Messages in this thread | | | Date | Thu, 26 Mar 2009 12:15:16 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: Bug: ptrace issues under x86_64 Xen kernel 2.6.29 |
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Bryan Donlan wrote: > Using 2.6.29 or 2.6.28 as a 64-bit Xen domU, a number of ptrace() > users seem to have issues with unexpected breakpoints. ltrace and gdb > both seem to be affected, under both 64-bit and 32-bit userspace. > 32-bit kernels do not seem to be affected. Typical symptoms look like: >
Thanks for the reminder. I'd noticed it in passing, but haven't investigated it.
J
> x86 li63-205:/# ltrace /bin/true > unexpected breakpoint at 0xf7e6d89f > unexpected breakpoint at 0xf7e60a3f > unexpected breakpoint at 0xf7e6464f > unexpected breakpoint at 0x804933f > unexpected breakpoint at 0xf7ea509f > unexpected breakpoint at 0xf7e9b1ff > unexpected breakpoint at 0xf7efef66 > +++ exited (status 0) +++ > > x64 li63-205:~/linux-2.6# ltrace true > unexpected breakpoint at 0x7f3379878f1f > unexpected breakpoint at 0x7f337986ca3f > unexpected breakpoint at 0x7f337986fd3f > unexpected breakpoint at 0x402bdf > unexpected breakpoint at 0x7f33798b07bf > unexpected breakpoint at 0x7f33798a696f > unexpected breakpoint at 0x7f3379905e3f > +++ exited (status 0) +++ > > li63-205:~# gdb /bin/true > GNU gdb 6.8-debian > Copyright (C) 2008 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show copying" > and "show warranty" for details. > This GDB was configured as "x86_64-linux-gnu"... > (no debugging symbols found) > (gdb) run > Starting program: /bin/true > (no debugging symbols found) > (no debugging symbols found) > > Program received signal SIGTRAP, Trace/breakpoint trap. > 0x00007f640680e4e7 in ?? () from /lib64/ld-linux-x86-64.so.2 > (gdb) > > In the specific case of the above gdb session, here is /proc/pid/maps > from the tracee: > 00400000-00407000 r-xp 00000000 ca:00 9531 > /bin/true > 00607000-00608000 rw-p 00007000 ca:00 9531 > /bin/true > 7f64067f9000-7f6406816000 r-xp 00000000 ca:00 1678 > /lib/ld-2.9.so > 7f6406a12000-7f6406a15000 rw-p 7f6406a12000 00:00 0 > 7f6406a15000-7f6406a17000 rw-p 0001c000 ca:00 1678 > /lib/ld-2.9.so > 7fff0ea01000-7fff0ea16000 rw-p 7ffffffea000 00:00 0 [stack] > 7fff0ebfe000-7fff0ebff000 r-xp 7fff0ebfe000 00:00 0 [vdso] > ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 > [vsyscall] > > strace seems(?) to be unaffected. > > I've attached my .config, dmesg, and strace output for running ltrace > (32-bit) on /bin/true on the affected system. Unfortunately, I'm not > enough of a ptrace guru to interpret what the cause might be.
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