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NMI Handler: Save 512 bytes of RAM via NMI stack space. Add stack overflow detection.

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This commit is contained in:
Angus Gratton 2015-09-29 17:31:38 +10:00
parent 697d5b72bc
commit d39b3f6bb6
1 changed files with 36 additions and 2 deletions
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38
core/exception_vectors.S
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@ -25,9 +25,16 @@
.section .bss .section .bss
/* Stack space for NMI handler
NMI handler stack high water mark measured at 0x134 bytes. Any use
of the NMI timer callback will add stack overhead as well.
The NMI handler does a basic check for stack overflow
*/
.balign 16 .balign 16
NMIHandlerStack: # stack space for NMI handler NMIHandlerStack:
.skip 4*0x100 .skip 0x200
.NMIHandlerStackTop: .NMIHandlerStackTop:
.balign 16 .balign 16
@ -368,6 +375,8 @@ call_user_start:
/*************************** NMI Exception Handler ***************************/ /*************************** NMI Exception Handler ***************************/
#define NMI_STACK_CANARY 0xABBABABA
.section .vecbase.text, "x" .section .vecbase.text, "x"
.literal_position .literal_position
@ -401,8 +410,20 @@ NMIExceptionHandler:
movi a0, 0x23 # Override PS for NMI handler movi a0, 0x23 # Override PS for NMI handler
wsr a0, ps wsr a0, ps
rsync rsync
/* mark the stack overflow point before we call the actual NMI handler */
movi a0, NMIHandlerStack
movi a2, NMI_STACK_CANARY
s32i a2, a0, 0x00
call0 sdk_wDev_ProcessFiq call0 sdk_wDev_ProcessFiq
/* verify we didn't overflow */
movi a0, NMIHandlerStack
l32i a3, a0, 0
movi a2, NMI_STACK_CANARY
bne a3, a2, .NMIFatalStackOverflow
l32i a0, sp, 0x3c l32i a0, sp, 0x3c
wsr a0, sar wsr a0, sar
l32i a0, sp, 0x38 l32i a0, sp, 0x38
@ -438,6 +459,19 @@ NMIExceptionHandler:
xsr a1, excsave3 # Load stack back from excsave3, clear excsave3 xsr a1, excsave3 # Load stack back from excsave3, clear excsave3
rfi 3 rfi 3
.section .rodata
.NMIStackOverflowErrorMsg:
.string "\nFATAL: NMI Stack Overflow\n"
.section .vecbase.text, "x"
.NMIFatalStackOverflow:
movi a2, .NMIStackOverflowErrorMsg
call0 printf
.NMIInfiniteLoop:
j .NMIInfiniteLoop /* TODO: replace with call to abort() */
/*********************** General UserException Handler ***********************/ /*********************** General UserException Handler ***********************/
.section .vecbase.text, "x" .section .vecbase.text, "x"