[Buildroot] [PATCH v2] LT.old: Make __errno_location/__h_errno_location thread safe

[Vineet Gupta]

WHY: errno in uClibc is not thread safe

HOW: __errno_location and it's sibling __h_errno_location need to be called
     via PLT - even from within libc. That way when linked with pthread,
     intra-uClibc callers will also use the thread safe version.

Verified with ARC LT.old and ARM cubieboard2 buildroot (LT.old)
NPTL is unaffected by this bug.

------------ History behind this patch ---------------------

This is a long standing bug (https://bugs.busybox.net/show_bug.cgi?id=2089)

Others have tried to fix it in past (alteast Peter Korsgaard's patch in 2010),
but somehow failed to be merged (or were backed out afterwards).
http://lists.uclibc.org/pipermail/uclibc/2010-July/044176.html

One of the causes could be side effect of atleast one more bug related to
pthreads and static link which has now been fixed.
http://lists.uclibc.org/pipermail/uclibc/2013-October/047958.html

I have solved this w/o looking at other pacthes but would like to give
credit to Peter and others for confirming that it makes sense.

Cc: Christian Ruppert <christian.ruppert at abilis.com>
CC: Francois Bedard <Francois.Bedard at synopsys.com>
Cc: Joern Rennecke  <joern.rennecke at embecosm.com>
Cc: Jeremy Bennett <jeremy.bennett at embecosm.com>
Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Cc: Peter Korsgaard <peter at korsgaard.com>
Cc: Khem Raj <raj.khem at gmail.com>
Cc: buildroot at busybox.net
Signed-off-by: Vineet Gupta <vgupta at synopsys.com>
---
Changes since v1 (http://lists.uclibc.org/pipermail/uclibc/2014-March/048273.html

- Rebased to trunk
- Added handling for h_errno_location

Signed-off-by: Vineet Gupta <vgupta at synopsys.com>
---
 include/netdb.h                          | 3 ---
 libc/misc/internals/__errno_location.c   | 1 -
 libc/misc/internals/__h_errno_location.c | 1 -
 libc/sysdeps/linux/common/bits/errno.h   | 3 ---
 4 files changed, 8 deletions(-)

diff --git a/include/netdb.h b/include/netdb.h
index 8fdfa0fccc7d..0f361bb6f662 100644
--- a/include/netdb.h
+++ b/include/netdb.h
@@ -59,11 +59,8 @@ __BEGIN_DECLS
 /* Function to get address of global `h_errno' variable.  */
 extern int *__h_errno_location (void) __THROW __attribute__ ((__const__));
 #ifdef _LIBC
-# if !defined(__UCLIBC_HAS_TLS__) && !defined(__UCLIBC_HAS_THREADS__)
 extern int weak_const_function *__h_errno_location(void);
-# endif
 #endif
-libc_hidden_proto(__h_errno_location)
 
 /* Macros for accessing h_errno from inside libc.  */
 #ifdef _LIBC
diff --git a/libc/misc/internals/__errno_location.c b/libc/misc/internals/__errno_location.c
index be7a9093efa3..9bbc2d779653 100644
--- a/libc/misc/internals/__errno_location.c
+++ b/libc/misc/internals/__errno_location.c
@@ -16,4 +16,3 @@ int *__errno_location(void)
 {
     return &errno;
 }
-libc_hidden_weak(__errno_location)
diff --git a/libc/misc/internals/__h_errno_location.c b/libc/misc/internals/__h_errno_location.c
index 6653681cbf09..b30859e81f19 100644
--- a/libc/misc/internals/__h_errno_location.c
+++ b/libc/misc/internals/__h_errno_location.c
@@ -16,4 +16,3 @@ int *__h_errno_location(void)
 {
     return &h_errno;
 }
-libc_hidden_weak(__h_errno_location)
diff --git a/libc/sysdeps/linux/common/bits/errno.h b/libc/sysdeps/linux/common/bits/errno.h
index 777338fb1e0a..611b8359001a 100644
--- a/libc/sysdeps/linux/common/bits/errno.h
+++ b/libc/sysdeps/linux/common/bits/errno.h
@@ -43,11 +43,8 @@
 /* Function to get address of global `errno' variable.  */
 extern int *__errno_location (void) __THROW __attribute__ ((__const__));
 #  ifdef _LIBC
-#   if !defined(__UCLIBC_HAS_TLS__) && !defined(__UCLIBC_HAS_THREADS__)
 extern int weak_const_function *__errno_location(void);
-#   endif
 #  endif
-libc_hidden_proto(__errno_location)
 
 #  ifdef __UCLIBC_HAS_THREADS__
 /* When using threads, errno is a per-thread value.  */
-- 
1.8.3.2