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(2001-1c00-0c32-7800-5bfa-a036-83f0-f9ec.cable.dynamic.v6.ziggo.nl. [2001:1c00:c32:7800:5bfa:a036:83f0:f9ec]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a8d25d3597asm629355766b.186.2024.09.11.09.24.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Sep 2024 09:24:54 -0700 (PDT) Message-ID: <181dec64-5906-4cdd-bb29-40bc7c02d63e@redhat.com> Date: Wed, 11 Sep 2024 18:24:54 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH hotfix 6.11] minmax: reduce egregious min/max macro expansion To: Lorenzo Stoakes , Andrew Morton Cc: Richard Narron , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Mauro Carvalho Chehab , Sakari Ailus , Greg Kroah-Hartman , Marcin Wojtas , Russell King , "David S . Miller" , Arnd Bergmann , Linus Torvalds , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-staging@lists.linux.dev, linux-mm@kvack.org, stable@vger.kernel.org References: <20240911153457.1005227-1-lorenzo.stoakes@oracle.com> Content-Language: en-US, nl From: Hans de Goede In-Reply-To: <20240911153457.1005227-1-lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Lorenzo, On 9/11/24 5:34 PM, Lorenzo Stoakes wrote: > Avoid nested min()/max() which results in egregious macro expansion. > > This issue was introduced by commit 867046cc7027 ("minmax: relax check to > allow comparison between unsigned arguments and signed constants") [2]. > > Work has been done to address the issue of egregious min()/max() macro > expansion in commit 22f546873149 ("minmax: improve macro expansion and type > checking") and related, however it appears that some issues remain on more > tightly constrained systems. > > Adjust a few known-bad cases of deeply nested macros to avoid doing so to > mitigate this. Porting the patch first proposed in [1] to Linus's tree. > > Running an allmodconfig build using the methodology described in [2] we > observe a 35 MiB reduction in generated code. > > The difference is much more significant prior to recent minmax fixes which > were not backported. As per [1] prior these the reduction is more like 200 > MiB. > > This resolves an issue with slackware 15.0 32-bit compilation as reported > by Richard Narron. > > Presumably the min/max fixups would be difficult to backport, this patch > should be easier and fix's Richard's problem in 5.15. > > [0]:https://lore.kernel.org/all/b97faef60ad24922b530241c5d7c933c@AcuMS.aculab.com/ > [1]:https://lore.kernel.org/lkml/5882b96e-1287-4390-8174-3316d39038ef@lucifer.local/ > [2]:https://lore.kernel.org/linux-mm/36aa2cad-1db1-4abf-8dd2-fb20484aabc3@lucifer.local/ > > Reported-by: Richard Narron > Closes: https://lore.kernel.org/all/4a5321bd-b1f-1832-f0c-cea8694dc5aa@aaazen.com/ > Fixes: 867046cc7027 ("minmax: relax check to allow comparison between unsigned arguments and signed constants") > Cc: stable@vger.kernel.org > Signed-off-by: Lorenzo Stoakes Thank you for your patch. I must say that I'm not a fan of that this is patching 3 totally unrelated files here in a single patch. This is e.g. going to be a problem if we need to revert one of the changes because of regressions... So I would prefer this to be split into 3 patches. One review comment for the atomisp bits inline / below. > --- > drivers/net/ethernet/marvell/mvpp2/mvpp2.h | 2 +- > .../staging/media/atomisp/pci/sh_css_frac.h | 26 ++++++++++++++----- > include/linux/skbuff.h | 6 ++++- > 3 files changed, 25 insertions(+), 9 deletions(-) > > diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2.h b/drivers/net/ethernet/marvell/mvpp2/mvpp2.h > index e809f91c08fb..8b431f90efc3 100644 > --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2.h > +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2.h > @@ -23,7 +23,7 @@ > /* The PacketOffset field is measured in units of 32 bytes and is 3 bits wide, > * so the maximum offset is 7 * 32 = 224 > */ > -#define MVPP2_SKB_HEADROOM min(max(XDP_PACKET_HEADROOM, NET_SKB_PAD), 224) > +#define MVPP2_SKB_HEADROOM clamp_t(int, XDP_PACKET_HEADROOM, NET_SKB_PAD, 224) > > #define MVPP2_XDP_PASS 0 > #define MVPP2_XDP_DROPPED BIT(0) > diff --git a/drivers/staging/media/atomisp/pci/sh_css_frac.h b/drivers/staging/media/atomisp/pci/sh_css_frac.h > index b90b5b330dfa..a973394c5bc0 100644 > --- a/drivers/staging/media/atomisp/pci/sh_css_frac.h > +++ b/drivers/staging/media/atomisp/pci/sh_css_frac.h > @@ -32,12 +32,24 @@ > #define uISP_VAL_MAX ((unsigned int)((1 << uISP_REG_BIT) - 1)) > > /* a:fraction bits for 16bit precision, b:fraction bits for ISP precision */ > -#define sDIGIT_FITTING(v, a, b) \ > - min_t(int, max_t(int, (((v) >> sSHIFT) >> max(sFRACTION_BITS_FITTING(a) - (b), 0)), \ > - sISP_VAL_MIN), sISP_VAL_MAX) > -#define uDIGIT_FITTING(v, a, b) \ > - min((unsigned int)max((unsigned)(((v) >> uSHIFT) \ > - >> max((int)(uFRACTION_BITS_FITTING(a) - (b)), 0)), \ > - uISP_VAL_MIN), uISP_VAL_MAX) > +static inline int sDIGIT_FITTING(short v, int a, int b) > +{ drivers/staging/media/atomisp/pci/isp/kernels/s3a/s3a_1.0/ia_css_s3a.host.c calls this with ia_css_3a_config.af_fir1_coef / .af_fir2_coef as first argument those are of the ia_css_s0_15 type which is: /* Signed fixed point value, 0 integer bits, 15 fractional bits */ typedef s32 ia_css_s0_15; please replace the "short v" with "int v" I think that you can then also replace clamp_t() with clamp() > + int fit_shift = sFRACTION_BITS_FITTING(a) - b; > + > + v >>= sSHIFT; > + v >>= fit_shift > 0 ? fit_shift : 0; > + > + return clamp_t(int, v, sISP_VAL_MIN, sISP_VAL_MAX); > +} > + > +static inline unsigned int uDIGIT_FITTING(unsigned int v, int a, int b) > +{ > + int fit_shift = uFRACTION_BITS_FITTING(a) - b; > + > + v >>= uSHIFT; > + v >>= fit_shift > 0 ? fit_shift : 0; > + > + return clamp_t(unsigned int, v, uISP_VAL_MIN, uISP_VAL_MAX); > +} Regular clamp() should work here ? all parameters are already unsigned ints. Regards, Hans > > #endif /* __SH_CSS_FRAC_H */ > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 29c3ea5b6e93..d53b296df504 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -3164,7 +3164,11 @@ static inline int pskb_network_may_pull(struct sk_buff *skb, unsigned int len) > * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8) > */ > #ifndef NET_SKB_PAD > -#define NET_SKB_PAD max(32, L1_CACHE_BYTES) > +#if L1_CACHE_BYTES < 32 > +#define NET_SKB_PAD 32 > +#else > +#define NET_SKB_PAD L1_CACHE_BYTES > +#endif > #endif > > int ___pskb_trim(struct sk_buff *skb, unsigned int len); > -- > 2.46.0 >