liblink: create new library based on linker code

There is an enormous amount of code moving around in this CL,
but the code is the same, and it is invoked in the same ways.
This CL is preparation for the new linker structure, not the new
structure itself.

The new library's definition is in include/link.h.

The main change is the use of a Link structure to hold all the
linker-relevant state, replacing the smattering of global variables.
The Link structure should both make it clearer which state must
be carried around and make it possible to parallelize more easily
later.

The main body of the linker has moved into the architecture-independent
cmd/ld directory. That includes the list of known header types, so the
distinction between Hplan9x32 and Hplan9x64 is removed (no other
header type distinguished 32- and 64-bit formats), and code for unused
formats such as ipaq kernels has been deleted.

The code being deleted from 5l, 6l, and 8l reappears in liblink or in ld.
Because multiple files are being merged in the liblink directory,
it is not possible to show the diffs nicely in hg.

The Prog and Addr structures have been unified into an
architecture-independent form and moved to link.h, where they will
be shared by all tools: the assemblers, the compilers, and the linkers.
The unification makes it possible to write architecture-independent
traversal of Prog lists, among other benefits.

The Sym structures cannot be unified: they are too fundamentally
different between the linker and the compilers. Instead, liblink defines
an LSym - a linker Sym - to be used in the Prog and Addr structures,
and the linker now refers exclusively to LSyms. The compilers will
keep using their own syms but will fill out the corresponding LSyms in
the Prog and Addr structures.

Although code from 5l, 6l, and 8l is now in a single library, the
code has been arranged so that only one architecture needs to
be linked into a particular program: 5l will not contain the code
needed for x86 instruction layout, for example.

The object file writing code in liblink/obj.c is from cmd/gc/obj.c.

Preparation for golang.org/s/go13linker work.

This CL does not build by itself. It depends on 35740044
and will be submitted at the same time.

R=iant
CC=golang-dev
https://codereview.appspot.com/35790044

1 files changed, 115 insertions, 0 deletions

diff --git a/src/liblink/pass.c b/src/liblink/pass.c
new file mode 100644
index 000000000..3fe77d61b
--- /dev/null
+++ b/src/liblink/pass.c
@@ -0,0 +1,115 @@
+// Inferno utils/6l/pass.c
+// http://code.google.com/p/inferno-os/source/browse/utils/6l/pass.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.
+
+// Code and data passes.
+
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <link.h>
+
+Prog*
+brchain(Link *ctxt, Prog *p)
+{
+	int i;
+
+	for(i=0; i<20; i++) {
+		if(p == nil || p->as != ctxt->arch->AJMP)
+			return p;
+		p = p->pcond;
+	}
+	return nil;
+}
+
+Prog*
+brloop(Link *ctxt, Prog *p)
+{
+	int c;
+	Prog *q;
+
+	c = 0;
+	for(q = p; q != nil; q = q->pcond) {
+		if(q->as != ctxt->arch->AJMP)
+			break;
+		c++;
+		if(c >= 5000)
+			return nil;
+	}
+	return q;
+}
+
+void
+linkpatch(Link *ctxt, LSym *sym)
+{
+	int32 c;
+	Prog *p, *q;
+	LSym *s;
+
+	ctxt->cursym = sym;
+	
+	for(p = sym->text; p != nil; p = p->link) {
+		if(ctxt->arch->progedit)
+			ctxt->arch->progedit(ctxt, p);
+		if(p->as == ctxt->arch->ACALL || (p->as == ctxt->arch->AJMP && p->to.type != ctxt->arch->D_BRANCH) || (p->as == ctxt->arch->ARET && p->to.sym != nil)) {
+			s = p->to.sym;
+			if(s) {
+				p->to.type = ctxt->arch->D_BRANCH;
+				continue;
+			}
+		}
+		if(p->to.type != ctxt->arch->D_BRANCH)
+			continue;
+		c = p->to.offset;
+		for(q = sym->text; q != nil;) {
+			if(c == q->pc)
+				break;
+			if(q->forwd != nil && c >= q->forwd->pc)
+				q = q->forwd;
+			else
+				q = q->link;
+		}
+		if(q == nil) {
+			ctxt->diag("branch out of range (%#ux)\n%P [%s]",
+				c, p, p->to.sym ? p->to.sym->name : "<nil>");
+			p->to.type = ctxt->arch->D_NONE;
+		}
+		p->pcond = q;
+	}
+	
+	for(p = sym->text; p != nil; p = p->link) {
+		p->mark = 0;	/* initialization for follow */
+		if(p->pcond != nil) {
+			p->pcond = brloop(ctxt, p->pcond);
+			if(p->pcond != nil)
+			if(p->to.type == ctxt->arch->D_BRANCH)
+				p->to.offset = p->pcond->pc;
+		}
+	}
+}