github.com/bgentry/go@v0.0.0-20150121062915-6cf5a733d54d/src/liblink/sym.c

// Derived from Inferno utils/6l/obj.c and utils/6l/span.c
// http://code.google.com/p/inferno-os/source/browse/utils/6l/obj.c
// http://code.google.com/p/inferno-os/source/browse/utils/6l/span.c
//
//	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
//	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
//	Portions Copyright © 1997-1999 Vita Nuova Limited
//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
//	Portions Copyright © 2004,2006 Bruce Ellis
//	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
//	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
//	Portions Copyright © 2009 The Go Authors.  All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <link.h>

static int
yy_isalpha(int c)
{
	return c >= 0 && c <= 0xFF && isalpha(c);
}

static struct {
	char *name;
	int val;
} headers[] = {
	{"android",	Hlinux},
	{"darwin",	Hdarwin},
	{"dragonfly",	Hdragonfly},
	{"elf",		Helf},
	{"freebsd",	Hfreebsd},
	{"linux",	Hlinux},
	{"nacl",		Hnacl},
	{"netbsd",	Hnetbsd},
	{"openbsd",	Hopenbsd},
	{"plan9",	Hplan9},
	{"solaris",	Hsolaris},
	{"windows",	Hwindows},
	{"windowsgui",	Hwindows},
};

int
headtype(char *name)
{
	int i;

	for(i=0; i < nelem(headers); i++)
		if(strcmp(name, headers[i].name) == 0)
			return headers[i].val;
	return -1;
}

char*
headstr(int v)
{
	static char buf[20];
	int i;

	for(i=0; i < nelem(headers); i++)
		if(v == headers[i].val)
			return headers[i].name;
	snprint(buf, sizeof buf, "%d", v);
	return buf;
}

Link*
linknew(LinkArch *arch)
{
	Link *ctxt;
	char *p;
	char buf[1024];

	linksetexp();
	nuxiinit(arch);
	
	ctxt = emallocz(sizeof *ctxt);
	ctxt->arch = arch;
	ctxt->version = HistVersion;
	ctxt->goroot = getgoroot();
	ctxt->goroot_final = getenv("GOROOT_FINAL");
	if(ctxt->goroot_final != nil && ctxt->goroot_final[0] == '\0')
		ctxt->goroot_final = nil;

	p = getgoarch();
	if(strcmp(p, arch->name) != 0)
		sysfatal("invalid goarch %s (want %s)", p, arch->name);
	
	if(getwd(buf, sizeof buf) == 0)
		strcpy(buf, "/???");
	if(yy_isalpha(buf[0]) && buf[1] == ':') {
		// On Windows.
		ctxt->windows = 1;

		// Canonicalize path by converting \ to / (Windows accepts both).
		for(p=buf; *p; p++)
			if(*p == '\\')
				*p = '/';
	}
	ctxt->pathname = strdup(buf);
	
	ctxt->headtype = headtype(getgoos());
	if(ctxt->headtype < 0)
		sysfatal("unknown goos %s", getgoos());
	
	// Record thread-local storage offset.
	// TODO(rsc): Move tlsoffset back into the linker.
	switch(ctxt->headtype) {
	default:
		sysfatal("unknown thread-local storage offset for %s", headstr(ctxt->headtype));
	case Hplan9:
	case Hwindows:
		break;
	case Hlinux:
	case Hfreebsd:
	case Hnetbsd:
	case Hopenbsd:
	case Hdragonfly:
	case Hsolaris:
		/*
		 * ELF uses TLS offset negative from FS.
		 * Translate 0(FS) and 8(FS) into -16(FS) and -8(FS).
		 * Known to low-level assembly in package runtime and runtime/cgo.
		 */
		ctxt->tlsoffset = -2*ctxt->arch->ptrsize;
		break;

	case Hnacl:
		switch(ctxt->arch->thechar) {
		default:
			sysfatal("unknown thread-local storage offset for nacl/%s", ctxt->arch->name);
		case '6':
			ctxt->tlsoffset = 0;
			break;
		case '8':
			ctxt->tlsoffset = -8;
			break;
		case '5':
			ctxt->tlsoffset = 0;
			break;
		}
		break;

	case Hdarwin:
		/*
		 * OS X system constants - offset from 0(GS) to our TLS.
		 * Explained in ../../runtime/cgo/gcc_darwin_*.c.
		 */
		switch(ctxt->arch->thechar) {
		default:
			sysfatal("unknown thread-local storage offset for darwin/%s", ctxt->arch->name);
		case '6':
			ctxt->tlsoffset = 0x8a0;
			break;
		case '8':
			ctxt->tlsoffset = 0x468;
			break;
		}
		break;
	}
	
	// On arm, record goarm.
	if(ctxt->arch->thechar == '5') {
		p = getgoarm();
		if(p != nil)
			ctxt->goarm = atoi(p);
		else
			ctxt->goarm = 6;
	}

	return ctxt;
}

LSym*
linknewsym(Link *ctxt, char *symb, int v)
{
	LSym *s;

	s = malloc(sizeof(*s));
	memset(s, 0, sizeof(*s));

	s->dynid = -1;
	s->plt = -1;
	s->got = -1;
	s->name = estrdup(symb);
	s->type = 0;
	s->version = v;
	s->value = 0;
	s->sig = 0;
	s->size = 0;
	ctxt->nsymbol++;

	s->allsym = ctxt->allsym;
	ctxt->allsym = s;

	return s;
}

static LSym*
_lookup(Link *ctxt, char *symb, int v, int creat)
{
	LSym *s;
	char *p;
	uint32 h;
	int c;

	h = v;
	for(p=symb; c = *p; p++)
		h = h+h+h + c;
	h &= 0xffffff;
	h %= LINKHASH;
	for(s = ctxt->hash[h]; s != nil; s = s->hash)
		if(s->version == v && strcmp(s->name, symb) == 0)
			return s;
	if(!creat)
		return nil;

	s = linknewsym(ctxt, symb, v);
	s->extname = s->name;
	s->hash = ctxt->hash[h];
	ctxt->hash[h] = s;

	return s;
}

LSym*
linklookup(Link *ctxt, char *name, int v)
{
	return _lookup(ctxt, name, v, 1);
}

// read-only lookup
LSym*
linkrlookup(Link *ctxt, char *name, int v)
{
	return _lookup(ctxt, name, v, 0);
}

int
linksymfmt(Fmt *f)
{
	LSym *s;
	
	s = va_arg(f->args, LSym*);
	if(s == nil)
		return fmtstrcpy(f, "<nil>");
	
	return fmtstrcpy(f, s->name);
}