Implement _dl_catch_error, _dl_signal_error in libc.so [BZ #16628]

This change moves the main implementation of _dl_catch_error,
_dl_signal_error to libc.so, where TLS variables can be used
directly.  This removes a writable function pointer from the
rtld_global variable.

For use during initial relocation, minimal implementations of these
functions are provided in ld.so.  These are eventually interposed
by the libc.so implementations.  This is implemented by compiling
elf/dl-error-skeleton.c twice, via elf/dl-error.c and
elf/dl-error-minimal.c.

As a side effect of this change, the static version of dl-error.c
no longer includes support for the
_dl_signal_cerror/_dl_receive_error mechanism because it is only
used in ld.so.

1 files changed, 6 insertions, 0 deletions

diff --git a/elf/Versions b/elf/Versions
index 23deda984f..05e5449f4d 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -26,6 +26,9 @@ libc {
     _dl_open_hook;
     _dl_sym; _dl_vsym;
     __libc_dlclose; __libc_dlopen_mode; __libc_dlsym;
+
+    # Internal error handling support.  Interposes the functions in ld.so.
+    _dl_signal_error; _dl_catch_error;
   }
 }
 
@@ -64,5 +67,8 @@ ld {
 
     # Pointer protection.
     __pointer_chk_guard;
+
+    # Internal error handling support.  Interposed by libc.so.
+    _dl_signal_error; _dl_catch_error;
   }
 }