Openmoko Bug #1890: gdb problems (single stepping and debug symbol table)

Openmoko Public Trac bugs at
Thu Aug 28 14:32:31 CEST 2008

#1890: gdb problems (single stepping and debug symbol table)
 Reporter:  h.koenig  |          Owner:  openmoko-devel
     Type:  defect    |         Status:  new           
 Priority:  normal    |      Milestone:                
Component:  unknown   |        Version:                
 Severity:  normal    |       Keywords:                
Blockedby:            |   Reproducible:                
 Blocking:            |  
 trying to debug Xglamo I have (at least) two problems with gdb (Om 2008.8
 + zecke-dev) :

 using instruction stepping (si) doesn't seem to work for
 instruction "bxcc lr" -- the program just "continues" in free run.
 for "bx lr" gdb stops at address lr as expected.

 btw: where can I find some (gnu) arm assembler docs/tutorial
 which mention and explain bxcc (and the other opcodes;) ?

 working example with "bx lr":

 0x000fdfa4 in ?? ()
 1: x/i $pc  0xfdfa4:    bx      lr
 (gdb) print/x $lr
 $2 = 0xf5be4
 (gdb) si
 0x000f5be4 in GetTimeInMillis ()
 1: x/i $pc  0xf5be4 <GetTimeInMillis+44>:       add     r0, r4, r0


 non-working example with "bxcc lr":

 0x401f88b0 in gettimeofday () from /lib/
 1: x/i $pc  0x401f88b0 <gettimeofday+16>:       cmn     r0, #4096       ;
 (gdb) si
 0x401f88b4 in gettimeofday () from /lib/
 1: x/i $pc  0x401f88b4 <gettimeofday+20>:       bxcc    lr
 (gdb) p/x $lr
 $3 = 0xf5bcc
 (gdb) si

 Breakpoint 2, 0x000f5bcc in GetTimeInMillis ()
 1: x/i $pc  0xf5bcc <GetTimeInMillis+20>:       mov     r3, #1000       ;

 without that breakpoint #2 at address 0xf5bcc gdb wouldn't have stopped

 btw:  address 0x000fdfa4 in the 1st example is in __divsi3, one
 of the many "invisible" symbols (only ~350 out of 3314 symbols
 show up in gdb for Xglamo)

       nm .debug/Xglamo |  sort | grep ^000f
       000fdef0 T __aeabi_idiv
       000fdef0 T __divsi3
       000fe01c T __aeabi_idivmod

 this is my other big gdb problem:

 gdb doesn't show/use all symbols in the debug symbol image. e.g. for
 symbols starting with "w" only 6 out of 12 symbols can be used:

 (gdb) b W<TAB>
 WantFontInfo          WellKnownConnections  WindowTable
 WriteToClient         Write_CVT             Write_CVT_Stretched


 harald om > nm .debug/Xglamo | grep -i " t w" | sort +2 | wc
      12      36     359
 harald om > nm .debug/Xglamo | grep -i " t w" | sort +2
 000ed7f8 T WaitForSomething
 0001ef3c T WakeupHandler
 000245e8 T WalkTree
 00024a18 t WindowExtents
 0003d5f8 T WindowHasNewCursor
 0003fe68 T WindowsRestructured
 0003bb64 T WriteEventsToClient
 000462d8 T WriteSConnSetupPrefix
 000478d8 T WriteSConnectionInfo
 000ae73c t WriteSwappedPortNotifyEvent
 000ae698 t WriteSwappedVideoNotifyEvent
 000f297c T WriteToClient

 more examples on devel-list "Subject: Xglamo loops and hangs..."

 any help or insights ?


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