[K42-discussion] Problem debugging linux user mode apps with K42 remote gdb

[Bryan S Rosenburg]

Patrick,

My first thought was that null-dup is a 32-bit executable.  That doesn't 
seem to be the case, given the way you've built it, but would you check? 
It doesn't matter whether it's 32-bit or 64-bit, but if it's 32-bit you 
should give gdb some arbitrary 64-bit program instead.  More on that 
below.  Also, I've never had to add the libk42sys.so.1.dbg symbol file.  I 
don't know that it hurts anything, but you might try leaving that step 
out.

We've never had good debugging support for actual application code, but 
there should be no problem debugging K42 library code triggered by the 
application.  I assume the breakpoint you've compiled in is in dup2.C in 
kitch-linux/lib/emu?  That should work just fine.  Gdb gets confused, 
however, if you give it a 32-bit program and then try to debug 64-bit 
library code.  So it's important to give gdb a 64-bit executable no matter 
how your actual executable is built.  I usually say "gdb 
<...>/tests/linux/copy.dbg" no matter what my actual test program is. Then 
"add-symbol-file <,,,>/lib/exec.so.dbg".  I'm not debugging the program 
itself anyway, so it doesn't matter if I have the program symbols right.

Let us know whether any of that helps.

- Bryan





Patrick Bozeman <PEBozeman at lbl.gov> 
Sent by: k42-discussion-bounces+rosnbrg=us.ibm.com at ozlabs.org
08/25/2006 04:52 PM
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Subject
[K42-discussion] Problem debugging linux user mode apps with K42 remote 
gdb






I can debug native K42 apps just fine, e.g. baseServers, but am having a 
problem with debugging linux user mode apps.  Hopefully, someone can 
point out what I am doing wrong.

Thanks.

#
# I compile the app with debug support.  This is a small program that 
triggers
# a problem between dup2 and some other code I added to K42 file
# system layers.
#
console>  powerpc64-linux-gcc -g null-dup.c -o null-dup

#
# I run the app..
#
k42> /tmp/null-dup

#
# An asert I added to dup2.C gets triggered.  (Note, nothing about the
# process should be corrupt, this is just to serve as a condidtional
# break point to kick off debugging.)
#
# K42 hw console output...
#
breakpoint pid 0x1f, progName /tmp/null-dup
GDB got trap: Program Interrupt
vector=0x700, sr=0x900000000002f032, pc=0x1000702e18b4 lr=0x1000702e1880
User program pid=31(0x1f) connecting to GDB via port 2223

#
# I attach via gdb and it complains a litte bit..
# note that the symbol files for exec.so.dbg and libk42sys.so.1.dbg are 
added.
#
console> powerpc64-linux-gdb null-dup
(gdb) hw-debug 10.0.0.2:2223
The target architecture is assumed to be powerpc:a35
add symbol table from file 
"/home/peb/src/k42-devel/k42/powerpc/partDeb/lib/exec.so.dbg" at
add symbol table from file 
"/home/peb/src/k42-devel/k42/powerpc/partDeb/lib/libk42sys.so.1.dbg" at
<signal handler called>
warning: Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code.
Current language:  auto; currently c++

#
# I try to get a back trace and both gdb and the k42 hw console complain
#
(gdb) bt
#0  <signal handler called>
#1  0x2fa0000040be001c in ?? ()
#2  0x2fad000040be001c in ?? ()
Previous frame identical to this frame (corrupt stack?)

#
# hw console output as a result of the bt
#
/home/peb/src/k42-devel/k42/kitchsrc/os/kernel/proc/ProcessReplicated.C,565: 

Invalid memory access: processID 0x1f addr 0x0, type 200000 vp=0 
this=0x8002000020790a00 myRoot=0x8002000000376a00 myRef=0x8000000010001f50
WARNING: file 
"/home/peb/src/k42-devel/k42/kitchsrc/os/kernel/exception/ExceptionLocal.C", 

line 352
User-mode bad-address fault: commID 0x1f00000000, pc 0x1000702e852c, 
addr 0, rc 8000000005cd6416.
/home/peb/src/k42-devel/k42/kitchsrc/os/kernel/proc/ProcessReplicated.C,565: 

Invalid memory access: processID 0x1f addr 0x0, type 200000 vp=0 
this=0x8002000020790a00 myRoot=0x8002000000376a00 myRef=0x8000000010001f50
WARNING: file 
"/home/peb/src/k42-devel/k42/kitchsrc/os/kernel/exception/ExceptionLocal.C", 

line 352
User-mode bad-address fault: commID 0x1f00000000, pc 0x1000702e852c, 
addr 0, rc 8000000005cd6416.

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