prof: properly save and restore RARG for amd64

amd64 passes first argument in RARG (BP) register
which has the be preserved duing _profin() and
_profout() calls. to handle this we introduce
_saveret() and _savearg(). _saveret() returns
AX, _savearg() returns RARG (BP). for archs other
and amd64, _saveret() and _savearg() are the
same function, doing nothing.

restoing works with dummy function:

uintptr
_restore(uintptr, uintptr ret)
{
	return ret;
}

...

ret = _saveret();
arg = _savearg();
...
return _restore(arg, ret);

as we pass arg as the first argument, RARG (BP) is
restored.

1 files changed, 18 insertions, 9 deletions

diff --git a/sys/src/ape/lib/ap/plan9/profile.c b/sys/src/ape/lib/ap/plan9/profile.c
index a69e65f2b..969a74076 100644
--- a/sys/src/ape/lib/ap/plan9/profile.c
+++ b/sys/src/ape/lib/ap/plan9/profile.c
@@ -23,7 +23,8 @@ typedef unsigned long long uvlong;
 
 extern	void*	sbrk(ulong);
 extern	long	_callpc(void**);
-extern	long	_savearg(void);
+extern	void*	_savearg(void);
+extern	void*	_saveret(void);
 extern	void	_cycles(uvlong*);	/* 64-bit value of the cycle counter if there is one, 0 if there isn't */
 
 static ulong	khz;
@@ -43,20 +44,27 @@ struct	Plink
 
 #pragma profile off
 
-ulong
+static void*
+_restore(void*, void *ret)
+{
+	return ret;
+}
+
+void*
 _profin(void)
 {
 	void *dummy;
 	long pc;
 	Plink *pp, *p;
-	ulong arg;
+	void *ret, *arg;
 	vlong t;
 
+	ret = _saveret();
 	arg = _savearg();
 	pc = _callpc(&dummy);
 	pp = _tos->prof.pp;
 	if(pp == 0 || (_tos->prof.pid && _tos->pid != _tos->prof.pid))
-		return arg;
+		return _restore(arg, ret);
 
 	for(p=pp->down; p; p=p->link)
 		if(p->pc == pc)
@@ -65,7 +73,7 @@ _profin(void)
 	if(p >= _tos->prof.last){
 		_tos->prof.pp = 0;
 		perr++;
-		return arg;
+		return _restore(arg, ret);
 	}
 	_tos->prof.next = p;
 	p->link = pp->down;
@@ -96,16 +104,17 @@ out:
 		p->time = p->time - _tos->clock;
 		break;
 	}
-	return arg;		/* disgusting linkage */
+	return _restore(arg, ret);
 }
 
-ulong
+void*
 _profout(void)
 {
 	Plink *p;
-	ulong arg;
+	void *ret, *arg;
 	vlong t;
 
+	ret = _saveret();
 	arg = _savearg();
 	p = _tos->prof.pp;
 	if (p == NULL || (_tos->prof.pid != 0 && _tos->pid != _tos->prof.pid))
@@ -127,7 +136,7 @@ _profout(void)
 		break;
 	}
 	_tos->prof.pp = p->old;
-	return arg;
+	return _restore(arg, ret);
 }
 
 /* stdio may not be ready for us yet */