Date: Thu, 11 Aug 2022 20:44:51 +0200 From: FreeBSD User <freebsd@walstatt-de.de> To: Warner Losh <imp@bsdimp.com> 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: <20220811204518.452625ea@thor.intern.walstatt.dynvpn.de> In-Reply-To: <20220811204324.00b64b02@thor.intern.walstatt.dynvpn.de> References: <202208110331.27B3Va7M007335@gitrepo.freebsd.org> <20220811202204.106f7188@thor.intern.walstatt.dynvpn.de> <CANCZdfq-Nr2%2B48dJhBq7jz%2BK6iBpGzRko21j3vwgGfNP81JKcA@mail.gmail.com> <20220811204324.00b64b02@thor.intern.walstatt.dynvpn.de>
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Am Thu, 11 Aug 2022 20:42:57 +0200 FreeBSD User <freebsd@walstatt-de.de> schrieb: > Am Thu, 11 Aug 2022 12:23:59 -0600 > Warner Losh <imp@bsdimp.com> schrieb: > > > 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 > > Hello, > I have a custom kernel with several drivers enabled, others disabled, but I'm not aware of > any knowb I triggered by purpose that could change the size. Can you help me with some hints > which knobs this might trigger? Since it happens on ALL boxes with CURRENT and different but > similar custom kernel settings (mostly driver and disabling debugging et cetera it must be > something very trivial that triggers that misbehaviour ... I doubt that kernel config is the > cause, but anyway, I'll give you some extra configs I put on one box that fails: > > [... kernel conf ...] > > # The defaults are 64K and 128K respectively. > options DFLTPHYS=(64*1024) > #options MAXPHYS=(512*1024) > options MAXPHYS=(1024*1024) > > options CC_CDG > options CC_CHD > options CC_CUBIC > options CC_DCTCP > options CC_HD > options CC_HTCP > options CC_VEGAS > options RATELIMIT # TX rate > > options ZFS # ZFS > options GEOM_NOP # NOP GEOM class > options GEOM_ELI > > options LIBICONV # kernels iconv > options LIBMCHAIN # mchain library > options KGSSAPI # Kernel GSS API modulue > > options MSDOSFS_ICONV # MSDOS Filesystem > options CD9660_ICONV # ISO 9660 Filesystem > > options FDESCFS #File descriptor filesystem > options FUSEFS #FUSE support module > options AUTOFS # automounter filesystem > options NULLFS > > #options P1003_1B_SEMAPHORES # POSIX-style semaphores > #options P1003_1B_MQUEUE # POSIX message queue > > options TCPHPTS # TCP High Precission timer > #options TCPPCAP # keeps the last n packets > #options MROUTING # Multicast routing > options IPSEC # Internet Protocol Security protocol > #options TCP_SIGNATURE # #include support for RFC 2385 > options SCTP # Stream Control Transmission Protocol > > # > options MAC_BSDEXTENDED # ugidfw > options MAC_PORTACL # > options MAC_NTPD # > # > options CAM_IOSCHED_DYNAMIC # CAM iosched NCQ TRIM > > The src.conf: # more /etc/src.conf # CPUTYPE?= native # CFLAGS+= -O3 # for the kernel COPTFLAGS+= -O3 # #CXXFLAGS+= -std=c++20 # WITH_CLANG_EXTRAS= YES #WITH_LLVM_BINUTILS= YES # #WITH_BSD_GREP= YES # WITH_OFED_EXTRA= YES #WITH_CTF= YES # WITH_BEARSSL= YES # WITH_SORT_THREADS= YES # WITH_ZONEINFO_LEAPSECONDS_SUPPORT= YES # WITH_MALLOC_PRODUCTION= YES # WITHOUT_ASSERT_DEBUG= YES WITHOUT_TESTS= YES WITHOUT_DEBUG_FILES= YES # WITHOUT_CLEAN= YES # WITHOUT_REPRODUCIBLE_BUILD= YES # INSTALL_NODEBUG= YES # -- O. Hartmann
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