github.com/hbdrawn/golang@v0.0.0-20141214014649-6b835209aba2/src/cmd/ld/go.c

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// go-specific code shared across loaders (5l, 6l, 8l).

#include	"l.h"
#include	"../ld/lib.h"

// accumulate all type information from .6 files.
// check for inconsistencies.

// TODO:
//	generate debugging section in binary.
//	once the dust settles, try to move some code to
//		libmach, so that other linkers and ar can share.

/*
 *	package import data
 */
typedef struct Import Import;
struct Import
{
	Import *hash;	// next in hash table
	char *prefix;	// "type", "var", "func", "const"
	char *name;
	char *def;
	char *file;
};
enum {
	NIHASH = 1024
};
static Import *ihash[NIHASH];
static int nimport;
static void imported(char *pkg, char *import);

static int
hashstr(char *name)
{
	uint32 h;
	char *cp;

	h = 0;
	for(cp = name; *cp; h += *cp++)
		h *= 1119;
	h &= 0xffffff;
	return h;
}

static Import *
ilookup(char *name)
{
	int h;
	Import *x;

	h = hashstr(name) % NIHASH;
	for(x=ihash[h]; x; x=x->hash)
		if(x->name[0] == name[0] && strcmp(x->name, name) == 0)
			return x;
	x = mal(sizeof *x);
	x->name = estrdup(name);
	x->hash = ihash[h];
	ihash[h] = x;
	nimport++;
	return x;
}

static void loadpkgdata(char*, char*, char*, int);
static void loadcgo(char*, char*, char*, int);
static int parsemethod(char**, char*, char**);
static int parsepkgdata(char*, char*, char**, char*, char**, char**, char**);

void
ldpkg(Biobuf *f, char *pkg, int64 len, char *filename, int whence)
{
	char *data, *p0, *p1, *name;

	if(debug['g'])
		return;

	if((int)len != len) {
		fprint(2, "%s: too much pkg data in %s\n", argv0, filename);
		if(debug['u'])
			errorexit();
		return;
	}
	data = mal(len+1);
	if(Bread(f, data, len) != len) {
		fprint(2, "%s: short pkg read %s\n", argv0, filename);
		if(debug['u'])
			errorexit();
		return;
	}
	data[len] = '\0';

	// first \n$$ marks beginning of exports - skip rest of line
	p0 = strstr(data, "\n$$");
	if(p0 == nil) {
		if(debug['u'] && whence != ArchiveObj) {
			fprint(2, "%s: cannot find export data in %s\n", argv0, filename);
			errorexit();
		}
		return;
	}
	p0 += 3;
	while(*p0 != '\n' && *p0 != '\0')
		p0++;

	// second marks end of exports / beginning of local data
	p1 = strstr(p0, "\n$$");
	if(p1 == nil) {
		fprint(2, "%s: cannot find end of exports in %s\n", argv0, filename);
		if(debug['u'])
			errorexit();
		return;
	}
	while(p0 < p1 && (*p0 == ' ' || *p0 == '\t' || *p0 == '\n'))
		p0++;
	if(p0 < p1) {
		if(strncmp(p0, "package ", 8) != 0) {
			fprint(2, "%s: bad package section in %s - %s\n", argv0, filename, p0);
			if(debug['u'])
				errorexit();
			return;
		}
		p0 += 8;
		while(p0 < p1 && (*p0 == ' ' || *p0 == '\t' || *p0 == '\n'))
			p0++;
		name = p0;
		while(p0 < p1 && *p0 != ' ' && *p0 != '\t' && *p0 != '\n')
			p0++;
		if(debug['u'] && whence != ArchiveObj &&
		   (p0+6 > p1 || memcmp(p0, " safe\n", 6) != 0)) {
			fprint(2, "%s: load of unsafe package %s\n", argv0, filename);
			nerrors++;
			errorexit();
		}
		if(p0 < p1) {
			if(*p0 == '\n')
				*p0++ = '\0';
			else {
				*p0++ = '\0';
				while(p0 < p1 && *p0++ != '\n')
					;
			}
		}
		if(strcmp(pkg, "main") == 0 && strcmp(name, "main") != 0) {
			fprint(2, "%s: %s: not package main (package %s)\n", argv0, filename, name);
			nerrors++;
			errorexit();
		}
		loadpkgdata(filename, pkg, p0, p1 - p0);
	}
	
	// __.PKGDEF has no cgo section - those are in the C compiler-generated object files.
	if(whence == Pkgdef)
		return;

	// look for cgo section
	p0 = strstr(p1, "\n$$  // cgo");
	if(p0 != nil) {
		p0 = strchr(p0+1, '\n');
		if(p0 == nil) {
			fprint(2, "%s: found $$ // cgo but no newline in %s\n", argv0, filename);
			if(debug['u'])
				errorexit();
			return;
		}
		p1 = strstr(p0, "\n$$");
		if(p1 == nil)
			p1 = strstr(p0, "\n!\n");
		if(p1 == nil) {
			fprint(2, "%s: cannot find end of // cgo section in %s\n", argv0, filename);
			if(debug['u'])
				errorexit();
			return;
		}
		loadcgo(filename, pkg, p0 + 1, p1 - (p0+1));
	}
}

static void
loadpkgdata(char *file, char *pkg, char *data, int len)
{
	char *p, *ep, *prefix, *name, *def;
	Import *x;

	file = estrdup(file);
	p = data;
	ep = data + len;
	while(parsepkgdata(file, pkg, &p, ep, &prefix, &name, &def) > 0) {
		x = ilookup(name);
		if(x->prefix == nil) {
			x->prefix = prefix;
			x->def = estrdup(def);
			x->file = file;
		} else if(strcmp(x->prefix, prefix) != 0) {
			fprint(2, "%s: conflicting definitions for %s\n", argv0, name);
			fprint(2, "%s:\t%s %s ...\n", x->file, x->prefix, name);
			fprint(2, "%s:\t%s %s ...\n", file, prefix, name);
			nerrors++;
		} else if(strcmp(x->def, def) != 0) {
			fprint(2, "%s: conflicting definitions for %s\n", argv0, name);
			fprint(2, "%s:\t%s %s %s\n", x->file, x->prefix, name, x->def);
			fprint(2, "%s:\t%s %s %s\n", file, prefix, name, def);
			nerrors++;
		}
		free(name);
		free(def);
	}
	free(file);
}

static int
parsepkgdata(char *file, char *pkg, char **pp, char *ep, char **prefixp, char **namep, char **defp)
{
	char *p, *prefix, *name, *def, *edef, *meth;
	int n, inquote;

	// skip white space
	p = *pp;
loop:
	while(p < ep && (*p == ' ' || *p == '\t' || *p == '\n'))
		p++;
	if(p == ep || strncmp(p, "$$\n", 3) == 0)
		return 0;

	// prefix: (var|type|func|const)
	prefix = p;
	if(p + 7 > ep)
		return -1;
	if(strncmp(p, "var ", 4) == 0)
		p += 4;
	else if(strncmp(p, "type ", 5) == 0)
		p += 5;
	else if(strncmp(p, "func ", 5) == 0)
		p += 5;
	else if(strncmp(p, "const ", 6) == 0)
		p += 6;
	else if(strncmp(p, "import ", 7) == 0) {
		p += 7;
		while(p < ep && *p != ' ')
			p++;
		p++;
		name = p;
		while(p < ep && *p != '\n')
			p++;
		if(p >= ep) {
			fprint(2, "%s: %s: confused in import line\n", argv0, file);
			nerrors++;
			return -1;
		}
		*p++ = '\0';
		imported(pkg, name);
		goto loop;
	}
	else {
		fprint(2, "%s: %s: confused in pkg data near <<%.40s>>\n", argv0, file, prefix);
		nerrors++;
		return -1;
	}
	p[-1] = '\0';

	// name: a.b followed by space
	name = p;
	inquote = 0;
	while(p < ep) {
		if (*p == ' ' && !inquote)
			break;

		if(*p == '\\')
			p++;
		else if(*p == '"')
			inquote = !inquote;

		p++;
	}

	if(p >= ep)
		return -1;
	*p++ = '\0';

	// def: free form to new line
	def = p;
	while(p < ep && *p != '\n')
		p++;
	if(p >= ep)
		return -1;
	edef = p;
	*p++ = '\0';

	// include methods on successive lines in def of named type
	while(parsemethod(&p, ep, &meth) > 0) {
		*edef++ = '\n';	// overwrites '\0'
		if(edef+1 > meth) {
			// We want to indent methods with a single \t.
			// 6g puts at least one char of indent before all method defs,
			// so there will be room for the \t.  If the method def wasn't
			// indented we could do something more complicated,
			// but for now just diagnose the problem and assume
			// 6g will keep indenting for us.
			fprint(2, "%s: %s: expected methods to be indented %p %p %.10s\n", argv0,
				file, edef, meth, meth);
			nerrors++;
			return -1;
		}
		*edef++ = '\t';
		n = strlen(meth);
		memmove(edef, meth, n);
		edef += n;
	}

	name = expandpkg(name, pkg);
	def = expandpkg(def, pkg);

	// done
	*pp = p;
	*prefixp = prefix;
	*namep = name;
	*defp = def;
	return 1;
}

static int
parsemethod(char **pp, char *ep, char **methp)
{
	char *p;

	// skip white space
	p = *pp;
	while(p < ep && (*p == ' ' || *p == '\t'))
		p++;
	if(p == ep)
		return 0;

	// might be a comment about the method
	if(p + 2 < ep && strncmp(p, "//", 2) == 0)
		goto useline;
	
	// if it says "func (", it's a method
	if(p + 6 < ep && strncmp(p, "func (", 6) == 0)
		goto useline;
	return 0;

useline:
	// definition to end of line
	*methp = p;
	while(p < ep && *p != '\n')
		p++;
	if(p >= ep) {
		fprint(2, "%s: lost end of line in method definition\n", argv0);
		*pp = ep;
		return -1;
	}
	*p++ = '\0';
	*pp = p;
	return 1;
}

static void
loadcgo(char *file, char *pkg, char *p, int n)
{
	char *pend, *next, *p0, *q;
	char *f[10], *local, *remote, *lib;
	int nf;
	LSym *s;

	USED(file);
	pend = p + n;
	p0 = nil;
	for(; p<pend; p=next) {
		next = strchr(p, '\n');
		if(next == nil)
			next = "";
		else
			*next++ = '\0';

		free(p0);
		p0 = estrdup(p); // save for error message
		nf = tokenize(p, f, nelem(f));
		
		if(strcmp(f[0], "cgo_import_dynamic") == 0) {
			if(nf < 2 || nf > 4)
				goto err;
			
			local = f[1];
			remote = local;
			if(nf > 2)
				remote = f[2];
			lib = "";
			if(nf > 3)
				lib = f[3];
			
			if(debug['d']) {
				fprint(2, "%s: %s: cannot use dynamic imports with -d flag\n", argv0, file);
				nerrors++;
				return;
			}
		
			if(strcmp(local, "_") == 0 && strcmp(remote, "_") == 0) {
				// allow #pragma dynimport _ _ "foo.so"
				// to force a link of foo.so.
				havedynamic = 1;
				adddynlib(lib);
				continue;
			}

			local = expandpkg(local, pkg);
			q = strchr(remote, '#');
			if(q)
				*q++ = '\0';
			s = linklookup(ctxt, local, 0);
			if(local != f[1])
				free(local);
			if(s->type == 0 || s->type == SXREF || s->type == SHOSTOBJ) {
				s->dynimplib = lib;
				s->extname = remote;
				s->dynimpvers = q;
				if(s->type != SHOSTOBJ)
					s->type = SDYNIMPORT;
				havedynamic = 1;
			}
			continue;
		}
		
		if(strcmp(f[0], "cgo_import_static") == 0) {
			if(nf != 2)
				goto err;
			local = f[1];
			s = linklookup(ctxt, local, 0);
			s->type = SHOSTOBJ;
			s->size = 0;
			continue;
		}

		if(strcmp(f[0], "cgo_export_static") == 0 || strcmp(f[0], "cgo_export_dynamic") == 0) {
			// TODO: Remove once we know Windows is okay.
			if(strcmp(f[0], "cgo_export_static") == 0 && HEADTYPE == Hwindows)
				continue;

			if(nf < 2 || nf > 3)
				goto err;
			local = f[1];
			if(nf > 2)
				remote = f[2];
			else
				remote = local;
			local = expandpkg(local, pkg);
			s = linklookup(ctxt, local, 0);

			if(flag_shared && s == linklookup(ctxt, "main", 0))
				continue;

			// export overrides import, for openbsd/cgo.
			// see issue 4878.
			if(s->dynimplib != nil) {
				s->dynimplib = nil;
				s->extname = nil;
				s->dynimpvers = nil;
				s->type = 0;
			}

			if(s->cgoexport == 0) {
				s->extname = remote;
				if(ndynexp%32 == 0)
					dynexp = erealloc(dynexp, (ndynexp+32)*sizeof dynexp[0]);
				dynexp[ndynexp++] = s;
			} else if(strcmp(s->extname, remote) != 0) {
				fprint(2, "%s: conflicting cgo_export directives: %s as %s and %s\n", argv0, s->name, s->extname, remote);
				nerrors++;
				return;
			}
			if(strcmp(f[0], "cgo_export_static") == 0)
				s->cgoexport |= CgoExportStatic;
			else
				s->cgoexport |= CgoExportDynamic;
			if(local != f[1])
				free(local);
			continue;
		}
		
		if(strcmp(f[0], "cgo_dynamic_linker") == 0) {
			if(nf != 2)
				goto err;
			
			if(!debug['I']) { // not overridden by command line
				if(interpreter != nil && strcmp(interpreter, f[1]) != 0) {
					fprint(2, "%s: conflict dynlinker: %s and %s\n", argv0, interpreter, f[1]);
					nerrors++;
					return;
				}
				free(interpreter);
				interpreter = estrdup(f[1]);
			}
			continue;
		}
		
		if(strcmp(f[0], "cgo_ldflag") == 0) {
			if(nf != 2)
				goto err;
			if(nldflag%32 == 0)
				ldflag = erealloc(ldflag, (nldflag+32)*sizeof ldflag[0]);
			ldflag[nldflag++] = estrdup(f[1]);
			continue;
		}
	}
	free(p0);
	return;

err:
	fprint(2, "%s: %s: invalid dynimport line: %s\n", argv0, file, p0);
	nerrors++;
}

static LSym *markq;
static LSym *emarkq;

static void
mark1(LSym *s, LSym *parent)
{
	if(s == S || s->reachable)
		return;
	if(strncmp(s->name, "go.weak.", 8) == 0)
		return;
	s->reachable = 1;
	s->reachparent = parent;
	if(markq == nil)
		markq = s;
	else
		emarkq->queue = s;
	emarkq = s;
}

void
mark(LSym *s)
{
	mark1(s, nil);
}

static void
markflood(void)
{
	Auto *a;
	LSym *s;
	int i;
	
	for(s=markq; s!=S; s=s->queue) {
		if(s->type == STEXT) {
			if(debug['v'] > 1)
				Bprint(&bso, "marktext %s\n", s->name);
			for(a=s->autom; a; a=a->link)
				mark1(a->gotype, s);
		}
		for(i=0; i<s->nr; i++)
			mark1(s->r[i].sym, s);
		if(s->pcln) {
			for(i=0; i<s->pcln->nfuncdata; i++)
				mark1(s->pcln->funcdata[i], s);
		}
		mark1(s->gotype, s);
		mark1(s->sub, s);
		mark1(s->outer, s);
	}
}

static char*
markextra[] =
{
	"runtime.morestack",
	"runtime.morestackx",

	"runtime.morestack00",
	"runtime.morestack10",
	"runtime.morestack01",
	"runtime.morestack11",

	"runtime.morestack8",
	"runtime.morestack16",
	"runtime.morestack24",
	"runtime.morestack32",
	"runtime.morestack40",
	"runtime.morestack48",
	
	// on arm, lock in the div/mod helpers too
	"_div",
	"_divu",
	"_mod",
	"_modu",
};

void
deadcode(void)
{
	int i;
	LSym *s, *last, *p;
	Fmt fmt;

	if(debug['v'])
		Bprint(&bso, "%5.2f deadcode\n", cputime());

	mark(linklookup(ctxt, INITENTRY, 0));
	for(i=0; i<nelem(markextra); i++)
		mark(linklookup(ctxt, markextra[i], 0));

	for(i=0; i<ndynexp; i++)
		mark(dynexp[i]);

	markflood();
	
	// keep each beginning with 'typelink.' if the symbol it points at is being kept.
	for(s = ctxt->allsym; s != S; s = s->allsym) {
		if(strncmp(s->name, "go.typelink.", 12) == 0)
			s->reachable = s->nr==1 && s->r[0].sym->reachable;
	}

	// remove dead text but keep file information (z symbols).
	last = nil;
	for(s = ctxt->textp; s != nil; s = s->next) {
		if(!s->reachable)
			continue;
		// NOTE: Removing s from old textp and adding to new, shorter textp.
		if(last == nil)
			ctxt->textp = s;
		else
			last->next = s;
		last = s;
	}
	if(last == nil)
		ctxt->textp = nil;
	else
		last->next = nil;
	
	for(s = ctxt->allsym; s != S; s = s->allsym)
		if(strncmp(s->name, "go.weak.", 8) == 0) {
			s->special = 1;  // do not lay out in data segment
			s->reachable = 1;
			s->hide = 1;
		}
	
	// record field tracking references
	fmtstrinit(&fmt);
	for(s = ctxt->allsym; s != S; s = s->allsym) {
		if(strncmp(s->name, "go.track.", 9) == 0) {
			s->special = 1;  // do not lay out in data segment
			s->hide = 1;
			if(s->reachable) {
				fmtprint(&fmt, "%s", s->name+9);
				for(p=s->reachparent; p; p=p->reachparent)
					fmtprint(&fmt, "\t%s", p->name);
				fmtprint(&fmt, "\n");
			}
			s->type = SCONST;
			s->value = 0;
		}
	}
	if(tracksym == nil)
		return;
	s = linklookup(ctxt, tracksym, 0);
	if(!s->reachable)
		return;
	addstrdata(tracksym, fmtstrflush(&fmt));
}

void
doweak(void)
{
	LSym *s, *t;

	// resolve weak references only if
	// target symbol will be in binary anyway.
	for(s = ctxt->allsym; s != S; s = s->allsym) {
		if(strncmp(s->name, "go.weak.", 8) == 0) {
			t = linkrlookup(ctxt, s->name+8, s->version);
			if(t && t->type != 0 && t->reachable) {
				s->value = t->value;
				s->type = t->type;
				s->outer = t;
			} else {
				s->type = SCONST;
				s->value = 0;
			}
			continue;
		}
	}
}

void
addexport(void)
{
	int i;
	
	if(HEADTYPE == Hdarwin)
		return;

	for(i=0; i<ndynexp; i++)
		adddynsym(ctxt, dynexp[i]);
}

/* %Z from gc, for quoting import paths */
int
Zconv(Fmt *fp)
{
	Rune r;
	char *s, *se;
	int n;

	s = va_arg(fp->args, char*);
	if(s == nil)
		return fmtstrcpy(fp, "<nil>");

	se = s + strlen(s);

	// NOTE: Keep in sync with ../gc/go.c:/^Zconv.
	while(s < se) {
		n = chartorune(&r, s);
		s += n;
		switch(r) {
		case Runeerror:
			if(n == 1) {
				fmtprint(fp, "\\x%02x", (uchar)*(s-1));
				break;
			}
			// fall through
		default:
			if(r < ' ') {
				fmtprint(fp, "\\x%02x", r);
				break;
			}
			fmtrune(fp, r);
			break;
		case '\t':
			fmtstrcpy(fp, "\\t");
			break;
		case '\n':
			fmtstrcpy(fp, "\\n");
			break;
		case '\"':
		case '\\':
			fmtrune(fp, '\\');
			fmtrune(fp, r);
			break;
		case 0xFEFF: // BOM, basically disallowed in source code
			fmtstrcpy(fp, "\\uFEFF");
			break;
		}
	}
	return 0;
}


typedef struct Pkg Pkg;
struct Pkg
{
	uchar mark;
	uchar checked;
	Pkg *next;
	char *path;
	Pkg **impby;
	int nimpby;
	int mimpby;
	Pkg *all;
};

static Pkg *phash[1024];
static Pkg *pkgall;

static Pkg*
getpkg(char *path)
{
	Pkg *p;
	int h;
	
	h = hashstr(path) % nelem(phash);
	for(p=phash[h]; p; p=p->next)
		if(strcmp(p->path, path) == 0)
			return p;
	p = mal(sizeof *p);
	p->path = estrdup(path);
	p->next = phash[h];
	phash[h] = p;
	p->all = pkgall;
	pkgall = p;
	return p;
}

static void
imported(char *pkg, char *import)
{
	Pkg *p, *i;
	
	// everyone imports runtime, even runtime.
	if(strcmp(import, "\"runtime\"") == 0)
		return;

	pkg = smprint("\"%Z\"", pkg);  // turn pkg path into quoted form, freed below
	p = getpkg(pkg);
	i = getpkg(import);
	if(i->nimpby >= i->mimpby) {
		i->mimpby *= 2;
		if(i->mimpby == 0)
			i->mimpby = 16;
		i->impby = erealloc(i->impby, i->mimpby*sizeof i->impby[0]);
	}
	i->impby[i->nimpby++] = p;
	free(pkg);
}

static Pkg*
cycle(Pkg *p)
{
	int i;
	Pkg *bad;

	if(p->checked)
		return 0;

	if(p->mark) {
		nerrors++;
		print("import cycle:\n");
		print("\t%s\n", p->path);
		return p;
	}
	p->mark = 1;
	for(i=0; i<p->nimpby; i++) {
		if((bad = cycle(p->impby[i])) != nil) {
			p->mark = 0;
			p->checked = 1;
			print("\timports %s\n", p->path);
			if(bad == p)
				return nil;
			return bad;
		}
	}
	p->checked = 1;
	p->mark = 0;
	return 0;
}

void
importcycles(void)
{
	Pkg *p;
	
	for(p=pkgall; p; p=p->all)
		cycle(p);
}

void
setlinkmode(char *arg)
{
	if(strcmp(arg, "internal") == 0)
		linkmode = LinkInternal;
	else if(strcmp(arg, "external") == 0)
		linkmode = LinkExternal;
	else if(strcmp(arg, "auto") == 0)
		linkmode = LinkAuto;
	else {
		fprint(2, "unknown link mode -linkmode %s\n", arg);
		errorexit();
	}
}