Hi!
I'm still trying to get my first application run with eCos, on
TWR-K70F120M board.
I've got it compiling, and debugging thru openocd. I'm now using eCos
gnutools 4.6.3
for compilation, now my problem is that everything seems ok, but my
main() function
never gets called.
I've seen there is no reference to in in the whole disassembled image, I suppose
then the "hello world" tutorial in the docs is outdated?
I've tried changing main() into cyg_user_start().
Then I see a change, as in cyg_start() I see a cyg_user_start() call:
00001f64 <cyg_start>:
1f64: b508 push {r3, lr}
1f66: f000 f807 bl 1f78 <cyg_prestart>
1f6a: f000 f807 bl 1f7c <cyg_package_start>
1f6e: f7fe eab0 blx 4d0 <cyg_user_start>
1f72: f002 f9b7 bl 42e4 <_ZN13Cyg_Scheduler5startEv>
1f76: bf00 nop
My problem now is that when I hit that "blx 4d0" line, instead of
correctly going into cyg_user_start at 0x4d0,
things go there:
0000043c <hal_default_exception_vsr>:
43c: f3ef 8009 mrs r0, PSP
440: f1a0 0130 sub.w r1, r0, #48 ; 0x30
444: f381 8809 msr PSP, r1
448: f04f 0101 mov.w r1, #1
44c: f3ef 8205 mrs r2, IPSR
450: f3ef 8311 mrs r3, BASEPRI
454: e920 4ffe stmdb r0!, {r1, r2, r3, r4, r5, r6, r7, r8,
r9, sl, fp, lr}
458: 4604 mov r4, r0
45a: f000 fc65 bl d28 <hal_deliver_exception>
45e: 4620 mov r0, r4
460: e8b0 4ffe ldmia.w r0!, {r1, r2, r3, r4, r5, r6, r7, r8,
r9,
sl, fp, lr}
464: f380 8809 msr PSP, r0
468: f383 8811 msr BASEPRI, r3
46c: 4770 bx lr
And i get, into openocd, a message that indicates that an exception has risen;
here is a debug session:
... reset halt thing ...
> bp 0x1f6e 4
breakpoint set at 0x00001f6e
breakpoint set at 0x00001f6e
> resume
> target state: halted
target halted due to breakpoint, current mode: Thread
xPSR: 0x61000000 pc: 0x00001f6e psp: 0x2000ffe8
target state: halted
target halted due to breakpoint, current mode: Thread
xPSR: 0x61000000 pc: 0x00001f6e psp: 0x2000ffe8
> rbp 0x1f6e
> step
target state: halted
target halted due to single-step, current mode: Handler UsageFault
xPSR: 0x610000
06 pc: 0x0000043c msp: 0x2000ffd0target state: halted
target halted due to single-step, current mode: Handler UsageFault
xPSR: 0x61000006 pc: 0x0000043c msp: 0x2000ffd0
>
I see "current mode" going to Handles UsageFault.
I looked into cortex-m architecture reference manual, and seen that "blx"
can raise such an exception. Anybody has any clue on what is happening?
Another thing I cannot understand is that: I see that line in disassembly:
1f6e: f7fe eab0 blx 4d0 <cyg_user_start>
that seems to indicate a 32bit-encoded instruction, but on the Arm-M
Reference Manual
I can only find a 16-bit encoded "BLX" instruction, being referred to
a register, not
to an absolute / relative jump. Is that a mis-disassembly? Or am I
missing something?
I've tried compiling eCos in 2 configurations, the first using
defaults (twr-k70f120m with lwip stack),
the second changing compile flags to have -mcpu=cortex-m4 instead oc
-mcpu=cortex-m3;
anyway, the "BLX" problem happens...
Thanks for any help :)
Pyper
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