nptl: Open libgcc.so with RTLD_NOW during pthread_cancel [BZ #22636]

Disabling lazy binding reduces stack usage during unwinding.

Note that RTLD_NOW only makes a difference if libgcc.so has not
already been loaded, so this is only a partial fix.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

diff --git a/ChangeLog b/ChangeLog
index b1da834f8e01bf410d3bdeb1b195090f5a00855c..10658831cc271d5c84a16098453660b615caeaa7 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2018-01-10  Florian Weimer  <fweimer@redhat.com>
+
+       [BZ #22636]
+       * sysdeps/nptl/unwind-forcedunwind.c (pthread_cancel_init): Open
+       libgcc.so with RTLD_NOW, to avoid lazy binding during unwind.
+
 2018-01-10  Samuel Thibault  <samuel.thibault@ens-lyon.org>
 
        * hurd/hurd/fd.h: Include <fcntl.h>

diff --git a/sysdeps/nptl/unwind-forcedunwind.c b/sysdeps/nptl/unwind-forcedunwind.c
index ab4350de99fd9b031d645e6dd706eaae7669255c..67b8e74b5367c1a21b290c3164f3448fe283d25d 100644 (file)
--- a/sysdeps/nptl/unwind-forcedunwind.c
+++ b/sysdeps/nptl/unwind-forcedunwind.c
@@ -49,7 +49,7 @@ pthread_cancel_init (void)
       return;
     }
 
-  handle = __libc_dlopen (LIBGCC_S_SO);
+  handle = __libc_dlopen_mode (LIBGCC_S_SO, RTLD_NOW | __RTLD_DLOPEN);
 
   if (handle == NULL
       || (resume = __libc_dlsym (handle, "_Unwind_Resume")) == NULL