6l: OpenBSD support

Add linker support for OpenBSD ELF-64.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4815066

src/cmd/6l/asm.c

@@ -43,6 +43,7 @@
 
 char linuxdynld[] = "/lib64/ld-linux-x86-64.so.2";
 char freebsddynld[] = "/libexec/ld-elf.so.1";
+char openbsddynld[] = "/usr/libexec/ld.so";
 
 char	zeroes[32];
 
@@ -554,7 +555,7 @@ doelf(void)
 {
 	Sym *s, *shstrtab, *dynstr;
 
-	if(HEADTYPE != Hlinux && HEADTYPE != Hfreebsd)
+	if(HEADTYPE != Hlinux && HEADTYPE != Hfreebsd && HEADTYPE != Hopenbsd)
 		return;
 
 	/* predefine strings we need for section headers */
@@ -746,6 +747,7 @@ asmb(void)
 		break;
 	case Hlinux:
 	case Hfreebsd:
+	case Hopenbsd:
 		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 */
@@ -780,6 +782,7 @@ asmb(void)
 			break;
 		case Hlinux:
 		case Hfreebsd:
+		case Hopenbsd:
 			symo = rnd(HEADR+segtext.len, INITRND)+segdata.filelen;
 			symo = rnd(symo, INITRND);
 			break;
@@ -849,6 +852,7 @@ asmb(void)
 		break;
 	case Hlinux:
 	case Hfreebsd:
+	case Hopenbsd:
 		/* elf amd-64 */
 
 		eh = getElfEhdr();
@@ -891,6 +895,9 @@ asmb(void)
 				case Hfreebsd:
 					interpreter = freebsddynld;
 					break;
+				case Hopenbsd:
+					interpreter = openbsddynld;
+					break;
 				}
 			}
 			elfinterp(sh, startva, interpreter);
@@ -1053,7 +1060,9 @@ asmb(void)
 		eh->ident[EI_MAG2] = 'L';
 		eh->ident[EI_MAG3] = 'F';
 		if(HEADTYPE == Hfreebsd)
-			eh->ident[EI_OSABI] = 9;
+			eh->ident[EI_OSABI] = ELFOSABI_FREEBSD;
+		else if(HEADTYPE == Hopenbsd)
+			eh->ident[EI_OSABI] = ELFOSABI_OPENBSD;
 		eh->ident[EI_CLASS] = ELFCLASS64;
 		eh->ident[EI_DATA] = ELFDATA2LSB;
 		eh->ident[EI_VERSION] = EV_CURRENT;

src/cmd/6l/doc.go

@@ -34,6 +34,8 @@ Options new in this version:
 	Write Linux ELF binaries (default when $GOOS is linux)
 -Hfreebsd
 	Write FreeBSD ELF binaries (default when $GOOS is freebsd)
+-Hopenbsd
+	Write OpenBSD ELF binaries (default when $GOOS is openbsd)
 -Hwindows
 	Write Windows PE32+ binaries (default when $GOOS is windows)
 -I interpreter

src/cmd/6l/obj.c

@@ -50,6 +50,7 @@ Header headers[] = {
    "darwin", Hdarwin,
    "linux", Hlinux,
    "freebsd", Hfreebsd,
+   "openbsd", Hopenbsd,
    "windows", Hwindows,
    "windowsgui", Hwindows,
    0, 0
@@ -62,6 +63,7 @@ Header headers[] = {
  *	-Hdarwin -Tx -Rx		is apple MH-exec
  *	-Hlinux -Tx -Rx			is linux elf-exec
  *	-Hfreebsd -Tx -Rx		is FreeBSD elf-exec
+ *	-Hopenbsd -Tx -Rx		is OpenBSD elf-exec
  *	-Hwindows -Tx -Rx		is MS Windows PE32+
  *
  *	options used: 189BLQSWabcjlnpsvz
@@ -194,7 +196,8 @@ main(int argc, char *argv[])
 			INITDAT = 0;
 		break;
 	case Hlinux:	/* elf64 executable */
-	case Hfreebsd: /* freebsd */
+	case Hfreebsd:	/* freebsd */
+	case Hopenbsd:	/* openbsd */
 		/*
 		 * ELF uses TLS offset negative from FS.
 		 * Translate 0(FS) and 8(FS) into -16(FS) and -8(FS).

src/cmd/6l/pass.c

@@ -294,7 +294,8 @@ patch(void)
 				p->from.offset = 0x58;
 			}
 		}
-		if(HEADTYPE == Hlinux || HEADTYPE == Hfreebsd) {
+		if(HEADTYPE == Hlinux || HEADTYPE == Hfreebsd
+		|| HEADTYPE == Hopenbsd) {
 			// ELF uses FS instead of GS.
 			if(p->from.type == D_INDIR+D_GS)
 				p->from.type = D_INDIR+D_FS;
@@ -419,7 +420,8 @@ dostkoff(void)
 		if(!(p->from.scale & NOSPLIT)) {
 			p = appendp(p);	// load g into CX
 			p->as = AMOVQ;
-			if(HEADTYPE == Hlinux || HEADTYPE == Hfreebsd)	// ELF uses FS
+			if(HEADTYPE == Hlinux || HEADTYPE == Hfreebsd
+			|| HEADTYPE == Hopenbsd)	// ELF uses FS
 				p->from.type = D_INDIR+D_FS;
 			else
 				p->from.type = D_INDIR+D_GS;

src/cmd/ld/lib.h

@@ -263,6 +263,7 @@ enum {
 	Hlinux,		// Linux ELF
 	Hfreebsd,	// FreeBSD ELF
 	Hwindows,	// MS Windows PE
+	Hopenbsd,	// OpenBSD ELF
 };
 
 typedef struct Header Header;