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Add CFI frame unwind info in portable/IAR/RXv2/port_asm.s #1341

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Add CFI frame unwind info in portable/IAR/RXv2/port_asm.s #1341

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53 changes: 53 additions & 0 deletions portable/IAR/RXv2/port_asm.s
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,37 @@
EXTERN _pxCurrentTCB
EXTERN _vTaskSwitchContext

CFI Names cfiNames0
CFI StackFrame CFA SP DATA
CFI VirtualResource ?RET:32
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@ShunichiroNakamura ShunichiroNakamura Jan 7, 2026

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@bernd-edlinger ,
I have a quick question regarding resource naming: does the '?' have any specific meaning? I checked the manual, but I couldn’t find any clear guidelines on naming conventions or common practices.

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@bernd-edlinger bernd-edlinger Jan 7, 2026

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This is apparently the name of the return address, I have not found it in any documentation either...
I saw this syntax in the assembler files, generated by the IAR compiler when I added the option -la .
to save the intermediate assembler file with debug info generated by the compiler. Some of the
interrupts are written in C with syntax like __interrupt void vTickISR( void ) etc.
But the ?RET is used everywhere, normal functions have the return addess at Frame(CFA, -4)
and Interrupts have it at Frame(CFA, -8) while at Frame(CFA, -4) is probably the interrupted
processor flags or something that the debugger does not care about for the call stack.

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@ShunichiroNakamura ShunichiroNakamura Jan 8, 2026

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@bernd-edlinger , thank you for your response.

I saw this syntax in the assembler files, generated by the IAR compiler when I added the option -la .

I understand that the name is based on one generated by the IAR compiler. In that case, there should be no problem.

But the ?RET is used everywhere, normal functions have the return addess at Frame(CFA, -4)
and Interrupts have it at Frame(CFA, -8) while at Frame(CFA, -4) is probably the interrupted
processor flags or something that the debugger does not care about for the call stack.

I don't have sufficient knowledge about the CFI of the IAR compiler, so this is just a guess, but here is what I assume. Please refer to the RX Instruction Set Architecture manual, especially the JSR and INT instructions:

  • The Frame(CFA, -4) in normal functions represents the stack area used to store the caller's PC register.
  • The Frame(CFA, -8) in interrupts represents the stack area used to store the PC and PSW registers from immediately before the interrupt.

CFI Resource R1:32, R2:32, R3:32, R4:32, R5:32, R6:32, R7:32, R8:32
CFI Resource R9:32, R10:32, R11:32, R12:32, R13:32, R14:32, R15:32
CFI Resource SP:32
CFI EndNames cfiNames0

CFI Common cfiCommon0 Using cfiNames0
CFI CodeAlign 1
CFI DataAlign 1
CFI ReturnAddress ?RET CODE
CFI CFA SP+4
CFI ?RET Frame(CFA, -4)
CFI R1 Undefined
CFI R2 Undefined
CFI R3 Undefined
CFI R4 Undefined
CFI R5 Undefined
CFI R6 SameValue
CFI R7 SameValue
CFI R8 SameValue
CFI R9 SameValue
CFI R10 SameValue
CFI R11 SameValue
CFI R12 SameValue
CFI R13 SameValue
CFI R14 Undefined
CFI R15 Undefined
CFI EndCommon cfiCommon0

RSEG CODE:CODE(4)

_prvStartFirstTask:
Expand Down Expand Up @@ -91,6 +122,9 @@ _prvStartFirstTask:
/*-----------------------------------------------------------*/

/* The software interrupt - overwrite the default 'weak' definition. */
CFI Block cfiBlock0 Using cfiCommon0
CFI Function ___interrupt_27
CODE
___interrupt_27:

/* Re-enable interrupts. */
Expand Down Expand Up @@ -151,6 +185,24 @@ ___interrupt_27:
MVTIPL #configMAX_SYSCALL_INTERRUPT_PRIORITY

/* Select the next task to run. */
CFI ?RET Frame(CFA, -8)
CFI R15 Frame(CFA, -12)
CFI R14 Frame(CFA, -16)
CFI R13 Frame(CFA, -20)
CFI R12 Frame(CFA, -24)
CFI R11 Frame(CFA, -28)
CFI R10 Frame(CFA, -32)
CFI R9 Frame(CFA, -36)
CFI R8 Frame(CFA, -40)
CFI R7 Frame(CFA, -44)
CFI R6 Frame(CFA, -48)
CFI R5 Frame(CFA, -52)
CFI R4 Frame(CFA, -56)
CFI R3 Frame(CFA, -60)
CFI R2 Frame(CFA, -64)
CFI R1 Frame(CFA, -68)
CFI CFA SP+96
CFI FunCall _vTaskSwitchContext
BSR.A _vTaskSwitchContext

/* Reset the interrupt mask as no more data structure access is required. */
Expand Down Expand Up @@ -194,6 +246,7 @@ ___interrupt_27:
RTE
NOP
NOP
CFI EndBlock cfiBlock0

/*-----------------------------------------------------------*/

Expand Down
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