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Fixing setjmp / longjmp.

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Nicolas Noble 2020-07-23 14:16:31 -07:00 committed by GitHub
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kernelbios.md
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@ -194,8 +194,8 @@ The return value (if any) is stored in R2 register.<br/>
A(10h) atoi(src)
A(11h) atol(src)
A(12h) atob(src,num_dst)
A(13h) SaveState(buf)
A(14h) RestoreState(buf,param)
A(13h) setjmp(buf)
A(14h) longjmp(buf,param)
A(15h) strcat(dst,src)
A(16h) strncat(dst,src,maxlen)
A(17h) strcmp(str1,str2)
@ -2129,8 +2129,8 @@ Executes "RestoreState(ioabortbuffer,param)". Internally used to recover from
failed I/O operations, param should be nonzero to notify the SaveState caller
that the abort has occurred.<br/>
#### A(13h) - SaveState(buf)
Stores some (not all) CPU registers in the specified buffer (30h bytes):<br/>
#### A(13h) - setjmp(buf)
This is a somewhat incomplete implementation of posix's setjmp, by storing the ABI-saved CPU registers in the specified buffer (30h bytes):<br/>
```
00h 4 r31 (ra) (aka caller's pc)
04h 4 r29 (sp)
@ -2140,18 +2140,23 @@ Stores some (not all) CPU registers in the specified buffer (30h bytes):<br/>
```
That type of buffer can be used with "ioabort", "RestoreState", and also
"SetCustomExitFromException(addr)".<br/>
The "SaveState" function (initially) returns 0, however, it may return again -
to the same return address - with another return value (which should be usually
The "setjmp" function returns 0 when called directly. However, it may return again -
to the same return address, and the same stack pointer - with another return value (which should be usually
non-zero, to indicate that the state has been restored (eg. ioabort passes 1 as
return value).<br/>
Also noteworthy from what a compliant setjmp implementation should be doing
is the absence of saving the state of cop0 and cop2, thus making this slightly
unsuitable for a typical coroutine system implementation.<br/>
#### A(14h) - RestoreState(buf, param)
Restores the R16-R23,GP,SP,FP,RA registers from a previously recorded SaveState
buffer, and "returns" to that new RA address (rather than to the caller of the
RestoreState function), the "param" value is passed as "return value" to the
code at RA, ie. usually to the caller of the original SaveState call) (since
SaveState returns 0, "param" should be usually 1, or another non-zero value to
inidicate that RestoreState has occurred). See SaveState for further details.<br/>
#### A(14h) - longjmp(buf, param)
Restores the R16-R23,GP,SP,FP,RA registers from a previously recorded
jmp_buf buffer, and "returns" to that new RA address (rather than to the caller of the
longjmp function). The "param" value is passed as "return value" to the
code at RA, ie. usually to the caller of the original setjmp call. Noteworthy difference
from a conformant longjmp implementation is that the "param" value won't be clamped to 1 if
you pass 0 to it. So since setjmp returns 0 on the first call, the caller of longjmp must take
care that "param" is non-zero, so the callsite of setjmp can make the difference between the first
call and a rollback. See setjmp for further details.<br/>
#### A(53h) - set\_ioabort\_handler(src) ;PS2 only ;PSX: SystemError
Normally the ioabort handler is changed only internally during booting, with