[User-mode-linux-user] Ptrace broken since 2.4.0-test8pre4?...

[Yuri P. <yu...@as...>]

Hi!

Beeing an active user mode linux user :-) I can say that since
2.4.0-test8 (host kernel) I cannot run uml-linux successfully.

In contrast with popular feeling that "threaded programes screwed
signal handling on test8.", it is actually a  small change to
arch/i386/ptrace.c introduced since test8pre4.

Also, I remember complains from  Andi Kleen noticed that new kernels
break ups (an alternative debugger).

See the following postings -

  http://kernelnotes.org/lnxlists/linux-kernel/lk_0009_01/msg00265.html
  http://kernelnotes.org/lnxlists/linux-kernel/lk_0009_01/msg00283.html

resulted in this change -

--- v2.4.0-test7/linux/arch/i386/kernel/ptrace.c Fri Jun 23 21:55:07 2000
+++ linux/arch/i386/kernel/ptrace.c Sat Sep 2 12:00:02 2000
@@ -99,6 +99,11 @@
                case EFL:
                        value &= FLAG_MASK;
                        value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;
+                       break;
+               case EIP:
+                       /* Mark us as not being in a system call, so that no restart issues happen */
+                       put_stack_long(child, 4*ORIG_EAX - sizeof(struct pt_regs), -1);
+                       break;
        }
        if (regno > GS*4)
                regno -= 2*4;

While I cannot comment on the above change from technical point of view,
it seems the patch breaks more then it cures. Time to consider reversing?


Regards,
Yuri Pudgorodsky