libthread: use consistent stack calculation code in makecontext

Also reduce duplication: makecontext is per-arch not per-os-arch.

May fix #353.

src/libthread/386-ucontext.c

@@ -5,7 +5,7 @@ makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
 {
 	int *sp;
 
-	sp = (int*)ucp->uc_stack.ss_sp+ucp->uc_stack.ss_size/4;
+	sp = USPALIGN(ucp, 4);
 	sp -= argc;
 	memmove(sp, &argc+1, argc*sizeof(int));
 	*--sp = 0;		/* return address */

src/libthread/COPYRIGHT

@@ -45,9 +45,9 @@ Contains parts of an earlier library that has:
 
 ===
 
-The above notices do *NOT* apply to Linux-sparc64-context.S 
-or to Linux-sparc64-swapcontext.c.  Those are functions from 
+The above notices do *NOT* apply to Linux-sparc64-context.S
+or to sparc64-ucontext.c.  Those are functions from
 the GNU C library and are provided for systems that use the GNU C
-library but somehow are missing those functions.  They are 
+library but somehow are missing those functions.  They are
 distributed under the Lesser GPL; see COPYING.SPARC64-CONTEXT.
 

src/libthread/Darwin-x86_64-swapcontext.c

@@ -1,38 +0,0 @@
-#include "threadimpl.h"
-
-void
-makecontext(ucontext_t *uc, void (*fn)(void), int argc, ...)
-{
-	uintptr *sp;
-	va_list arg;
-
-//fprint(2, "makecontext %d\n", argc);
-	if(argc != 2)
-		sysfatal("libthread: makecontext misused");
-	va_start(arg, argc);
-	uc->mc.di = va_arg(arg, uint);
-	uc->mc.si = va_arg(arg, uint);
-//fprint(2, "%ux %ux\n", uc->mc.di, uc->mc.si);
-	va_end(arg);
-
-	sp = (uintptr*)((char*)uc->uc_stack.ss_sp+uc->uc_stack.ss_size);
-	/*
-	 * Stack pointer at call instruction (before return address
-	 * gets pushed) must be 16-byte aligned.
-	 */
-	if((uintptr)sp%4)
-		abort();
-	while((uintptr)sp%16 != 0)
-		sp--;
-	*--sp = 0;  // fn's return address
-	*--sp = (uintptr)fn;  // return address of setcontext
-	uc->mc.sp = (uintptr)sp;
-}
-
-int
-swapcontext(ucontext_t *oucp, ucontext_t *ucp)
-{
-	if(getcontext(oucp) == 0)
-		setcontext(ucp);
-	return 0;
-}

src/libthread/NetBSD.c

@@ -435,28 +435,3 @@ _threadpexit(void)
 {
 	_exit(0);
 }
-
-#ifdef __arm__
-void
-makecontext(ucontext_t *uc, void (*fn)(void), int argc, ...)
-{
-	int i, *sp;
-	va_list arg;
-
-	sp = (int*)uc->uc_stack.ss_sp+uc->uc_stack.ss_size/4;
-	va_start(arg, argc);
-	for(i=0; i<4 && i<argc; i++)
-		uc->uc_mcontext.gregs[i] = va_arg(arg, uint);
-	va_end(arg);
-	uc->uc_mcontext.gregs[13] = (uint)sp;
-	uc->uc_mcontext.gregs[14] = (uint)fn;
-}
-
-int
-swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
-{
-	if(getcontext(oucp) == 0)
-		setcontext(ucp);
-	return 0;
-}
-#endif

src/libthread/arm-ucontext.c

@@ -6,7 +6,7 @@ makecontext(ucontext_t *uc, void (*fn)(void), int argc, ...)
 	int i, *sp;
 	va_list arg;
 
-	sp = (int*)uc->uc_stack.ss_sp+uc->uc_stack.ss_size/4;
+	sp = USPALIGN(uc, 4);
 	va_start(arg, argc);
 	for(i=0; i<4 && i<argc; i++)
 		(&uc->uc_mcontext.arm_r0)[i] = va_arg(arg, uint);

src/libthread/mkfile

@@ -37,8 +37,8 @@ OpenBSD-%-asm.$O:	OpenBSD-%-asm.S
 Linux-sparc64-context.$O: Linux-sparc64-context.S
 	$CC -m64 -mcpu=v9 $CFLAGS Linux-sparc64-context.S
 
-Linux-sparc64-swapcontext.$O: Linux-sparc64-swapcontext.c
-	$CC -m64 -mcpu=v9 $CFLAGS Linux-sparc64-swapcontext.c
+sparc64-ucontext.$O: sparc64-ucontext.c
+	$CC -m64 -mcpu=v9 $CFLAGS sparc64-ucontext.c
 
 test:V: tprimes tspawn
 	primes 1 10007 >p1.txt

src/libthread/power-ucontext.c

@@ -6,12 +6,14 @@ makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
 	ulong *sp, *tos;
 	va_list arg;
 
-	tos = (ulong*)ucp->uc_stack.ss_sp+ucp->uc_stack.ss_size/sizeof(ulong);
-	sp = (ulong*)((ulong)(tos-16) & ~15);
+	if(argc != 2)
+		sysfatal("libthread: makecontext misused");
+	sp = USPALIGN(ucp, 16);
 	ucp->mc.pc = (long)func;
 	ucp->mc.sp = (long)sp;
 	va_start(arg, argc);
 	ucp->mc.r3 = va_arg(arg, long);
+	ucp->mc.r4 = va_arg(arg, long);
 	va_end(arg);
 }
 

src/libthread/sysofiles.sh

@@ -7,24 +7,37 @@ NetBSD)
 	echo ${SYSNAME}-${OBJTYPE}-asm.o $SYSNAME.o stkmalloc.o
 	;;
 OpenBSD)
-	echo ${SYSNAME}-${OBJTYPE}-asm.o ${SYSNAME}-${OBJTYPE}.o pthread.o stkmmap.o
+	echo ${SYSNAME}-${OBJTYPE}-asm.o pthread.o stkmmap.o
 	;;
 *)
 	echo pthread.o stkmalloc.o
 esac
 
+# Various libc don't supply swapcontext, makecontext, so we do.
 case "$OBJTYPE-$SYSNAME" in
-sparc64-Linux)
-	# Debian glibc doesn't supply swapcontext, makecontext
-	# so we supply our own copy from the latest glibc.
-	echo Linux-sparc64-context.o Linux-sparc64-swapcontext.o
+386-OpenBSD)
+	echo 386-ucontext.o
 	;;
 arm-Linux)
-	# ARM doesn't supply them either.
-	echo Linux-arm-context.o Linux-arm-swapcontext.o
+	echo arm-ucontext.o
+	echo Linux-arm-context.o # setcontext, getcontext
+	;;
+arm-NetBSD)
+	echo arm-ucontext.o
+	;;
+power-OpenBSD)
+	echo power-ucontext.o
+	;;
+sparc64-Linux)
+	echo sparc64-ucontext.o
+	echo Linux-sparc64-swapcontext.o # setcontext, getcontext
 	;;
 x86_64-Darwin)
-	echo Darwin-x86_64-asm.o Darwin-x86_64-swapcontext.o
+	echo x86_64-ucontext.o
+	echo Darwin-x86_64-asm.o # setcontext, getcontext
+	;;
+x86_64-OpenBSD)
+	echo x86_64-ucontext.o
 	;;
 esac
 

src/libthread/threadimpl.h

@@ -188,3 +188,6 @@ extern void _threadpexit(void);
 extern void _threaddaemonize(void);
 extern void *_threadstkalloc(int);
 extern void _threadstkfree(void*, int);
+
+#define USPALIGN(ucp, align) \
+	(void*)((((uintptr)(ucp)->uc_stack.ss_sp+(ucp)->uc_stack.ss_size)-(align))&~((align)-1))

src/libthread/x86_64-ucontext.c

@@ -6,16 +6,14 @@ makecontext(ucontext_t *uc, void (*fn)(void), int argc, ...)
 	uintptr *sp;
 	va_list arg;
 
-//fprint(2, "makecontext %d\n", argc);
 	if(argc != 2)
 		sysfatal("libthread: makecontext misused");
 	va_start(arg, argc);
 	uc->mc.di = va_arg(arg, uint);
 	uc->mc.si = va_arg(arg, uint);
-//fprint(2, "%ux %ux\n", uc->mc.di, uc->mc.si);
 	va_end(arg);
 
-	sp = (uintptr*)((char*)uc->uc_stack.ss_sp+uc->uc_stack.ss_size);
+	sp = USPALIGN(uc, 16);
 	*--sp = 0;  // fn's return address
 	*--sp = (uintptr)fn;  // return address of setcontext
 	uc->mc.sp = (uintptr)sp;