linux-kernel - RE: [PATCH] kcsan: Use min() to fix Coccinelle warning

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Date: Fri, 28 Jun 2024 14:51:19 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Marco Elver' <elver@...gle.com>, Thorsten Blum <thorsten.blum@...lux.com>
CC: "dvyukov@...gle.com" <dvyukov@...gle.com>, "kasan-dev@...glegroups.com"
	<kasan-dev@...glegroups.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] kcsan: Use min() to fix Coccinelle warning

From: Marco Elver
> Sent: 24 June 2024 08:03
> >
> > Fixes the following Coccinelle/coccicheck warning reported by
> > minmax.cocci:
> >
> >         WARNING opportunity for min()
> >
> > Use size_t instead of int for the result of min().
> >
> > Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
> 
> Reviewed-by: Marco Elver <elver@...gle.com>
> 
> Thanks for polishing (but see below). Please compile-test with
> CONFIG_KCSAN=y if you haven't.
> 
> > ---
> >  kernel/kcsan/debugfs.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c
> > index 1d1d1b0e4248..11b891fe6f7a 100644
> > --- a/kernel/kcsan/debugfs.c
> > +++ b/kernel/kcsan/debugfs.c
> > @@ -225,7 +225,7 @@ debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *o
> >  {
> >         char kbuf[KSYM_NAME_LEN];
> >         char *arg;
> > -       int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
> > +       size_t read_len = min(count, (sizeof(kbuf) - 1));
> 
> While we're here polishing things this could be:
> 
> const size_t read_len = min(count, sizeof(kbuf) - 1);
> 
> ( +const, remove redundant () )

Pretty much no one makes variables 'const', it mostly just makes the code harder to read.

	David

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