Unbreak sparc64 after r276630 by calling __sparc_sigtramp_setup signal

trampoline as part of the MD __sys_sigaction again.

Submitted by:	kib (initial versions)
MFC after:	3 days

lib/libc/sparc64/sys/Makefile.inc

@@ -12,7 +12,7 @@ SRCS+=	__sparc_sigtramp_setup.c \
 
 CFLAGS+= -I${LIBC_SRCTOP}/sparc64/fpu
 
-MDASM+=	brk.S cerror.S exect.S pipe.S ptrace.S sbrk.S setlogin.S sigaction.S
+MDASM+=	brk.S cerror.S exect.S pipe.S ptrace.S sbrk.S setlogin.S sigaction1.S
 
 # Don't generate default code for these syscalls:
 NOASM=	break.o exit.o getlogin.o openbsd_poll.o sstk.o yield.o

lib/libc/sparc64/sys/sigaction1.S

@@ -29,7 +29,8 @@ __FBSDID("$FreeBSD$");
 
 #include "SYS.h"
 
-_SYSENTRY(sigaction)
+	WEAK_REFERENCE(__sys_sigaction, _sigaction)
+ENTRY(__sys_sigaction)
 	PIC_PROLOGUE(%o3, %o4)
 	SET(sigcode_installed, %o4, %o3)
 	lduw	[%o3], %o4
@@ -44,6 +45,6 @@ _SYSENTRY(sigaction)
 1:	_SYSCALL(sigaction)
 	retl
 	 nop
-_SYSEND(sigaction)
+END(__sys_sigaction)
 
 	.comm	sigcode_installed, 4, 4

lib/libc/sys/Makefile.inc

@@ -65,7 +65,6 @@ INTERPOSED = \
 	sendmsg \
 	sendto \
 	setcontext \
-	sigaction \
 	sigprocmask \
 	sigsuspend \
 	sigtimedwait \
@@ -76,6 +75,13 @@ INTERPOSED = \
 	write \
 	writev
 
+.if ${MACHINE_CPUARCH} == "sparc64"
+SRCS+=	sigaction.c
+NOASM+=	sigaction.o
+.else
+INTERPOSED+= sigaction
+.endif
+
 SRCS+=	${INTERPOSED:S/$/.c/}
 NOASM+=	${INTERPOSED:S/$/.o/}
 PSEUDO+=	${INTERPOSED:C/^.*$/_&.o/}

sys/sparc64/include/asm.h

@@ -102,6 +102,16 @@ CNAME(x):
 #define	ENTRY(x)	_ENTRY(x)
 #define	END(x)		.size x, . - x
 
+/*
+ * WEAK_REFERENCE(): create a weak reference alias from sym.
+ * The macro is not a general asm macro that takes arbitrary names,
+ * but one that takes only C names.  It does the non-null name
+ * translation inside the macro.
+ */
+#define	WEAK_REFERENCE(sym, alias) \
+	.weak	CNAME(alias); \
+	.equ	CNAME(alias),CNAME(sym)
+
 /*
  * Kernel RCS ID tag and copyright macros
  */