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

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@xxxxxxxxxxxxxxxxxxxxxxxxx>
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

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