[Xen-devel] Xen gdb -- unable to set breakpoints on x86-64 PV linux domU

[shanth@xxxxxxxxxxx]

Hi,

Does gdb on x86_64 work on a recent xen-3.1-testing branch??

I followed the instructions in tools/debugger/gdb/README, to setup a  
gdb session on a x84-64 PV Linux domU. I'm unable to set any  
breakpoints. Similar errors were reported earlier in two e-mail threads:
1. http://lists.xensource.com/archives/html/xen-devel/2006-10/msg00205.html
   - This was in PAE mode. Keir found the problem:
      "Ah, the lookup function is mapping the PTE page with write permissions.
       That won't work. I'll check in a fix."
       I want to verify if my sources includes it. But, I've not been able
       to trace the fix.

2. http://lists.xensource.com/archives/html/xen-tools/2007-05/msg00001.html
   - This was a more recent error report on x86_64. But, no response.

Any tips? More details on the error below.

Thanks,
Shanth

GDB reports:
  (gdb) break schedule
  Breakpoint 1 at 0xffffffff803e2884: file  
include2/asm/thread_info.h, line 63.
  (gdb) target remote 127.0.0.1:9999
  Remote debugging using 127.0.0.1:9999
  [New Thread 0]
  [Switching to Thread 0]
  0xffffffff802063aa in hypercall_page ()
  (gdb) bt
  #0  0xffffffff802063aa in hypercall_page ()
  #1  0x0000000000000000 in ?? ()
  (gdb) c
  Continuing.
  Warning:
  Cannot insert breakpoint 1.
  Error accessing memory address 0xffffffff803e2884: Input/output error.
  Cannot insert breakpoint -2.
  Error accessing memory address 0xffffffff80200000: Input/output error.

Xen hypervisor reports:
  (XEN) mm.c:625:d0 Non-privileged (11) attempt to map I/O space 00000000
  (XEN) mm.c:625:d0 Non-privileged (11) attempt to map I/O space 00000000
  (XEN) mm.c:649:d0 Error getting mfn ee02d (pfn 10622d) from L1  
entry 80000000ee02d125 for dom11
  (XEN) mm.c:649:d0 Error getting mfn ee02d (pfn 10622d) from L1  
entry 80000000ee02d125 for dom11
  (XEN) mm.c:649:d0 Error getting mfn fafff (pfn 5555555555555555)  
from L1 entry 80000000fafff125 for dom11
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