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Add option to keep the main stack intact on CM7

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I was surprised by that behaviour, and apparently I'm not the only one:
https://forums.freertos.org/t/silently-breaking-compiler-standards-by-corrupting-main-stack/11165
https://forums.freertos.org/t/main-stack-pointer-reset-when-starting-the-scheduler/5227

Add an option to disable that. My use case is that I initialize some
stuff before the OS and give it to the tasks. No global variable,
because I want to reduce the visibility.
This commit is contained in:
Björn Schäpers 2024-08-01 08:37:01 +02:00
parent fffed5e809
commit b5149c0141
1 changed files with 8 additions and 4 deletions
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12
portable/GCC/ARM_CM7/r0p1/port.c
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@ -272,15 +272,19 @@ void vPortSVCHandler( void )
static void prvPortStartFirstTask( void )
{
/* Start the first task. This also clears the bit that indicates the FPU is
* in use in case the FPU was used before the scheduler was started - which
* would otherwise result in the unnecessary leaving of space in the SVC stack
* for lazy saving of FPU registers. */
#ifndef configKEEP_MAIN_STACK
__asm volatile (
" ldr r0, =0xE000ED08 \n" /* Use the NVIC offset register to locate the stack. */
" ldr r0, [r0] \n"
" ldr r0, [r0] \n"
" msr msp, r0 \n" /* Set the msp back to the start of the stack. */
);
#endif
/* Start the first task. This also clears the bit that indicates the FPU is
* in use in case the FPU was used before the scheduler was started - which
* would otherwise result in the unnecessary leaving of space in the SVC stack
* for lazy saving of FPU registers. */
__asm volatile (
" mov r0, #0 \n" /* Clear the bit that indicates the FPU is in use, see comment above. */
" msr control, r0 \n"
" cpsie i \n" /* Globally enable interrupts. */