[uml-devel] Re: 2.4.32-bs2

[Antoine Martin <antoine@nagafix.co.uk>]

On Sun, 2005-12-11 at 17:47 +0100, Blaisorblade wrote:
> On Thursday 08 December 2005 03:10, Antoine Martin wrote:
> > All,
> >
> > Talking about tty logging and fake ide reminded of the current state of
> > UML on 2.4 kernels:
> > http://uml.nagafix.co.uk/uml-2.4.32-bs2.patch.bz2
> > Is Blaisorblade's 2.4.28-bs2 patch tweaked to apply cleanly on 2.4.32.
> 
> There should be (I think) just offsets, not even fuzzes, so there should be no 
> problem.
There were some offsets and one empty reject, so no real problem.

> > Plus another tweak to avoid duplicated symbols when linking with newer
> > libc.a, the patch is based on this one:
> > http://seclists.org/lists/linux-kernel/2004/Nov/1048.html
> > But I'm not sure I did it right, so please check it (bottom of this
> > email is the modified Makefile)
> 
> Seems correct for what I can see. Ah, no, there's a 2.4 / 2.6 conversion 
> problem, see below.
> 
> > /usr/lib/libc.a: could not read symbols: Bad value
> 
> I'd like to see the exact cmd line producing this. Possibly seeing also gcc -v 
> output with that cmd line would help.
# gcc -v -Wl,-T,arch/um/link.ld -static -Wl,--wrap,malloc
-Wl,--wrap,free -Wl,--wrap,calloc         -o linux arch/um/main.o
vmlinux.o -L/usr/lib -lutil
Reading specs from /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/specs
Configured with: /var/tmp/portage/gcc-3.4.4-r1/work/gcc-3.4.4/configure
--prefix=/usr --bindir=/usr/i686-pc-linux-gnu/gcc-bin/3.4.4
--includedir=/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/include
--datadir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.4
--mandir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.4/man
--infodir=/usr/share/gcc-data/i686-pc-linux-gnu/3.4.4/info
--with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/include/g
++-v3 --host=i686-pc-linux-gnu --build=i686-pc-linux-gnu
--disable-altivec --enable-nls --without-included-gettext
--with-system-zlib --disable-checking --disable-werror
--disable-libunwind-exceptions --disable-multilib --disable-libmudflap
--disable-libgcj --enable-languages=c,c++ --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
Thread model: posix
gcc version 3.4.4 (Gentoo Hardened 3.4.4-r1, HTB-3.4.4-1.00,
ssp-3.4.4-1.0, pie-8.7.8)
 /usr/libexec/gcc/i686-pc-linux-gnu/3.4.4/collect2 -m elf_i386 -static
-z relro -z now -o
linux /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../crt1.o /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../crti.o /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/crtbeginT.o -L/usr/lib -L/usr/lib/gcc/i686-pc-linux-gnu/3.4.4 -L/usr/lib/gcc/i686-pc-linux-gnu/3.4.4 -L/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../../i686-pc-linux-gnu/lib -L/usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../.. -T arch/um/link.ld --wrap malloc --wrap free --wrap calloc arch/um/main.o vmlinux.o -lutil --start-group -lgcc -lgcc_eh -lc --end-group /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/crtend.o /usr/lib/gcc/i686-pc-linux-gnu/3.4.4/../../../crtn.o
/usr/lib/libc.a: could not read symbols: Bad value
collect2: ld returned 1 exit status

> (After seeing if there's anything strange with the file itself, but I think 
> you can compile on the same box some 
> 
> > Any idea why that is? It happens when I use:
> > i686-pc-linux-gnu-3.4.4-vanilla
> > but not with:
> > i686-pc-linux-gnu-3.3.6-vanilla 
Trying again today with 3.3.6, I get a new warning (bcmp) and the same
error. I have no idea what I've done different!

gcc -Wl,-T,arch/um/link.ld -static -Wl,--wrap,malloc -Wl,--wrap,free
-Wl,--wrap,calloc \
        -o linux arch/um/main.o vmlinux.o -L/usr/lib -lutil
/usr/lib/libc.a(memcmp.o): In function `bcmp':
../sysdeps/i386/i686/memcmp.S:(.text+0x0): multiple definition of
`memcmp'
vmlinux.o:/usr/src/linux-2.4.32-bs2/lib/string.c:452: first defined here
/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/../../../../i686-pc-linux-gnu/bin/ld: Warning: size of symbol `memcmp' changed from 53 in vmlinux.o to 128 in /usr/lib/libc.a(memcmp.o)
/usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/libgcc.a: could not read
symbols: Bad value
collect2: ld returned 1 exit status
make: *** [linux] Error 1


> 
> The first thing I'd do there (since this is the fscking 2.4, not the shining 
> 2.6) is doing a make mrproper ARCH=um between the two compiles... 2.4 kbuild 
> was so erratic that even recently I was bitten from it, too... I started 
> writing a patch (missing export_symbol, I thought) to discover that a) the 
> code seemed right and b) the code _was_ right.
(Good way to waste some time ;) I have used mrproper.

> Afterwards I'd be curious if some strange Gentoo thing is mixing 
> runtime .so/.a libraries of the two compilers (I've had this happening for 
> c++, and programs crashing after linking with both gcc 3.3 and gcc 3.4 stdc++ 
> libraries - fix_libtool_files.sh on Gentoo was my friend in the end). Note 
> that you need to be especially lucky to trigger this - of the whole KDE 
> 3.4.3, most was linked this way, but only "juk" suffered.
fix_libtool_files.sh did fix some libs when I upgraded to 3.4 - but did
not help in this case.

> No idea, I'll look at it a bit (maybe), but it's very strange. Note that I 
> recall compiling that with GCC 3.4.x (.3?) - I wanted to support 3.4 when 
> releasing -bs2.
> 
> > Problem is that the resulting kernel cannot be executed!
> > $ kernel32-2.4.32-bs2: cannot execute binary file
> 
> file vmlinux-* and/or dmesg|tail would maybe help on what was going on.
/home/viper/kernel32-2.4.32-bs2: ELF 32-bit LSB relocatable, Intel
80386, version 1 (SYSV), not stripped

(nothing in dmesg)
> 
> > The other problem with this patch is that I can't get it to compile with
> > SUBARCH=i386 on amd64.
> > (even though -bs2 contains a SUBARCH fix - maybe I didn't merge it
> > properly?)
> 
> Hmm, I never compiled 2.4 kernels on x86_64 machines. Probably I backported 
> just an earlier attempt - in fact I thought I'd done it on 2.6, but until I 
> started testing it, it didn't work.
Not to worry, I just thought it was meant to work.
How would I go about building a 32-bit pcap enabled kernel in the
chroot? Do I copy the pcap.a from outside the chroot?

> For that, I'm sorry but you need a chroot - just too much work and I've not 
> the time to work on this.
2.4 is not worth spending too much time on anyway.

> > Here is the modified Makefile
> 
> Next time send a patch (even cut 'n' paste, but a patch).
I almost did, but the patch was twice as long... will do next time.

> > $ cat linux-2.4.32-bs2/arch/um/kernel/tt/Makefile
> > #
> > # Copyright (C) 2002 - 2003 Jeff Dike (jdike@addtoit.com)
> > # Licensed under the GPL
> > #
> >
> > O_TARGET = tt.o
> >
> > obj-y = exec_kern.o exec_user.o gdb.o ksyms.o mem.o mem_user.o
> > process_kern.o \
> >         syscall_kern.o syscall_user.o time.o tlb.o tracer.o trap_user.o
> > \
> >         uaccess.o uaccess_user.o
> 
> > extra-y := unmap_fin.o
> > clean-files := unmap_tmp.o
> 
> Get rid of these lines, they didn't exist. Extra-y must be expressed, but ok, 
> it's already coded (see below). (clean-files is for make clean).
ok

> > obj-$(CONFIG_PT_PROXY) += gdb_kern.o
> >
> > subdir-y = sys-$(SUBARCH)
> > subdir-$(CONFIG_PT_PROXY) += ptproxy
> >
> > obj-y += $(join $(subdir-y),$(subdir-y:%=/%.o))
> >
> > export-objs = ksyms.o
> >
> > USER_OBJS = $(filter %_user.o,$(obj-y)) gdb.o time.o tracer.o
> >
> > UNMAP_CFLAGS := $(patsubst -pg -DPROFILING,,$(USER_CFLAGS))
> > UNMAP_CFLAGS := $(patsubst -fprofile-arcs -ftest-coverage,,
> > $(UNMAP_CFLAGS))
> >
> > include $(TOPDIR)/Rules.make
> >
> > $(USER_OBJS) : %.o: %.c
> >         $(CC) $(CFLAGS_$@) $(USER_CFLAGS) -c -o $@ $<
> 
> USER_CFLAGS and CFLAGS_$@ are in the wrong order, the latter must be able to 
> override the former. Not that it should be a problem here... (and it's even 
> in the original, so don't worry).
I've swapped them.

> > $(O_TARGET) : unmap_fin.o
> 
> The above is the (approximate) equivalent of extra-y setting.
> 
> > unmap.o: unmap.c
> >         $(CC) $(UNMAP_CFLAGS) -c -o $@ $<
> >
> > unmap_fin.o : unmap.o
> >         ld -r -o unmap_tmp.o unmap.o -lc -L/usr/lib
> >         objcopy unmap_tmp.o unmap_fin.o -G switcheroo
I'll send a patch when the whole thing works.

Antoine



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