ARM (Thumb Mode) _CPU_Context_switch_arm

[Matthew J Fletcher]

Sebastian,

I am using 4.10.2 and the standard rtl22xx_t compiler options of
-mcpu=arm7tdmi -mthumb -mstructure-size-boundary=8 -mfpu=vfp
-mfloat-abi=soft -mapcs-frame -fno-schedule-insns2

The registers at before the 'bx lr' instruction in _restore() in cpu.asm.s
are;

r0 = 0x81485f54
r1 = 0x814879a4
r2 = 0x13
r3 = 0x81485ee4
sp = 0x40001c80
lr = 0x7fffe369
pc = 0x81189178

gdb says 'p _Thread_Handler'
$2 = {void (void)} 0x811999f4 <_Thread_Handler>




On 22 February 2013 08:17, Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> On 02/21/2013 06:02 PM, Matthew J Fletcher wrote:
>
>> Hi,
>>
>> As you may have guessed from the title my BSP is now running right up to
>> context switching into the first task, i can see from the heir structures
>> that
>> its got the correct function pointer into my Init task.
>>
>> Looking at the #ifdef __thumb__ where it restores the context it fails at
>> the
>> bx instruction, the lr register is not a valid address. Before RTEMS we
>> used a
>> home grown executive and the asm to swap contexts looks very different.
>>
>> Does anyone run an arm BSP in thumb mode ?
>>
>
> Which RTEMS version do you use and which BSP?  Which compiler options do
> you use?  We use Thumb mode on the lpc24xx and lpc32xx BSPs all the time.
>
> What do you mean with "the lr register is not a valid address"?  For the
> first context switch in Thumb mode it should be the address of
> _Thread_Handler + 1.
>
> --
> Sebastian Huber, embedded brains GmbH
>
> Address : Dornierstr. 4, D-82178 Puchheim, Germany
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>
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regards
---
Matthew J Fletcher
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