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Date: Sun, 24 Jun 2018 22:18:34 -1000
From: cpb <>
Subject: Re: Minor problem with kernel 431stab123.1 VZ container

On Thu, Jun 21, 2018 at 12:18:46PM +0200, Solar Designer wrote:

> Other issues I found is that strace and gdb fail on 32-bit binaries when
> running a 64-bit kernel.  strace doesn't report any syscalls, gdb
> complains that it fails to insert a breakpoint.  Again, these issues
> don't appear for same bitness of kernel and program being traced.
> . . .
> You may try booting with the nopti kernel parameter.  Then verify that

Hi, I just wanted to report back on the issues inside 32-bit containers
under the 64-bit OpenVZ+Owl 2.6.18-431.el5.028stab123.1.owl1 kernel.
The only things to report are:

1. kernel cmdline option "nopti" has no effect (good suggestion though)
2. ltrace seems to have the same problem as gdb: cannot insert breakpoints

There is no need to pursue this issue, it is not a problem for me, and
I will report anything relevant that I find. I captured the output of
"ltrace -D077 ifconfig" under both the -419 and -431 kernels, but I don't
think it's helpful. The output diverges when ltrace under the "good" -419
kernel does this:

  DEBUG: events.c:51: event from pid 419
  DEBUG: events.c:68: event: SYSCALL: pid=419, sysnum=45
  DEBUG: handle_event.c:41: handle_event(pid=419, type=4)
  DEBUG: handle_event.c:290: sysname(pid=419, sysnum=45)
  DEBUG: handle_event.c:65: event: syscall (SYS_brk [45])
  DEBUG: handle_event.c:388: handle_syscall(pid=419, sysnum=45)
  DEBUG: handle_event.c:640: callstack_push_syscall(pid=419, sysnum=45)
  DEBUG: trace.c:136: continue_process: pid=419
  DEBUG: events.c:24: next_event()

and the "bad" -431 kernel does this instead:

  DEBUG: events.c:51: event from pid 431
  DEBUG: events.c:160: event: BREAKPOINT: pid=431, addr=0x72
  DEBUG: handle_event.c:41: handle_event(pid=431, type=10)
  DEBUG: handle_event.c:95: event: breakpoint
  DEBUG: handle_event.c:504: handle_breakpoint(pid=431, addr=0x72)
  DEBUG: handle_event.c:505: event: breakpoint (0x72)
  DEBUG: breakpoints.c:17: address2bpstruct(pid=431, addr=0x72)
  DEBUG: dict.c:111: dict_find_entry()
  unexpected breakpoint at 0x72

This is just restating the problem, and I'm fine with kernel 419. Thanks.

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