linux-hardening - Re: [PATCH 117/141] rtl8xxxu: Fix fall-through warnings for Clang

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Date:   Tue, 24 Nov 2020 10:09:06 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Jes Sorensen <jes.sorensen@...il.com>
Cc:     Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 117/141] rtl8xxxu: Fix fall-through warnings for Clang

On Fri, Nov 20, 2020 at 04:39:42PM -0500, Jes Sorensen wrote:
> On 11/20/20 1:38 PM, Gustavo A. R. Silva wrote:
> > In preparation to enable -Wimplicit-fallthrough for Clang, fix
> > multiple warnings by replacing /* fall through */ comments with
> > the new pseudo-keyword macro fallthrough; instead of letting the
> > code fall through to the next case.
> > 
> > Notice that Clang doesn't recognize /* fall through */ comments as
> > implicit fall-through markings.
> > 
> > Link: https://github.com/KSPP/linux/issues/115
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> > ---
> >  drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> While I wasn't CC'ed on the cover-letter I see Jakub also raised issues
> about this unnecessary patch noise.
> 
> Quite frankly, this seems to be patch churn for the sake of patch churn.
> If clang is broken, fix clang instead.

Just notice that the idea behind this and the following patch is exactly
the same:

https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers-next.git/commit/?id=3f95e92c8a8516b745594049dfccc8c5f8895eea

I could resend this same patch with a different changelog text, but I
don't think such a thing is necessary. However, if people prefer that
approach, just let me know and I can do it.

Thanks
--
Gustavo

> > diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> > index 5cd7ef3625c5..afc97958fa4d 100644
> > --- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> > +++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
> > @@ -1145,7 +1145,7 @@ void rtl8xxxu_gen1_config_channel(struct ieee80211_hw *hw)
> >  	switch (hw->conf.chandef.width) {
> >  	case NL80211_CHAN_WIDTH_20_NOHT:
> >  		ht = false;
> > -		/* fall through */
> > +		fallthrough;
> >  	case NL80211_CHAN_WIDTH_20:
> >  		opmode |= BW_OPMODE_20MHZ;
> >  		rtl8xxxu_write8(priv, REG_BW_OPMODE, opmode);
> > @@ -1272,7 +1272,7 @@ void rtl8xxxu_gen2_config_channel(struct ieee80211_hw *hw)
> >  	switch (hw->conf.chandef.width) {
> >  	case NL80211_CHAN_WIDTH_20_NOHT:
> >  		ht = false;
> > -		/* fall through */
> > +		fallthrough;
> >  	case NL80211_CHAN_WIDTH_20:
> >  		rf_mode_bw |= WMAC_TRXPTCL_CTL_BW_20;
> >  		subchannel = 0;
> > @@ -1741,11 +1741,11 @@ static int rtl8xxxu_identify_chip(struct rtl8xxxu_priv *priv)
> >  		case 3:
> >  			priv->ep_tx_low_queue = 1;
> >  			priv->ep_tx_count++;
> > -			/* fall through */
> > +			fallthrough;
> >  		case 2:
> >  			priv->ep_tx_normal_queue = 1;
> >  			priv->ep_tx_count++;
> > -			/* fall through */
> > +			fallthrough;
> >  		case 1:
> >  			priv->ep_tx_high_queue = 1;
> >  			priv->ep_tx_count++;
> > 
>