cmd/5l, cmd/ld: support generating ELF binaries for NetBSD/ARM

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/7261043

src/cmd/5l/asm.c

@@ -40,7 +40,7 @@ static Prog *PP;
 char linuxdynld[] = "/lib/ld-linux.so.3"; // 2 for OABI, 3 for EABI
 char freebsddynld[] = "/usr/libexec/ld-elf.so.1";
 char openbsddynld[] = "XXX";
-char netbsddynld[] = "XXX";
+char netbsddynld[] = "/libexec/ld.elf_so";
 
 int32
 entryvalue(void)
@@ -581,9 +581,6 @@ asmb(void)
 		case Hplan9x32:
 			symo = HEADR+segtext.len+segdata.filelen;
 			break;
-		case Hnetbsd:
-			symo = rnd(segdata.filelen, 4096);
-			break;
 		ElfSym:
 			symo = rnd(HEADR+segtext.filelen, INITRND)+segdata.filelen;
 			symo = rnd(symo, INITRND);

src/cmd/5l/obj.c

@@ -48,21 +48,22 @@ Header headers[] = {
    "noheader", Hnoheader,
    "risc", Hrisc,
    "plan9", Hplan9x32,
-   "netbsd", Hnetbsd,
    "ixp1200", Hixp1200,
    "ipaq", Hipaq,
    "linux", Hlinux,
    "freebsd", Hfreebsd,
+   "netbsd", Hnetbsd,
    0, 0
 };
 
 /*
  *	-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
+ *	-Hfreebsd			is freebsd elf
+ *	-Hnetbsd			is netbsd elf
  */
 
 void
@@ -166,15 +167,6 @@ main(int argc, char *argv[])
 		if(INITRND == -1)
 			INITRND = 4096;
 		break;
-	case Hnetbsd:	/* boot for NetBSD */
-		HEADR = 32L;
-		if(INITTEXT == -1)
-			INITTEXT = 0xF0000020L;
-		if(INITDAT == -1)
-			INITDAT = 0;
-		if(INITRND == -1)
-			INITRND = 4096;
-		break;
 	case Hixp1200: /* boot for IXP1200 */
 		HEADR = 0L;
 		if(INITTEXT == -1)
@@ -195,6 +187,7 @@ main(int argc, char *argv[])
 		break;
 	case Hlinux:	/* arm elf */
 	case Hfreebsd:
+	case Hnetbsd:
 		debug['d'] = 0;	// with dynamic linking
 		tlsoffset = -8; // hardcoded number, first 4-byte word for g, and then 4-byte word for m
 		                // this number is known to ../../pkg/runtime/cgo/gcc_linux_arm.c

src/cmd/ld/elf.c

@@ -55,7 +55,9 @@ elfinit(void)
 
 	// 32-bit architectures
 	case '5':
-		hdr.flags = 0x5000002; // has entry point, Version5 EABI
+		// we only use EABI on linux/arm
+		if(HEADTYPE == Hlinux)
+			hdr.flags = 0x5000002; // has entry point, Version5 EABI
 		// fallthrough
 	default:
 		hdr.phoff = ELF32HDRSIZE;	/* Must be be ELF32HDRSIZE: first PHdr must follow ELF header */
@@ -1303,6 +1305,7 @@ asmbelf(vlong symo)
 			sh->type = SHT_REL;
 			sh->flags = SHF_ALLOC;
 			sh->entsize = ELF32RELSIZE;
+			sh->link = elfshname(".dynsym")->shnum;
 			shsym(sh, lookup(".rel.plt", 0));
 
 			sh = elfshname(".rel");
@@ -1375,15 +1378,17 @@ asmbelf(vlong symo)
 		}
 	}
 
-	ph = newElfPhdr();
-	ph->type = PT_GNU_STACK;
-	ph->flags = PF_W+PF_R;
-	ph->align = PtrSize;
-	
-	ph = newElfPhdr();
-	ph->type = PT_PAX_FLAGS;
-	ph->flags = 0x2a00; // mprotect, randexec, emutramp disabled
-	ph->align = PtrSize;
+	if(HEADTYPE == Hlinux) {
+		ph = newElfPhdr();
+		ph->type = PT_GNU_STACK;
+		ph->flags = PF_W+PF_R;
+		ph->align = PtrSize;
+		
+		ph = newElfPhdr();
+		ph->type = PT_PAX_FLAGS;
+		ph->flags = 0x2a00; // mprotect, randexec, emutramp disabled
+		ph->align = PtrSize;
+	}
 
 elfobj:
 	sh = elfshname(".shstrtab");