cmd/ld: add -B option to set build ID

Background on build ID:
http://fedoraproject.org/wiki/RolandMcGrath/BuildID

R=rsc
CC=golang-dev
https://golang.org/cl/6625072

src/cmd/5l/asm.c

@@ -79,6 +79,7 @@ enum {
 	ElfStrGnuVersionR,
 	ElfStrNoteNetbsdIdent,
 	ElfStrNoteOpenbsdIdent,
+	ElfStrNoteBuildInfo,
 	ElfStrNoPtrData,
 	ElfStrNoPtrBss,
 	NElfStr
@@ -523,6 +524,8 @@ doelf(void)
 		elfstr[ElfStrNoteNetbsdIdent] = addstring(shstrtab, ".note.netbsd.ident");
 	if(HEADTYPE == Hopenbsd)
 		elfstr[ElfStrNoteOpenbsdIdent] = addstring(shstrtab, ".note.openbsd.ident");
+	if(buildinfolen > 0)
+		elfstr[ElfStrNoteBuildInfo] = addstring(shstrtab, ".note.gnu.build-id");
 	addstring(shstrtab, ".rodata");
 	addstring(shstrtab, ".gcdata");
 	addstring(shstrtab, ".gcbss");
@@ -669,7 +672,7 @@ asmb(void)
 	int a, dynsym;
 	uint32 fo, symo, startva, resoff;
 	ElfEhdr *eh;
-	ElfPhdr *ph, *pph;
+	ElfPhdr *ph, *pph, *pnote;
 	ElfShdr *sh;
 	Section *sect;
 	int o;
@@ -706,6 +709,8 @@ asmb(void)
 		}
 		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd)
 			elftextsh += 1;
+		if(buildinfolen > 0)
+			elftextsh += 1;
 	}
 
 	/* output symbol table */
@@ -876,6 +881,7 @@ asmb(void)
 			phsh(ph, sh);
 		}
 
+		pnote = nil;
 		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd) {
 			sh = nil;
 			switch(HEADTYPE) {
@@ -889,10 +895,22 @@ asmb(void)
 				break;
 			}
 
-			ph = newElfPhdr();
-			ph->type = PT_NOTE;
-			ph->flags = PF_R;
-			phsh(ph, sh);
+			pnote = newElfPhdr();
+			pnote->type = PT_NOTE;
+			pnote->flags = PF_R;
+			phsh(pnote, sh);
+		}
+
+		if(buildinfolen > 0) {
+			sh = newElfShdr(elfstr[ElfStrNoteBuildInfo]);
+			resoff -= elfbuildinfo(sh, startva, resoff);
+
+			if(pnote == nil) {
+				pnote = newElfPhdr();
+				pnote->type = PT_NOTE;
+				pnote->flags = PF_R;
+			}
+			phsh(pnote, sh);
 		}
 
 		elfphload(&segtext);
@@ -1079,6 +1097,8 @@ asmb(void)
 			a += elfwritenetbsdsig(elfstr[ElfStrNoteNetbsdIdent]);
 		if(HEADTYPE == Hopenbsd)
 			a += elfwriteopenbsdsig(elfstr[ElfStrNoteOpenbsdIdent]);
+		if(buildinfolen > 0)
+			a += elfwritebuildinfo(elfstr[ElfStrNoteBuildInfo]);
 		if(a > ELFRESERVE)	
 			diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE);
 		break;

src/cmd/5l/obj.c

@@ -143,6 +143,10 @@ main(int argc, char *argv[])
 		val = EARGF(usage());
 		addstrdata(name, val);
 		break;
+	case 'B':
+		val = EARGF(usage());
+		addbuildinfo(val);
+		break;
 	} ARGEND
 
 	USED(argc);

src/cmd/6l/asm.c

@@ -96,6 +96,7 @@ enum {
 	ElfStrGnuVersionR,
 	ElfStrNoteNetbsdIdent,
 	ElfStrNoteOpenbsdIdent,
+	ElfStrNoteBuildInfo,
 	ElfStrNoPtrData,
 	ElfStrNoPtrBss,
 	NElfStr
@@ -597,6 +598,8 @@ doelf(void)
 		elfstr[ElfStrNoteNetbsdIdent] = addstring(shstrtab, ".note.netbsd.ident");
 	if(HEADTYPE == Hopenbsd)
 		elfstr[ElfStrNoteOpenbsdIdent] = addstring(shstrtab, ".note.openbsd.ident");
+	if(buildinfolen > 0)
+		elfstr[ElfStrNoteBuildInfo] = addstring(shstrtab, ".note.gnu.build-id");
 	addstring(shstrtab, ".elfdata");
 	addstring(shstrtab, ".rodata");
 	addstring(shstrtab, ".gcdata");
@@ -734,7 +737,7 @@ asmb(void)
 	int a, dynsym;
 	vlong vl, startva, symo, dwarfoff, machlink, resoff;
 	ElfEhdr *eh;
-	ElfPhdr *ph, *pph;
+	ElfPhdr *ph, *pph, *pnote;
 	ElfShdr *sh;
 	Section *sect;
 	Sym *sym;
@@ -807,6 +810,8 @@ asmb(void)
 		}
 		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd)
 			elftextsh += 1;
+		if(buildinfolen > 0)
+			elftextsh += 1;
 		break;
 	case Hwindows:
 		break;
@@ -976,6 +981,7 @@ asmb(void)
 			phsh(ph, sh);
 		}
 
+		pnote = nil;
 		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd) {
 			sh = nil;
 			switch(HEADTYPE) {
@@ -989,10 +995,22 @@ asmb(void)
 				break;
 			}
 
-			ph = newElfPhdr();
-			ph->type = PT_NOTE;
-			ph->flags = PF_R;
-			phsh(ph, sh);
+			pnote = newElfPhdr();
+			pnote->type = PT_NOTE;
+			pnote->flags = PF_R;
+			phsh(pnote, sh);
+		}
+
+		if(buildinfolen > 0) {
+			sh = newElfShdr(elfstr[ElfStrNoteBuildInfo]);
+			resoff -= elfbuildinfo(sh, startva, resoff);
+
+			if(pnote == nil) {
+				pnote = newElfPhdr();
+				pnote->type = PT_NOTE;
+				pnote->flags = PF_R;
+			}
+			phsh(pnote, sh);
 		}
 
 		elfphload(&segtext);
@@ -1179,6 +1197,8 @@ asmb(void)
 			a += elfwritenetbsdsig(elfstr[ElfStrNoteNetbsdIdent]);
 		if(HEADTYPE == Hopenbsd)
 			a += elfwriteopenbsdsig(elfstr[ElfStrNoteOpenbsdIdent]);
+		if(buildinfolen > 0)
+			a += elfwritebuildinfo(elfstr[ElfStrNoteBuildInfo]);
 		if(a > ELFRESERVE)	
 			diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE);
 		break;

src/cmd/6l/obj.c

@@ -140,6 +140,10 @@ main(int argc, char *argv[])
 		val = EARGF(usage());
 		addstrdata(name, val);
 		break;
+	case 'B':
+		val = EARGF(usage());
+		addbuildinfo(val);
+		break;
 	} ARGEND
 
 	if(argc != 1)

src/cmd/8l/asm.c

@@ -92,6 +92,7 @@ enum {
 	ElfStrGnuVersionR,
 	ElfStrNoteNetbsdIdent,
 	ElfStrNoteOpenbsdIdent,
+	ElfStrNoteBuildInfo,
 	ElfStrNoPtrData,
 	ElfStrNoPtrBss,
 	NElfStr
@@ -573,6 +574,8 @@ doelf(void)
 		elfstr[ElfStrNoteNetbsdIdent] = addstring(shstrtab, ".note.netbsd.ident");
 	if(HEADTYPE == Hopenbsd)
 		elfstr[ElfStrNoteOpenbsdIdent] = addstring(shstrtab, ".note.openbsd.ident");
+	if(buildinfolen > 0)
+		elfstr[ElfStrNoteBuildInfo] = addstring(shstrtab, ".note.gnu.build-id");
 	addstring(shstrtab, ".elfdata");
 	addstring(shstrtab, ".rodata");
 	addstring(shstrtab, ".gcdata");
@@ -710,7 +713,7 @@ asmb(void)
 	int a, dynsym;
 	uint32 symo, startva, dwarfoff, machlink, resoff;
 	ElfEhdr *eh;
-	ElfPhdr *ph, *pph;
+	ElfPhdr *ph, *pph, *pnote;
 	ElfShdr *sh;
 	Section *sect;
 	Sym *sym;
@@ -764,6 +767,8 @@ asmb(void)
 		}
 		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd)
 			elftextsh += 1;
+		if(buildinfolen > 0)
+			elftextsh += 1;
 	}
 
 	symsize = 0;
@@ -1036,6 +1041,7 @@ asmb(void)
 			phsh(ph, sh);
 		}
 
+		pnote = nil;
 		if(HEADTYPE == Hnetbsd || HEADTYPE == Hopenbsd) {
 			sh = nil;
 			switch(HEADTYPE) {
@@ -1049,10 +1055,22 @@ asmb(void)
 				break;
 			}
 
-			ph = newElfPhdr();
-			ph->type = PT_NOTE;
-			ph->flags = PF_R;
-			phsh(ph, sh);
+			pnote = newElfPhdr();
+			pnote->type = PT_NOTE;
+			pnote->flags = PF_R;
+			phsh(pnote, sh);
+		}
+
+		if(buildinfolen > 0) {
+			sh = newElfShdr(elfstr[ElfStrNoteBuildInfo]);
+			resoff -= elfbuildinfo(sh, startva, resoff);
+
+			if(pnote == nil) {
+				pnote = newElfPhdr();
+				pnote->type = PT_NOTE;
+				pnote->flags = PF_R;
+			}
+			phsh(pnote, sh);
 		}
 
 		// Additions to the reserved area must be above this line.
@@ -1249,6 +1267,8 @@ asmb(void)
 			a += elfwritenetbsdsig(elfstr[ElfStrNoteNetbsdIdent]);
 		if(HEADTYPE == Hopenbsd)
 			a += elfwriteopenbsdsig(elfstr[ElfStrNoteOpenbsdIdent]);
+		if(buildinfolen > 0)
+			a += elfwritebuildinfo(elfstr[ElfStrNoteBuildInfo]);
 		if(a > ELFRESERVE)	
 			diag("ELFRESERVE too small: %d > %d", a, ELFRESERVE);
 		break;

src/cmd/8l/obj.c

@@ -145,6 +145,10 @@ main(int argc, char *argv[])
 		val = EARGF(usage());
 		addstrdata(name, val);
 		break;
+	case 'B':
+		val = EARGF(usage());
+		addbuildinfo(val);
+		break;
 	} ARGEND
 
 	if(argc != 1)

src/cmd/ld/doc.go

@@ -58,5 +58,8 @@ Options new in this version:
 		as displayed in the symbol table printed by "go tool nm".
 	-b
 		Link with race detection libraries.
+	-B value
+		Add a NT_GNU_BUILD_ID note when using ELF.  The value
+		should start with 0x and be an even number of hex digits.
 */
 package documentation

src/cmd/ld/elf.c

@@ -31,6 +31,8 @@ struct Elfstring
 static Elfstring elfstr[100];
 static int nelfstr;
 
+static char buildinfo[32];
+
 /*
  Initialize the global variable that describes the ELF header. It will be updated as
  we write section and prog headers.
@@ -455,6 +457,77 @@ elfwriteopenbsdsig(vlong stridx)
 	return sh->size;
 }
 
+void
+addbuildinfo(char *val)
+{
+	char *ov;
+	int i, b, j;
+
+	if(val[0] != '0' || val[1] != 'x') {
+		fprint(2, "%s: -B argument must start with 0x: %s\n", argv0, val);
+		exits("usage");
+	}
+	ov = val;
+	val += 2;
+	i = 0;
+	while(*val != '\0') {
+		if(val[1] == '\0') {
+			fprint(2, "%s: -B argument must have even number of digits: %s\n", argv0, ov);
+			exits("usage");
+		}
+		b = 0;
+		for(j = 0; j < 2; j++, val++) {
+			b *= 16;
+		  	if(*val >= '0' && *val <= '9')
+				b += *val - '0';
+			else if(*val >= 'a' && *val <= 'f')
+				b += *val - 'a' + 10;
+			else if(*val >= 'A' && *val <= 'F')
+				b += *val - 'A' + 10;
+			else {
+				fprint(2, "%s: -B argument contains invalid hex digit %c: %s\n", argv0, *val, ov);
+				exits("usage");
+			}
+		}
+		if(i >= nelem(buildinfo)) {
+			fprint(2, "%s: -B option too long (max %d digits): %s\n", argv0, (int)nelem(buildinfo), ov);
+			exits("usage");
+		}
+		buildinfo[i++] = b;
+	}
+	buildinfolen = i;
+}
+
+// Build info note
+#define ELF_NOTE_BUILDINFO_NAMESZ	4
+#define ELF_NOTE_BUILDINFO_TAG		3
+#define ELF_NOTE_BUILDINFO_NAME		"GNU\0"
+
+int
+elfbuildinfo(ElfShdr *sh, uint64 startva, uint64 resoff)
+{
+	int n;
+
+	n = ELF_NOTE_BUILDINFO_NAMESZ + rnd(buildinfolen, 4);
+	return elfnote(sh, startva, resoff, n);
+}
+
+int
+elfwritebuildinfo(vlong stridx)
+{
+	ElfShdr *sh;
+
+	sh = elfwritenotehdr(stridx, ELF_NOTE_BUILDINFO_NAMESZ, buildinfolen, ELF_NOTE_BUILDINFO_TAG);
+	if(sh == nil)
+		return 0;
+
+	cwrite(ELF_NOTE_BUILDINFO_NAME, ELF_NOTE_BUILDINFO_NAMESZ);
+	cwrite(buildinfo, buildinfolen);
+	cwrite("\0\0\0", rnd(buildinfolen, 4) - buildinfolen);
+
+	return sh->size;
+}
+
 extern int nelfsym;
 int elfverneed;
 

src/cmd/ld/elf.h

@@ -979,6 +979,9 @@ int	elfnetbsdsig(ElfShdr*, uint64, uint64);
 int	elfwritenetbsdsig(vlong);
 int	elfopenbsdsig(ElfShdr*, uint64, uint64);
 int	elfwriteopenbsdsig(vlong);
+void	addbuildinfo(char*);
+int	elfbuildinfo(ElfShdr*, uint64, uint64);
+int	elfwritebuildinfo(vlong);
 void	elfdynhash(void);
 ElfPhdr* elfphload(Segment*);
 ElfShdr* elfshbits(Section*);
@@ -988,6 +991,7 @@ void	elfaddverneed(Sym*);
 EXTERN	int	elfstrsize;
 EXTERN	char*	elfstrdat;
 EXTERN	int	elftextsh;
+EXTERN	int	buildinfolen;
 
 /*
  * Total amount of space to reserve at the start of the file