linker work

  * use //ffi comments in package import data
    to generate relocation entries and library loads.
  * call initffi in rt0.s if present

R=r
DELTA=117  (91 added, 3 deleted, 23 changed)
OCL=33739
CL=33750

src/cmd/5l/l.h

@@ -119,6 +119,7 @@ struct	Sym
 	short	frame;
 	uchar	subtype;
 	uchar	reachable;
+	uchar	ffitype;
 	ushort	file;
 	int32	value;
 	int32	sig;
@@ -131,6 +132,8 @@ struct	Sym
 	Prog*	text;
 	Prog*	data;
 	Sym*	gotype;
+	char*	ffiname;
+	char*	ffilib;
 };
 
 #define SIGNINTERN	(1729*325*1729)

src/cmd/6l/asm.c

@@ -258,10 +258,27 @@ enum {
 
 vlong elfstr[NElfStr];
 
+static int
+needlib(char *name)
+{
+	char *p;
+	Sym *s;
+
+	/* reuse hash code in symbol table */
+	p = smprint(".elfload.%s", name);
+	s = lookup(p, 0);
+	if(s->type == 0) {
+		s->type = 100;	// avoid SDATA, etc.
+		return 1;
+	}
+	return 0;
+}
+
 void
 doelf(void)
 {
-	Sym *s, *shstrtab;
+	Sym *s, *shstrtab, *dynamic, *dynstr, *d;
+	int h, nsym, t;
 
 	if(HEADTYPE != 7)
 		return;
@@ -279,8 +296,6 @@ doelf(void)
 	elfstr[ElfStrShstrtab] = addstring(shstrtab, ".shstrtab");
 
 	if(!debug['d']) {	/* -d suppresses dynamic loader format */
-		Sym *dynamic, *dynstr;
-
 		elfstr[ElfStrInterp] = addstring(shstrtab, ".interp");
 		elfstr[ElfStrHash] = addstring(shstrtab, ".hash");
 		elfstr[ElfStrGot] = addstring(shstrtab, ".got");
@@ -338,28 +353,45 @@ doelf(void)
 		dynamic = s;
 
 		/*
-		 * relocation demo - overwrite go func
-		 * var main.extern_c_fib with fib symbol from fib.so
+		 * relocation entries for extern ffi symbols
 		 */
-		Sym *fib;
-		fib = lookup("main·extern_c_fib", 0);
-		if(fib->type == SDATA || fib->type == SBSS) {
-			s = lookup(".rela", 0);
-			addaddr(s, fib);
-			adduint64(s, ELF64_R_INFO(1, R_X86_64_64));	// 1 = first symbol in dynsym
-			adduint64(s, 0);
+		nsym = 1;	// sym 0 is reserved
+		for(h=0; h<NHASH; h++) {
+			for(s=hash[h]; s!=S; s=s->link) {
+				if(!s->reachable || (s->type != SDATA && s->type != SBSS) || s->ffiname == nil)
+					continue;
 
-			s = lookup(".dynsym", 0);
-			adduint32(s, addstring(lookup(".dynstr", 0), "fib"));
-			adduint8(s, (STB_GLOBAL<<4) | STT_FUNC);
-			adduint8(s, 0);		/* reserved */
-			adduint16(s, SHN_UNDEF);	/* section where symbol is defined */
-			adduint64(s, 0);	/* value */
-			adduint64(s, 0);	/* size of object */
-
-			elfwritedynent(dynamic, DT_NEEDED, addstring(dynstr, "fib.so"));
+				d = lookup(".rela", 0);
+				addaddr(d, s);
+				adduint64(d, ELF64_R_INFO(nsym, R_X86_64_64));
+				adduint64(d, 0);
+				nsym++;
+
+				d = lookup(".dynsym", 0);
+				adduint32(d, addstring(lookup(".dynstr", 0), s->ffiname));
+				t = STB_GLOBAL << 4;
+				switch(s->ffitype) {
+				case 'T':
+					t |= STT_FUNC;
+					break;
+				case 'D':
+					t |= STT_OBJECT;
+					break;
+				}
+				adduint8(d, t);
+				adduint8(d, 0);	/* reserved */
+				adduint16(d, SHN_UNDEF);	/* section where symbol is defined */
+				adduint64(d, 0);	/* value */
+				adduint64(d, 0);	/* size of object */
+
+				if(needlib(s->ffilib))
+					elfwritedynent(dynamic, DT_NEEDED, addstring(dynstr, s->ffilib));
+			}
 		}
 
+		/*
+		 * .dynamic table
+		 */
 		s = dynamic;
 		elfwritedynentsym(s, DT_HASH, lookup(".hash", 0));
 		elfwritedynentsym(s, DT_SYMTAB, lookup(".dynsym", 0));

src/cmd/6l/l.h

@@ -119,6 +119,7 @@ struct	Sym
 	uchar	subtype;
 	uchar	dupok;
 	uchar	reachable;
+	uchar	ffitype;
 	vlong	value;
 	vlong	size;
 	int32	sig;
@@ -126,6 +127,8 @@ struct	Sym
 	Prog*	text;
 	Prog*	data;
 	Sym*	gotype;
+	char*	ffiname;
+	char*	ffilib;
 };
 struct	Optab
 {

src/cmd/8l/l.h

@@ -116,6 +116,7 @@ struct	Sym
 	uchar	subtype;
 	uchar	dupok;
 	uchar	reachable;
+	uchar	ffitype;
 	ushort	file;
 	int32	value;
 	int32	sig;
@@ -123,6 +124,9 @@ struct	Sym
 	Prog*	text;
 	Prog*	data;
 	Sym*	gotype;
+	char*	ffiname;
+	char*	ffilib;
+
 };
 struct	Optab
 {

src/cmd/ld/go.c

@@ -190,6 +190,7 @@ parsepkgdata(char *file, char **pp, char *ep, char **prefixp, char **namep, char
 	char *p, *prefix, *name, *def, *edef, *meth;
 	int n;
 
+again:
 	// skip white space
 	p = *pp;
 	while(p < ep && (*p == ' ' || *p == '\t' || *p == '\n'))
@@ -211,8 +212,46 @@ parsepkgdata(char *file, char **pp, char *ep, char **prefixp, char **namep, char
 		p += 5;
 	else if(strncmp(p, "const ", 6) == 0)
 		p += 6;
-	else{
-		fprint(2, "%s: confused in pkg data near <<%.20s>>\n", argv0, p);
+	else if(strncmp(p, "//ffi ", 6) == 0) {
+		Sym *s;
+		char type, *lib;
+
+		p += 6;
+		if(*p == 0 || *(p+1) != ' ')
+			goto err;
+		type = *p;
+		p += 2;
+		name = p;
+		p = strchr(name, ' ');
+		if(p == nil)
+			goto err;
+		while(*p == ' ')
+			p++;
+		def = p;
+		p = strchr(def, ' ');
+		if(p == nil)
+			goto err;
+		while(*p == ' ')
+			p++;
+		lib = p;
+		p = strchr(lib, '\n');
+		if(p == nil)
+			goto err;
+
+		// successful parse: now can edit the line
+		*strchr(name, ' ') = 0;
+		*strchr(def, ' ') = 0;
+		*strchr(lib, '\n') = 0;
+		*pp = p+1;
+
+		s = lookup(name, 0);
+		s->ffitype = type;
+		s->ffilib = lib;
+		s->ffiname = def;
+		goto again;
+	} else {
+	err:
+		fprint(2, "%s: confused in pkg data near <<%.20s>>\n", argv0, prefix);
 		nerrors++;
 		return -1;
 	}

src/pkg/runtime/linux/amd64/rt0.s

@@ -5,5 +5,12 @@
 // Darwin and Linux use the same linkage to main
 
 TEXT	_rt0_amd64_linux(SB),7,$-8
+	MOVQ	_initffi(SB), AX
+	TESTQ	AX, AX
+	JZ	2(PC)
+	CALL	AX
+
 	MOVQ	$_rt0_amd64(SB), AX
 	JMP	AX
+
+GLOBL _initffi(SB), $8