cmd/ld: add a text generation pass

This will be used by ppc64 to add call stubs to the .text section.
ARM needs a similar pass to generate veneers for arm->thumb
transitions.

Change-Id: Iaee74036e60643a56fab15b564718f359c5910eb
Reviewed-on: https://go-review.googlesource.com/2004
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/5l/asm.c

@@ -69,6 +69,11 @@ static void	addpltsym(Link*, LSym*);
 static void	addgotsym(Link*, LSym*);
 static void	addgotsyminternal(Link*, LSym*);
 
+void
+gentext(void)
+{
+}
+
 // Preserve highest 8 bits of a, and do addition to lower 24-bit
 // of a and b; used to adjust ARM branch intruction's target
 static int32

src/cmd/6l/asm.c

@@ -73,6 +73,11 @@ int nelfsym = 1;
 static void addpltsym(LSym*);
 static void addgotsym(LSym*);
 
+void
+gentext(void)
+{
+}
+
 void
 adddynrela(LSym *rela, LSym *s, Reloc *r)
 {

src/cmd/8l/asm.c

@@ -69,6 +69,11 @@ int	nelfsym = 1;
 static void	addpltsym(Link*, LSym*);
 static void	addgotsym(Link*, LSym*);
 
+void
+gentext(void)
+{
+}
+
 void
 adddynrela(LSym *rela, LSym *s, Reloc *r)
 {

src/cmd/9l/asm.c

@@ -65,6 +65,11 @@ needlib(char *name)
 
 int	nelfsym = 1;
 
+void
+gentext(void)
+{
+}
+
 void
 adddynrela(LSym *rel, LSym *s, Reloc *r)
 {

src/cmd/ld/lib.h

@@ -227,6 +227,7 @@ vlong	entryvalue(void);
 void	errorexit(void);
 void	follow(void);
 void	genasmsym(void (*put)(LSym*, char*, int, vlong, vlong, int, LSym*));
+void	gentext(void);
 void	growdatsize(vlong *datsizep, LSym *s);
 char*	headstr(int v);
 int	headtype(char *name);

src/cmd/ld/pobj.c

@@ -184,6 +184,7 @@ main(int argc, char *argv[])
 	if(HEADTYPE == Hwindows)
 		dope();
 	addexport();
+	gentext();		// trampolines, call stubs, etc.
 	textaddress();
 	pclntab();
 	symtab();