NMI Handler: Save 512 bytes of RAM via NMI stack space. Add stack overflow detection.
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1 changed files with 36 additions and 2 deletions
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@ -25,9 +25,16 @@
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.section .bss
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/* Stack space for NMI handler
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NMI handler stack high water mark measured at 0x134 bytes. Any use
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of the NMI timer callback will add stack overhead as well.
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The NMI handler does a basic check for stack overflow
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*/
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.balign 16
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NMIHandlerStack: # stack space for NMI handler
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.skip 4*0x100
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NMIHandlerStack:
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.skip 0x200
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.NMIHandlerStackTop:
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.balign 16
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@ -368,6 +375,8 @@ call_user_start:
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/*************************** NMI Exception Handler ***************************/
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#define NMI_STACK_CANARY 0xABBABABA
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.section .vecbase.text, "x"
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.literal_position
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@ -401,8 +410,20 @@ NMIExceptionHandler:
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movi a0, 0x23 # Override PS for NMI handler
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wsr a0, ps
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rsync
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/* mark the stack overflow point before we call the actual NMI handler */
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movi a0, NMIHandlerStack
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movi a2, NMI_STACK_CANARY
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s32i a2, a0, 0x00
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call0 sdk_wDev_ProcessFiq
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/* verify we didn't overflow */
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movi a0, NMIHandlerStack
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l32i a3, a0, 0
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movi a2, NMI_STACK_CANARY
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bne a3, a2, .NMIFatalStackOverflow
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l32i a0, sp, 0x3c
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wsr a0, sar
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l32i a0, sp, 0x38
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@ -438,6 +459,19 @@ NMIExceptionHandler:
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xsr a1, excsave3 # Load stack back from excsave3, clear excsave3
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rfi 3
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.section .rodata
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.NMIStackOverflowErrorMsg:
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.string "\nFATAL: NMI Stack Overflow\n"
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.section .vecbase.text, "x"
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.NMIFatalStackOverflow:
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movi a2, .NMIStackOverflowErrorMsg
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call0 printf
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.NMIInfiniteLoop:
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j .NMIInfiniteLoop /* TODO: replace with call to abort() */
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/*********************** General UserException Handler ***********************/
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.section .vecbase.text, "x"
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