From 6e94624a627c388f3ecf306f99a064e7b3d685cc Mon Sep 17 00:00:00 2001
From: thorpej <thorpej@NetBSD.org>
Date: Fri, 14 Dec 2001 00:53:06 +0000
Subject: [PATCH] Add code to peek into the PLT and determine which PLT entry
 format is being used.

---
 libexec/ld.elf_so/arch/alpha/Makefile.inc  |  3 +-
 libexec/ld.elf_so/arch/alpha/alpha_reloc.c | 58 +++++++++++++++++++---
 libexec/ld.elf_so/reloc.c                  |  4 +-
 libexec/ld.elf_so/rtld.h                   |  4 +-
 4 files changed, 58 insertions(+), 11 deletions(-)

diff --git a/libexec/ld.elf_so/arch/alpha/Makefile.inc b/libexec/ld.elf_so/arch/alpha/Makefile.inc
index d7c9f4273328..c69459f2c47c 100644
--- a/libexec/ld.elf_so/arch/alpha/Makefile.inc
+++ b/libexec/ld.elf_so/arch/alpha/Makefile.inc
@@ -1,7 +1,8 @@
-#	$NetBSD: Makefile.inc,v 1.5 2001/12/13 22:34:52 thorpej Exp $
+#	$NetBSD: Makefile.inc,v 1.6 2001/12/14 00:53:07 thorpej Exp $
 
 SRCS+=	rtld_start.S alpha_reloc.c
 
 CPPFLAGS+= -fpic -mno-fp-regs -DELFSIZE=64
+#CPPFLAGS+= -DRTLD_DEBUG_ALPHA
 LDFLAGS+= -Bshareable -Bsymbolic -e _rtld_start
 LDFLAGS+= --script ${.CURDIR}/arch/alpha/ld.so.script
diff --git a/libexec/ld.elf_so/arch/alpha/alpha_reloc.c b/libexec/ld.elf_so/arch/alpha/alpha_reloc.c
index 3edad5afbe5e..e9207ad43ffa 100644
--- a/libexec/ld.elf_so/arch/alpha/alpha_reloc.c
+++ b/libexec/ld.elf_so/arch/alpha/alpha_reloc.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: alpha_reloc.c,v 1.1 2001/12/13 22:34:52 thorpej Exp $	*/
+/*	$NetBSD: alpha_reloc.c,v 1.2 2001/12/14 00:53:07 thorpej Exp $	*/
 
 /*
  * Copyright (c) 2001 Wasabi Systems, Inc.
@@ -39,6 +39,13 @@
 #include <sys/stat.h>
 
 #include "rtld.h"
+#include "debug.h"
+
+#ifdef RTLD_DEBUG_ALPHA
+#define	adbg(x)		if (dodebug) xprintf x
+#else
+#define	adbg(x)		/* nothing */
+#endif
 
 /*
  * _rtld_setup_alpha_pltgot:
@@ -46,16 +53,54 @@
  *	Set up the Alpha pltgot glue.
  */
 void
-_rtld_setup_alpha_pltgot(const Obj_Entry *obj)
+_rtld_setup_alpha_pltgot(const Obj_Entry *obj, bool dodebug)
 {
+	uint32_t word0;
 
 	/*
-	 * XXX We need to look at the one of the PLT entries and
-	 * XXX see which format it's in, and set the binding routine
-	 * XXX appropriately.
+	 * The PLTGOT on the Alpha looks like this:
+	 *
+	 *	PLT HEADER
+	 *	.
+	 *	. 32 bytes
+	 *	.
+	 *	PLT ENTRY #0
+	 *	.
+	 *	. 12 bytes
+	 *	.
+	 *	PLT ENTRY #1
+	 *	.
+	 *	. 12 bytes
+	 *	.
+	 *	etc.
+	 *
+	 * The old-format entries look like (displacements filled in
+	 * by the linker):
+	 *
+	 *	ldah	$28, 0($31)		# 0x279f0000
+	 *	lda	$28, 0($28)		# 0x239c0000
+	 *	br	$31, plt0		# 0xc3e00000
+	 *
+	 * The new-format entries look like:
+	 *
+	 *	br	$28, plt0		# 0xc3800000
+	 *					# 0x00000000
+	 *					# 0x00000000
+	 *
+	 * What we do is fetch the first PLT entry and check to
+	 * see the first word of it matches the first word of the
+	 * old format.  If so, we use a binding routine that can
+	 * handle the old format, otherwise we use a binding routine
+	 * that handles the new format.
+	 *
+	 * Note that this is done on a per-object basis, we can mix
+	 * and match shared objects build with both the old and new
+	 * linker.
 	 */
-	if (1) {
+	word0 = *(uint32_t *)(((char *) obj->pltgot) + 32);
+	if ((word0 & 0xffff0000) == 0x279f0000) {
 		/* Old PLT entry format. */
+		adbg(("ALPHA: object %p has old PLT format\n", obj));
 		obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start_old;
 		obj->pltgot[3] = (Elf_Addr) obj;
 
@@ -63,6 +108,7 @@ _rtld_setup_alpha_pltgot(const Obj_Entry *obj)
 	}
 
 	/* New PLT entry format. */
+	adbg(("ALPHA: object %p has new PLT format\n", obj));
 	obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
 	obj->pltgot[3] = (Elf_Addr) obj;
 }
diff --git a/libexec/ld.elf_so/reloc.c b/libexec/ld.elf_so/reloc.c
index a65113599dde..1c9ba08b2ad8 100644
--- a/libexec/ld.elf_so/reloc.c
+++ b/libexec/ld.elf_so/reloc.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: reloc.c,v 1.44 2001/12/13 22:34:51 thorpej Exp $	 */
+/*	$NetBSD: reloc.c,v 1.45 2001/12/14 00:53:06 thorpej Exp $	 */
 
 /*
  * Copyright 1996 John D. Polstra.
@@ -778,7 +778,7 @@ _rtld_relocate_objects(first, bind_now, dodebug)
 			obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start;
 #endif
 #if defined(__alpha__)
-			_rtld_setup_alpha_pltgot(obj);
+			_rtld_setup_alpha_pltgot(obj, dodebug);
 #endif
 #if defined(__mips__)
 			_rtld_relocate_mips_got(obj);
diff --git a/libexec/ld.elf_so/rtld.h b/libexec/ld.elf_so/rtld.h
index d8d7cb177f31..a169290f4511 100644
--- a/libexec/ld.elf_so/rtld.h
+++ b/libexec/ld.elf_so/rtld.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: rtld.h,v 1.31 2001/12/13 22:34:52 thorpej Exp $	 */
+/*	$NetBSD: rtld.h,v 1.32 2001/12/14 00:53:07 thorpej Exp $	 */
 
 /*
  * Copyright 1996 John D. Polstra.
@@ -293,7 +293,7 @@ Obj_Entry *_rtld_obj_new(void);
 
 #if defined(__alpha__)
 /* alpha_reloc.c */
-void	_rtld_setup_alpha_pltgot __P((const Obj_Entry *));
+void	_rtld_setup_alpha_pltgot __P((const Obj_Entry *, bool));
 
 /* rtld_start.S */
 void	_rtld_bind_start_old __P((void));