[PATCH 3/3] Add frame pointer unwinding for aarch64

[Mark Wielaard <mark at klomp dot org>]

From: Ulf Hermann <ulf.hermann@qt.io>

If we don't find any debug information for a given frame, we usually
cannot unwind any further. However, the binary in question might have
been compiled with frame pointers, in which case we can look up the
well known frame pointer locations in the stack snapshot and use them
to bridge the frames without debug information.

The unwinding on aarch64 is pretty similar to the one on arm, the
difference is in the offsets of LR and FP on the stack.

Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>
---
 backends/ChangeLog                     |   6 +++++
 backends/Makefile.am                   |   2 +-
 backends/aarch64_init.c                |   1 +
 backends/aarch64_unwind.c              |  41 +++++++++++++++++++++++++++++++++
 tests/ChangeLog                        |   7 ++++++
 tests/Makefile.am                      |   5 ++--
 tests/backtrace.aarch64.fp.core.bz2    | Bin 0 -> 7302 bytes
 tests/backtrace.aarch64.fp.exec.bz2    | Bin 0 -> 272102 bytes
 tests/run-backtrace-fp-core-aarch64.sh |  33 ++++++++++++++++++++++++++
 9 files changed, 92 insertions(+), 3 deletions(-)
 create mode 100644 backends/aarch64_unwind.c
 create mode 100644 tests/backtrace.aarch64.fp.core.bz2
 create mode 100755 tests/backtrace.aarch64.fp.exec.bz2
 create mode 100755 tests/run-backtrace-fp-core-aarch64.sh

diff --git a/backends/ChangeLog b/backends/ChangeLog
index 6837a49..02efb00 100644
--- a/backends/ChangeLog
+++ b/backends/ChangeLog
@@ -1,5 +1,11 @@
 2017-02-09  Ulf Hermann  <ulf.hermann@qt.io>
 
+	* aarch64_unwind.c: New file
+	* Makefile.am (aarch64_SRCS): Add aarch64_unwind.c
+	* aarch64_init.c (aarch64_init): Hook aarch64_unwind
+
+2017-02-09  Ulf Hermann  <ulf.hermann@qt.io>
+
 	* arm_unwind.c: New file
 	* Makefile.am (arm_SRCS): Add arm_unwind.c
 	* arm_init.c (arm_init): Hook arm_unwind
diff --git a/backends/Makefile.am b/backends/Makefile.am
index 14cbf04..bfb6b84 100644
--- a/backends/Makefile.am
+++ b/backends/Makefile.am
@@ -81,7 +81,7 @@ am_libebl_arm_pic_a_OBJECTS = $(arm_SRCS:.c=.os)
 
 aarch64_SRCS = aarch64_init.c aarch64_regs.c aarch64_symbol.c	\
 	       aarch64_corenote.c aarch64_retval.c aarch64_cfi.c \
-	       aarch64_initreg.c
+	       aarch64_initreg.c aarch64_unwind.c
 libebl_aarch64_pic_a_SOURCES = $(aarch64_SRCS)
 am_libebl_aarch64_pic_a_OBJECTS = $(aarch64_SRCS:.c=.os)
 
diff --git a/backends/aarch64_init.c b/backends/aarch64_init.c
index 6395f11..0866494 100644
--- a/backends/aarch64_init.c
+++ b/backends/aarch64_init.c
@@ -63,6 +63,7 @@ aarch64_init (Elf *elf __attribute__ ((unused)),
      + ALT_FRAME_RETURN_COLUMN (used when LR isn't used) = 97 DWARF regs. */
   eh->frame_nregs = 97;
   HOOK (eh, set_initial_registers_tid);
+  HOOK (eh, unwind);
 
   return MODVERSION;
 }
diff --git a/backends/aarch64_unwind.c b/backends/aarch64_unwind.c
new file mode 100644
index 0000000..bd95878
--- /dev/null
+++ b/backends/aarch64_unwind.c
@@ -0,0 +1,41 @@
+/* Get previous frame state for an existing frame state.
+   Copyright (C) 2016 The Qt Company Ltd.
+   This file is part of elfutils.
+
+   This file is free software; you can redistribute it and/or modify
+   it under the terms of either
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at
+       your option) any later version
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at
+       your option) any later version
+
+   or both in parallel, as here.
+
+   elfutils 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 copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#define BACKEND aarch64_
+#define FP_REG 29
+#define LR_REG 30
+#define SP_REG 31
+#define FP_OFFSET 0
+#define LR_OFFSET 8
+#define SP_OFFSET 16
+
+#include "arm_unwind.c"
diff --git a/tests/ChangeLog b/tests/ChangeLog
index 2c210ea..71dba42 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,10 @@
+2017-02-13  Ulf Hermann  <ulf.hermann@qt.io>
+
+	* Makefile.am: Add test for unwinding with frame pointers on aarch64
+	* backtrace.aarch64.fp.core.bz2: New file
+	* backtrace.aarch64.fp.exec.bz2: New file
+	* run-backtrace-fp-core-aarch64.sh: New file
+
 2017-02-09  Ulf Hermann  <ulf.hermann@qt.io>
 
 	* Makefile.am: Add test for unwinding with frame pointers on arm
diff --git a/tests/Makefile.am b/tests/Makefile.am
index b72befc..d120ed9 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -114,7 +114,7 @@ TESTS = run-arextract.sh run-arsymtest.sh newfile test-nlist \
 	run-backtrace-native-biarch.sh run-backtrace-native-core.sh \
 	run-backtrace-native-core-biarch.sh run-backtrace-core-x86_64.sh \
 	run-backtrace-fp-core-x86_64.sh \
-	run-backtrace-fp-core-arm.sh \
+	run-backtrace-fp-core-arm.sh run-backtrace-fp-core-aarch64.sh \
 	run-backtrace-core-x32.sh \
 	run-backtrace-core-i386.sh run-backtrace-core-ppc.sh \
 	run-backtrace-core-s390x.sh run-backtrace-core-s390.sh \
@@ -294,8 +294,9 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh \
 	     run-backtrace-core-x86_64.sh run-backtrace-core-i386.sh \
 	     run-backtrace-fp-core-x86_64.sh \
 	     run-backtrace-core-x32.sh \
-	     run-backtrace-fp-core-arm.sh \
+	     run-backtrace-fp-core-arm.sh run-backtrace-fp-core-aarch64.sh \
 	     backtrace.arm.fp.core.bz2 backtrace.arm.fp.exec.bz2 \
+	     backtrace.aarch64.fp.core.bz2 backtrace.aarch64.fp.exec.bz2 \
 	     backtrace-subr.sh backtrace.i386.core.bz2 backtrace.i386.exec.bz2 \
 	     backtrace.x86_64.core.bz2 backtrace.x86_64.exec.bz2 \
 	     backtrace.x86_64.fp.core.bz2 backtrace.x86_64.fp.exec.bz2 \
diff --git a/tests/run-backtrace-fp-core-aarch64.sh b/tests/run-backtrace-fp-core-aarch64.sh
new file mode 100755
index 0000000..64887d2
--- /dev/null
+++ b/tests/run-backtrace-fp-core-aarch64.sh
@@ -0,0 +1,33 @@
+#! /bin/bash
+# Copyright (C) 2017 The Qt Company
+# This file is part of elfutils.
+#
+# This file 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.
+#
+# elfutils 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/>.
+
+. $srcdir/backtrace-subr.sh
+
+# The binary is generated by compiling backtrace-child without debug
+# information, but with -fno-omit-frame-pointer.
+#
+# gcc -static -O2 -fno-omit-frame-pointer -D_GNU_SOURCE \
+#     -pthread -o backtrace.aarch64.fp.exec backtrace-child.c \
+#
+# Then strip the .eh_frame and .eh_frame_hdr sections from the binary:
+#
+# strip -R .eh_frame backtrace.aarch64.fp.exec
+# strip -R .eh_frame_hdr backtrace.aarch64.fp.exec
+#
+# The core is generated by calling the binary with --gencore
+
+check_core aarch64.fp --allow-unknown
-- 
1.8.3.1