8l, runtime: place G and M pointers relative to _tos on Plan 9, instead of hardcoded values for USTKTOP.

This should allow executing both on native Plan 9 and inside 9vx.

R=rsc
CC=golang-dev
https://golang.org/cl/3993044

src/cmd/8l/obj.c

@@ -188,6 +188,7 @@ main(int argc, char *argv[])
 			INITRND = 0;
 		break;
 	case 2:	/* plan 9 */
+		tlsoffset = -8;
 		HEADR = 32L;
 		if(INITTEXT == -1)
 			INITTEXT = 4096+32;

src/cmd/8l/pass.c

@@ -250,6 +250,7 @@ patch(void)
 	Prog *p, *q;
 	Sym *s;
 	int32 vexit;
+	Sym *plan9_tos;
 
 	if(debug['v'])
 		Bprint(&bso, "%5.2f mkfwd\n", cputime());
@@ -260,6 +261,10 @@ patch(void)
 	Bflush(&bso);
 	s = lookup("exit", 0);
 	vexit = s->value;
+	
+	if(HEADTYPE == 2)
+		plan9_tos = lookup("_tos", 0);
+	
 	for(cursym = textp; cursym != nil; cursym = cursym->next) {
 		for(p = cursym->text; p != P; p = p->link) {
 			if(HEADTYPE == 10) {	// Windows
@@ -303,9 +308,15 @@ patch(void)
 			if(HEADTYPE == 2) {	// Plan 9
 				if(p->from.type == D_INDIR+D_GS
 				&& p->to.type >= D_AX && p->to.type <= D_DI) {
+					q = appendp(p);
+					q->from = p->from;
+					q->from.type = D_INDIR + p->to.type;
+					q->to = p->to;
+					q->as = p->as;
 					p->as = AMOVL;
-					p->from.type = D_ADDR+D_STATIC;
+					p->from.type = D_EXTERN;
-					p->from.offset += 0xdfffefc0;
+					p->from.sym = plan9_tos;
+					p->from.offset = 0;
 				}
 			}
 			if(p->as == ACALL || (p->as == AJMP && p->to.type != D_BRANCH)) {
@@ -389,6 +400,7 @@ dostkoff(void)
 	int a;
 	Prog *pmorestack;
 	Sym *symmorestack;
+	Sym *plan9_tos;
 
 	pmorestack = P;
 	symmorestack = lookup("runtime.morestack", 0);
@@ -400,6 +412,9 @@ dostkoff(void)
 		symmorestack->text->from.scale |= NOSPLIT;
 	}
 	
+	if(HEADTYPE == 2)	
+		plan9_tos = lookup("_tos", 0);
+
 	for(cursym = textp; cursym != nil; cursym = cursym->next) {
 		if(cursym->text == nil || cursym->text->link == nil)
 			continue;
@@ -443,8 +458,14 @@ dostkoff(void)
 			
 			case 2:	// Plan 9
 				p->as = AMOVL;
-				p->from.type = D_ADDR+D_STATIC;
+				p->from.type = D_EXTERN;
-				p->from.offset = 0xdfffefc0;
+				p->from.sym = plan9_tos;
+				p->to.type = D_CX;
+				
+				p = appendp(p);
+				p->as = AMOVL;
+				p->from.type = D_INDIR+D_CX;
+				p->from.offset = tlsoffset + 0;
 				p->to.type = D_CX;				
 				break;
 			

src/pkg/runtime/mkasmh.sh

@@ -25,9 +25,9 @@ case "$GOARCH" in
 		echo '#define	m(r)	4(r)'
 		;;
 	plan9)
-		echo '#define	get_tls(r)'
+		echo '#define	get_tls(r)	MOVL _tos(SB), r '
-		echo '#define	g(r)	0xdfffefc0'
+		echo '#define	g(r)	-8(r)'
-		echo '#define	m(r)	0xdfffefc4'
+		echo '#define	m(r)	-4(r)'
 		;;
 	linux)
 		# On Linux systems, what we call 0(GS) and 4(GS) for g and m

src/pkg/runtime/plan9/386/defs.h

@@ -1 +1,2 @@
 // nothing to see here
+#define tos_pid 48

src/pkg/runtime/plan9/386/sys.s

@@ -58,7 +58,8 @@ TEXT runtime·rfork(SB),7,$0
 	MOVL	BX, m(AX)
 
 	// Initialize AX from _tos->pid
-	MOVL	0xdfffeff8, AX
+	MOVL	_tos(SB), AX
+	MOVL	tos_pid(AX), AX
 	MOVL	AX, m_procid(BX)	// save pid as m->procid
 	
 	CALL	runtime·stackcheck(SB)	// smashes AX, CX

src/pkg/runtime/plan9/mem.c

@@ -10,40 +10,47 @@ static byte *bloc = { end };
 
 enum
 {
-	Round = 7
+	Round = 4095
 };
 
 void*
-runtime·SysAlloc(uintptr ask)
+runtime·SysAlloc(uintptr nbytes)
 {
 	uintptr bl;
 	
 	// Plan 9 sbrk from /sys/src/libc/9sys/sbrk.c
 	bl = ((uintptr)bloc + Round) & ~Round;
-	if(runtime·brk_((void*)(bl + ask)) < 0)
+	if(runtime·brk_((void*)(bl + nbytes)) < 0)
 		return (void*)-1;
-	bloc = (byte*)bl + ask;
+	bloc = (byte*)bl + nbytes;
 	return (void*)bl;
 }
 
 void
-runtime·SysFree(void *v, uintptr n)
+runtime·SysFree(void *v, uintptr nbytes)
 {
 	// from tiny/mem.c
 	// Push pointer back if this is a free
 	// of the most recent SysAlloc.
-	n += (n + Round) & ~Round;
+	nbytes += (nbytes + Round) & ~Round;
-	if(bloc == (byte*)v+n)
+	if(bloc == (byte*)v+nbytes)
-		bloc -= n;	
+		bloc -= nbytes;	
 }
 
 void
-runtime·SysUnused(void *v, uintptr n)
+runtime·SysUnused(void *v, uintptr nbytes)
 {
-	USED(v, n);
+	USED(v, nbytes);
 }
 
 void
-runtime·SysMemInit(void)
+runtime·SysMap(void *v, uintptr nbytes)
 {
+	USED(v, nbytes);
+}
+
+void*
+runtime·SysReserve(void *v, uintptr nbytes)
+{
+	return runtime·SysAlloc(nbytes);
 }