ld: modify macho linkedit segment to enable OS X code signing

Move string table to the end of the __LINKEDIT segment.

This change allows Apple's codesign(1) utility to successfully sign
Go binaries, as long as they don't contain DWARF data (-w flag to
8l/6l).  This is because codesign(1) expects the string table to be
the last part of the file.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5271050

src/cmd/ld/macho.c

@@ -413,9 +413,9 @@ asmbmacho(void)
 
 		// must match domacholink below
 		s1 = lookup(".dynsym", 0);
-		s2 = lookup(".dynstr", 0);
-		s3 = lookup(".linkedit.plt", 0);
-		s4 = lookup(".linkedit.got", 0);
+		s2 = lookup(".linkedit.plt", 0);
+		s3 = lookup(".linkedit.got", 0);
+		s4 = lookup(".dynstr", 0);
 
 		ms = newMachoSeg("__LINKEDIT", 0);
 		ms->vaddr = va+v+rnd(segdata.len, INITRND);
@@ -428,8 +428,8 @@ asmbmacho(void)
 		ml = newMachoLoad(2, 4);	/* LC_SYMTAB */
 		ml->data[0] = linkoff;	/* symoff */
 		ml->data[1] = s1->size / (macho64 ? 16 : 12);	/* nsyms */
-		ml->data[2] = linkoff + s1->size;	/* stroff */
-		ml->data[3] = s2->size;	/* strsize */
+		ml->data[2] = linkoff + s1->size + s2->size + s3->size;	/* stroff */
+		ml->data[3] = s4->size;	/* strsize */
 
 		ml = newMachoLoad(11, 18);	/* LC_DYSYMTAB */
 		ml->data[0] = 0;	/* ilocalsym */
@@ -444,8 +444,8 @@ asmbmacho(void)
 		ml->data[9] = 0;	/* nmodtab */
 		ml->data[10] = 0;	/* extrefsymoff */
 		ml->data[11] = 0;	/* nextrefsyms */
-		ml->data[12] = linkoff + s1->size + s2->size;	/* indirectsymoff */
-		ml->data[13] = (s3->size + s4->size) / 4;	/* nindirectsyms */
+		ml->data[12] = linkoff + s1->size;	/* indirectsymoff */
+		ml->data[13] = (s2->size + s3->size) / 4;	/* nindirectsyms */
 		ml->data[14] = 0;	/* extreloff */
 		ml->data[15] = 0;	/* nextrel */
 		ml->data[16] = 0;	/* locreloff */
@@ -495,12 +495,12 @@ domacholink(void)
 	// write data that will be linkedit section
 	s1 = lookup(".dynsym", 0);
 	relocsym(s1);
-	s2 = lookup(".dynstr", 0);
-	s3 = lookup(".linkedit.plt", 0);
-	s4 = lookup(".linkedit.got", 0);
+	s2 = lookup(".linkedit.plt", 0);
+	s3 = lookup(".linkedit.got", 0);
+	s4 = lookup(".dynstr", 0);
 
-	while(s2->size%4)
-		adduint8(s2, 0);
+	while(s4->size%4)
+		adduint8(s4, 0);
 	
 	size = s1->size + s2->size + s3->size + s4->size;