git: 1235d276b78a - main - lib{c,sys}: stop exposing errno symbol

The branch main has been updated by brooks:

URL: https://cgit.FreeBSD.org/src/commit/?id=1235d276b78a769bded01d51c9bf3cdc480db9fb

commit 1235d276b78a769bded01d51c9bf3cdc480db9fb
Author:     Brooks Davis <brooks@FreeBSD.org>
AuthorDate: 2024-09-27 19:27:46 +0000
Commit:     Brooks Davis <brooks@FreeBSD.org>
CommitDate: 2024-09-27 19:27:46 +0000

    lib{c,sys}: stop exposing errno symbol
    
    Officially since C11 (and in reality FreeBSD since 3.0 with commit
    1b46cb523df3) errno has been defined to be a macro.  Rename the symbol
    to __libsys_errno and move it to FBSDprivate_1.0 and confine it entierly
    to libsys for use by libthr.  Add a FBSD_1.0 compat symbol for existing
    binaries that were incorrectly linked to the errno symbol during
    libc.so.7's lifetime.
    
    This deliberately breaks linking software that directly links to errno.
    Such software is broken and will fail in surprising ways if it becomes
    threaded (e.g., if it triggers loading of a pam or nss module that
    uses threads.)
    
    Reviewed by:    kib
    Differential Revision:  https://reviews.freebsd.org/D46780
---
 lib/libsys/Makefile          |  2 ++
 lib/libsys/Symbol.map        |  1 +
 lib/libsys/Symbol.sys.map    |  1 -
 lib/libsys/__error.c         | 10 +++++-----
 lib/libthr/sys/thr_error.c   |  5 ++---
 lib/libthr/thread/thr_rtld.c |  7 +++----
 6 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/lib/libsys/Makefile b/lib/libsys/Makefile
index b4c0e91e860c..b4b4662ae47f 100644
--- a/lib/libsys/Makefile
+++ b/lib/libsys/Makefile
@@ -25,6 +25,8 @@ MK_SSP=		no
 
 INCS=	libsys.h _libsys.h
 
+CFLAGS+=-DLIBSYS
+
 CFLAGS+=-I${LIBSYS_SRCTOP}/include -I${LIBC_SRCTOP}/include
 CFLAGS+=-I${LIBSYS_SRCTOP}/${LIBC_ARCH}
 CFLAGS+=-I${LIBC_SRCTOP}/${LIBC_ARCH}
diff --git a/lib/libsys/Symbol.map b/lib/libsys/Symbol.map
index b2bc69108bbb..51ea1b5da231 100644
--- a/lib/libsys/Symbol.map
+++ b/lib/libsys/Symbol.map
@@ -1,5 +1,6 @@
 FBSDprivate_1.0 {
 	__elf_aux_vector;
+	__libsys_errno;
 	__getosreldate;
 	__libsys_interposing_slot;
 	__realpathat;
diff --git a/lib/libsys/Symbol.sys.map b/lib/libsys/Symbol.sys.map
index 5a4e66baf3c4..85373b1f9cda 100644
--- a/lib/libsys/Symbol.sys.map
+++ b/lib/libsys/Symbol.sys.map
@@ -72,7 +72,6 @@ FBSD_1.0 {
 	extattr_set_file;
 	extattr_set_link;
 	extattrctl;
-	errno;
 	fchdir;
 	fchflags;
 	fchmod;
diff --git a/lib/libsys/__error.c b/lib/libsys/__error.c
index 1132bdba9c65..41016e9a1ed2 100644
--- a/lib/libsys/__error.c
+++ b/lib/libsys/__error.c
@@ -31,13 +31,15 @@
 
 #include "libc_private.h"
 
-int errno;
+int __libsys_errno;
+#ifdef LIBSYS
+__sym_compat(errno, __libsys_errno, FBSD_1.0);
+#endif
 
 static int *
 __error_unthreaded(void)
 {
-
-	return (&errno);
+	return (&__libsys_errno);
 }
 
 static int *(*__error_selector)(void) = __error_unthreaded;
@@ -45,13 +47,11 @@ static int *(*__error_selector)(void) = __error_unthreaded;
 void
 __set_error_selector(int *(*arg)(void))
 {
-
 	__error_selector = arg;
 }
 
 int *
 __error(void)
 {
-
 	return (__error_selector());
 }
diff --git a/lib/libthr/sys/thr_error.c b/lib/libthr/sys/thr_error.c
index 7ce3a84fab6b..ec7a57bf6610 100644
--- a/lib/libthr/sys/thr_error.c
+++ b/lib/libthr/sys/thr_error.c
@@ -39,8 +39,7 @@
 #include "libc_private.h"
 #include "thr_private.h"
 
-#undef errno
-extern	int	errno;
+extern int __libsys_errno;
 
 __weak_reference(__error_threaded, __error);
 int *
@@ -53,5 +52,5 @@ __error_threaded(void)
 		if (curthread != NULL && curthread != _thr_initial)
 			return (&curthread->error);
 	}
-	return (&errno);
+	return (&__libsys_errno);
 }
diff --git a/lib/libthr/thread/thr_rtld.c b/lib/libthr/thread/thr_rtld.c
index 68a02e9aca1b..e5a7f86de288 100644
--- a/lib/libthr/thread/thr_rtld.c
+++ b/lib/libthr/thread/thr_rtld.c
@@ -39,8 +39,7 @@
 #include "rtld_lock.h"
 #include "thr_private.h"
 
-#undef errno
-extern int errno;
+extern int __libsys_errno;
 
 static int	_thr_rtld_clr_flag(int);
 static void	*_thr_rtld_lock_create(void);
@@ -96,14 +95,14 @@ _thr_rtld_lock_destroy(void *lock)
 	if (curthread != _thr_initial)		\
 		errsave = curthread->error;	\
 	else					\
-		errsave = errno;		\
+		errsave = __libsys_errno;	\
 }
 
 #define RESTORE_ERRNO()	{ 			\
 	if (curthread != _thr_initial)  	\
 		curthread->error = errsave;	\
 	else					\
-		errno = errsave;		\
+		__libsys_errno = errsave;	\
 }
 
 static void