Date: Thu, 11 Aug 2022 12:23:59 -0600 From: Warner Losh <imp@bsdimp.com> To: FreeBSD User <freebsd@walstatt-de.de> Cc: Warner Losh <imp@freebsd.org>, src-committers <src-committers@freebsd.org>, "<dev-commits-src-all@freebsd.org>" <dev-commits-src-all@freebsd.org>, dev-commits-src-main@freebsd.org Subject: Re: git: 39fdad34e220 - main - stand: impose 510,000 byte limit for /boot/loader and /boot/pxeldr Message-ID: <CANCZdfq-Nr2%2B48dJhBq7jz%2BK6iBpGzRko21j3vwgGfNP81JKcA@mail.gmail.com> In-Reply-To: <20220811202204.106f7188@thor.intern.walstatt.dynvpn.de> References: <202208110331.27B3Va7M007335@gitrepo.freebsd.org> <20220811202204.106f7188@thor.intern.walstatt.dynvpn.de>
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--0000000000009a1ded05e5fb4574 Content-Type: text/plain; charset="UTF-8" On Thu, Aug 11, 2022 at 12:22 PM FreeBSD User <freebsd@walstatt-de.de> wrote: > Am Thu, 11 Aug 2022 03:31:36 GMT > Warner Losh <imp@FreeBSD.org> schrieb: > > > The branch main has been updated by imp: > > > > URL: > https://cgit.FreeBSD.org/src/commit/?id=39fdad34e220c52a433e78f20c8c39412429014e > > > > commit 39fdad34e220c52a433e78f20c8c39412429014e > > Author: Warner Losh <imp@FreeBSD.org> > > AuthorDate: 2022-08-11 03:19:01 +0000 > > Commit: Warner Losh <imp@FreeBSD.org> > > CommitDate: 2022-08-11 03:29:20 +0000 > > > > stand: impose 510,000 byte limit for /boot/loader and /boot/pxeldr > > > > The BIOS method of booting imposes an absolute limit of 640k for the > > size of the program being run due to btx. In practice, this means > that > > programs larger than about 500kiB will fail in odd ways as the stack > / > > heap will overflow. > > > > Pick 510,000 as the cutoff line semi-arbitrarily. loader_lua is now > > almost too big and we want to break the build when it crosses this > > threshold. In my experience, below 500,000 always works, above > 520,000 > > always seems to fail with things getting bad somewhere between > 512,000 > > to 515,000. 510,000 is as close to the line as I think we can go, > though > > experience may dictate we need to lower this in the future. > > > > This is at-best a stop-breakage until we have a better way to subset > the > > boot loader for BIOS booting to allow better, more fined-tuned > > /boot/loaders for the many different environments they have to run > > in. This likely means we'll have a graphical loader than understands > a > > few filesystmes for installation, and a non-graphical loader that > > understands the most filesystems possible for everything else in the > > future. Our build infrastructure needs some work before we can do > that, > > however. > > > > At this late date, it likely isn't worth the efforts to move parts of > > the loader into high memory. There's a number of assumptions about > where > > the stack is, where buffers reside, etc that are fulfilled when it > lives > > in the first 640k that would need bounce buffers and/or other counter > > measures if we were to split it up. All BIOS calls are done in 16-bit > > mode with SEG:OFF addresses, requiring them to be in the first 640k > of > > RAM. And nearly all machines in the last decade can boot with UEFI > > (though there's some exceptions, so it isn't worth killing outright > > yet). > > > > Sponsored by: Netflix > > Reviewed by: kevans > > Differential Revision: https://reviews.freebsd.org/D36129 > > --- > > stand/i386/loader/Makefile | 5 +++++ > > stand/i386/pxeldr/Makefile | 3 +++ > > 2 files changed, 8 insertions(+) > > > > diff --git a/stand/i386/loader/Makefile b/stand/i386/loader/Makefile > > index 3685281ffd2c..cde1513aac06 100644 > > --- a/stand/i386/loader/Makefile > > +++ b/stand/i386/loader/Makefile > > @@ -19,6 +19,8 @@ PROG= ${LOADER}.sym > > INTERNALPROG= > > NEWVERSWHAT?= "bootstrap loader" x86 > > VERSION_FILE= ${.CURDIR}/../loader/version > > +LOADERSIZE= 510000 # Largest known safe size > > + > > > > .PATH: ${BOOTSRC}/i386/loader > > > > @@ -79,9 +81,12 @@ CFLAGS+= -I${BOOTSRC}/i386 > > 8x16.c: ${SRCTOP}/contrib/terminus/ter-u16b.bdf > > vtfontcvt -f compressed-source -o ${.TARGET} ${.ALLSRC} > > > > + > > ${LOADER}: ${LOADER}.bin ${BTXLDR} ${BTXKERN} > > btxld -v -f elf -e ${LOADER_ADDRESS} -o ${.TARGET} -l ${BTXLDR} \ > > -b ${BTXKERN} ${LOADER}.bin > > + @set -- `${SIZE} ${.TARGET} | tail -1` ; > x=$$((${LOADERSIZE}-$$4)); \ > > + echo "$$x bytes available"; test $$x -ge 0 > > > > ${LOADER}.bin: ${LOADER}.sym > > ${STRIPBIN} -R .comment -R .note -o ${.TARGET} ${.ALLSRC} > > diff --git a/stand/i386/pxeldr/Makefile b/stand/i386/pxeldr/Makefile > > index a44dc0de2885..f8bc1eae9a31 100644 > > --- a/stand/i386/pxeldr/Makefile > > +++ b/stand/i386/pxeldr/Makefile > > @@ -13,6 +13,7 @@ BOOT= pxeboot > > LDR= pxeldr > > ORG= 0x7c00 > > LOADER= loader > > +PXELDRSIZE= 510000 # Largest known safe size > > > > .if defined(BOOT_PXELDR_PROBE_KEYBOARD) > > CFLAGS+=-DPROBE_KEYBOARD > > @@ -41,5 +42,7 @@ CLEANFILES+= ${LOADER} > > ${LOADER}: ${LOADERBIN} ${BTXLDR} ${BTXKERN} > > btxld -v -f elf -e ${LOADER_ADDRESS} -o ${.TARGET} -l ${BTXLDR} \ > > -b ${BTXKERN} ${LOADERBIN} > > + @set -- `${SIZE} ${.TARGET} | tail -1` ; > x=$$((${PXELDRSIZE}-$$4)); \ > > + echo "$$x bytes available"; test $$x -ge 0 > > > > .include <bsd.prog.mk> > > > > On recent CURRENT (FreeBSD 14.0-CURRENT #10 main-n257258-348164aa9e5d: Wed > Aug 10 22:39:17 > CEST 2022 amd64), buildworld fails here on several boxes: > > [...] > > ===> lib/flua/libjail (all) > --- all_subdir_stand --- > --- loader --- > btxld -v -f elf -e 0x200000 -o loader -l > /usr/obj/usr/src/amd64.amd64/stand/i386/btx/btxldr/btxldr -b > /usr/obj/usr/src/amd64.amd64/stand/i386/btx/btx/btx > /usr/obj/usr/src/amd64.amd64/stand/i386/loader_lua/loader_lua.bin kernel: > ver=1.02 size=690 > load=9000 entry=9010 map=16M pgctl=0:84 client: fmt=elf size=8a3f0 > text=836bc data=5238 > bss=8070 entry=0 output: fmt=elf size=8ae39 text=289 data=8aa80 org=200000 > entry=200000 > -58585 bytes available 6.64 real > 8.48 user 2.84 sys > I'm sorry, but however you are building /boot/loader, it won't work when it's that big. What are your settings that increase its size by so much? Warner --0000000000009a1ded05e5fb4574 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">= <div dir=3D"ltr" class=3D"gmail_attr">On Thu, Aug 11, 2022 at 12:22 PM Free= BSD User <<a href=3D"mailto:freebsd@walstatt-de.de">freebsd@walstatt-de.= de</a>> wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margi= n:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex= ">Am Thu, 11 Aug 2022 03:31:36 GMT<br> Warner Losh <imp@FreeBSD.org> schrieb:<br> <br> > The branch main has been updated by imp:<br> > <br> > URL: <a href=3D"https://cgit.FreeBSD.org/src/commit/?id=3D39fdad34e220= c52a433e78f20c8c39412429014e" rel=3D"noreferrer" target=3D"_blank">https://= cgit.FreeBSD.org/src/commit/?id=3D39fdad34e220c52a433e78f20c8c39412429014e<= /a><br> > <br> > commit 39fdad34e220c52a433e78f20c8c39412429014e<br> > Author:=C2=A0 =C2=A0 =C2=A0Warner Losh <imp@FreeBSD.org><br> > AuthorDate: 2022-08-11 03:19:01 +0000<br> > Commit:=C2=A0 =C2=A0 =C2=A0Warner Losh <imp@FreeBSD.org><br> > CommitDate: 2022-08-11 03:29:20 +0000<br> > <br> >=C2=A0 =C2=A0 =C2=A0stand: impose 510,000 byte limit for /boot/loader a= nd /boot/pxeldr<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0The BIOS method of booting imposes an absolute limi= t of 640k for the<br> >=C2=A0 =C2=A0 =C2=A0size of the program being run due to btx. In practi= ce, this means that<br> >=C2=A0 =C2=A0 =C2=A0programs larger than about 500kiB will fail in odd = ways as the stack /<br> >=C2=A0 =C2=A0 =C2=A0heap will overflow.<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0Pick 510,000 as the cutoff line semi-arbitrarily. l= oader_lua is now<br> >=C2=A0 =C2=A0 =C2=A0almost too big and we want to break the build when = it crosses this<br> >=C2=A0 =C2=A0 =C2=A0threshold. In my experience, below 500,000 always w= orks, above 520,000<br> >=C2=A0 =C2=A0 =C2=A0always seems to fail with things getting bad somewh= ere between 512,000<br> >=C2=A0 =C2=A0 =C2=A0to 515,000. 510,000 is as close to the line as I th= ink we can go, though<br> >=C2=A0 =C2=A0 =C2=A0experience may dictate we need to lower this in the= future.<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0This is at-best a stop-breakage until we have a bet= ter way to subset the<br> >=C2=A0 =C2=A0 =C2=A0boot loader for BIOS booting to allow better, more = fined-tuned<br> >=C2=A0 =C2=A0 =C2=A0/boot/loaders for the many different environments t= hey have to run<br> >=C2=A0 =C2=A0 =C2=A0in. This likely means we'll have a graphical lo= ader than understands a<br> >=C2=A0 =C2=A0 =C2=A0few filesystmes for installation, and a non-graphic= al loader that<br> >=C2=A0 =C2=A0 =C2=A0understands the most filesystems possible for every= thing else in the<br> >=C2=A0 =C2=A0 =C2=A0future. Our build infrastructure needs some work be= fore we can do that,<br> >=C2=A0 =C2=A0 =C2=A0however.<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0At this late date, it likely isn't worth the ef= forts to move parts of<br> >=C2=A0 =C2=A0 =C2=A0the loader into high memory. There's a number o= f assumptions about where<br> >=C2=A0 =C2=A0 =C2=A0the stack is, where buffers reside, etc that are fu= lfilled when it lives<br> >=C2=A0 =C2=A0 =C2=A0in the first 640k that would need bounce buffers an= d/or other counter<br> >=C2=A0 =C2=A0 =C2=A0measures if we were to split it up. All BIOS calls = are done in 16-bit<br> >=C2=A0 =C2=A0 =C2=A0mode with SEG:OFF addresses, requiring them to be i= n the first 640k of<br> >=C2=A0 =C2=A0 =C2=A0RAM. And nearly all machines in the last decade can= boot with UEFI<br> >=C2=A0 =C2=A0 =C2=A0(though there's some exceptions, so it isn'= t worth killing outright<br> >=C2=A0 =C2=A0 =C2=A0yet).<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0Sponsored by:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0Netflix<br> >=C2=A0 =C2=A0 =C2=A0Reviewed by:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 kevans<br> >=C2=A0 =C2=A0 =C2=A0Differential Revision:=C2=A0 <a href=3D"https://rev= iews.freebsd.org/D36129" rel=3D"noreferrer" target=3D"_blank">https://revie= ws.freebsd.org/D36129</a><br> > ---<br> >=C2=A0 stand/i386/loader/Makefile | 5 +++++<br> >=C2=A0 stand/i386/pxeldr/Makefile | 3 +++<br> >=C2=A0 2 files changed, 8 insertions(+)<br> > <br> > diff --git a/stand/i386/loader/Makefile b/stand/i386/loader/Makefile<b= r> > index 3685281ffd2c..cde1513aac06 100644<br> > --- a/stand/i386/loader/Makefile<br> > +++ b/stand/i386/loader/Makefile<br> > @@ -19,6 +19,8 @@ PROG=3D=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0${LOADER}.sym<br> >=C2=A0 INTERNALPROG=3D<br> >=C2=A0 NEWVERSWHAT?=3D=C2=A0 =C2=A0 =C2=A0 =C2=A0 "bootstrap loade= r" x86<br> >=C2=A0 VERSION_FILE=3D=C2=A0 =C2=A0 =C2=A0 =C2=A0 ${.CURDIR}/../loader/= version<br> > +LOADERSIZE=3D=C2=A0 510000=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 # Larges= t known safe size<br> > +<br> >=C2=A0 <br> >=C2=A0 .PATH:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0${B= OOTSRC}/i386/loader<br> >=C2=A0 <br> > @@ -79,9 +81,12 @@ CFLAGS+=3D=C2=A0 =C2=A0-I${BOOTSRC}/i386<br> >=C2=A0 8x16.c: ${SRCTOP}/contrib/terminus/ter-u16b.bdf<br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0vtfontcvt -f compressed-source -o ${.TARGET}= ${.ALLSRC}<br> >=C2=A0 <br> > +<br> >=C2=A0 ${LOADER}: ${LOADER}.bin ${BTXLDR} ${BTXKERN}<br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0btxld -v -f elf -e ${LOADER_ADDRESS} -o ${.T= ARGET} -l ${BTXLDR} \<br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0-b ${BTXKERN} ${= LOADER}.bin<br> > +=C2=A0 =C2=A0 =C2=A0@set -- `${SIZE} ${.TARGET} | tail -1` ; x=3D$$((= ${LOADERSIZE}-$$4)); \<br> > +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0echo "$$x bytes available"= ;; test $$x -ge 0<br> >=C2=A0 <br> >=C2=A0 ${LOADER}.bin: ${LOADER}.sym<br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0${STRIPBIN} -R .comment -R .note -o ${.TARGE= T} ${.ALLSRC}<br> > diff --git a/stand/i386/pxeldr/Makefile b/stand/i386/pxeldr/Makefile<b= r> > index a44dc0de2885..f8bc1eae9a31 100644<br> > --- a/stand/i386/pxeldr/Makefile<br> > +++ b/stand/i386/pxeldr/Makefile<br> > @@ -13,6 +13,7 @@ BOOT=3D=C2=A0 =C2=A0 =C2=A0 =C2=A0pxeboot<br> >=C2=A0 LDR=3D pxeldr<br> >=C2=A0 ORG=3D 0x7c00<br> >=C2=A0 LOADER=3D=C2=A0 =C2=A0 =C2=A0 loader<br> > +PXELDRSIZE=3D 510000=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0# Larges= t known safe size<br> >=C2=A0 <br> >=C2=A0 .if defined(BOOT_PXELDR_PROBE_KEYBOARD)<br> >=C2=A0 CFLAGS+=3D-DPROBE_KEYBOARD<br> > @@ -41,5 +42,7 @@ CLEANFILES+=3D ${LOADER}<br> >=C2=A0 ${LOADER}: ${LOADERBIN} ${BTXLDR} ${BTXKERN}<br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0btxld -v -f elf -e ${LOADER_ADDRESS} -o ${.T= ARGET} -l ${BTXLDR} \<br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0-b ${BTXKERN} ${LOADERBIN}<br> > +=C2=A0 =C2=A0 =C2=A0@set -- `${SIZE} ${.TARGET} | tail -1` ; x=3D$$((= ${PXELDRSIZE}-$$4)); \<br> > +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0echo "$$x bytes available"= ;; test $$x -ge 0<br> >=C2=A0 <br> >=C2=A0 .include <<a href=3D"http://bsd.prog.mk" rel=3D"noreferrer" t= arget=3D"_blank">bsd.prog.mk</a>><br> > <br> <br> On recent CURRENT (FreeBSD 14.0-CURRENT #10 main-n257258-348164aa9e5d: Wed = Aug 10 22:39:17<br> CEST 2022 amd64), buildworld fails here on several boxes:<br> <br> [...]<br> <br> =3D=3D=3D> lib/flua/libjail (all)<br> --- all_subdir_stand ---<br> --- loader ---<br> btxld -v -f elf -e 0x200000 -o loader -l<br> /usr/obj/usr/src/amd64.amd64/stand/i386/btx/btxldr/btxldr=C2=A0 -b<br> /usr/obj/usr/src/amd64.amd64/stand/i386/btx/btx/btx<br> /usr/obj/usr/src/amd64.amd64/stand/i386/loader_lua/loader_lua.bin kernel: v= er=3D1.02 size=3D690<br> load=3D9000 entry=3D9010 map=3D16M pgctl=3D0:84 client: fmt=3Delf size=3D8a= 3f0 text=3D836bc data=3D5238<br> bss=3D8070 entry=3D0 output: fmt=3Delf size=3D8ae39 text=3D289 data=3D8aa80= org=3D200000 entry=3D200000 <br> -58585 bytes available 6.64 real=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0<br> 8.48 user=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A02.84 sys<br></blockquote><div><b= r></div><div>I'm sorry, but however you are building /boot/loader, it w= on't work when it's that big. What are your settings that increase = its size by so much?</div><div><br></div><div>Warner</div></div></div> --0000000000009a1ded05e5fb4574--
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