Avoiding sysctl at program startup using ELF aux vector (was: concurrent sysctl implementation)

Mon Aug 16 14:22:38 UTC 2010

On Sat, 14 Aug 2010 17:32:25 +0300
Kostik Belousov <kostikbel at gmail.com> wrote:

> On Sat, Aug 07, 2010 at 09:37:22PM +0200, Marius Strobl wrote:
> > On Sat, Aug 07, 2010 at 09:09:04PM +0300, Kostik Belousov wrote:
> > > On Sat, Aug 07, 2010 at 03:59:39PM +0200, Marius Strobl wrote:
> > > > On Fri, Aug 06, 2010 at 02:11:31PM +0300, Kostik Belousov wrote:
> > > > > On Fri, Aug 06, 2010 at 01:08:08PM +0200, Marius Strobl wrote:
> > > > > > On Fri, Aug 06, 2010 at 12:04:04PM +0300, Kostik Belousov
> > > > > > wrote:
> > > > > > > On Fri, Aug 06, 2010 at 07:06:33AM +0200, Jeremie Le Hen
> > > > > > > wrote:
> > > > > > > > Hi Kib,
> > > > > > > > 
> > > > > > > > In-Reply-To:
> > > > > > > > <20100629083901.GG13238 at deviant.kiev.zoral.com.ua> On
> > > > > > > > Tue, Jun 29, 2010 at 11:39:01AM +0300, Kostik Belousov
> > > > > > > > wrote:
> > > > > > > > > On Tue, Jun 29, 2010 at 10:26:39AM +0200, Marius
> > > > > > > > > Strobl wrote:
> > > > > > > > > > On Mon, Jun 28, 2010 at 05:48:59PM +0300, Kostik
> > > > > > > > > > Belousov wrote:
> > > > > > > > > > > On Wed, Jun 23, 2010 at 11:09:59PM +0200, Jeremie
> > > > > > > > > > > Le Hen wrote:
> > > > > > > > > > > > Hi Kostik,
> > > > > > > > > > > > 
> > > > > > > > > > > > This patch seems to have faded out from
> > > > > > > > > > > > memory.  Is it possible to go forward and
> > > > > > > > > > > > commit it?
> > > > > > > > > > > I refreshed the patch. Hopefully, nobody will
> > > > > > > > > > > object, and I commit it shortly.
> > > > > > > > > > > 
> > > > > > > > > > > > 
> > > > > > > > > > > > Thanks,
> > > > > > > > > > > > Regards.
> > > > > > > > > > > > 
> > > > > > > > > > > > On Sat, Jul 25, 2009 at 12:29:16AM +0300,
> > > > > > > > > > > > Kostik Belousov wrote:
> > > > > > > > > > > > > Below is the prototype that seems to work for
> > > > > > > > > > > > > me both with patched and old rtld on i386.
> > > > > > > > > > > > > Patch also contains bits for amd64 that I did
> > > > > > > > > > > > > not tested yet. All other arches are not
> > > > > > > > > > > > > buildable for now.
> > > > > > > > > > > > > 
> > > > > > > > > > > > > Patch completely eliminates sysctl syscalls
> > > > > > > > > > > > > from the rtld and libc startup. Without the
> > > > > > > > > > > > > patch, a single run of /bin/ls did 6 sysctls,
> > > > > > > > > > > > > with the patch, no sysctls is queried at all.
> > > > > > > > > > > > > 
> > > > > > > > > > > Comparing with the originally posted patch, I
> > > > > > > > > > > added support for all architectures, tested amd64
> > > > > > > > > > > and ia32 on amd64, and converted getpagesizes(3)
> > > > > > > > > > > that added two more startup sysctls.
> > > > > > > > > > > 
> > > > > > > > > > > Would be nice to get a testing for at least
> > > > > > > > > > > some !x86 architectures before the commit, I
> > > > > > > > > > > added some people who helped me in past, to the
> > > > > > > > > > > Cc:.
> > > > > > > > > > > 
> > > > > > > > > > 
> > > > > > > > > > Doesn't look good on sparc64:
> > > > > > > > > > <...>
> > > > > > > > > > NFS ROOT: 192.168.1.40:/usr/data/nfsroot/sparc64
> > > > > > > > > > dc1: link state changed to UP
> > > > > > > > > > pid 24 (ifconfig), uid 0: exited on signal 11
> > > > > > > > > > Segmentation fault
> > > > > > > > > > Interface  IP-Address  Broadcast
> > > > > > > > > > pid 29 (rcorder), uid 0: exited on signal 11
> > > > > > > > > > Segmentation fault
> > > > > > > > > > pid 30 (grep), uid 0: exited on signal 11
> > > > > > > > > > Segmentation fault
> > > > > > > > > > pid 31 (rcorder), uid 0: exited on signal 11
> > > > > > > > > > Segmentation fault
> > > > > > > > > >  
> > > > > > > > > > pid 32 (date), uid 0: exited on signal 11
> > > > > > > > > > Segmentation fault
> > > > > > > > > > Jun 29 12:20:50 getty[36]: open /dev/ttyv3: No such
> > > > > > > > > > file or directory <...>
> > > > > > > > > > 
> > > > > > > > > > Unfortunately, I currently lack the time to debug
> > > > > > > > > > this.
> > > > > > > > > 
> > > > > > > > > Thank you.
> > > > > > > > 
> > > > > > > > Did yu have time to look at this problem?  It would be
> > > > > > > > nice to have this in the tree.
> > > > > > > 
> > > > > > > I cannot move forward without the help from somebody
> > > > > > > having access to sparc64 system where the problem is
> > > > > > > reproducable.
> > > > > > 
> > > > > > Do you have a debug version of the patch which outputs the
> > > > > > necessary information?
> > > > > 
> > > > > I would suggest to build rtld and libc with debugging symbols
> > > > > and get full backtrace from the faults.
> > > > 
> > > > v100# gdb /sbin/ifconfig ifconfig.core
> > > > GNU gdb 6.1.1 [FreeBSD]
> > > > Copyright 2004 Free Software Foundation, Inc.
> > > > GDB is free software, covered by the GNU General Public
> > > > License, and you are welcome to change it and/or distribute
> > > > copies of it under certain conditions. Type "show copying" to
> > > > see the conditions. There is absolutely no warranty for GDB.
> > > > Type "show warranty" for details. This GDB was configured as
> > > > "sparc64-marcel-freebsd"... Core was generated by `ifconfig'.
> > > > Program terminated with signal 11, Segmentation fault.
> > > > Reading symbols from /lib/libbsdxml.so.4...done.
> > > > Loaded symbols for /lib/libbsdxml.so.4
> > > > Reading symbols from /lib/libjail.so.1...done.
> > > > Loaded symbols for /lib/libjail.so.1
> > > > Reading symbols from /lib/libsbuf.so.5...done.
> > > > Loaded symbols for /lib/libsbuf.so.5
> > > > Reading symbols from /lib/libipx.so.5...done.
> > > > Loaded symbols for /lib/libipx.so.5
> > > > Reading symbols from /lib/libc.so.7...done.
> > > > Loaded symbols for /lib/libc.so.7
> > > > Reading symbols from /libexec/ld-elf.so.1...done.
> > > > Loaded symbols for /libexec/ld-elf.so.1
> > > > #0  0x000000004089ebdc in getpagesizes (pagesize=0x7fdffffe2f8,
> > > > nelem=1)
> > > > at /usr/home/marius/co/head/src/lib/libc/gen/getpagesizes.c:75
> > > > 75                      while (nops > 0 && ps[nops - 1] == 0)
> > > > (gdb) bt #0  0x000000004089ebdc in getpagesizes
> > > > (pagesize=0x7fdffffe2f8, nelem=1)
> > > > at /usr/home/marius/co/head/src/lib/libc/gen/getpagesizes.c:75
> > > > #1  0x00000000407f4314 in malloc_init ()
> > > > at /usr/home/marius/co/head/src/lib/libc/stdlib/malloc.c:5418
> > > > #2  0x00000000407f67d8 in malloc (size=32)
> > > > at /usr/home/marius/co/head/src/lib/libc/stdlib/malloc.c:5932
> > > > #3  0x00000000001069ac in clone_setdefcallback
> > > > (ifprefix=0x11b8a8 "wlan", p=0x10a1a0 <wlan_create>)
> > > > at /usr/home/marius/co/head/src/sbin/ifconfig/ifclone.c:106 #4
> > > > 0x0000000000119864 in __do_global_ctors_aux () #5
> > > > 0x000000000010243c in _init () #6  0x0000000000102508 in _start
> > > > () #7  0x000000004022719c in .rtld_start ()
> > > >     at /usr/home/marius/co/head/src/libexec/rtld-elf/sparc64/rtld_start.S:59
> > > > #8  0x000000004022719c in .rtld_start ()
> > > >     at /usr/home/marius/co/head/src/libexec/rtld-elf/sparc64/rtld_start.S:59
> > > > Previous frame identical to this frame (corrupt stack?)
> > > > 
> > > > All faults I've looked at died the same why.
> > > Thank you. I think I found the reason, which was an unitialized
> > > variable. I also fixed a sillyness with osrelver.
> > > 
> > > In the patched tree, there is tools/test/auxinfo that could be
> > > used to quick-check the system.
> > > 
> > > Updated patch is available at
> > > http://people.freebsd.org/~kib/misc/rtld_auxinfo.1.patch
> > 
> > I can confirm that this versions works on sparc64.
> After the discussion with Alexander, I made the change to allow libc
> to access aux vectors, instead of providing rtld interface to fetch
> values.
> 
> I decided to keep the single function that fetch the values, because
> it is convenient place to do digesting of the vector.
> 
> http://people.freebsd.org/~kib/misc/rtld_auxinfo.2.patch

No objections here.

-- 
Alexander Kabaev
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