cmd/{ld,5l,6l,8l}: add support for OpenBSD ELF signatures

OpenBSD now requires ELF binaries to have a PT_NOTE that identifies
it as an OpenBSD binary. Refactor the existing NetBSD ELF signature
code and implement support for OpenBSD ELF signatures.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6489131

src/cmd/5l/asm.c

@@ -77,6 +77,7 @@ enum {
 	ElfStrGnuVersion,
 	ElfStrGnuVersionR,
 	ElfStrNoteNetbsdIdent,
+	ElfStrNoteOpenbsdIdent,
 	ElfStrNoPtrData,
 	ElfStrNoPtrBss,
 	NElfStr
@@ -504,6 +505,8 @@ doelf(void)
 	elfstr[ElfStrNoPtrBss] = addstring(shstrtab, ".noptrbss");
 	if(HEADTYPE == Hnetbsd)
 		elfstr[ElfStrNoteNetbsdIdent] = addstring(shstrtab, ".note.netbsd.ident");
+	if(HEADTYPE == Hopenbsd)
+		elfstr[ElfStrNoteOpenbsdIdent] = addstring(shstrtab, ".note.openbsd.ident");
 	addstring(shstrtab, ".rodata");
 	addstring(shstrtab, ".gcdata");
 	addstring(shstrtab, ".gcbss");
@@ -685,7 +688,7 @@ asmb(void)
 			if(elfverneed)
 				elftextsh += 2;
 		}
-		if(HEADTYPE == Hnetbsd)
+		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd)
 			elftextsh += 1;
 	}
 
@@ -846,12 +849,18 @@ asmb(void)
 			phsh(ph, sh);
 		}
 
-		if(HEADTYPE == Hnetbsd) {
+		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd) {
+			sh = nil;
+			switch(HEADTYPE) {
+			case Hnetbsd:
 				sh = newElfShdr(elfstr[ElfStrNoteNetbsdIdent]);
-			sh->type = SHT_NOTE;
-			sh->flags = SHF_ALLOC;
-			sh->addralign = 4;
 				resoff -= elfnetbsdsig(sh, startva, resoff);
+				break;
+			case Hopenbsd:
+				sh = newElfShdr(elfstr[ElfStrNoteOpenbsdIdent]);
+				resoff -= elfopenbsdsig(sh, startva, resoff);
+				break;
+			}
 
 			ph = newElfPhdr();
 			ph->type = PT_NOTE;
@@ -1027,6 +1036,8 @@ asmb(void)
 		a += elfwriteinterp(elfstr[ElfStrInterp]);
 		if(HEADTYPE == Hnetbsd)
 			a += elfwritenetbsdsig(elfstr[ElfStrNoteNetbsdIdent]);
+		if(HEADTYPE == Hopenbsd)
+			a += elfwriteopenbsdsig(elfstr[ElfStrNoteOpenbsdIdent]);
 		if(a > ELFRESERVE)	
 			diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE);
 		break;

src/cmd/6l/asm.c

@@ -95,6 +95,7 @@ enum {
 	ElfStrGnuVersion,
 	ElfStrGnuVersionR,
 	ElfStrNoteNetbsdIdent,
+	ElfStrNoteOpenbsdIdent,
 	ElfStrNoPtrData,
 	ElfStrNoPtrBss,
 	NElfStr
@@ -577,6 +578,8 @@ doelf(void)
 	elfstr[ElfStrNoPtrBss] = addstring(shstrtab, ".noptrbss");
 	if(HEADTYPE == Hnetbsd)
 		elfstr[ElfStrNoteNetbsdIdent] = addstring(shstrtab, ".note.netbsd.ident");
+	if(HEADTYPE == Hopenbsd)
+		elfstr[ElfStrNoteOpenbsdIdent] = addstring(shstrtab, ".note.openbsd.ident");
 	addstring(shstrtab, ".elfdata");
 	addstring(shstrtab, ".rodata");
 	addstring(shstrtab, ".gcdata");
@@ -785,7 +788,7 @@ asmb(void)
 			if(elfverneed)
 				elftextsh += 2;
 		}
-		if(HEADTYPE == Hnetbsd)
+		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd)
 			elftextsh += 1;
 		break;
 	case Hwindows:
@@ -956,12 +959,18 @@ asmb(void)
 			phsh(ph, sh);
 		}
 
-		if(HEADTYPE == Hnetbsd) {
+		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd) {
+			sh = nil;
+			switch(HEADTYPE) {
+			case Hnetbsd:
 				sh = newElfShdr(elfstr[ElfStrNoteNetbsdIdent]);
-			sh->type = SHT_NOTE;
-			sh->flags = SHF_ALLOC;
-			sh->addralign = 4;
 				resoff -= elfnetbsdsig(sh, startva, resoff);
+				break;
+			case Hopenbsd:
+				sh = newElfShdr(elfstr[ElfStrNoteOpenbsdIdent]);
+				resoff -= elfopenbsdsig(sh, startva, resoff);
+				break;
+			}
 
 			ph = newElfPhdr();
 			ph->type = PT_NOTE;
@@ -1151,6 +1160,8 @@ asmb(void)
 		a += elfwriteinterp(elfstr[ElfStrInterp]);
 		if(HEADTYPE == Hnetbsd)
 			a += elfwritenetbsdsig(elfstr[ElfStrNoteNetbsdIdent]);
+		if(HEADTYPE == Hopenbsd)
+			a += elfwriteopenbsdsig(elfstr[ElfStrNoteOpenbsdIdent]);
 		if(a > ELFRESERVE)	
 			diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE);
 		break;

src/cmd/8l/asm.c

@@ -91,6 +91,7 @@ enum {
 	ElfStrGnuVersion,
 	ElfStrGnuVersionR,
 	ElfStrNoteNetbsdIdent,
+	ElfStrNoteOpenbsdIdent,
 	ElfStrNoPtrData,
 	ElfStrNoPtrBss,
 	NElfStr
@@ -534,6 +535,8 @@ doelf(void)
 	elfstr[ElfStrNoPtrBss] = addstring(shstrtab, ".noptrbss");
 	if(HEADTYPE == Hnetbsd)
 		elfstr[ElfStrNoteNetbsdIdent] = addstring(shstrtab, ".note.netbsd.ident");
+	if(HEADTYPE == Hopenbsd)
+		elfstr[ElfStrNoteOpenbsdIdent] = addstring(shstrtab, ".note.openbsd.ident");
 	addstring(shstrtab, ".elfdata");
 	addstring(shstrtab, ".rodata");
 	addstring(shstrtab, ".gcdata");
@@ -723,7 +726,7 @@ asmb(void)
 			if(elfverneed)
 				elftextsh += 2;
 		}
-		if(HEADTYPE == Hnetbsd)
+		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd)
 			elftextsh += 1;
 	}
 
@@ -997,12 +1000,18 @@ asmb(void)
 			phsh(ph, sh);
 		}
 
-		if(HEADTYPE == Hnetbsd) {
+		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd) {
+			sh = nil;
+			switch(HEADTYPE) {
+			case Hnetbsd:
 				sh = newElfShdr(elfstr[ElfStrNoteNetbsdIdent]);
-			sh->type = SHT_NOTE;
-			sh->flags = SHF_ALLOC;
-			sh->addralign = 4;
 				resoff -= elfnetbsdsig(sh, startva, resoff);
+				break;
+			case Hopenbsd:
+				sh = newElfShdr(elfstr[ElfStrNoteOpenbsdIdent]);
+				resoff -= elfopenbsdsig(sh, startva, resoff);
+				break;
+			}
 
 			ph = newElfPhdr();
 			ph->type = PT_NOTE;
@@ -1202,6 +1211,8 @@ asmb(void)
 		a += elfwriteinterp(elfstr[ElfStrInterp]);
 		if(HEADTYPE == Hnetbsd)
 			a += elfwritenetbsdsig(elfstr[ElfStrNoteNetbsdIdent]);
+		if(HEADTYPE == Hopenbsd)
+			a += elfwriteopenbsdsig(elfstr[ElfStrNoteOpenbsdIdent]);
 		if(a > ELFRESERVE)	
 			diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE);
 		break;

src/cmd/ld/elf.c

@@ -351,10 +351,48 @@ elfwriteinterp(vlong stridx)
 	return sh->size;
 }
 
-// Defined in NetBSD's sys/exec_elf.h
+int
-#define ELF_NOTE_TYPE_NETBSD_TAG	1
+elfnote(ElfShdr *sh, uint64 startva, uint64 resoff, int sz)
+{
+	uint64 n;
+
+	n = sizeof(Elf_Note) + sz + resoff % 4;
+
+	sh->type = SHT_NOTE;
+	sh->flags = SHF_ALLOC;
+	sh->addralign = 4;
+	sh->addr = startva + resoff - n;
+	sh->off = resoff - n;
+	sh->size = n;
+
+	return n;
+}
+
+ElfShdr *
+elfwritenotehdr(vlong stridx, uint32 namesz, uint32 descsz, uint32 tag)
+{
+	ElfShdr *sh = nil;
+	int i;
+
+	for(i = 0; i < hdr.shnum; i++)
+		if(shdr[i]->name == stridx)
+			sh = shdr[i];
+	if(sh == nil)
+		return nil;
+
+	// Write Elf_Note header.
+	cseek(sh->off);
+	LPUT(namesz);
+	LPUT(descsz);
+	LPUT(tag);
+
+	return sh;
+}
+
+// NetBSD Signature (as per sys/exec_elf.h)
 #define ELF_NOTE_NETBSD_NAMESZ		7
 #define ELF_NOTE_NETBSD_DESCSZ		4
+#define ELF_NOTE_NETBSD_TAG		1
 #define ELF_NOTE_NETBSD_NAME		"NetBSD\0\0"
 #define ELF_NOTE_NETBSD_VERSION		599000000	/* NetBSD 5.99 */
 
@@ -363,37 +401,60 @@ elfnetbsdsig(ElfShdr *sh, uint64 startva, uint64 resoff)
 {
 	int n;
 
-	n = sizeof(Elf_Note) + ELF_NOTE_NETBSD_NAMESZ + ELF_NOTE_NETBSD_DESCSZ + 1;
+	n = ELF_NOTE_NETBSD_NAMESZ + ELF_NOTE_NETBSD_DESCSZ + 1;
-	n += resoff % 4;
+	return elfnote(sh, startva, resoff, n);
-	sh->addr = startva + resoff - n;
-	sh->off = resoff - n;
-	sh->size = n;
-
-	return n;
 }
 
 int
-elfwritenetbsdsig(vlong stridx) {
+elfwritenetbsdsig(vlong stridx)
-	ElfShdr *sh = nil;
+{
-	int i;
+	ElfShdr *sh;
 
-	for(i = 0; i < hdr.shnum; i++)
+	// Write Elf_Note header.
-		if(shdr[i]->name == stridx)
+	sh = elfwritenotehdr(stridx, ELF_NOTE_NETBSD_NAMESZ, ELF_NOTE_NETBSD_DESCSZ, ELF_NOTE_NETBSD_TAG);
-			sh = shdr[i];
 	if(sh == nil)
 		return 0;
 
-	// Write Elf_Note header followed by NetBSD string.
+	// Followed by NetBSD string and version.
-	cseek(sh->off);
+	cwrite(ELF_NOTE_NETBSD_NAME, ELF_NOTE_NETBSD_NAMESZ + 1);
-	LPUT(ELF_NOTE_NETBSD_NAMESZ);
-	LPUT(ELF_NOTE_NETBSD_DESCSZ);
-	LPUT(ELF_NOTE_TYPE_NETBSD_TAG);
-	cwrite(ELF_NOTE_NETBSD_NAME, 8);
 	LPUT(ELF_NOTE_NETBSD_VERSION);
 
 	return sh->size;
 }
 
+// OpenBSD Signature
+#define ELF_NOTE_OPENBSD_NAMESZ		8
+#define ELF_NOTE_OPENBSD_DESCSZ		4
+#define ELF_NOTE_OPENBSD_TAG		1
+#define ELF_NOTE_OPENBSD_NAME		"OpenBSD\0"
+#define ELF_NOTE_OPENBSD_VERSION	0
+
+int
+elfopenbsdsig(ElfShdr *sh, uint64 startva, uint64 resoff)
+{
+	int n;
+
+	n = ELF_NOTE_OPENBSD_NAMESZ + ELF_NOTE_OPENBSD_DESCSZ;
+	return elfnote(sh, startva, resoff, n);
+}
+
+int
+elfwriteopenbsdsig(vlong stridx)
+{
+	ElfShdr *sh;
+
+	// Write Elf_Note header.
+	sh = elfwritenotehdr(stridx, ELF_NOTE_OPENBSD_NAMESZ, ELF_NOTE_OPENBSD_DESCSZ, ELF_NOTE_OPENBSD_TAG);
+	if(sh == nil)
+		return 0;
+
+	// Followed by OpenBSD string and version.
+	cwrite(ELF_NOTE_OPENBSD_NAME, ELF_NOTE_OPENBSD_NAMESZ);
+	LPUT(ELF_NOTE_OPENBSD_VERSION);
+
+	return sh->size;
+}
+
 extern int nelfsym;
 int elfverneed;
 

src/cmd/ld/elf.h

@@ -976,6 +976,8 @@ int	elfinterp(ElfShdr*, uint64, uint64, char*);
 int	elfwriteinterp(vlong);
 int	elfnetbsdsig(ElfShdr*, uint64, uint64);
 int	elfwritenetbsdsig(vlong);
+int	elfopenbsdsig(ElfShdr*, uint64, uint64);
+int	elfwriteopenbsdsig(vlong);
 void	elfdynhash(void);
 ElfPhdr* elfphload(Segment*);
 ElfShdr* elfshbits(Section*);