Re: [uml-devel] 2.4.22-[67] problems

[Matt Zimmerman <mdz@debian.org>]

On Sat, Dec 20, 2003 at 05:06:56PM -0800, Matt Zimmerman wrote:

> On Sat, Dec 20, 2003 at 04:52:57PM -0800, Matt Zimmerman wrote:
> 
> > sh-2.05a# apt-get source -b hello
> > apt-get: error while loading shared libraries: /lib/libm.so.6: cannot read
> > file data: Error 38
> > sh-2.05a# 
> > sh-2.05a# apt-get source -b hello
> > Reading Package Lists... Done
> > Building Dependency Tree... Done
> > 
> > And of course, I haven't been able to get this to happen in the debugger
> > (yet).
> 
> Well, with enough attempts, I'm able to get it to happen in gdb.  However, I
> can't get it down to a single syscall, and can't do it reliably.  I tried
> setting a breakpoint at the point in syscall_kern.c where it can return
> -ENOSYS, but it never hits it.

It looks like in the case where it breaks, the system call number is 0, so
it is passing the test in execute_syscall_skas, and instead invoking
sys_ni_syscall.  Here is the regs struct in one instance:

$16 = {regs = {tt = {syscall = 2, sc = 0xbfffd68c}, skas = {regs = {2, 
        3221214860, 14, 14, 3221214860, 3221214492, 4294967258, 43, 43, 0, 0, 
        4, 1074631684, 35, 2097815, 3221214444, 43}, fp = {
        0 <repeats 27 times>}, xfp = {2098047, 0 <repeats 31 times>, 
        4294967295, 2734743551, 16401, 0, 0, 3413842944, 16404, 
        0 <repeats 88 times>, 2726428672}, fault_addr = 0, fault_type = 1, 
      trap_type = 0, syscall = 0, is_user = 1}}}

The process isn't invoking syscall 0 (in this case it was actually __NR_select
(82)).  syscall matches ORIG_EAX, though, so I guess something is going wrong
earlier, maybe in move_registers?

-- 
 - mdz


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