From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 52B86C30653 for ; Fri, 5 Jul 2024 02:08:22 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sPYMU-0006cU-Gk; Thu, 04 Jul 2024 22:07:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sPYMT-0006bz-1A; Thu, 04 Jul 2024 22:07:45 -0400 Received: from gandalf.ozlabs.org ([150.107.74.76] helo=mail.ozlabs.org) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sPYMP-0000GC-EF; Thu, 04 Jul 2024 22:07:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202312; t=1720145250; bh=1L4XNRnFgvSO0mJFB4QWcl9+pd+/N//pdHt1Q5HdMHs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jegd3oM/gZsRRCHVMulno5blpXrJaXZEpAfSu9EIgdZH1UHIK7tCrJPi/NjWVQUPM rsoQ+PsbnHFwbDmhc/6Ge2KcSAbTOVFE/NL6m2phLAxUWBJdn7icMbLPP7oBYJBhjU DzUNqFWiTTvQJBQdfnXhlfhuLZo1QVzQOwDw+NYceCtih+FPJX7IdYZhWY490dW5ic MVcncqrKfU2apF6TaY8IQ1abp6ivEOyBJeoVDpvys1z0yAWT6ewzU/dz0UzJcAbFxN Femv7CmhHrGQ8cIUUNSNQTfZXoa/Wk9qWPR1f6+5c2bsrSlYDYOoeditHCP8nrBqK5 b/8nlp9htyvxQ== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4WFcNL69Srz4wnx; Fri, 5 Jul 2024 12:07:30 +1000 (AEST) Date: Fri, 5 Jul 2024 11:41:13 +1000 From: David Gibson To: Nicholas Piggin Cc: Peter Maydell , Akihiko Odaki , Eduardo Habkost , Marcel Apfelbaum , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Yanan Wang , John Snow , BALATON Zoltan , Jiaxun Yang , Daniel Henrique Barboza , Harsh Prateek Bora , Alexey Kardashevskiy , "Michael S. Tsirkin" , Alex =?iso-8859-1?Q?Benn=E9e?= , Peter Xu , Fabiano Rosas , Paolo Bonzini , David Hildenbrand , Thomas Huth , Laurent Vivier , qemu-devel@nongnu.org, qemu-block@nongnu.org, qemu-ppc@nongnu.org Subject: Re: [PATCH v2 06/15] ppc/vof: Fix unaligned FDT property access Message-ID: References: <20240627-san-v2-0-750bb0946dbd@daynix.com> <20240627-san-v2-6-750bb0946dbd@daynix.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ji4OZ74Eg4G6xax6" Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=150.107.74.76; envelope-from=dgibson@gandalf.ozlabs.org; helo=mail.ozlabs.org X-Spam_score_int: -39 X-Spam_score: -4.0 X-Spam_bar: ---- X-Spam_report: (-4.0 / 5.0 requ) BAYES_00=-1.9, DKIM_INVALID=0.1, DKIM_SIGNED=0.1, HEADER_FROM_DIFFERENT_DOMAINS=0.001, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --ji4OZ74Eg4G6xax6 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jul 05, 2024 at 11:18:47AM +1000, Nicholas Piggin wrote: > On Thu Jul 4, 2024 at 10:15 PM AEST, Peter Maydell wrote: > > On Sat, 29 Jun 2024 at 04:17, David Gibson wrote: > > > > > > On Fri, Jun 28, 2024 at 04:20:02PM +0100, Peter Maydell wrote: > > > > On Thu, 27 Jun 2024 at 14:39, Akihiko Odaki wrote: > > > > > > > > > > FDT properties are aligned by 4 bytes, not 8 bytes. > > > > > > > > > > Signed-off-by: Akihiko Odaki > > > > > --- > > > > > hw/ppc/vof.c | 2 +- > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > diff --git a/hw/ppc/vof.c b/hw/ppc/vof.c > > > > > index e3b430a81f4f..b5b6514d79fc 100644 > > > > > --- a/hw/ppc/vof.c > > > > > +++ b/hw/ppc/vof.c > > > > > @@ -646,7 +646,7 @@ static void vof_dt_memory_available(void *fdt= , GArray *claimed, uint64_t base) > > > > > mem0_reg =3D fdt_getprop(fdt, offset, "reg", &proplen); > > > > > g_assert(mem0_reg && proplen =3D=3D sizeof(uint32_t) * (ac += sc)); > > > > > if (sc =3D=3D 2) { > > > > > - mem0_end =3D be64_to_cpu(*(uint64_t *)(mem0_reg + sizeof= (uint32_t) * ac)); > > > > > + mem0_end =3D ldq_be_p(mem0_reg + sizeof(uint32_t) * ac); > > > > > } else { > > > > > mem0_end =3D be32_to_cpu(*(uint32_t *)(mem0_reg + sizeof= (uint32_t) * ac)); > > > > > } > > > > > > > > I did wonder if there was a better way to do what this is doing, > > > > but neither we (in system/device_tree.c) nor libfdt seem to > > > > provide one. > > > > > > libfdt does provide unaligned access helpers (fdt32_ld() etc.), but > > > not an automatic aligned-or-unaligned helper. Maybe we should add t= hat? > > > > fdt32_ld() and friends only do the "load from this bit of memory" > > part, which we already have QEMU utility functions for (and which > > are this patch uses). > > > > This particular bit of code is dealing with an fdt property ("memory") > > that is an array of (address, size) tuples where address and size > > can independently be either 32 or 64 bits, and it wants the > > size value of tuple 0. So the missing functionality is something at > > a higher level than fdt32_ld() which would let you say "give me > > tuple N field X" with some way to specify the tuple layout. (Which > > is an awkward kind of API to write in C.) > > > > Slightly less general, but for this case we could perhaps have > > something like the getprop equivalent of qemu_fdt_setprop_sized_cells(): > > > > uint64_t value_array[2]; > > qemu_fdt_getprop_sized_cells(fdt, nodename, "memory", &value_array, > > ac, sc); > > /* > > * fills in value_array[0] with address, value_array[1] with size, > > * probably barfs if the varargs-list of cell-sizes doesn't > > * cover the whole property, similar to the current assert on > > * proplen. > > */ > > mem0_end =3D value_array[0]; >=20 > Since 4/8 byte cells are most common and size is probably > normally known, what about something simpler to start with? Hrm, I don't think this helps much. As Peter points out the actual load isn't really the issue, it's locating the right spot for it. >=20 > Thanks, > Nick >=20 > --- > diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h > index 0677fea..c4b6355 100644 > --- a/libfdt/libfdt.h > +++ b/libfdt/libfdt.h > @@ -148,6 +148,15 @@ static inline uint32_t fdt32_ld(const fdt32_t *p) > | bp[3]; > } > =20 > +/* > + * Load the value from a 32-bit cell of a property. Cells are 32-bit ali= gned > + * so can use a single load. > + */ > +static inline uint32_t fdt32_ld_prop(const fdt32_t *p) > +{ > + return fdt32_to_cpu(*p); > +} > + > static inline void fdt32_st(void *property, uint32_t value) > { > uint8_t *bp =3D (uint8_t *)property; > @@ -172,6 +181,18 @@ static inline uint64_t fdt64_ld(const fdt64_t *p) > | bp[7]; > } > =20 > +/* > + * Load the value from a 64-bit cell of a property. Cells are 32-bit ali= gned > + * so can use two loads. > + */ > +static inline uint64_t fdt64_ld_prop(const fdt64_t *p) > +{ > + const fdt64_t *_p =3D p; > + > + return ((uint64_t)fdt32_to_cpu(_p[0]) << 32) > + | fdt32_to_cpu(_p[1]); > +} > + > static inline void fdt64_st(void *property, uint64_t value) > { > uint8_t *bp =3D (uint8_t *)property; >=20 --=20 David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson --ji4OZ74Eg4G6xax6 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEO+dNsU4E3yXUXRK2zQJF27ox2GcFAmaHTzgACgkQzQJF27ox 2GfIVQ//buJxQREoyNhlOkJ3HcOChDv3x5gjNg5SEXyhw1jF4RsBu7SSq/jeykVj R5JuvuCa66IDJN+1uXW5nuzh18Qg8NXhIpz6QHXkMA6/H4sKBCNszdgNRNrFAwbJ zHM80m1xT4k+sbE9GKRUTgDB3SD+DdpG7t6BJ7lh04z3u8q/ryOj1F3Nl41jJjmX PASCAbhiv9/NcK84Nk2vh80PxYbiaA//6f/ae5kCaOiOKYEnuoIObgS130NSqxh6 oPN+x9+Ki4TpMRA6AbGJ+IrNt/4u+OMcOS2gOGYayJE/S7dCrDC/0bWSUAlizQUN G38GzjYJsEoqWJIcVTrmRMGIKOd0BKaNevbU1N/sNxDJbIHhiINf2o3h6JksMVP/ d0xIUFVwEhDtEoGZhQDd77ojBU6SuD74hwMdi/k5ZujLNHNJEe1BPahn5Obirhor aROKY9wARRSF8LrWC2t7c29VL5EsFxo0KM280wsxYOObforuxOxuxJuEkPBQ68tB srwVhaYWIwAyn/VU4LZm0OhJbsB30/g5s5MZDAnv612Hndwl6qnwwKH6MObu+aKs ghfDZOj/7ckVshyj5l1HMrDc90wCv2Oaufer0znrMgFr02Wy4ywHddNmropN6WzH Ok0t7dJHBP5S08GuR/pi3ciP8/lBnoAHL+KTYR5Sdc173YDDNBI= =BQnL -----END PGP SIGNATURE----- --ji4OZ74Eg4G6xax6--