linux-kernel - RE: [PATCH RFCv3 3/3] lib/test_printf: add test cases for '%pD'

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Message-ID: <AM6PR08MB4376D63563682BDB626BE79DF7309@AM6PR08MB4376.eurprd08.prod.outlook.com>
Date:   Tue, 15 Jun 2021 07:15:11 +0000
From:   Justin He <Justin.He@....com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
CC:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Eric Biggers <ebiggers@...gle.com>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH RFCv3 3/3] lib/test_printf: add test cases for '%pD'

Hi Rasmus

> -----Original Message-----
> From: Justin He
> Sent: Tuesday, June 15, 2021 3:06 PM
> To: Rasmus Villemoes <linux@...musvillemoes.dk>; Petr Mladek
> <pmladek@...e.com>; Steven Rostedt <rostedt@...dmis.org>; Sergey
> Senozhatsky <senozhatsky@...omium.org>; Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com>; Jonathan Corbet <corbet@....net>;
> Alexander Viro <viro@...iv.linux.org.uk>; Linus Torvalds <torvalds@...ux-
> foundation.org>
> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>; Eric Biggers
> <ebiggers@...gle.com>; Ahmed S. Darwish <a.darwish@...utronix.de>; linux-
> doc@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
> fsdevel@...r.kernel.org
> Subject: RE: [PATCH RFCv3 3/3] lib/test_printf: add test cases for '%pD'
>
> Hi Rasmus
>
> > -----Original Message-----
> > From: Rasmus Villemoes <linux@...musvillemoes.dk>
> > Sent: Saturday, June 12, 2021 5:40 AM
> > To: Justin He <Justin.He@....com>; Petr Mladek <pmladek@...e.com>; Steven
> > Rostedt <rostedt@...dmis.org>; Sergey Senozhatsky
> > <senozhatsky@...omium.org>; Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com>; Jonathan Corbet <corbet@....net>;
> > Alexander Viro <viro@...iv.linux.org.uk>; Linus Torvalds <torvalds@...ux-
> > foundation.org>
> > Cc: Peter Zijlstra (Intel) <peterz@...radead.org>; Eric Biggers
> > <ebiggers@...gle.com>; Ahmed S. Darwish <a.darwish@...utronix.de>; linux-
> > doc@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
> > fsdevel@...r.kernel.org
> > Subject: Re: [PATCH RFCv3 3/3] lib/test_printf: add test cases for '%pD'
> >
> > On 11/06/2021 17.59, Jia He wrote:
> > > After the behaviour of specifier '%pD' is changed to print full path
> > > of struct file, the related test cases are also updated.
> > >
> > > Given the string is prepended from the end of the buffer, the check
> > > of "wrote beyond the nul-terminator" should be skipped.
> >
> > Sorry, that is far from enough justification.
> >
> > I should probably have split the "wrote beyond nul-terminator" check in
> two:
> >
> > One that checks whether any memory beyond the buffer given to
> > vsnprintf() was touched (including all the padding, but possibly more
> > for the cases where we pass a known-too-short buffer), symmetric to the
> > "wrote before buffer" check.
> >
> > And then another that checks the area between the '\0' and the end of
> > the given buffer - I suppose that it's fair game for vsnprintf to use
> > all of that as scratch space, and for that it could be ok to add that
> > boolean knob.
> >
> Sorry, I could have thought sth like "write beyond the buffer" had been
> checked by
> old test cases, but seems not.
> I will split the "wrote beyond nul-terminator" check into 2 parts. One for
> Non-%pD case, the other for %pD.
>
> For %pD, it needs to check whether the space beyond test_buffer[] is
> written
>
>

Another question is about precision,
Do you think I should add some test cases e.g. "%.10pD" here?
I once added some, but the gcc report warning:
warning: precision used with '%p' gnu_printf

What do you think of that?


--
Cheers,
Justin (Jia He)




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