Arm-elf-gdb (target remote) breakpoint issue

Started by Michael Anburaj February 4, 2005

Tools used:
GNU gdb 5.3 (insight)
LPC2106 board running ARM remote GDB stubs (over UART)

Short description:
When I try to set a breakpoint at a thumb C-function
starting at address 0x40000278, GDB debugger (insight)
sends a (GDB protocol) command to write 0xbebe
(Instruction which would generate a Undef exception)
at 0x40000282 & not at 0x40000278. Which is actually
the functions exit & not the entry.

Detailed description:
I issue the following commands on the GDBs console

$ target /dev/com1
$ load
$ b APP_vMain
$ c

And GDB log file reads as follows <Just the important
lines are included here>:

c b APP_vMain
w $m40000278,2#60
r +$00b5#f7
w +$m4000027a,2#89
r +$0248#ce
w +$m4000027c,2#8b
r +$00f0#f6
w +$m4000027e,2#8d
r +$02fb#2a
w +$m40000280,2#59
r +$01bc#26
w +
c c
w $Z0,40000282,2#a4
r +$#00
w +$m40000282,2#5b
r +$0047#cb
w +$M40000282,2:bebe#03
r +$OK#9a
w +$Hc0#db Clipping from the image disassembly around APP_vMain()

40000274: 4000fc00 andmi pc, r0, r0, lsl #24

40000278 <APP_vMain>:
40000278: b500 push {lr}
4000027a: 4802 ldr r0, [pc, #8] (40000284
4000027c: fb02f000 bl 40000884 <CONSOL_SendString>
40000280: bc01 pop {r0}
40000282: 4700 bx r0
40000284: 0ff0 lsr r0, r6, #31
40000286: 4000 and r0, r0

GDB reads the 1st 5 instructions staring 0x40000274
(APP_vMain) & finally sets the Break (Undef)
instruction at the 6th instruction. Why?

Please help me understand the issue behind this.

-Mike. __________________________________________________

An Engineer's Guide to the LPC2100 Series