cmd/ld: fix gcdata and gcbss symbols

These two symbols don't show up in the Go symbol table
since they're defined in dodata which is called sometime
after symtab. They do, however, show up in the ELF symbol
table.

This regression was introduced in changeset 01c40d533367.

Also, remove the corresponding strings from the ELF strtab
section now that they're unused.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/8650043

src/cmd/ld/data.c

@@ -1047,13 +1047,8 @@ dodata(void)
 		Bprint(&bso, "%5.2f dodata\n", cputime());
 	Bflush(&bso);
 
-	// define garbage collection symbols
 	gcdata1 = lookup("gcdata", 0);
-	gcdata1->type = STYPE;
-	gcdata1->reachable = 1;
 	gcbss1 = lookup("gcbss", 0);
-	gcbss1->type = STYPE;
-	gcbss1->reachable = 1;
 
 	// size of .data and .bss section. the zero value is later replaced by the actual size of the section.
 	adduintxx(gcdata1, 0, PtrSize);
@@ -1477,11 +1472,11 @@ address(void)
 	}
 
 	sym = lookup("gcdata", 0);
-	xdefine("egcdata", STYPE, symaddr(sym) + sym->size);
+	xdefine("egcdata", SRODATA, symaddr(sym) + sym->size);
 	lookup("egcdata", 0)->sect = sym->sect;
 
 	sym = lookup("gcbss", 0);
-	xdefine("egcbss", STYPE, symaddr(sym) + sym->size);
+	xdefine("egcbss", SRODATA, symaddr(sym) + sym->size);
 	lookup("egcbss", 0)->sect = sym->sect;
 
 	xdefine("symtab", SRODATA, symtab->vaddr);

src/cmd/ld/elf.c

@@ -905,8 +905,6 @@ doelf(void)
 	addstring(shstrtab, ".typelink");
 	if(flag_shared)
 		addstring(shstrtab, ".data.rel.ro");
-	addstring(shstrtab, ".gcdata");
-	addstring(shstrtab, ".gcbss");
 	addstring(shstrtab, ".gosymtab");
 	addstring(shstrtab, ".gopclntab");
 	
@@ -918,8 +916,6 @@ doelf(void)
 			addstring(shstrtab, ".rela.text");
 			addstring(shstrtab, ".rela.rodata");
 			addstring(shstrtab, ".rela.typelink");
-			addstring(shstrtab, ".rela.gcdata");
-			addstring(shstrtab, ".rela.gcbss");
 			addstring(shstrtab, ".rela.gosymtab");
 			addstring(shstrtab, ".rela.gopclntab");
 			addstring(shstrtab, ".rela.noptrdata");
@@ -928,8 +924,6 @@ doelf(void)
 			addstring(shstrtab, ".rel.text");
 			addstring(shstrtab, ".rel.rodata");
 			addstring(shstrtab, ".rel.typelink");
-			addstring(shstrtab, ".rel.gcdata");
-			addstring(shstrtab, ".rel.gcbss");
 			addstring(shstrtab, ".rel.gosymtab");
 			addstring(shstrtab, ".rel.gopclntab");
 			addstring(shstrtab, ".rel.noptrdata");

src/cmd/ld/symtab.c

@@ -481,8 +481,6 @@ symtab(void)
 		xdefine("datarelro", SDATARELRO, 0);
 		xdefine("edatarelro", SDATARELRO, 0);
 	}
-	xdefine("egcdata", STYPE, 0);
-	xdefine("egcbss", STYPE, 0);
 	xdefine("noptrdata", SNOPTRDATA, 0);
 	xdefine("enoptrdata", SNOPTRDATA, 0);
 	xdefine("data", SDATA, 0);
@@ -495,6 +493,19 @@ symtab(void)
 	xdefine("epclntab", SRODATA, 0);
 	xdefine("esymtab", SRODATA, 0);
 
+	// garbage collection symbols
+	s = lookup("gcdata", 0);
+	s->type = SRODATA;
+	s->size = 0;
+	s->reachable = 1;
+	xdefine("egcdata", SRODATA, 0);
+
+	s = lookup("gcbss", 0);
+	s->type = SRODATA;
+	s->size = 0;
+	s->reachable = 1;
+	xdefine("egcbss", SRODATA, 0);
+
 	// pseudo-symbols to mark locations of type, string, and go string data.
 	s = lookup("type.*", 0);
 	s->type = STYPE;