From 08bfbd43594b7642de0d2487550f36b0ee1eceba Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sat, 10 Apr 2021 15:32:24 +0300
Subject: [PATCH] rtld: workaround for broken ABI

Right now, libthr does not initialize RtldLockInfo.rtli_version when calling
_rtld_thread_init(), which makes versioning the interface troublesome.

Add a workaround: if the calling object of _rtld_thread_init() exports
the "_pli_rtli_version" symbol, then consider rtli_version initialized.
Otherwise, forcibly set it to RTLI_VERSION_ONE, currently defined as
RTLI_VERSION.

Export "_pli_rtli_version" from libthr and properly initialize rtli_version.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D29633
---
 lib/libthr/pthread.map       |  3 +++
 lib/libthr/thread/thr_rtld.c |  8 ++++++++
 libexec/rtld-elf/rtld_lock.c | 17 ++++++++++++++++-
 libexec/rtld-elf/rtld_lock.h |  4 +++-
 4 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/lib/libthr/pthread.map b/lib/libthr/pthread.map
index 232d65084ba9..15195ce0847b 100644
--- a/lib/libthr/pthread.map
+++ b/lib/libthr/pthread.map
@@ -296,6 +296,9 @@ FBSDprivate_1.0 {
 	_thread_size_key;
 	_thread_state_running;
 	_thread_state_zoombie;
+
+	/* ABI bug workaround, indicate that pli->rtli_version is valid */
+	_pli_rtli_version;
 };
 
 FBSD_1.1 {
diff --git a/lib/libthr/thread/thr_rtld.c b/lib/libthr/thread/thr_rtld.c
index 291ca17e2068..5848fc6d5f61 100644
--- a/lib/libthr/thread/thr_rtld.c
+++ b/lib/libthr/thread/thr_rtld.c
@@ -182,6 +182,13 @@ _thr_rtld_clr_flag(int mask __unused)
 	return (0);
 }
 
+/*
+ * ABI bug workaround: This symbol must be present for rtld to accept
+ * RTLI_VERSION from RtldLockInfo
+ */
+extern char _pli_rtli_version;
+char _pli_rtli_version;
+
 void
 _thr_rtld_init(void)
 {
@@ -205,6 +212,7 @@ _thr_rtld_init(void)
 	mprotect(NULL, 0, 0);
 	_rtld_get_stack_prot();
 
+	li.rtli_version = RTLI_VERSION;
 	li.lock_create  = _thr_rtld_lock_create;
 	li.lock_destroy = _thr_rtld_lock_destroy;
 	li.rlock_acquire = _thr_rtld_rlock_acquire;
diff --git a/libexec/rtld-elf/rtld_lock.c b/libexec/rtld-elf/rtld_lock.c
index d94bd1a283e9..4d54c687ee6f 100644
--- a/libexec/rtld-elf/rtld_lock.c
+++ b/libexec/rtld-elf/rtld_lock.c
@@ -344,8 +344,23 @@ lockdflt_init(void)
 void
 _rtld_thread_init(struct RtldLockInfo *pli)
 {
-	int flags, i;
+	const Obj_Entry *obj;
+	SymLook req;
 	void *locks[RTLD_LOCK_CNT];
+	int flags, i, res;
+
+	if (pli == NULL) {
+		lockinfo.rtli_version = RTLI_VERSION;
+	} else {
+		lockinfo.rtli_version = RTLI_VERSION_ONE;
+		obj = obj_from_addr(pli->lock_create);
+		if (obj != NULL) {
+			symlook_init(&req, "_pli_rtli_version");
+			res = symlook_obj(&req, obj);
+			if (res == 0)
+				lockinfo.rtli_version = pli->rtli_version;
+		}
+	}
 
 	/* disable all locking while this function is running */
 	flags =	thread_mask_set(~0);
diff --git a/libexec/rtld-elf/rtld_lock.h b/libexec/rtld-elf/rtld_lock.h
index ecc733a06e44..7a61a1a525e2 100644
--- a/libexec/rtld-elf/rtld_lock.h
+++ b/libexec/rtld-elf/rtld_lock.h
@@ -30,7 +30,9 @@
 #ifndef _RTLD_LOCK_H_
 #define	_RTLD_LOCK_H_
 
-#define	RTLI_VERSION	0x01
+#define	RTLI_VERSION_ONE	0x01
+#define	RTLI_VERSION		0x01
+
 #define	MAX_RTLD_LOCKS	8
 
 struct RtldLockInfo