Date: Tue, 1 Dec 2015 12:22:12 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Michal Marek <mmarek@suse.cz>, Stephen Boyd <sboyd@codeaurora.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-arm-msm@vger.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
        linux-kbuild@vger.kernel.org, Nicolas Pitre <nico@fluxnic.net>,
        Arnd Bergmann <arnd@arndb.de>,
        =?UTF-8?B?TcOlbnMgUnVsbGfDpXJk?= <mans@mansr.com>
Subject: Re: [PATCH v2 1/2] scripts: Add a recorduidiv program
Message-ID: <20151201122212.474afce5@gandalf.local.home>
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On Tue, 1 Dec 2015 17:10:14 +0000
Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:

> Another suggestion - maybe recordmcount, which fstat()s the file,
> should check the st_nlink before modifying the file, and error out
> with a helpful error message telling people not to use hardlinks,
> which would stop nasty surprises (and make it a rule that this should
> be implemented as a general principle for good build behaviour) - iow,

Actually I like this solution the best.

> something like this (untested):

Can you test it to see if it gives you the error, otherwise I need to
set up a CCACHE_HARDLINK environment :-)

I guess another solution is to do a copy instead of modifying in place
if it detects the multiple hard link?

-- Steve


> 
>  scripts/recordmcount.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> index 698768bdc581..bb7589fd7392 100644
> --- a/scripts/recordmcount.c
> +++ b/scripts/recordmcount.c
> @@ -203,6 +203,10 @@ static void *mmap_file(char const *fname)
>  		fprintf(stderr, "not a regular file: %s\n", fname);
>  		fail_file();
>  	}
> +	if (sb.st_nlink != 1) {
> +		fprintf(stderr, "file is hard linked: %s\n", fname);
> +		fail_file();
> +	}
>  	addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
>  		    fd_map, 0);
>  	mmap_failed = 0;
> 
> 

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