dk> In-Reply-To: <20200219082155.6787-1-linux@rasmusvillemoes.dk> From: Ilya Dryomov Date: Wed, 19 Feb 2020 12:20:53 +0100 Message-ID: Subject: Re: [PATCH] vsprintf: sanely handle NULL passed to %pe To: Rasmus Villemoes Cc: Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Jonathan Corbet , Kees Cook , "Tobin C . Harding" , Linus Torvalds , linux-doc@vger.kernel.org, LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 19, 2020 at 9:21 AM Rasmus Villemoes wrote: > > Extend %pe to pretty-print NULL in addition to ERR_PTRs, > i.e. everything IS_ERR_OR_NULL(). > > Suggested-by: Linus Torvalds > Signed-off-by: Rasmus Villemoes > --- > Something like this? The actual code change is +2,-1 with another +1 > for a test case. > > Documentation/core-api/printk-formats.rst | 9 +++++---- > lib/errname.c | 4 ++++ > lib/test_printf.c | 1 + > lib/vsprintf.c | 4 ++-- > 4 files changed, 12 insertions(+), 6 deletions(-) > > diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst > index 8ebe46b1af39..964b55291445 100644 > --- a/Documentation/core-api/printk-formats.rst > +++ b/Documentation/core-api/printk-formats.rst > @@ -86,10 +86,11 @@ Error Pointers > > %pe -ENOSPC > > -For printing error pointers (i.e. a pointer for which IS_ERR() is true) > -as a symbolic error name. Error values for which no symbolic name is > -known are printed in decimal, while a non-ERR_PTR passed as the > -argument to %pe gets treated as ordinary %p. > +For printing error pointers (i.e. a pointer for which IS_ERR() is > +true) as a symbolic error name. Error values for which no symbolic > +name is known are printed in decimal. A NULL pointer is printed as > +NULL. All other pointer values (i.e. anything !IS_ERR_OR_NULL()) get > +treated as ordinary %p. > > Symbols/Function Pointers > ------------------------- > diff --git a/lib/errname.c b/lib/errname.c > index 0c4d3e66170e..7757bc00f564 100644 > --- a/lib/errname.c > +++ b/lib/errname.c > @@ -11,9 +11,13 @@ > * allocated errnos (with EHWPOISON = 257 on parisc, and EDQUOT = 1133 > * on mips), so this wastes a bit of space on those - though we > * special case the EDQUOT case. > + * > + * For the benefit of %pe being able to print any ERR_OR_NULL pointer > + * symbolically, 0 is also treated specially. > */ > #define E(err) [err + BUILD_BUG_ON_ZERO(err <= 0 || err > 300)] = "-" #err > static const char *names_0[] = { > + [0] = "NULL", > E(E2BIG), > E(EACCES), > E(EADDRINUSE), > diff --git a/lib/test_printf.c b/lib/test_printf.c > index 2d9f520d2f27..3a37d0e9e735 100644 > --- a/lib/test_printf.c > +++ b/lib/test_printf.c > @@ -641,6 +641,7 @@ errptr(void) > test("[-EIO ]", "[%-8pe]", ERR_PTR(-EIO)); > test("[ -EIO]", "[%8pe]", ERR_PTR(-EIO)); > test("-EPROBE_DEFER", "%pe", ERR_PTR(-EPROBE_DEFER)); > + test("[NULL]", "[%pe]", NULL); > #endif > } > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index 7c488a1ce318..b7118d78eb20 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -2247,8 +2247,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, > case 'x': > return pointer_string(buf, end, ptr, spec); > case 'e': > - /* %pe with a non-ERR_PTR gets treated as plain %p */ > - if (!IS_ERR(ptr)) > + /* %pe with a non-ERR_OR_NULL ptr gets treated as plain %p */ > + if (!IS_ERR_OR_NULL(ptr)) > break; FWIW I was about to post a patch that just special cases NULL here. I think changing errname() to return "NULL" for 0 is overkill. People will sooner or later discover that function and start using it in contexts that don't have anything to do with pointers. Returning _some_ string for 0 (instead of NULL) makes it very close to standard strerror(), and "NULL" for 0 (i.e. success) seems rather odd. Thanks, Ilya