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Date: Wed, 19 Oct 2022 08:46:11 +0200 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Madalin Bucur <madalin.bucur@....com> Cc: Sean Anderson <sean.anderson@...o.com>, Andrew Lunn <andrew@...n.ch>, Andrew Davis <afd@...com>, "David S . Miller" <davem@...emloft.net>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jakub Kicinski <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Camelia Alexandra Groza <camelia.groza@....com> Subject: Re: [PATCH net] net: fman: Use physical address for userspace interfaces Hi Madalin, On Wed, Oct 19, 2022 at 7:20 AM Madalin Bucur <madalin.bucur@....com> wrote: > > -----Original Message----- > > From: Sean Anderson <sean.anderson@...o.com> > > Sent: 19 October 2022 00:47 > > To: Andrew Lunn <andrew@...n.ch>; Andrew Davis <afd@...com> > > Cc: David S . Miller <davem@...emloft.net>; netdev@...r.kernel.org; > > linux-kernel@...r.kernel.org; Madalin Bucur <madalin.bucur@....com>; > > Jakub Kicinski <kuba@...nel.org>; Eric Dumazet <edumazet@...gle.com>; > > Paolo Abeni <pabeni@...hat.com>; Camelia Alexandra Groza > > <camelia.groza@....com>; Geert Uytterhoeven <geert@...ux-m68k.org> > > Subject: Re: [PATCH net] net: fman: Use physical address for userspace > > interfaces > > > > > > > > On 10/18/22 5:39 PM, Andrew Lunn wrote: > > > On Tue, Oct 18, 2022 at 01:33:55PM -0500, Andrew Davis wrote: > > >> On 10/18/22 12:37 PM, Sean Anderson wrote: > > >> > Hi Andrew, > > >> > > > >> > On 10/18/22 1:22 PM, Andrew Lunn wrote: > > >> > > On Mon, Oct 17, 2022 at 12:28:06PM -0400, Sean Anderson wrote: > > >> > > > For whatever reason, the address of the MAC is exposed to > > userspace in > > >> > > > several places. We need to use the physical address for this > > purpose to > > >> > > > avoid leaking information about the kernel's memory layout, and > > to keep > > >> > > > backwards compatibility. > > >> > > > > >> > > How does this keep backwards compatibility? Whatever is in user > > space > > >> > > using this virtual address expects a virtual address. If it now > > gets a > > >> > > physical address it will probably do the wrong thing. Unless there > > is > > >> > > a one to one mapping, and you are exposing virtual addresses > > anyway. > > >> > > > > >> > > If you are going to break backwards compatibility Maybe it would > > be > > >> > > better to return 0xdeadbeef? Or 0? > > >> > > > > >> > > Andrew > > >> > > > > >> > > > >> > The fixed commit was added in v6.1-rc1 and switched from physical to > > >> > virtual. So this is effectively a partial revert to the previous > > >> > behavior (but keeping the other changes). See [1] for discussion. > > > > > > Please don't assume a reviewer has seen the previous > > > discussion. Include the background in the commit message to help such > > > reviewers. > > >> I see it asked in that thread, but not answered. Why are you exposing > > >> "physical" addresses to userspace? There should be no reason for that. > > > > > > I don't see anything about needing physical or virtual address in the > > > discussion, or i've missed it. > > > > Well, Madalin originally added this, so perhaps she has some insight. > > > > I have no idea why we set the IFMAP stuff, since that seems like it's for > > PCMCIA. Not sure about sysfs either. > > > > > If nobody knows why it is needed, either use an obfusticated value, or > > > remove it all together. If somebody/something does need it, they will > > > report the regression. > > > > I'd rather apply this (or v2 of this) and then remove the "feature" in > > follow-up. > > > > --Sean > > > root@...alhost:~# grep 1ae /etc/udev/rules.d/72-fsl-dpaa-persistent-networking.rules > SUBSYSTEM=="net", DRIVERS=="fsl_dpa*", ATTR{device_addr}=="1ae0000", NAME="fm1-mac1" > SUBSYSTEM=="net", DRIVERS=="fsl_dpa*", ATTR{device_addr}=="1ae2000", NAME="fm1-mac2" > SUBSYSTEM=="net", DRIVERS=="fsl_dpa*", ATTR{device_addr}=="1ae4000", NAME="fm1-mac3" > SUBSYSTEM=="net", DRIVERS=="fsl_dpa*", ATTR{device_addr}=="1ae6000", NAME="fm1-mac4" > SUBSYSTEM=="net", DRIVERS=="fsl_dpa*", ATTR{device_addr}=="1ae8000", NAME="fm1-mac5" > SUBSYSTEM=="net", DRIVERS=="fsl_dpa*", ATTR{device_addr}=="1aea000", NAME="fm1-mac6" So you rely on the physical address. It's a pity this uses a custom sysfs file. Can't you obtain this information some other way? Anyway, as this is in use, it became part of the ABI. > root@...alhost:~# grep 1ae /sys/devices/platform/soc/soc:fsl,dpaa/soc:fsl,dpaa:ethernet@...et/fm1-mac*/device_addr > /sys/devices/platform/soc/soc:fsl,dpaa/soc:fsl,dpaa:ethernet@...et/fm1-mac3/device_addr:1ae4000 > /sys/devices/platform/soc/soc:fsl,dpaa/soc:fsl,dpaa:ethernet@...et/fm1-mac4/device_addr:1ae6000 > /sys/devices/platform/soc/soc:fsl,dpaa/soc:fsl,dpaa:ethernet@...et/fm1-mac5/device_addr:1ae8000 > /sys/devices/platform/soc/soc:fsl,dpaa/soc:fsl,dpaa:ethernet@...et/fm1-mac6/device_addr:1aea000 Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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