5l/6l/8l: use enums for header type and symbolic strings for -H option values

Thanks to rsc for the suggestion.

R=r
CC=golang-dev
https://golang.org/cl/4174060

15 files changed, 248 insertions, 187 deletions

diff --git a/src/cmd/5l/asm.c b/src/cmd/5l/asm.c
index 7163997c0f..adc4ae7478 100644
--- a/src/cmd/5l/asm.c
+++ b/src/cmd/5l/asm.c
@@ -331,21 +331,21 @@ asmb(void)
 			Bprint(&bso, "%5.2f sym\n", cputime());
 		Bflush(&bso);
 		switch(HEADTYPE) {
-		case 0:
-		case 1:
-		case 4:
-		case 5:
+		case Hnoheader:
+		case Hrisc:
+		case Hixp1200:
+		case Hipaq:
 			debug['s'] = 1;
 			break;
-		case 2:
+		case Hplan9x32:
 			OFFSET = HEADR+textsize+segdata.filelen;
 			seek(cout, OFFSET, 0);
 			break;
-		case 3:
+		case Hnetbsd:
 			OFFSET += rnd(segdata.filelen, 4096);
 			seek(cout, OFFSET, 0);
 			break;
-		case 6:
+		case Hlinux:
 			OFFSET += segdata.filelen;
 			seek(cout, rnd(OFFSET, INITRND), 0);
 			break;
@@ -362,9 +362,9 @@ asmb(void)
 	OFFSET = 0;
 	seek(cout, OFFSET, 0);
 	switch(HEADTYPE) {
-	case 0:	/* no header */
+	case Hnoheader:	/* no header */
 		break;
-	case 1:	/* aif for risc os */
+	case Hrisc:	/* aif for risc os */
 		lputl(0xe1a00000);		/* NOP - decompress code */
 		lputl(0xe1a00000);		/* NOP - relocation code */
 		lputl(0xeb000000 + 12);		/* BL - zero init code */
@@ -394,7 +394,7 @@ asmb(void)
 			lputl(0xe1a00000);	/* NOP - zero init code */
 		lputl(0xe1a0f00e);		/* B (R14) - zero init return */
 		break;
-	case 2:	/* plan 9 */
+	case Hplan9x32:	/* plan 9 */
 		lput(0x647);			/* magic */
 		lput(textsize);			/* sizes */
 		lput(segdata.filelen);
@@ -404,7 +404,7 @@ asmb(void)
 		lput(0L);
 		lput(lcsize);
 		break;
-	case 3:	/* boot for NetBSD */
+	case Hnetbsd:	/* boot for NetBSD */
 		lput((143<<16)|0413);		/* magic */
 		lputl(rnd(HEADR+textsize, 4096));
 		lputl(rnd(segdata.filelen, 4096));
@@ -414,15 +414,15 @@ asmb(void)
 		lputl(0L);
 		lputl(0L);
 		break;
-	case 4: /* boot for IXP1200 */
+	case Hixp1200: /* boot for IXP1200 */
 		break;
-	case 5: /* boot for ipaq */
+	case Hipaq: /* boot for ipaq */
 		lputl(0xe3300000);		/* nop */
 		lputl(0xe3300000);		/* nop */
 		lputl(0xe3300000);		/* nop */
 		lputl(0xe3300000);		/* nop */
 		break;
-	case 6:
+	case Hlinux:
 		/* elf arm */
 		eh = getElfEhdr();
 		fo = HEADR;
diff --git a/src/cmd/5l/doc.go b/src/cmd/5l/doc.go
index d266b92331..aa7ccebfc9 100644
--- a/src/cmd/5l/doc.go
+++ b/src/cmd/5l/doc.go
@@ -23,6 +23,8 @@ Options new in this version:
 -F
 	Force use of software floating point.
 	Also implied by setting GOARM=5 in the environment.
+-Hlinux
+	Write Linux ELF binaries (default when $GOOS is linux)
 -I interpreter
 	Set the ELF dynamic linker to use.
 -L dir1 -L dir2
diff --git a/src/cmd/5l/obj.c b/src/cmd/5l/obj.c
index b976e300bc..c929b3291e 100644
--- a/src/cmd/5l/obj.c
+++ b/src/cmd/5l/obj.c
@@ -43,12 +43,24 @@
 char	*noname		= "<none>";
 char	*thestring 	= "arm";
 
+Header headers[] = {
+   "noheader", Hnoheader,
+   "risc", Hrisc,
+   "plan9", Hplan9x32,
+   "netbsd", Hnetbsd,
+   "ixp1200", Hixp1200,
+   "ipaq", Hipaq,
+   "linux", Hlinux,
+   0, 0
+};
+
 /*
- *	-H1 -T0x10005000 -R4		is aif for risc os
- *	-H2 -T4128 -R4096		is plan9 format
- *	-H3 -T0xF0000020 -R4		is NetBSD format
- *	-H4				is IXP1200 (raw)
- *	-H5 -T0xC0008010 -R1024		is ipaq
+ *	-Hrisc -T0x10005000 -R4		is aif for risc os
+ *	-Hplan9 -T4128 -R4096		is plan9 format
+ *	-Hnetbsd -T0xF0000020 -R4	is NetBSD format
+ *	-Hixp1200			is IXP1200 (raw)
+ *	-Hipaq -T0xC0008010 -R1024	is ipaq
+ *	-Hlinux -Tx -Rx			is linux elf
  */
 
 static char*
@@ -118,7 +130,7 @@ main(int argc, char *argv[])
 		rpath = EARGF(usage());
 		break;
 	case 'H':
-		HEADTYPE = atolwhex(EARGF(usage()));
+		HEADTYPE = headtype(EARGF(usage()));
 		/* do something about setting INITTEXT */
 		break;
 	case 'V':
@@ -137,18 +149,18 @@ main(int argc, char *argv[])
 		debug[DEFAULT] = 1;
 	if(HEADTYPE == -1) {
 		if(debug['U'])
-			HEADTYPE = 0;
+			HEADTYPE = Hnoheader;
 		if(debug['B'])
-			HEADTYPE = 1;
+			HEADTYPE = Hrisc;
 		if(debug['9'])
-			HEADTYPE = 2;
-		HEADTYPE = 6;
+			HEADTYPE = Hplan9x32;
+		HEADTYPE = Hlinux;
 	}
 	switch(HEADTYPE) {
 	default:
 		diag("unknown -H option");
 		errorexit();
-	case 0:	/* no header */
+	case Hnoheader:	/* no header */
 		HEADR = 0L;
 		if(INITTEXT == -1)
 			INITTEXT = 0;
@@ -157,7 +169,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4;
 		break;
-	case 1:	/* aif for risc os */
+	case Hrisc:	/* aif for risc os */
 		HEADR = 128L;
 		if(INITTEXT == -1)
 			INITTEXT = 0x10005000 + HEADR;
@@ -166,7 +178,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4;
 		break;
-	case 2:	/* plan 9 */
+	case Hplan9x32:	/* plan 9 */
 		HEADR = 32L;
 		if(INITTEXT == -1)
 			INITTEXT = 4128;
@@ -175,7 +187,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case 3:	/* boot for NetBSD */
+	case Hnetbsd:	/* boot for NetBSD */
 		HEADR = 32L;
 		if(INITTEXT == -1)
 			INITTEXT = 0xF0000020L;
@@ -184,7 +196,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case 4: /* boot for IXP1200 */
+	case Hixp1200: /* boot for IXP1200 */
 		HEADR = 0L;
 		if(INITTEXT == -1)
 			INITTEXT = 0x0;
@@ -193,7 +205,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4;
 		break;
-	case 5: /* boot for ipaq */
+	case Hipaq: /* boot for ipaq */
 		HEADR = 16L;
 		if(INITTEXT == -1)
 			INITTEXT = 0xC0008010;
@@ -202,7 +214,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 1024;
 		break;
-	case 6:	/* arm elf */
+	case Hlinux:	/* arm elf */
 		debug['d'] = 1;	// no dynamic linking
 		elfinit();
 		HEADR = ELFRESERVE;
diff --git a/src/cmd/6l/asm.c b/src/cmd/6l/asm.c
index d179e77b1e..fb041d83a5 100644
--- a/src/cmd/6l/asm.c
+++ b/src/cmd/6l/asm.c
@@ -262,7 +262,7 @@ adddynrel(Sym *s, Reloc *r)
 			r->type = 256;	// ignore during relocsym
 			return;
 		}
-		if(HEADTYPE == 6 && s->size == PtrSize && r->off == 0) {
+		if(HEADTYPE == Hdarwin && s->size == PtrSize && r->off == 0) {
 			// Mach-O relocations are a royal pain to lay out.
 			// They use a compact stateful bytecode representation
 			// that is too much bother to deal with.
@@ -365,7 +365,7 @@ addpltsym(Sym *s)
 		adduint64(rela, 0);
 		
 		s->plt = plt->size - 16;
-	} else if(HEADTYPE == 6) {	// Mach-O
+	} else if(HEADTYPE == Hdarwin) {
 		// To do lazy symbol lookup right, we're supposed
 		// to tell the dynamic loader which library each 
 		// symbol comes from and format the link info
@@ -412,7 +412,7 @@ addgotsym(Sym *s)
 		addaddrplus(rela, got, s->got);
 		adduint64(rela, ELF64_R_INFO(s->dynid, R_X86_64_GLOB_DAT));
 		adduint64(rela, 0);
-	} else if(HEADTYPE == 6) {	// Mach-O
+	} else if(HEADTYPE == Hdarwin) {
 		adduint32(lookup(".linkedit.got", 0), s->dynid);
 	} else {
 		diag("addgotsym: unsupported binary format");
@@ -486,7 +486,7 @@ adddynsym(Sym *s)
 			elfwritedynent(lookup(".dynamic", 0), DT_NEEDED,
 				addstring(lookup(".dynstr", 0), s->dynimplib));
 		}
-	} else if(HEADTYPE == 6) {
+	} else if(HEADTYPE == Hdarwin) {
 		// Mach-o symbol nlist64
 		d = lookup(".dynsym", 0);
 		name = s->dynimpname;
@@ -539,7 +539,7 @@ adddynlib(char *lib)
 		if(s->size == 0)
 			addstring(s, "");
 		elfwritedynent(lookup(".dynamic", 0), DT_NEEDED, addstring(s, lib));
-	} else if(HEADTYPE == 6) {	// Mach-O
+	} else if(HEADTYPE == Hdarwin) {
 		machoadddynlib(lib);
 	} else {
 		diag("adddynlib: unsupported binary format");
@@ -551,7 +551,7 @@ doelf(void)
 {
 	Sym *s, *shstrtab, *dynstr;
 
-	if(HEADTYPE != 7 && HEADTYPE != 9)
+	if(HEADTYPE != Hlinux && HEADTYPE != Hfreebsd)
 		return;
 
 	/* predefine strings we need for section headers */
@@ -717,20 +717,20 @@ asmb(void)
 	datblk(segdata.vaddr, segdata.filelen);
 
 	machlink = 0;
-	if(HEADTYPE == 6)
+	if(HEADTYPE == Hdarwin)
 		machlink = domacholink();
 
 	switch(HEADTYPE) {
 	default:
 		diag("unknown header type %d", HEADTYPE);
-	case 2:
-	case 5:
+	case Hplan9x32:
+	case Helf:
 		break;
-	case 6:
+	case Hdarwin:
 		debug['8'] = 1;	/* 64-bit addresses */
 		break;
-	case 7:
-	case 9:
+	case Hlinux:
+	case Hfreebsd:
 		debug['8'] = 1;	/* 64-bit addresses */
 		/* index of elf text section; needed by asmelfsym, double-checked below */
 		/* !debug['d'] causes extra sections before the .text section */
@@ -738,7 +738,7 @@ asmb(void)
 		if(!debug['d'])
 			elftextsh += 10;
 		break;
-	case 10:
+	case Hwindows:
 		break;
 	}
 
@@ -752,20 +752,20 @@ asmb(void)
 		Bflush(&bso);
 		switch(HEADTYPE) {
 		default:
-		case 2:
-		case 5:
+		case Hplan9x32:
+		case Helf:
 			debug['s'] = 1;
 			symo = HEADR+segtext.len+segdata.filelen;
 			break;
-		case 6:
+		case Hdarwin:
 			symo = rnd(HEADR+segtext.len, INITRND)+rnd(segdata.filelen, INITRND)+machlink;
 			break;
-		case 7:
-		case 9:
+		case Hlinux:
+		case Hfreebsd:
 			symo = rnd(HEADR+segtext.len, INITRND)+segdata.filelen;
 			symo = rnd(symo, INITRND);
 			break;
-		case 10:
+		case Hwindows:
 			symo = rnd(HEADR+segtext.filelen, PEFILEALIGN)+segdata.filelen;
 			symo = rnd(symo, PEFILEALIGN);
 			break;
@@ -791,7 +791,7 @@ asmb(void)
 		lputl(symsize);
 		lputl(lcsize);
 		cflush();
-		if(HEADTYPE != 10 && !debug['s']) {
+		if(HEADTYPE != Hwindows && !debug['s']) {
 			elfsymo = symo+8+symsize+lcsize;
 			seek(cout, elfsymo, 0);
 			asmelfsym64();
@@ -813,7 +813,7 @@ asmb(void)
 	seek(cout, 0L, 0);
 	switch(HEADTYPE) {
 	default:
-	case 2:	/* plan9 */
+	case Hplan9x32:	/* plan9 */
 		magic = 4*26*26+7;
 		magic |= 0x00008000;		/* fat header */
 		lputb(magic);			/* magic */
@@ -827,7 +827,7 @@ asmb(void)
 		lputb(lcsize);			/* line offsets */
 		vputb(vl);			/* va of entry */
 		break;
-	case 3:	/* plan9 */
+	case Hplan9x64:	/* plan9 */
 		magic = 4*26*26+7;
 		lputb(magic);			/* magic */
 		lputb(segtext.filelen);		/* sizes */
@@ -838,11 +838,11 @@ asmb(void)
 		lputb(spsize);			/* sp offsets */
 		lputb(lcsize);			/* line offsets */
 		break;
-	case 6:
+	case Hdarwin:
 		asmbmacho();
 		break;
-	case 7:
-	case 9:
+	case Hlinux:
+	case Hfreebsd:
 		/* elf amd-64 */
 
 		eh = getElfEhdr();
@@ -871,10 +871,10 @@ asmb(void)
 			sh->addralign = 1;
 			if(interpreter == nil) {
 				switch(HEADTYPE) {
-				case 7:
+				case Hlinux:
 					interpreter = linuxdynld;
 					break;
-				case 9:
+				case Hfreebsd:
 					interpreter = freebsddynld;
 					break;
 				}
@@ -1032,7 +1032,7 @@ asmb(void)
 		eh->ident[EI_MAG1] = 'E';
 		eh->ident[EI_MAG2] = 'L';
 		eh->ident[EI_MAG3] = 'F';
-		if(HEADTYPE == 9)
+		if(HEADTYPE == Hfreebsd)
 			eh->ident[EI_OSABI] = 9;
 		eh->ident[EI_CLASS] = ELFCLASS64;
 		eh->ident[EI_DATA] = ELFDATA2LSB;
@@ -1055,7 +1055,7 @@ asmb(void)
 		if(a+elfwriteinterp() > ELFRESERVE)
 			diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE);
 		break;
-	case 10:
+	case Hwindows:
 		asmbpe();
 		break;
 	}
diff --git a/src/cmd/6l/doc.go b/src/cmd/6l/doc.go
index 97fa2cc5a2..cc7782cfeb 100644
--- a/src/cmd/6l/doc.go
+++ b/src/cmd/6l/doc.go
@@ -28,10 +28,14 @@ Options new in this version:
 -e
 	Emit an extra ELF-compatible symbol table useful with tools such as
 	nm, gdb, and oprofile. This option makes the binary file considerably larger.
--H6
+-Hdarwin
 	Write Apple Mach-O binaries (default when $GOOS is darwin)
--H7
+-Hlinux
 	Write Linux ELF binaries (default when $GOOS is linux)
+-Hfreebsd
+	Write FreeBSD ELF binaries (default when $GOOS is freebsd)
+-Hwindows
+	Write Windows PE32+ binaries (default when $GOOS is windows)
 -I interpreter
 	Set the ELF dynamic linker to use.
 -L dir1 -L dir2
diff --git a/src/cmd/6l/obj.c b/src/cmd/6l/obj.c
index 3dabb4c178..6ade3800a2 100644
--- a/src/cmd/6l/obj.c
+++ b/src/cmd/6l/obj.c
@@ -43,13 +43,25 @@ char	*noname		= "<none>";
 char*	thestring 	= "amd64";
 char*	paramspace	= "FP";
 
+Header headers[] = {
+   "plan9x32", Hplan9x32,
+   "plan9", Hplan9x64,
+   "elf", Helf,
+   "darwin", Hdarwin,
+   "linux", Hlinux,
+   "freebsd", Hfreebsd,
+   "windows", Hwindows,
+   0, 0
+};
+
 /*
- *	-H2 -T4136 -R4096		is plan9 64-bit format
- *	-H3 -T4128 -R4096		is plan9 32-bit format
- *	-H5 -T0x80110000 -R4096		is ELF32
- *	-H6 -Tx -Rx			is apple MH-exec
- *	-H7 -Tx -Rx			is linux elf-exec
- *      -H9 -Tx -Rx			is FreeBSD elf-exec
+ *	-Hplan9x32 -T4136 -R4096	is plan9 64-bit format
+ *	-Hplan9 -T4128 -R4096		is plan9 32-bit format
+ *	-Helf -T0x80110000 -R4096	is ELF32
+ *	-Hdarwin -Tx -Rx		is apple MH-exec
+ *	-Hlinux -Tx -Rx			is linux elf-exec
+ *	-Hfreebsd -Tx -Rx		is FreeBSD elf-exec
+ *	-Hwindows -Tx -Rx		is MS Windows PE32+
  *
  *	options used: 189BLQSWabcjlnpsvz
  */
@@ -93,7 +105,7 @@ main(int argc, char *argv[])
 		INITENTRY = EARGF(usage());
 		break;
 	case 'H':
-		HEADTYPE = atolwhex(EARGF(usage()));
+		HEADTYPE = headtype(EARGF(usage()));
 		break;
 	case 'I':
 		interpreter = EARGF(usage());
@@ -123,28 +135,14 @@ main(int argc, char *argv[])
 
 	libinit();
 
-	if(HEADTYPE == -1) {
-		HEADTYPE = 2;
-		if(strcmp(goos, "linux") == 0)
-			HEADTYPE = 7;
-		else
-		if(strcmp(goos, "darwin") == 0)
-			HEADTYPE = 6;
-		else
-		if(strcmp(goos, "freebsd") == 0)
-			HEADTYPE = 9;
-		else
-		if(strcmp(goos, "windows") == 0)
-			HEADTYPE = 10;
-		else
-			print("goos is not known: %s\n", goos);
-	}
+	if(HEADTYPE == -1)
+		HEADTYPE = headtype(goos);
 
 	switch(HEADTYPE) {
 	default:
 		diag("unknown -H option");
 		errorexit();
-	case 2:	/* plan 9 */
+	case Hplan9x32:	/* plan 9 */
 		HEADR = 32L+8L;
 		if(INITTEXT == -1)
 			INITTEXT = 4096+HEADR;
@@ -153,7 +151,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case 3:	/* plan 9 */
+	case Hplan9x64:	/* plan 9 */
 		HEADR = 32L;
 		if(INITTEXT == -1)
 			INITTEXT = 4096+32;
@@ -162,7 +160,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case 5:	/* elf32 executable */
+	case Helf:	/* elf32 executable */
 		HEADR = rnd(52L+3*32L, 16);
 		if(INITTEXT == -1)
 			INITTEXT = 0x80110000L;
@@ -171,7 +169,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case 6:	/* apple MACH */
+	case Hdarwin:	/* apple MACH */
 		/*
 		 * OS X system constant - offset from 0(GS) to our TLS.
 		 * Explained in ../../libcgo/darwin_amd64.c.
@@ -186,8 +184,8 @@ main(int argc, char *argv[])
 		if(INITDAT == -1)
 			INITDAT = 0;
 		break;
-	case 7:	/* elf64 executable */
-	case 9: /* freebsd */
+	case Hlinux:	/* elf64 executable */
+	case Hfreebsd: /* freebsd */
 		/*
 		 * ELF uses TLS offset negative from FS.
 		 * Translate 0(FS) and 8(FS) into -16(FS) and -8(FS).
@@ -204,7 +202,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case 10: /* PE executable */
+	case Hwindows: /* PE executable */
 		peinit();
 		HEADR = PEFILEHEADR;
 		if(INITTEXT == -1)
@@ -249,7 +247,7 @@ main(int argc, char *argv[])
 	patch();
 	follow();
 	doelf();
-	if(HEADTYPE == 6)
+	if(HEADTYPE == Hdarwin)
 		domacho();
 	dostkoff();
 	dostkcheck();
@@ -260,7 +258,7 @@ main(int argc, char *argv[])
 		else
 			doprof2();
 	span();
-	if(HEADTYPE == 10)
+	if(HEADTYPE == Hwindows)
 		dope();
 	addexport();
 	textaddress();
diff --git a/src/cmd/6l/pass.c b/src/cmd/6l/pass.c
index 9d94cfc854..98a32a7624 100644
--- a/src/cmd/6l/pass.c
+++ b/src/cmd/6l/pass.c
@@ -271,7 +271,7 @@ patch(void)
 	vexit = s->value;
 	for(cursym = textp; cursym != nil; cursym = cursym->next)
 	for(p = cursym->text; p != P; p = p->link) {
-		if(HEADTYPE == 10) { 
+		if(HEADTYPE == Hwindows) { 
 			// Windows
 			// Convert
 			//   op   n(GS), reg
@@ -294,7 +294,7 @@ patch(void)
 				p->from.offset = 0x58;
 			}
 		}
-		if(HEADTYPE == 7 || HEADTYPE == 9) {
+		if(HEADTYPE == Hlinux || HEADTYPE == Hfreebsd) {
 			// ELF uses FS instead of GS.
 			if(p->from.type == D_INDIR+D_GS)
 				p->from.type = D_INDIR+D_FS;
@@ -422,13 +422,13 @@ dostkoff(void)
 		if(!(p->from.scale & NOSPLIT)) {
 			p = appendp(p);	// load g into CX
 			p->as = AMOVQ;
-			if(HEADTYPE == 7 || HEADTYPE == 9)	// ELF uses FS
+			if(HEADTYPE == Hlinux || HEADTYPE == Hfreebsd)	// ELF uses FS
 				p->from.type = D_INDIR+D_FS;
 			else
 				p->from.type = D_INDIR+D_GS;
 			p->from.offset = tlsoffset+0;
 			p->to.type = D_CX;
-			if(HEADTYPE == 10) { // Windows
+			if(HEADTYPE == Hwindows) {
 				// movq %gs:0x58, %rcx
 				// movq (%rcx), %rcx
 				p->as = AMOVQ;
diff --git a/src/cmd/8l/asm.c b/src/cmd/8l/asm.c
index d90eab7e7d..1e760d89e5 100644
--- a/src/cmd/8l/asm.c
+++ b/src/cmd/8l/asm.c
@@ -246,7 +246,7 @@ adddynrel(Sym *s, Reloc *r)
 			r->sym = S;
 			return;
 		}
-		if(HEADTYPE == 6 && s->size == PtrSize && r->off == 0) {
+		if(HEADTYPE == Hdarwin && s->size == PtrSize && r->off == 0) {
 			// Mach-O relocations are a royal pain to lay out.
 			// They use a compact stateful bytecode representation
 			// that is too much bother to deal with.
@@ -356,7 +356,7 @@ addpltsym(Sym *s)
 		adduint32(rel, ELF32_R_INFO(s->dynid, R_386_JMP_SLOT));
 		
 		s->plt = plt->size - 16;
-	} else if(HEADTYPE == 6) {	// Mach-O
+	} else if(HEADTYPE == Hdarwin) {
 		// Same laziness as in 6l.
 		
 		Sym *plt;
@@ -395,7 +395,7 @@ addgotsym(Sym *s)
 		rel = lookup(".rel", 0);
 		addaddrplus(rel, got, s->got);
 		adduint32(rel, ELF32_R_INFO(s->dynid, R_386_GLOB_DAT));
-	} else if(HEADTYPE == 6) {	// Mach-O
+	} else if(HEADTYPE == Hdarwin) {
 		adduint32(lookup(".linkedit.got", 0), s->dynid);
 	} else {
 		diag("addgotsym: unsupported binary format");
@@ -465,7 +465,7 @@ adddynsym(Sym *s)
 			}
 			adduint16(d, t);
 		}
-	} else if(HEADTYPE == 6) {
+	} else if(HEADTYPE == Hdarwin) {
 		// Mach-O symbol nlist32
 		d = lookup(".dynsym", 0);
 		name = s->dynimpname;
@@ -481,7 +481,7 @@ adddynsym(Sym *s)
 		adduint8(d, 0);	// section
 		adduint16(d, 0);	// desc
 		adduint32(d, 0);	// value
-	} else if(HEADTYPE != 10) {
+	} else if(HEADTYPE != Hwindows) {
 		diag("adddynsym: unsupported binary format");
 	}
 }
@@ -499,9 +499,9 @@ adddynlib(char *lib)
 		if(s->size == 0)
 			addstring(s, "");
 		elfwritedynent(lookup(".dynamic", 0), DT_NEEDED, addstring(s, lib));
-	} else if(HEADTYPE == 6) {	// Mach-O
+	} else if(HEADTYPE == Hdarwin) {
 		machoadddynlib(lib);
-	} else if(HEADTYPE != 10) {
+	} else if(HEADTYPE != Hwindows) {
 		diag("adddynlib: unsupported binary format");
 	}
 }
@@ -673,7 +673,7 @@ asmb(void)
 	datblk(segdata.vaddr, segdata.filelen);
 
 	machlink = 0;
-	if(HEADTYPE == 6)
+	if(HEADTYPE == Hdarwin)
 		machlink = domacholink();
 
 	if(iself) {
@@ -697,28 +697,28 @@ asmb(void)
 		default:
 			if(iself)
 				goto Elfsym;
-		case 0:
+		case Hgarbunix:
 			seek(cout, rnd(HEADR+segtext.filelen, 8192)+segdata.filelen, 0);
 			break;
-		case 1:
+		case Hunixcoff:
 			seek(cout, rnd(HEADR+segtext.filelen, INITRND)+segdata.filelen, 0);
 			break;
-		case 2:
+		case Hplan9x32:
 			symo = HEADR+segtext.filelen+segdata.filelen;
 			break;
-		case 3:
-		case 4:
+		case Hmsdoscom:
+		case Hmsdosexe:
 			debug['s'] = 1;
 			symo = HEADR+segtext.filelen+segdata.filelen;
 			break;
-		case 6:
+		case Hdarwin:
 			symo = rnd(HEADR+segtext.filelen, INITRND)+rnd(segdata.filelen, INITRND)+machlink;
 			break;
 		Elfsym:
 			symo = rnd(HEADR+segtext.filelen, INITRND)+segdata.filelen;
 			symo = rnd(symo, INITRND);
 			break;
-		case 10:
+		case Hwindows:
 			// TODO(brainman): not sure what symo meant to be, but it is not used for Windows PE for now anyway
 			symo = rnd(HEADR+segtext.filelen, PEFILEALIGN)+segdata.filelen;
 			symo = rnd(symo, PEFILEALIGN);
@@ -727,7 +727,7 @@ asmb(void)
 		if(!debug['s']) {
 			seek(cout, symo, 0);
 			
-			if(HEADTYPE == 2) {
+			if(HEADTYPE == Hplan9x32) {
 				asmplan9sym();
 				cflush();
 				
@@ -740,7 +740,7 @@ asmb(void)
 					cflush();
 				}
 				
-			} else if(HEADTYPE != 10) {
+			} else if(HEADTYPE != Hwindows) {
 				if(debug['v'])
 					Bprint(&bso, "%5.2f dwarf\n", cputime());
 				dwarfemitdebugsections();
@@ -755,7 +755,7 @@ asmb(void)
 	default:
 		if(iself)
 			goto Elfput;
-	case 0:	/* garbage */
+	case Hgarbunix:	/* garbage */
 		lputb(0x160L<<16);		/* magic and sections */
 		lputb(0L);			/* time and date */
 		lputb(rnd(HEADR+segtext.filelen, 4096)+segdata.filelen);
@@ -777,7 +777,7 @@ asmb(void)
 		lputb(~0L);			/* gp value ?? */
 		break;
 		lputl(0);			/* x */
-	case 1:	/* unix coff */
+	case Hunixcoff:	/* unix coff */
 		/*
 		 * file header
 		 */
@@ -845,7 +845,7 @@ asmb(void)
 		lputl(0);			/* relocation, line numbers */
 		lputl(0x200);			/* flags comment only */
 		break;
-	case 2:	/* plan9 */
+	case Hplan9x32:	/* plan9 */
 		magic = 4*11*11+7;
 		lputb(magic);		/* magic */
 		lputb(segtext.filelen);			/* sizes */
@@ -856,10 +856,10 @@ asmb(void)
 		lputb(spsize);			/* sp offsets */
 		lputb(lcsize);			/* line offsets */
 		break;
-	case 3:
+	case Hmsdoscom:
 		/* MS-DOS .COM */
 		break;
-	case 4:
+	case Hmsdosexe:
 		/* fake MS-DOS .EXE */
 		v = rnd(HEADR+segtext.filelen, INITRND)+segdata.filelen;
 		wputl(0x5A4D);			/* 'MZ' */
@@ -882,13 +882,13 @@ asmb(void)
 		wputl(0x0000);			/* overlay number */
 		break;
 
-	case 6:
+	case Hdarwin:
 		asmbmacho();
 		break;
 
 	Elfput:
 		/* elf 386 */
-		if(HEADTYPE == 11)
+		if(HEADTYPE == Htiny)
 			debug['d'] = 1;
 
 		eh = getElfEhdr();
@@ -917,10 +917,10 @@ asmb(void)
 			sh->addralign = 1;
 			if(interpreter == nil) {
 				switch(HEADTYPE) {
-				case 7:
+				case Hlinux:
 					interpreter = linuxdynld;
 					break;
-				case 9:
+				case Hfreebsd:
 					interpreter = freebsddynld;
 					break;
 				}
@@ -1068,7 +1068,7 @@ asmb(void)
 		eh->ident[EI_DATA] = ELFDATA2LSB;
 		eh->ident[EI_VERSION] = EV_CURRENT;
 		switch(HEADTYPE) {
-		case 9:
+		case Hfreebsd:
 			eh->ident[EI_OSABI] = 9;
 			break;
 		}
@@ -1093,7 +1093,7 @@ asmb(void)
 			diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE);
 		break;
 
-	case 10:
+	case Hwindows:
 		asmbpe();
 		break;
 	}
diff --git a/src/cmd/8l/doc.go b/src/cmd/8l/doc.go
index ef5ebc31db..b708889078 100644
--- a/src/cmd/8l/doc.go
+++ b/src/cmd/8l/doc.go
@@ -25,10 +25,16 @@ Options new in this version:
 	Elide the dynamic linking header.  With this option, the binary
 	is statically linked and does not refer to dynld.  Without this option
 	(the default), the binary's contents are identical but it is loaded with dynld.
--H6
+-Hplan9
+	Write Plan 9 32-bit format binaries (default when $GOOS is plan9)
+-Hdarwin
 	Write Apple Mach-O binaries (default when $GOOS is darwin)
--H7
+-Hlinux
 	Write Linux ELF binaries (default when $GOOS is linux)
+-Hfreebsd
+	Write FreeBSD ELF binaries (default when $GOOS is freebsd)
+-Hwindows
+	Write Windows PE32 binaries (default when $GOOS is windows)
 -I interpreter
 	Set the ELF dynamic linker to use.
 -L dir1 -L dir2
diff --git a/src/cmd/8l/obj.c b/src/cmd/8l/obj.c
index fb97e84266..6ea9108f4d 100644
--- a/src/cmd/8l/obj.c
+++ b/src/cmd/8l/obj.c
@@ -46,18 +46,33 @@
 char	*noname		= "<none>";
 char	*thestring 	= "386";
 
+Header headers[] = {
+   "garbunix", Hgarbunix,
+   "unixcoff", Hunixcoff,
+   "plan9", Hplan9x32,
+   "msdoscom", Hmsdoscom,
+   "msdosexe", Hmsdosexe,
+   "darwin", Hdarwin,
+   "linux", Hlinux,
+   "nacl", Hnacl,
+   "freebsd", Hfreebsd,
+   "windows", Hwindows,
+   "tiny", Htiny,
+   0, 0
+};
+
 /*
- *	-H0 -T0x40004C -D0x10000000	is garbage unix
- *	-H1 -T0xd0 -R4			is unix coff
- *	-H2 -T4128 -R4096		is plan9 format
- *	-H3 -Tx -Rx			is MS-DOS .COM
- *	-H4 -Tx -Rx			is fake MS-DOS .EXE
- *	-H6 -Tx -Rx			is Apple Mach-O
- *	-H7 -Tx -Rx			is Linux ELF32
- *	-H8 -Tx -Rx			was Google Native Client
- *	-H9 -Tx -Rx			is FreeBSD ELF32
- *	-H10 -Tx -Rx			is MS Windows PE
- *	-H11 -Tx -Rx			is tiny (os image)
+ *	-Hgarbunix -T0x40004C -D0x10000000	is garbage unix
+ *	-Hunixcoff -T0xd0 -R4			is unix coff
+ *	-Hplan9 -T4128 -R4096			is plan9 format
+ *	-Hmsdoscom -Tx -Rx			is MS-DOS .COM
+ *	-Hmsdosexe -Tx -Rx			is fake MS-DOS .EXE
+ *	-Hdarwin -Tx -Rx			is Apple Mach-O
+ *	-Hlinux -Tx -Rx				is Linux ELF32
+ *	-Hnacl -Tx -Rx				was Google Native Client
+ *	-Hfreebsd -Tx -Rx			is FreeBSD ELF32
+ *	-Hwindows -Tx -Rx			is MS Windows PE32
+ *	-Htiny -Tx -Rx				is tiny (os image)
  */
 
 void
@@ -99,7 +114,7 @@ main(int argc, char *argv[])
 		INITENTRY = EARGF(usage());
 		break;
 	case 'H':
-		HEADTYPE = atolwhex(EARGF(usage()));
+		HEADTYPE = headtype(EARGF(usage()));
 		break;
 	case 'I':
 		interpreter = EARGF(usage());
@@ -129,31 +144,11 @@ main(int argc, char *argv[])
 
 	mywhatsys();	// get goos
 
-	if(HEADTYPE == -1) {
-		HEADTYPE = 2;
-		if(strcmp(goos, "linux") == 0)
-			HEADTYPE = 7;
-		else
-		if(strcmp(goos, "darwin") == 0)
-			HEADTYPE = 6;
-		else
-		if(strcmp(goos, "freebsd") == 0)
-			HEADTYPE = 9;
-		else
-		if(strcmp(goos, "windows") == 0)
-			HEADTYPE = 10;
-		else
-		if(strcmp(goos, "tiny") == 0)
-			HEADTYPE = 11;
-		else
-		if(strcmp(goos, "plan9") == 0)
-			HEADTYPE = 2;
-		else
-			print("goos is not known: %s\n", goos);
-	}
+	if(HEADTYPE == -1)
+		HEADTYPE = headtype(goos);
 
 	if(outfile == nil) {
-		if(HEADTYPE == 10)
+		if(HEADTYPE == Hwindows)
 			outfile = "8.out.exe";
 		else
 			outfile = "8.out";
@@ -166,7 +161,7 @@ main(int argc, char *argv[])
 		diag("unknown -H option");
 		errorexit();
 
-	case 0:	/* this is garbage */
+	case Hgarbunix:	/* this is garbage */
 		HEADR = 20L+56L;
 		if(INITTEXT == -1)
 			INITTEXT = 0x40004CL;
@@ -175,7 +170,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 0;
 		break;
-	case 1:	/* is unix coff */
+	case Hunixcoff:	/* is unix coff */
 		HEADR = 0xd0L;
 		if(INITTEXT == -1)
 			INITTEXT = 0xd0;
@@ -184,7 +179,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 0;
 		break;
-	case 2:	/* plan 9 */
+	case Hplan9x32:	/* plan 9 */
 		tlsoffset = -8;
 		HEADR = 32L;
 		if(INITTEXT == -1)
@@ -194,7 +189,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 1;
 		break;
-	case 3:	/* MS-DOS .COM */
+	case Hmsdoscom:	/* MS-DOS .COM */
 		HEADR = 0;
 		if(INITTEXT == -1)
 			INITTEXT = 0x0100;
@@ -203,7 +198,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4;
 		break;
-	case 4:	/* fake MS-DOS .EXE */
+	case Hmsdosexe:	/* fake MS-DOS .EXE */
 		HEADR = 0x200;
 		if(INITTEXT == -1)
 			INITTEXT = 0x0100;
@@ -215,7 +210,7 @@ main(int argc, char *argv[])
 		if(debug['v'])
 			Bprint(&bso, "HEADR = 0x%d\n", HEADR);
 		break;
-	case 6:	/* apple MACH */
+	case Hdarwin:	/* apple MACH */
 		/*
 		 * OS X system constant - offset from %gs to our TLS.
 		 * Explained in ../../libcgo/darwin_386.c.
@@ -230,8 +225,8 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case 7:	/* elf32 executable */
-	case 9:
+	case Hlinux:	/* elf32 executable */
+	case Hfreebsd:
 		/*
 		 * ELF uses TLS offsets negative from %gs.
 		 * Translate 0(GS) and 4(GS) into -8(GS) and -4(GS).
@@ -248,7 +243,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case 10: /* PE executable */
+	case Hwindows: /* PE executable */
 		peinit();
 		HEADR = PEFILEHEADR;
 		if(INITTEXT == -1)
@@ -258,7 +253,7 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = PESECTALIGN;
 		break;
-	case 11:
+	case Htiny:
 		tlsoffset = 0;
 		elfinit();
 		HEADR = ELFRESERVE;
@@ -303,9 +298,9 @@ main(int argc, char *argv[])
 	patch();
 	follow();
 	doelf();
-	if(HEADTYPE == 6)
+	if(HEADTYPE == Hdarwin)
 		domacho();
-	if(HEADTYPE == 10)
+	if(HEADTYPE == Hwindows)
 		dope();
 	dostkoff();
 	if(debug['p'])
diff --git a/src/cmd/8l/pass.c b/src/cmd/8l/pass.c
index a5380ae130..bbb86cff7d 100644
--- a/src/cmd/8l/pass.c
+++ b/src/cmd/8l/pass.c
@@ -263,12 +263,12 @@ patch(void)
 	vexit = s->value;
 	
 	plan9_tos = S;
-	if(HEADTYPE == 2)
+	if(HEADTYPE == Hplan9x32)
 		plan9_tos = lookup("_tos", 0);
 	
 	for(cursym = textp; cursym != nil; cursym = cursym->next) {
 		for(p = cursym->text; p != P; p = p->link) {
-			if(HEADTYPE == 10) {	// Windows
+			if(HEADTYPE == Hwindows) {
 				// Convert
 				//   op	  n(GS), reg
 				// to
@@ -289,7 +289,7 @@ patch(void)
 					p->from.offset = 0x2C;
 				}
 			}
-			if(HEADTYPE == 7) {	// Linux
+			if(HEADTYPE == Hlinux) {
 				// Running binaries under Xen requires using
 				//	MOVL 0(GS), reg
 				// and then off(reg) instead of saying off(GS) directly
@@ -306,7 +306,7 @@ patch(void)
 					p->from.offset = 0;
 				}
 			}
-			if(HEADTYPE == 2) {	// Plan 9
+			if(HEADTYPE == Hplan9x32) {
 				if(p->from.type == D_INDIR+D_GS
 				&& p->to.type >= D_AX && p->to.type <= D_DI) {
 					q = appendp(p);
@@ -414,7 +414,7 @@ dostkoff(void)
 	}
 	
 	plan9_tos = S;
-	if(HEADTYPE == 2)	
+	if(HEADTYPE == Hplan9x32)
 		plan9_tos = lookup("_tos", 0);
 
 	for(cursym = textp; cursym != nil; cursym = cursym->next) {
@@ -432,7 +432,7 @@ dostkoff(void)
 		if(!(p->from.scale & NOSPLIT)) {
 			p = appendp(p);	// load g into CX
 			switch(HEADTYPE) {
-			case 10:	// Windows
+			case Hwindows:
 				p->as = AMOVL;
 				p->from.type = D_INDIR+D_FS;
 				p->from.offset = 0x2c;
@@ -445,7 +445,7 @@ dostkoff(void)
 				p->to.type = D_CX;
 				break;
 			
-			case 7:	// Linux
+			case Hlinux:
 				p->as = AMOVL;
 				p->from.type = D_INDIR+D_GS;
 				p->from.offset = 0;
@@ -458,7 +458,7 @@ dostkoff(void)
 				p->to.type = D_CX;
 				break;
 			
-			case 2:	// Plan 9
+			case Hplan9x32:
 				p->as = AMOVL;
 				p->from.type = D_EXTERN;
 				p->from.sym = plan9_tos;
diff --git a/src/cmd/ld/data.c b/src/cmd/ld/data.c
index 0551232cfc..a20b057ce5 100644
--- a/src/cmd/ld/data.c
+++ b/src/cmd/ld/data.c
@@ -241,7 +241,7 @@ dynrelocsym(Sym *s)
 {
 	Reloc *r;
 	
-	if(thechar == '8' && HEADTYPE == 10) { // Windows PE
+	if(HEADTYPE == Hwindows) {
 		Sym *rel, *targ;
 		
 		rel = lookup(".rel", 0);
@@ -898,9 +898,9 @@ address(void)
 	segdata.rwx = 06;
 	segdata.vaddr = va;
 	segdata.fileoff = va - segtext.vaddr + segtext.fileoff;
-	if((thechar == '6' || thechar == '8') && HEADTYPE == 10)	// Windows PE
+	if(HEADTYPE == Hwindows)
 		segdata.fileoff = segtext.fileoff + rnd(segtext.len, PEFILEALIGN);
-	if(thechar == '8' && HEADTYPE == 2) {	// Plan 9		
+	if(HEADTYPE == Hplan9x32) {
 		segdata.vaddr = va = rnd(va, 4096);
 		segdata.fileoff = segtext.fileoff + segtext.filelen;
 	}
diff --git a/src/cmd/ld/dwarf.c b/src/cmd/ld/dwarf.c
index 5df3515f5d..8c53d7d133 100644
--- a/src/cmd/ld/dwarf.c
+++ b/src/cmd/ld/dwarf.c
@@ -2302,7 +2302,7 @@ writegdbscript(void)
 static void
 align(vlong size)
 {
-	if((thechar == '6' || thechar == '8') && HEADTYPE == 10) // Only Windows PE need section align.
+	if(HEADTYPE == Hwindows) // Only Windows PE need section align.
 		strnput("", rnd(size, PEFILEALIGN) - size);
 }
 
diff --git a/src/cmd/ld/lib.c b/src/cmd/ld/lib.c
index 1838717bfe..998e28cf16 100644
--- a/src/cmd/ld/lib.c
+++ b/src/cmd/ld/lib.c
@@ -1264,3 +1264,16 @@ stkprint(Chain *ch, int limit)
 	if(ch->limit != limit)
 		print("\t%d\tafter %s uses %d\n", limit, name, ch->limit - limit);
 }
+
+int
+headtype(char *name)
+{
+	int i;
+
+	for(i=0; headers[i].name; i++)
+		if(strcmp(name, headers[i].name) == 0)
+			return headers[i].val;
+	fprint(2, "unknown header type -H %s\n", name);
+	errorexit();
+	return -1;  // not reached
+}
diff --git a/src/cmd/ld/lib.h b/src/cmd/ld/lib.h
index 1b37202271..234ea3198f 100644
--- a/src/cmd/ld/lib.h
+++ b/src/cmd/ld/lib.h
@@ -208,3 +208,34 @@ enum {
 	ArchiveObj,
 	Pkgdef
 };
+
+/* executable header types */
+enum {
+   Hgarbunix = 0,	// garbage unix
+   Hnoheader,		// no header
+   Hunixcoff,		// unix coff
+   Hrisc,		// aif for risc os
+   Hplan9x32,		// plan 9 32-bit format
+   Hplan9x64,		// plan 9 64-bit format
+   Hmsdoscom,		// MS-DOS .COM
+   Hnetbsd,		// NetBSD
+   Hmsdosexe,		// fake MS-DOS .EXE
+   Hixp1200,		// IXP1200 (raw)
+   Helf,		// ELF32
+   Hipaq,		// ipaq
+   Hdarwin,		// Apple Mach-O
+   Hlinux,		// Linux ELF
+   Hnacl,		// Google Native Client
+   Hfreebsd,		// FreeBSD ELF
+   Hwindows,		// MS Windows PE
+   Htiny		// tiny (os image)
+};
+
+typedef struct Header Header;
+struct Header {
+   char *name;
+   int val;
+};
+
+extern Header headers[];
+int headtype(char*);