RISC-V: properly terminate call chain (bug 23125)

Mark the ra register as undefined in _start, so that unwinding through
main works correctly.  Also, don't use a tail call so that ra points after
the call to __libc_start_main, not after the previous call.

2 files changed, 41 insertions, 1 deletions

diff --git a/elf/Makefile b/elf/Makefile
index e86874492e..d72e7b67f6 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -187,7 +187,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-nodelete2 tst-audit11 tst-audit12 tst-dlsym-error tst-noload \
 	 tst-latepthread tst-tls-manydynamic tst-nodelete-dlclose \
 	 tst-debug1 tst-main1 tst-absolute-sym tst-absolute-zero tst-big-note \
-	 tst-unwind-ctor
+	 tst-unwind-ctor tst-unwind-main
 #	 reldep9
 tests-internal += loadtest unload unload2 circleload1 \
 	 neededtest neededtest2 neededtest3 neededtest4 \
@@ -1495,3 +1495,5 @@ $(objpfx)tst-libc_dlvsym-static.out: $(objpfx)tst-libc_dlvsym-dso.so
 $(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so
 
 $(objpfx)tst-unwind-ctor: $(objpfx)tst-unwind-ctor-lib.so
+
+CFLAGS-tst-unwind-main.c += -funwind-tables
diff --git a/elf/tst-unwind-main.c b/elf/tst-unwind-main.c
new file mode 100644
index 0000000000..d1236032d7
--- /dev/null
+++ b/elf/tst-unwind-main.c
@@ -0,0 +1,38 @@
+/* Test unwinding through main.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <unwind.h>
+#include <unistd.h>
+#include <support/test-driver.h>
+
+static _Unwind_Reason_Code
+callback (struct _Unwind_Context *ctx, void *arg)
+{
+  return _URC_NO_REASON;
+}
+
+int
+main (void)
+{
+  /* Arrange for this test to be killed if _Unwind_Backtrace runs into an
+     endless loop.  We cannot use the test driver because the complete
+     call chain needs to be compiled with -funwind-tables so that
+     _Unwind_Backtrace is able to reach _start.  */
+  alarm (DEFAULT_TIMEOUT);
+  _Unwind_Backtrace (callback, 0);
+}