[PATCH, RFC, V3 7/8] unwinder: generate backtrace using CTF Frame format

[Indu Bhagat <indu.bhagat@oracle.com>]

From: Weimin Pan <weimin.pan@oracle.com>

[Changes from V2]
 - consistent use of terminology around CTF Frame and its components.
[End of changes from V2]

[Changes from V1]
 - buildsystem: changes have been made to build libctfbacktrace only when
   --gctf-frame support is available in the assembler.  These buildsystem
   changes are necessary because the CTF Frame based unwinder needs the CTF
   Frame unwind info for itself to work.
[End of changes from V1]

A simple unwinder based on CTF Frame format.

PS: libctfframe/configure has NOT been included in the patch.  Please
regenerate.

config/ChangeLog:

	* ctf-frame.m4: New file.

include/ChangeLog:

	* ctf-backtrace-api.h: New file.

ChangeLog:

	* libctfframe/Makefile.am: Build backtrace functionality in its
	own library.  Install libctfbacktrace conditionally.
	* libctfframe/Makefile.in: Regenerate.
	* libctfframe/aclocal.m4: Regenerate.
	* libctfframe/configure: Regenerate.  <--  [REMOVED FROM THE
	  PATCH.  PLEASE REGENERATE.  ]
	* libctfframe/configure.ac: Check if gas supports --gctf-frame
	command line option.
	* libctfframe/ctf-backtrace-err.c: New file.
	* libctfframe/ctf-backtrace.c: New file.
	* libctfframe/ttest.c: New file.
---
 config/ctf-frame.m4             |  16 +
 include/ctf-backtrace-api.h     |  57 +++
 libctfframe/Makefile.am         |  14 +-
 libctfframe/Makefile.in         |  69 +++-
 libctfframe/aclocal.m4          |   1 +
 libctfframe/configure.ac        |   7 +
 libctfframe/ctf-backtrace-err.c |  46 +++
 libctfframe/ctf-backtrace.c     | 617 ++++++++++++++++++++++++++++++++
 libctfframe/ttest.c             |  78 ++++
 9 files changed, 889 insertions(+), 16 deletions(-)
 create mode 100644 config/ctf-frame.m4
 create mode 100644 include/ctf-backtrace-api.h
 create mode 100644 libctfframe/ctf-backtrace-err.c
 create mode 100644 libctfframe/ctf-backtrace.c
 create mode 100644 libctfframe/ttest.c

diff --git a/config/ctf-frame.m4 b/config/ctf-frame.m4
new file mode 100644
index 00000000000..100840b805f
--- /dev/null
+++ b/config/ctf-frame.m4
@@ -0,0 +1,16 @@
+# CTF_CHECK_AS_CTF_FRAME
+# ----------------------
+# Check whether the assembler supports generation of CTF Frame
+# unwind information.
+#
+# Defines:
+# ac_cv_have_ctfframe
+
+AC_DEFUN([CTF_CHECK_AS_CTF_FRAME],[
+  ac_save_CFLAGS="$CFLAGS"
+  CFLAGS="$CFLAGS -Wa,--gctf-frame"
+  AC_MSG_CHECKING([for as that supports --gctf-frame])
+  AC_TRY_COMPILE([], [return 0;], [ac_cv_have_ctfframe=yes], [ac_cv_have_ctfframe=no])
+  AC_MSG_RESULT($ac_cv_have_ctfframe)
+  CFLAGS="$ac_save_CFLAGS"
+])
diff --git a/include/ctf-backtrace-api.h b/include/ctf-backtrace-api.h
new file mode 100644
index 00000000000..7b3463d88a3
--- /dev/null
+++ b/include/ctf-backtrace-api.h
@@ -0,0 +1,57 @@
+/* Public API to CTF backtrace.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of xxxxxx.    (FIXME)
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef	_CTF_BACKTRACE_API_H
+#define	_CTF_BACKTRACE_API_H
+
+#ifdef	__cplusplus
+extern "C"
+{
+#endif
+
+enum ctf_bt_errcode
+{
+  CTF_BT_OK,
+  CTF_BT_ERR_NOCTF,
+  CTF_BT_ERR_PHDR,
+  CTF_BT_ERR_ARG,
+  CTF_BT_ERR_MALLOC,
+  CTF_BT_ERR_REALLOC,
+  CTF_BT_ERR_OPEN,
+  CTF_BT_ERR_READLINK,
+  CTF_BT_ERR_LSEEK,
+  CTF_BT_ERR_READ,
+  CTF_BT_ERR_GETCONTEXT,
+  CTF_BT_ERR_DECODE,
+  CTF_BT_ERR_CFA_OFFSET,
+};
+
+/* Get the backtrace of the calling program by storing return addresses
+   in BUFFER. The SIZE argument specifies the maximum number of addresses
+   that can be stored in the buffer. Return the number of return addresses
+   collected or -1 if there is any error.  */
+extern int ctf_backtrace (void **buffer, int size, int *errp);
+
+extern const char *ctf_bt_errmsg (enum ctf_bt_errcode ecode);
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif				/* _CTF_BACKTRACE_API_H */
diff --git a/libctfframe/Makefile.am b/libctfframe/Makefile.am
index 712b5b8e773..f745b24dce1 100644
--- a/libctfframe/Makefile.am
+++ b/libctfframe/Makefile.am
@@ -23,8 +23,6 @@ AUTOMAKE_OPTIONS = dejagnu foreign no-texinfo.tex
 
 BASEDIR = $(srcdir)/..
 INCDIR = $(srcdir)/../include
-# include libctf for swap.h
-AM_CPPFLAGS = -D_GNU_SOURCE -I$(srcdir) -I$(srcdir)/../include -I$(srcdir)/../libctf
 AM_CFLAGS = -std=gnu99 @ac_libctfframe_warn_cflags@ @warn@ @c_warn@ @WARN_PEDANTIC@ @WERROR@
 
 if INSTALL_LIBBFD
@@ -39,6 +37,18 @@ libctfframe_la_SOURCES = ctf-frame.c ctf-frame-dump.c ctf-frame-error.c
 libctfframe_la_CPPFLAGS = -D_GNU_SOURCE -I$(srcdir) -I$(srcdir)/../include \
                           -I$(srcdir)/../libctf
 
+if HAVE_CTF_FRAME_AS
+  libctfbacktrace_la_SOURCES = ctf-backtrace.c ctf-backtrace-err.c
+  libctfbacktrace_la_CPPFLAGS = -I$(srcdir) -I$(srcdir)/../include
+  libctfbacktrace_la_CFLAGS = -Wa,--gctf-frame
+if INSTALL_LIBBFD
+  lib_LTLIBRARIES += libctfbacktrace.la
+  include_HEADERS += $(INCDIR)/ctf-backtrace-api.h
+else
+  noinst_LTLIBRARIES += libctfbacktrace.la
+endif
+endif
+
 # Setup the testing framework
 EXPECT = expect
 RUNTEST = runtest
diff --git a/libctfframe/Makefile.in b/libctfframe/Makefile.in
index 2fe55ad39d4..cbf014412cd 100644
--- a/libctfframe/Makefile.in
+++ b/libctfframe/Makefile.in
@@ -107,10 +107,14 @@ PRE_UNINSTALL = :
 POST_UNINSTALL = :
 build_triplet = @build@
 host_triplet = @host@
+@HAVE_CTF_FRAME_AS_TRUE@@INSTALL_LIBBFD_TRUE@am__append_1 = libctfbacktrace.la
+@HAVE_CTF_FRAME_AS_TRUE@@INSTALL_LIBBFD_TRUE@am__append_2 = $(INCDIR)/ctf-backtrace-api.h
+@HAVE_CTF_FRAME_AS_TRUE@@INSTALL_LIBBFD_FALSE@am__append_3 = libctfbacktrace.la
 subdir = .
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
 am__aclocal_m4_deps = $(top_srcdir)/../bfd/acinclude.m4 \
 	$(top_srcdir)/../config/acx.m4 \
+	$(top_srcdir)/../config/ctf-frame.m4 \
 	$(top_srcdir)/../config/depstand.m4 \
 	$(top_srcdir)/../config/jobserver.m4 \
 	$(top_srcdir)/../config/lead-dot.m4 \
@@ -159,15 +163,29 @@ am__uninstall_files_from_dir = { \
   }
 am__installdirs = "$(DESTDIR)$(libdir)" "$(DESTDIR)$(includedir)"
 LTLIBRARIES = $(lib_LTLIBRARIES) $(noinst_LTLIBRARIES)
+libctfbacktrace_la_LIBADD =
+am__libctfbacktrace_la_SOURCES_DIST = ctf-backtrace.c \
+	ctf-backtrace-err.c
+@HAVE_CTF_FRAME_AS_TRUE@am_libctfbacktrace_la_OBJECTS =  \
+@HAVE_CTF_FRAME_AS_TRUE@	libctfbacktrace_la-ctf-backtrace.lo \
+@HAVE_CTF_FRAME_AS_TRUE@	libctfbacktrace_la-ctf-backtrace-err.lo
+libctfbacktrace_la_OBJECTS = $(am_libctfbacktrace_la_OBJECTS)
+AM_V_lt = $(am__v_lt_@AM_V@)
+am__v_lt_ = $(am__v_lt_@AM_DEFAULT_V@)
+am__v_lt_0 = --silent
+am__v_lt_1 = 
+libctfbacktrace_la_LINK = $(LIBTOOL) $(AM_V_lt) --tag=CC \
+	$(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=link $(CCLD) \
+	$(libctfbacktrace_la_CFLAGS) $(CFLAGS) $(AM_LDFLAGS) \
+	$(LDFLAGS) -o $@
+@HAVE_CTF_FRAME_AS_TRUE@@INSTALL_LIBBFD_FALSE@am_libctfbacktrace_la_rpath =
+@HAVE_CTF_FRAME_AS_TRUE@@INSTALL_LIBBFD_TRUE@am_libctfbacktrace_la_rpath =  \
+@HAVE_CTF_FRAME_AS_TRUE@@INSTALL_LIBBFD_TRUE@	-rpath $(libdir)
 libctfframe_la_LIBADD =
 am_libctfframe_la_OBJECTS = libctfframe_la-ctf-frame.lo \
 	libctfframe_la-ctf-frame-dump.lo \
 	libctfframe_la-ctf-frame-error.lo
 libctfframe_la_OBJECTS = $(am_libctfframe_la_OBJECTS)
-AM_V_lt = $(am__v_lt_@AM_V@)
-am__v_lt_ = $(am__v_lt_@AM_DEFAULT_V@)
-am__v_lt_0 = --silent
-am__v_lt_1 = 
 @INSTALL_LIBBFD_FALSE@am_libctfframe_la_rpath =
 @INSTALL_LIBBFD_TRUE@am_libctfframe_la_rpath = -rpath $(libdir)
 AM_V_P = $(am__v_P_@AM_V@)
@@ -204,15 +222,16 @@ AM_V_CCLD = $(am__v_CCLD_@AM_V@)
 am__v_CCLD_ = $(am__v_CCLD_@AM_DEFAULT_V@)
 am__v_CCLD_0 = @echo "  CCLD    " $@;
 am__v_CCLD_1 = 
-SOURCES = $(libctfframe_la_SOURCES)
-DIST_SOURCES = $(libctfframe_la_SOURCES)
+SOURCES = $(libctfbacktrace_la_SOURCES) $(libctfframe_la_SOURCES)
+DIST_SOURCES = $(am__libctfbacktrace_la_SOURCES_DIST) \
+	$(libctfframe_la_SOURCES)
 am__can_run_installinfo = \
   case $$AM_UPDATE_INFO_DIR in \
     n|no|NO) false;; \
     *) (install-info --version) >/dev/null 2>&1;; \
   esac
-am__include_HEADERS_DIST = $(INCDIR)/ctf-frame.h \
-	$(INCDIR)/ctf-frame-api.h
+am__include_HEADERS_DIST = $(INCDIR)/ctf-backtrace-api.h \
+	$(INCDIR)/ctf-frame.h $(INCDIR)/ctf-frame-api.h
 HEADERS = $(include_HEADERS)
 am__tagged_files = $(HEADERS) $(SOURCES) $(TAGS_FILES) \
 	$(LISP)config.h.in
@@ -385,17 +404,20 @@ ACLOCAL_AMFLAGS = -I .. -I ../config
 AUTOMAKE_OPTIONS = dejagnu foreign no-texinfo.tex
 BASEDIR = $(srcdir)/..
 INCDIR = $(srcdir)/../include
-# include libctf for swap.h
-AM_CPPFLAGS = -D_GNU_SOURCE -I$(srcdir) -I$(srcdir)/../include -I$(srcdir)/../libctf
 AM_CFLAGS = -std=gnu99 @ac_libctfframe_warn_cflags@ @warn@ @c_warn@ @WARN_PEDANTIC@ @WERROR@
-@INSTALL_LIBBFD_TRUE@lib_LTLIBRARIES = libctfframe.la
-@INSTALL_LIBBFD_FALSE@include_HEADERS = 
-@INSTALL_LIBBFD_TRUE@include_HEADERS = $(INCDIR)/ctf-frame.h $(INCDIR)/ctf-frame-api.h
-@INSTALL_LIBBFD_FALSE@noinst_LTLIBRARIES = libctfframe.la
+@INSTALL_LIBBFD_TRUE@lib_LTLIBRARIES = libctfframe.la $(am__append_1)
+@INSTALL_LIBBFD_FALSE@include_HEADERS = $(am__append_2)
+@INSTALL_LIBBFD_TRUE@include_HEADERS = $(INCDIR)/ctf-frame.h \
+@INSTALL_LIBBFD_TRUE@	$(INCDIR)/ctf-frame-api.h $(am__append_2)
+@INSTALL_LIBBFD_FALSE@noinst_LTLIBRARIES = libctfframe.la \
+@INSTALL_LIBBFD_FALSE@	$(am__append_3)
 libctfframe_la_SOURCES = ctf-frame.c ctf-frame-dump.c ctf-frame-error.c
 libctfframe_la_CPPFLAGS = -D_GNU_SOURCE -I$(srcdir) -I$(srcdir)/../include \
                           -I$(srcdir)/../libctf
 
+@HAVE_CTF_FRAME_AS_TRUE@libctfbacktrace_la_SOURCES = ctf-backtrace.c ctf-backtrace-err.c
+@HAVE_CTF_FRAME_AS_TRUE@libctfbacktrace_la_CPPFLAGS = -I$(srcdir) -I$(srcdir)/../include
+@HAVE_CTF_FRAME_AS_TRUE@libctfbacktrace_la_CFLAGS = -Wa,--gctf-frame
 
 # Setup the testing framework
 EXPECT = expect
@@ -516,6 +538,9 @@ clean-noinstLTLIBRARIES:
 	  rm -f $${locs}; \
 	}
 
+libctfbacktrace.la: $(libctfbacktrace_la_OBJECTS) $(libctfbacktrace_la_DEPENDENCIES) $(EXTRA_libctfbacktrace_la_DEPENDENCIES) 
+	$(AM_V_CCLD)$(libctfbacktrace_la_LINK) $(am_libctfbacktrace_la_rpath) $(libctfbacktrace_la_OBJECTS) $(libctfbacktrace_la_LIBADD) $(LIBS)
+
 libctfframe.la: $(libctfframe_la_OBJECTS) $(libctfframe_la_DEPENDENCIES) $(EXTRA_libctfframe_la_DEPENDENCIES) 
 	$(AM_V_CCLD)$(LINK) $(am_libctfframe_la_rpath) $(libctfframe_la_OBJECTS) $(libctfframe_la_LIBADD) $(LIBS)
 
@@ -525,6 +550,8 @@ mostlyclean-compile:
 distclean-compile:
 	-rm -f *.tab.c
 
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libctfbacktrace_la-ctf-backtrace-err.Plo@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libctfbacktrace_la-ctf-backtrace.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libctfframe_la-ctf-frame-dump.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libctfframe_la-ctf-frame-error.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libctfframe_la-ctf-frame.Plo@am__quote@
@@ -550,6 +577,20 @@ distclean-compile:
 @AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
 @am__fastdepCC_FALSE@	$(AM_V_CC@am__nodep@)$(LTCOMPILE) -c -o $@ $<
 
+libctfbacktrace_la-ctf-backtrace.lo: ctf-backtrace.c
+@am__fastdepCC_TRUE@	$(AM_V_CC)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libctfbacktrace_la_CPPFLAGS) $(CPPFLAGS) $(libctfbacktrace_la_CFLAGS) $(CFLAGS) -MT libctfbacktrace_la-ctf-backtrace.lo -MD -MP -MF $(DEPDIR)/libctfbacktrace_la-ctf-backtrace.Tpo -c -o libctfbacktrace_la-ctf-backtrace.lo `test -f 'ctf-backtrace.c' || echo '$(srcdir)/'`ctf-backtrace.c
+@am__fastdepCC_TRUE@	$(AM_V_at)$(am__mv) $(DEPDIR)/libctfbacktrace_la-ctf-backtrace.Tpo $(DEPDIR)/libctfbacktrace_la-ctf-backtrace.Plo
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	$(AM_V_CC)source='ctf-backtrace.c' object='libctfbacktrace_la-ctf-backtrace.lo' libtool=yes @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCC_FALSE@	$(AM_V_CC@am__nodep@)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libctfbacktrace_la_CPPFLAGS) $(CPPFLAGS) $(libctfbacktrace_la_CFLAGS) $(CFLAGS) -c -o libctfbacktrace_la-ctf-backtrace.lo `test -f 'ctf-backtrace.c' || echo '$(srcdir)/'`ctf-backtrace.c
+
+libctfbacktrace_la-ctf-backtrace-err.lo: ctf-backtrace-err.c
+@am__fastdepCC_TRUE@	$(AM_V_CC)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libctfbacktrace_la_CPPFLAGS) $(CPPFLAGS) $(libctfbacktrace_la_CFLAGS) $(CFLAGS) -MT libctfbacktrace_la-ctf-backtrace-err.lo -MD -MP -MF $(DEPDIR)/libctfbacktrace_la-ctf-backtrace-err.Tpo -c -o libctfbacktrace_la-ctf-backtrace-err.lo `test -f 'ctf-backtrace-err.c' || echo '$(srcdir)/'`ctf-backtrace-err.c
+@am__fastdepCC_TRUE@	$(AM_V_at)$(am__mv) $(DEPDIR)/libctfbacktrace_la-ctf-backtrace-err.Tpo $(DEPDIR)/libctfbacktrace_la-ctf-backtrace-err.Plo
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	$(AM_V_CC)source='ctf-backtrace-err.c' object='libctfbacktrace_la-ctf-backtrace-err.lo' libtool=yes @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCC_FALSE@	$(AM_V_CC@am__nodep@)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libctfbacktrace_la_CPPFLAGS) $(CPPFLAGS) $(libctfbacktrace_la_CFLAGS) $(CFLAGS) -c -o libctfbacktrace_la-ctf-backtrace-err.lo `test -f 'ctf-backtrace-err.c' || echo '$(srcdir)/'`ctf-backtrace-err.c
+
 libctfframe_la-ctf-frame.lo: ctf-frame.c
 @am__fastdepCC_TRUE@	$(AM_V_CC)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libctfframe_la_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -MT libctfframe_la-ctf-frame.lo -MD -MP -MF $(DEPDIR)/libctfframe_la-ctf-frame.Tpo -c -o libctfframe_la-ctf-frame.lo `test -f 'ctf-frame.c' || echo '$(srcdir)/'`ctf-frame.c
 @am__fastdepCC_TRUE@	$(AM_V_at)$(am__mv) $(DEPDIR)/libctfframe_la-ctf-frame.Tpo $(DEPDIR)/libctfframe_la-ctf-frame.Plo
diff --git a/libctfframe/aclocal.m4 b/libctfframe/aclocal.m4
index 3a0b3426ebc..bda656c049c 100644
--- a/libctfframe/aclocal.m4
+++ b/libctfframe/aclocal.m4
@@ -1229,6 +1229,7 @@ AC_SUBST([am__untar])
 
 m4_include([../bfd/acinclude.m4])
 m4_include([../config/acx.m4])
+m4_include([../config/ctf-frame.m4])
 m4_include([../config/depstand.m4])
 m4_include([../config/jobserver.m4])
 m4_include([../config/lead-dot.m4])
diff --git a/libctfframe/configure.ac b/libctfframe/configure.ac
index d5e5db3c416..cd7ed5f7cdb 100644
--- a/libctfframe/configure.ac
+++ b/libctfframe/configure.ac
@@ -57,6 +57,13 @@ ACX_PROG_CC_WARNING_ALMOST_PEDANTIC([-Wno-long-long])
 # corrected.
 ACX_PROG_CC_WARNINGS_ARE_ERRORS([manual])
 
+dnl The libctfbacktrace library needs to be built with CTF Frame info.
+dnl If the build assembler is not capable of generate CTF Frame then
+dnl the library is not built.
+
+CTF_CHECK_AS_CTF_FRAME
+AM_CONDITIONAL([HAVE_CTF_FRAME_AS], [test "x$ac_cv_have_ctfframe" = "xyes"])
+
 AM_MAINTAINER_MODE
 AM_INSTALL_LIBBFD
 ACX_PROG_CC_WARNING_OPTS([-Wall], [ac_libctfframe_warn_cflags])
diff --git a/libctfframe/ctf-backtrace-err.c b/libctfframe/ctf-backtrace-err.c
new file mode 100644
index 00000000000..374ceaf3266
--- /dev/null
+++ b/libctfframe/ctf-backtrace-err.c
@@ -0,0 +1,46 @@
+/* ctf-backtrace-err.c - CTF Backtrace Error table.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of libctfbacktrace.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "ctf-backtrace-api.h"
+
+/* CTF backtrace error messages.  */
+static const char *const ctf_bt_errlist[] =
+{
+  "",
+  "File does not contain CTF Frame data",
+  "Iterating shared object reading error",
+  "Failed to malloc memory space",
+  "Failed to realloc memory space",
+  "Failed to open file",
+  "Failed on resolve canonical file name",
+  "Failed to reposition file offset",
+  "Failed to read from a file descriptor",
+  "Failed to get the user context",
+  "Failed to set up decode data",
+  "Illegal CFA offset"
+};
+
+/* ctf_bt_perror -Return the error message associated with the error code.  */
+
+const char *
+ctf_bt_errmsg (enum ctf_bt_errcode ecode)
+{
+  return ctf_bt_errlist[ecode];
+}
diff --git a/libctfframe/ctf-backtrace.c b/libctfframe/ctf-backtrace.c
new file mode 100644
index 00000000000..652877e26d0
--- /dev/null
+++ b/libctfframe/ctf-backtrace.c
@@ -0,0 +1,617 @@
+/* ctf-backtrace.c - The CTF Frame unwinder.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of libctfbacktrace.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include "config.h"
+#include <elf.h>
+#include <link.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <assert.h>
+#include <execinfo.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <ucontext.h>
+#include <stdarg.h>
+#include "ansidecl.h"
+#include "ctf-frame-api.h"
+#include "ctf-backtrace-api.h"
+
+#ifndef PT_CTF_FRAME
+#define PT_CTF_FRAME 0x6474e554		/* FIXME.  */
+#endif
+
+#define _cf_printflike_(string_index,first_to_check) \
+    __attribute__ ((__format__ (__printf__, (string_index), (first_to_check))))
+
+static int _ctf_unwind_debug;	/* Control for printing out debug info.  */
+static int no_of_entries = 32;
+
+/* CTF decode data for the main module or a DSO.  */
+struct ctf_decode_data
+{
+  char *cdd_data;			/* CTF decode data.  */
+  int cdd_data_size;			/* CTF decode data size.  */
+  uint64_t cdd_text_vma;		/* Text segment's virtual address.  */
+  int cdd_text_size;			/* Text segment's size.  */
+  uint64_t cdd_ctf_vma;			/* CTF segment's virtual address.  */	
+  ctf_frame_decoder_ctx *cdd_ctf_ctx;	/* CTF decoder context.  */
+};
+
+/* List that holds CTF Frame info for the shared libraries.  */
+struct dso_cfi_list
+{
+  int alloced;				/* Entries allocated.  */
+  int used;				/* Entries used.  */
+  struct ctf_decode_data *entry;	/* DSO's decode data.  */
+};
+
+/* Data that's passed through ctf_frame_callback.  */
+struct ctf_unwind_info
+{
+  int cui_fd;				/* File descriptor.  */
+  struct ctf_decode_data cui_ctx;	/* The decode data.  */
+  struct dso_cfi_list cui_dsos;		/* The DSO list.  */
+};
+
+static void
+ctf_unwind_init_debug (void)
+{
+  static int inited;
+
+  if (!inited)
+    {
+      _ctf_unwind_debug = getenv ("CTF_UNWIND_DEBUG") != NULL;
+      inited = 1;
+    }
+}
+
+_cf_printflike_ (1, 2)
+static void
+debug_printf (const char *format, ...)
+{
+  if (_ctf_unwind_debug)
+    {
+      va_list args;
+
+      va_start (args, format);
+      __builtin_vprintf (format, args);
+      va_end (args);
+    }
+}
+
+/* ctf_bt_errno - Check if there is error code in ERRP.  */
+
+static int
+ctf_bt_errno (int *errp)
+{
+  if (errp == NULL)
+    return 0;
+
+  return (*errp != CTF_BT_OK);
+}
+
+/* ctf_bt_set_errno - Store the specified error code ERROR into ERRP if
+   it is non-NULL.  */
+
+static void
+ctf_bt_set_errno (int *errp, int error)
+{
+  if (errp != NULL)
+    *errp = error;
+}
+
+/* ctf_add_dso - Add .ctf_frame info in D_DATA, which is associated with
+   a dynamic shared object, to D_LIST.  */
+
+static void
+ctf_add_dso (struct dso_cfi_list *d_list,
+	     struct ctf_decode_data d_data,
+	     int *errp)
+{
+  if (d_list->alloced == 0)
+    {
+      d_list->entry = malloc (no_of_entries * sizeof (struct ctf_decode_data));
+      if (d_list->entry == NULL)
+	{
+	  ctf_bt_set_errno (errp, CTF_BT_ERR_MALLOC);
+	  return;
+	}
+      memset (d_list->entry, 0,
+	      no_of_entries * sizeof (struct ctf_decode_data));
+      d_list->alloced = no_of_entries;
+    }
+  else if (d_list->used == d_list->alloced)
+    {
+      d_list->entry = realloc (d_list->entry,
+			(d_list->alloced + no_of_entries) *
+			sizeof (struct ctf_decode_data));
+      if (d_list->entry == NULL)
+	{
+	  ctf_bt_set_errno (errp, CTF_BT_ERR_REALLOC);
+	  return;
+	}
+
+      memset (&d_list->entry[d_list->alloced], 0,
+	      no_of_entries * sizeof (struct ctf_decode_data));
+      d_list->alloced += no_of_entries;
+    }
+
+  ctf_bt_set_errno (errp, CTF_BT_OK);
+  d_list->entry[d_list->used++] = d_data;
+}
+
+/* ctf_free_cfi - Free up space allocated for .ctf_frame info for CF.  */
+
+static void
+ctf_free_cfi (struct ctf_unwind_info *cf)
+{
+  struct dso_cfi_list *d_list;
+  int i;
+
+  if (cf == NULL)
+    return;
+
+  free (cf->cui_ctx.cdd_data);
+  ctf_frame_decoder_free (&cf->cui_ctx.cdd_ctf_ctx);
+  close (cf->cui_fd);
+
+  d_list = &cf-> cui_dsos;
+  if (d_list == NULL)
+    return;
+
+  for (i = 0; i < d_list->used; ++i)
+    {
+      free (d_list->entry[i].cdd_data);
+      ctf_frame_decoder_free (&d_list->entry[i].cdd_ctf_ctx);
+    }
+}
+
+/* ctf_find_context - Find the decode data that contains ADDR from CF.
+   Return the pointer to the decode data or NULL.  */
+
+static struct ctf_decode_data *
+ctf_find_context (struct ctf_unwind_info *cf, uint64_t addr)
+{
+  struct dso_cfi_list *d_list;
+  int i;
+
+  if (cf == NULL)
+    return NULL;
+
+  if (cf->cui_ctx.cdd_text_vma < addr
+      && cf->cui_ctx.cdd_text_vma + cf->cui_ctx.cdd_text_size > addr)
+    return &cf->cui_ctx;
+
+  d_list = &cf->cui_dsos;
+  for (i = 0; i < cf->cui_dsos.used; ++i)
+    {
+      if (d_list->entry[i].cdd_text_vma <= addr &&
+	  d_list->entry[i].cdd_text_vma
+	  + d_list->entry[i].cdd_text_size >= addr)
+	return &d_list->entry[i];
+    }
+
+  return NULL;
+}
+
+/* ctf_valid_addr - Check if ADDR is valid in CF. The address is considered
+   invalid, with regards to CTF, if it's not in any address range of the main
+   module or any of its DSO's. Return 1 if valid, 0 otherwise.  */
+
+static int
+ctf_valid_addr (struct ctf_unwind_info *cf, uint64_t addr)
+{
+  struct ctf_decode_data *cdp;
+
+  if (cf == NULL)
+    return 0;
+
+  cdp = ctf_find_context (cf, addr);
+  return cdp ? 1 : 0;
+}
+
+/* ctf_load_ctx - Call decoder to create and set up the ctf frame info for
+   either the main module or one of the DSOs from CF, based on the input
+   RADDR argument.  Return the newly created decode context or NULL.  */
+
+static ctf_frame_decoder_ctx *
+ctf_load_ctx (struct ctf_unwind_info *cf, uint64_t raddr)
+{
+  ctf_frame_decoder_ctx *nctx;
+  struct ctf_decode_data *cdp;
+
+  if (cf == NULL)
+    return NULL;
+
+  cdp = ctf_find_context (cf, raddr);
+  if (cdp == NULL)
+    return NULL;
+
+  if (cdp->cdd_ctf_ctx == NULL)
+    {
+      int err; 
+      nctx = ctf_frame_decode (cdp->cdd_data, cdp->cdd_data_size, &err);
+      if (nctx == NULL)
+	return NULL;
+      cdp->cdd_ctf_ctx = nctx;
+      return nctx;
+    }
+
+  return NULL;
+}
+
+/* ctf_update_ctx - Check if need to do a decode context switch, based on
+   the input RADDR argument, from CF. A new decode context will be created
+   and set up if it isn't already done so. Return the new decode context in
+   CTX and vma in CFI_VMA.  */
+
+static void
+ctf_update_ctx (struct ctf_unwind_info *cf, uint64_t raddr,
+		ctf_frame_decoder_ctx **ctx, uint64_t *cfi_vma)
+{
+  ctf_frame_decoder_ctx *nctx;
+  struct ctf_decode_data *cdp;
+
+  cdp = ctf_find_context (cf, raddr);
+  if (cdp != NULL)
+    {
+      if (cdp->cdd_ctf_ctx == NULL)
+	{
+	  int err; 
+	  nctx = ctf_frame_decode (cdp->cdd_data, cdp->cdd_data_size, &err);
+	  if (nctx == NULL)
+	    {
+	      *ctx = NULL;
+	      return;
+	    }
+	  cdp->cdd_ctf_ctx = nctx;
+	}
+	*ctx = cdp->cdd_ctf_ctx;
+	*cfi_vma = cdp->cdd_ctf_vma;
+    }
+}
+
+/* get_contents - Return contents at ADDR from file descriptor FD.  */
+
+static uint64_t
+get_contents (int fd, uint64_t addr, int *errp)
+{
+  uint64_t data;
+  size_t sz;
+
+  ctf_bt_set_errno (errp, CTF_BT_OK);
+  if (lseek (fd, addr, SEEK_SET) == -1)
+    {
+      ctf_bt_set_errno (errp, CTF_BT_ERR_LSEEK);
+      return 0;
+    }
+  sz = read (fd, &data, sizeof (uint64_t));
+  if (sz != sizeof (uint64_t))
+    {
+      ctf_bt_set_errno (errp, CTF_BT_ERR_READ);
+      return 0;
+    }
+
+  return data;
+}
+
+/* ctf_fd_open - Open /proc image associated with the process id and return
+   the file descriptor.  */
+
+static int
+ctf_fd_open (int *errp)
+{
+  char filename[PATH_MAX];
+  pid_t pid;
+  int fd;
+
+  pid = getpid ();
+  snprintf (filename, sizeof filename, "/proc/%d/task/%d/mem", pid, pid);
+  if ((fd = open (filename, O_RDONLY)) == -1)
+    {
+      ctf_bt_set_errno (errp, CTF_BT_ERR_OPEN);
+      return -1;
+    }
+
+  return fd;
+}
+
+/* ctf_frame_callback - The callback from dl_iterate_phdr with header info
+   in INFO.
+   Return CTF Frame info for either the main module or a DSO in DATA.  */
+
+static int
+ctf_frame_callback (struct dl_phdr_info *info,
+		    size_t size ATTRIBUTE_UNUSED,
+		    void *data)
+{
+  struct ctf_unwind_info *cf = (struct ctf_unwind_info *) data;
+  int p_type, i, fd, ctf_err;
+  ssize_t len;
+  uint64_t text_vma = 0;
+  int text_size = 0;
+
+  if (data == NULL || info == NULL)
+    return 1;
+
+  debug_printf ("-- name: %s %14p\n", info->dlpi_name, (void *)info->dlpi_addr);
+
+  for (i = 0; i < info->dlpi_phnum; i++)
+    {
+      debug_printf("    %2d: [%14p; memsz:%7lx] flags: 0x%x; \n", i,
+		   (void *) info->dlpi_phdr[i].p_vaddr,
+		   info->dlpi_phdr[i].p_memsz,
+		   info->dlpi_phdr[i].p_flags);
+
+      p_type = info->dlpi_phdr[i].p_type;
+      if (p_type == PT_LOAD && info->dlpi_phdr[i].p_flags & PF_X)
+	{
+	  text_vma = info->dlpi_addr + info->dlpi_phdr[i].p_vaddr;
+	  text_size = info->dlpi_phdr[i].p_memsz;
+	  continue;
+	}
+      if (p_type != PT_CTF_FRAME)
+	continue;
+
+      if (info->dlpi_name[0] == '\0')		/* the main module.  */
+	{
+	  fd = ctf_fd_open (&ctf_err);
+	  if (fd == -1)
+	    return 1;
+	  if (lseek (fd, info->dlpi_addr + info->dlpi_phdr[i].p_vaddr,
+		     SEEK_SET) == -1)
+	    {
+	      ctf_bt_set_errno (&ctf_err, CTF_BT_ERR_LSEEK);
+	      return 1;
+	    }
+
+	  cf->cui_ctx.cdd_data = (char *) malloc (info->dlpi_phdr[i].p_memsz);
+	  if (cf->cui_ctx.cdd_data == NULL)
+	    {
+	      ctf_bt_set_errno (&ctf_err, CTF_BT_ERR_MALLOC);
+	      return 1;
+	    }
+
+	  len = read (fd, cf->cui_ctx.cdd_data, info->dlpi_phdr[i].p_memsz);
+	  if (len == -1 || len != (ssize_t) info->dlpi_phdr[i].p_memsz)
+	    {
+	      ctf_bt_set_errno (&ctf_err, CTF_BT_ERR_READ);
+	      return 1;
+	    }
+
+	  assert (text_vma);
+	  cf->cui_ctx.cdd_data_size = len;
+	  cf->cui_ctx.cdd_ctf_vma = info->dlpi_addr + info->dlpi_phdr[i].p_vaddr;
+	  cf->cui_fd = fd;
+	  cf->cui_ctx.cdd_text_vma = text_vma;
+	  cf->cui_ctx.cdd_text_size = text_size;
+	  text_vma = 0;
+	  return 0;
+	}
+      else
+	{					/* a dynamic shared object.  */
+	  struct ctf_decode_data dt;
+	  memset (&dt, 0, sizeof (struct ctf_decode_data));
+	  assert (cf->cui_fd);
+	  if (lseek (cf->cui_fd, info->dlpi_addr + info->dlpi_phdr[i].p_vaddr,
+		     SEEK_SET) == -1)
+	    {
+	      ctf_bt_set_errno (&ctf_err, CTF_BT_ERR_LSEEK);
+	      return 1;
+	    }
+
+	  dt.cdd_data = (char *) malloc (info->dlpi_phdr[i].p_memsz);
+	  if (dt.cdd_data == NULL)
+	    {
+	      ctf_bt_set_errno (&ctf_err, CTF_BT_ERR_MALLOC);
+	      return 1;
+	    }
+
+	  len = read (cf->cui_fd, dt.cdd_data, info->dlpi_phdr[i].p_memsz);
+	  if (len == -1 || len != (ssize_t) info->dlpi_phdr[i].p_memsz)
+	    {
+	      ctf_bt_set_errno (&ctf_err, CTF_BT_ERR_READ);
+	      return 1;
+	    }
+
+	  assert (text_vma);
+	  dt.cdd_data_size = len;
+	  dt.cdd_ctf_vma = info->dlpi_addr + info->dlpi_phdr[i].p_vaddr;
+	  dt.cdd_text_vma = text_vma;
+	  dt.cdd_text_size = text_size;
+	  text_vma = 0;
+	  ctf_add_dso (&cf->cui_dsos, dt, &ctf_err);
+	  if (ctf_err != CTF_BT_OK)
+	    return 1;
+	  return 0;
+	}
+    }
+
+    return 0;
+}
+
+/* ctf_frame_unwind - Unwind the stack backtrace for CF. If successful,
+   store the return addresses in RA_LST. The RA_SIZE argument specifies
+   the maximum number of return addresses that can be stored in RA_LST
+   and contains the number of the addresses collected.  */
+
+static void
+ctf_frame_unwind (struct ctf_unwind_info *cf, void **ra_lst,
+		  int *ra_size, int *errp)
+{
+  uint64_t cfa, return_addr, ra_stack_loc, rfp_stack_loc;
+  ctf_frame_decoder_ctx *ctx;
+  int cfa_offset, rfp_offset, errnum, i, count;
+  ctf_frame_row_entry fred, *frep = &fred;
+  uint64_t pc, rfp, rsp, cfi_vma;
+  ucontext_t context, *cp = &context;
+
+  if (cf == NULL || ra_lst == NULL || ra_size == NULL)
+    {
+      ctf_bt_set_errno (errp, CTF_BT_ERR_ARG);
+      return;
+    }
+
+  /* Get the user context for its registers.  */
+  if (getcontext (cp) != 0)
+    {
+      ctf_bt_set_errno (errp, CTF_BT_ERR_GETCONTEXT);
+      return;
+    }
+  ctf_bt_set_errno (errp, CTF_BT_OK);
+
+#ifdef __x86_64__
+  pc = cp->uc_mcontext.gregs[REG_RIP];
+  rsp = cp->uc_mcontext.gregs[REG_RSP];
+  rfp = cp->uc_mcontext.gregs[REG_RBP];
+#else
+#ifdef __aarch64__
+#define UNWIND_AARCH64_X29		29	/* 64-bit frame pointer.  */
+#define UNWIND_AARCH64_X30		30	/* 64-bit link pointer.  */
+  pc = cp->uc_mcontext.pc;
+  rsp = cp->uc_mcontext.sp;
+  rfp = cp->uc_mcontext.regs[UNWIND_AARCH64_X29];
+  uint64_t ra = cp->uc_mcontext.regs[UNWIND_AARCH64_X30];
+#endif
+#endif
+
+  /* Load and set up the decoder.  */
+  ctx = ctf_load_ctx (cf, pc);
+  if (ctx == NULL)
+    {
+      ctf_bt_set_errno (errp, CTF_BT_ERR_DECODE);
+      return;
+    }
+  cfi_vma = cf->cui_ctx.cdd_ctf_vma;
+  count = *ra_size;
+
+  for (i = 0; i < count; ++i)
+    {
+      pc -= cfi_vma;
+      errnum = ctf_frame_find_fre (ctx, pc, frep);
+      if (errnum == 0)
+	{
+	  cfa_offset = ctf_frame_fre_get_cfa_offset (frep, &errnum);
+	  if (errnum == ECTF_FRAME_FREOFFSET_NOPRESENT)
+	    {
+	      ctf_bt_set_errno (errp, CTF_BT_ERR_CFA_OFFSET);
+	      return;
+	    }
+
+	  cfa = ((frep->fre_info & 0x1) == CTF_FRAME_BASE_REG_SP
+	    ? rsp : rfp) + cfa_offset;
+
+#ifdef __x86_64__
+	  /* For x86, read the return address from cfa - 8.  */
+	  ra_stack_loc = cfa - 8;
+	  return_addr = get_contents (cf->cui_fd, ra_stack_loc, errp);
+	  if (ctf_bt_errno (errp))
+	    return;
+#else
+#ifdef __aarch64__
+	  int ra_offset = ctf_frame_fre_get_ra_offset (frep, &errnum);
+	  if (errnum == 0)
+	    {
+	      ra_stack_loc = cfa + ra_offset;
+	      return_addr = get_contents (cf->cui_fd, ra_stack_loc, errp);
+	      if (ctf_bt_errno (errp))
+		return;
+	    }
+	  else
+	    return_addr = ra;
+#endif
+#endif
+
+	  /* Validate and add return address to the list.  */
+	  if (ctf_valid_addr (cf, return_addr) == 0)
+	    {
+	      i -= 1;
+	      goto find_fre_ra_err;
+	    }
+	  if (i != 0)		/* exclude self.  */
+	    ra_lst[i-1] = (void *)return_addr;
+
+	  /* Set up for the next frame.  */
+	  rfp_offset = ctf_frame_fre_get_fp_offset (frep, &errnum);
+	  if (errnum == 0)
+	    {
+	      rfp_stack_loc = cfa + rfp_offset;
+	      rfp = get_contents (cf->cui_fd, rfp_stack_loc, errp);
+	      if (ctf_bt_errno (errp))
+		return;
+	    }
+	  rsp = cfa;
+	  pc = return_addr;
+
+	  /* Check if need to update the decoder context and vma.  */
+	  ctf_update_ctx (cf, return_addr, &ctx, &cfi_vma);
+	  if (ctx == NULL)
+	    {
+	      ctf_bt_set_errno (errp, CTF_BT_ERR_DECODE);
+	      return;
+	    }
+	}
+      else
+	{
+	  i -= 1;
+	  goto find_fre_ra_err;
+	}
+    }
+
+find_fre_ra_err:
+  *ra_size = i;
+}
+
+/* ctf_backtrace - Main API that user program calls to get a backtrace.
+   The BUFFER argument provides space for the list of the return addresses
+   and the SIZE argument specifies the maximum number of addresses that
+   can be stored in the buffer.  Return the number of return addresses
+   collected or -1 if there is any error.  */
+
+int
+ctf_backtrace (void **buffer, int size, int *errp)
+{
+  struct ctf_unwind_info ctfinfo;
+
+  ctf_unwind_init_debug ();
+
+  memset (&ctfinfo, 0, sizeof (struct ctf_unwind_info));
+
+  /* find and set up the .ctf_frame sections.  */
+  (void) dl_iterate_phdr (ctf_frame_callback, (void *)&ctfinfo);
+  if (ctfinfo.cui_fd == 0)
+    {
+      ctf_bt_set_errno (errp, CTF_BT_ERR_NOCTF);
+      return -1;
+    }
+
+  /* Do the stack unwinding.  */
+  ctf_frame_unwind (&ctfinfo, buffer, &size, errp);
+  if (ctf_bt_errno (errp))
+    return -1;
+
+  ctf_free_cfi (&ctfinfo);
+
+  return size;
+}
diff --git a/libctfframe/ttest.c b/libctfframe/ttest.c
new file mode 100644
index 00000000000..c0b8434aad5
--- /dev/null
+++ b/libctfframe/ttest.c
@@ -0,0 +1,78 @@
+#include <execinfo.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include "ctf-backtrace-api.h"
+
+#define BT_BUF_SIZE 100
+
+/* funclist for running "ttest.x 3".  */
+static const char *const func_list[] =
+{
+  "myfunc3",
+  "()",
+  "myfunc",
+  "myfunc",
+  "myfunc",
+  "main"
+};
+
+void
+myfunc3 (void)
+{
+    void *buffer[BT_BUF_SIZE];
+    int j, nptrs, err;
+    char **strings;
+
+    /* Call the unwinder to get an array of return addresses.  */
+    nptrs = ctf_backtrace (buffer, BT_BUF_SIZE, &err);
+    if (nptrs == -1 || nptrs != 6)
+      {
+	printf ("CTF error: %s\n", ctf_bt_errmsg (err));
+	return;
+      }
+
+    /* Get these addresses symbolically.  */
+    strings = backtrace_symbols (buffer, nptrs);
+    if (strings == NULL) {
+        perror("backtrace_symbols");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Verify the results.  */
+    for (j = 0; j < nptrs; j++)
+      if (!strstr (strings[j], func_list[j]))
+	break;
+
+    free(strings);
+
+    printf ("%s\n", j == nptrs ? "PASS" : "FAIL");
+}
+
+static void   /* "static" means don't export the symbol... */
+myfunc2 (void)
+{
+    myfunc3 ();
+}
+
+void
+myfunc (int ncalls)
+{
+    if (ncalls > 1)
+        myfunc (ncalls - 1);
+    else
+        myfunc2 ();
+}
+
+int
+main (int argc, char *argv[])
+{
+    if (argc != 2) {
+        fprintf (stderr, "%s num-calls\n", argv[0]);
+        exit (EXIT_FAILURE);
+    }
+
+    myfunc (atoi(argv[1]));
+    exit (EXIT_SUCCESS);
+}
-- 
2.31.1