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arm: refactor fault handling stack pointer passing

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Find out on which stack the stack frame for an exception is in the assembly
code (__fault()) rather than in C (_Fault()). This will allow pushing
more registers on the stack when debugging is enabled.

Change-Id: I1c510b83098536f8930392b17df27511ccd04d80
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
This commit is contained in:
Benjamin Walsh 2015-10-26 14:01:39 -04:00 • committed by Anas Nashif
commit cfac189f98
2 changed files with 13 additions and 6 deletions
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7
arch/arm/core/fault.c
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@ -332,14 +332,13 @@ static void _FaultDump(const NANO_ESF *esf, int fault)
* interrupt was already being handled, it is passed a pointer to both and has * interrupt was already being handled, it is passed a pointer to both and has
* to find out on which the ESP is present. * to find out on which the ESP is present.
* *
* @param msp pointer to potential ESF on MSP * @param esf ESF on the stack, either MSP or PSP depending at what processor
* @param psp pointer to potential ESF on PSP * state the exception was taken.
* *
* @return This function does not return. * @return This function does not return.
*/ */
void _Fault(const NANO_ESF *msp, const NANO_ESF *psp) void _Fault(const NANO_ESF *esf)
{ {
const NANO_ESF *esf = _ScbIsNestedExc() ? msp : psp;
int fault = _ScbActiveVectorGet(); int fault = _ScbActiveVectorGet();
FAULT_DUMP(esf, fault); FAULT_DUMP(esf, fault);

12
arch/arm/core/fault_s.S
View file

@ -74,8 +74,16 @@ SECTION_SUBSEC_FUNC(TEXT,__fault,__reserved)
eors.n r0, r0 eors.n r0, r0
msr BASEPRI, r0 msr BASEPRI, r0
mrs r0, MSP /* this reimplements _ScbIsNestedExc() */
mrs r1, PSP ldr ip, =_SCS_ICSR
ldr ip, [ip]
ands.w ip, #_SCS_ICSR_RETTOBASE
ite eq /* is the RETTOBASE bit zero ? */
mrseq r0, MSP /* if so, we're not returning to thread mode, thus this
* is a nested exception: the stack frame is on the MSP */
mrsne r0, PSP /* if not, we are returning to thread mode, thus this is
* not a nested exception: the stack frame is on the PSP */
push {lr} push {lr}
bl _Fault bl _Fault