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Date: Tue, 19 May 2020 18:14:18 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 11/20] bpf: factor out a bpf_trace_copy_string helper
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-parisc@vger.kernel.org, Daniel Borkmann <daniel@iogearbox.net>, Netdev <netdev@vger.kernel.org>, the arch/x86 maintainers <x86@kernel.org>, linux-um <linux-um@lists.infradead.org>, Alexei Starovoitov <ast@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>, bpf@vger.kernel.org, Masami Hiramatsu <mhiramat@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Christoph Hellwig <hch@lst.de>

On Tue, May 19, 2020 at 09:07:55AM -0700, Linus Torvalds wrote:
> On Tue, May 19, 2020 at 6:45 AM Christoph Hellwig <hch@lst.de> wrote:
> >
> > +       switch (fmt_ptype) {
> > +       case 's':
> > +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> > +               strncpy_from_unsafe(buf, unsafe_ptr, bufsz);
> > +               break;
> > +#endif
> > +       case 'k':
> > +               strncpy_from_kernel_nofault(buf, unsafe_ptr, bufsz);
> > +               break;
> 
> That 's' case needs a "fallthrough;" for the overlapping case,
> methinks. Otherwise you'll get warnings.

I don't think we need it as the case of

	case 'a':
	case 'b':
		do_stuff();
		break;

has always been fine even with the fallthough warnings.  And the
rest of the stuff gets removed by cpp..

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