libc/execinfo: add backtrace support based on EABI Unwinder

1. Flags < -funwind-tables > is required
2. Keep the section ".exidx" in linker script

Signed-off-by: chao.an <anchao@xiaomi.com>

include/execinfo.h

@@ -0,0 +1,34 @@
+/****************************************************************************
+ * include/execinfo.h
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_EXECINFO_H
+#define __INCLUDE_EXECINFO_H
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/* Store up to SIZE return address of the current program state in
+ * ARRAY and return the exact number of values stored.
+ */
+
+extern int backtrace(FAR void **buffer, int size);
+
+#endif /* __INCLUDE_EXECINFO_H */

libs/libc/Kconfig

@@ -29,3 +29,4 @@ source libs/libc/wqueue/Kconfig
 source libs/libc/hex2bin/Kconfig
 source libs/libc/userfs/Kconfig
 source libs/libc/builtin/Kconfig
+source libs/libc/debug/Kconfig

libs/libc/Makefile

@@ -25,6 +25,7 @@ include assert/Make.defs
 include audio/Make.defs
 include builtin/Make.defs
 include ctype/Make.defs
+include debug/Make.defs
 include dirent/Make.defs
 include dlfcn/Make.defs
 include endian/Make.defs

libs/libc/debug/Kconfig

@@ -0,0 +1,22 @@
+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+# These are library functions that may be overriden by architecture-
+# specific implementations.  Not all architectures support implementations
+# for every library function.
+
+menu "Library Debugging"
+
+config EABI_UNWINDER
+	bool "EABI Stack Unwinder"
+	default "n"
+	---help---
+		This option enables stack unwinding support in NuttX
+		using the information automatically generated by the
+		compiler. The resulting image is slightly bigger but
+		the performance is not affected. Currently, this feature
+		only works with EABI compilers.
+
+endmenu # Library Debugging Support

libs/libc/debug/Make.defs

@@ -0,0 +1,30 @@
+############################################################################
+# libs/libc/debug/Make.defs
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+ifeq ($(CONFIG_EABI_UNWINDER),y)
+
+CSRCS += lib_backtrace.c
+
+endif
+
+# Include debug build support
+
+DEPPATH += --dep-path debug
+VPATH += :debug

libs/libc/debug/lib_backtrace.c

@@ -0,0 +1,128 @@
+/****************************************************************************
+ * libs/libc/debug/lib_backtrace.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <execinfo.h>
+#include <unwind.h>
+
+/****************************************************************************
+ * Private Data Types
+ ****************************************************************************/
+
+struct trace_arg
+{
+  FAR void    **array;
+  _Unwind_Word  cfa;
+  int           cnt;
+  int           size;
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+static inline weak_function
+FAR void *unwind_arch_adjustment(FAR void *prev, FAR void *addr)
+{
+  return addr;
+}
+
+static _Unwind_Reason_Code
+backtrace_helper(FAR struct _Unwind_Context *ctx, FAR void *a)
+{
+  FAR struct trace_arg *arg = a;
+
+  /* We are first called with address in the backtrace function.
+   * Skip it.
+   */
+
+  if (arg->cnt != -1)
+    {
+      arg->array[arg->cnt] = (FAR void *)_Unwind_GetIP(ctx);
+      if (arg->cnt > 0)
+        {
+          arg->array[arg->cnt]
+            = unwind_arch_adjustment(arg->array[arg->cnt - 1],
+                arg->array[arg->cnt]);
+        }
+
+      /* Check whether we make any progress. */
+
+      _Unwind_Word cfa = _Unwind_GetCFA(ctx);
+
+      if (arg->cnt > 0 &&
+          arg->array[arg->cnt - 1] == arg->array[arg->cnt] &&
+          cfa == arg->cfa)
+        {
+          return _URC_END_OF_STACK;
+        }
+
+      arg->cfa = cfa;
+    }
+
+  if (++arg->cnt == arg->size)
+    {
+      return _URC_END_OF_STACK;
+    }
+
+  return _URC_NO_REASON;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/* Store up to SIZE return address of the current program state in
+ * ARRAY and return the exact number of values stored.
+ */
+
+int backtrace(FAR void **buffer, int size)
+{
+  struct trace_arg arg;
+
+  arg.array = buffer;
+  arg.cfa = 0;
+  arg.size = size;
+  arg.cnt = -1;
+
+  if (size <= 0)
+    {
+      return 0;
+    }
+
+  _Unwind_Backtrace(backtrace_helper, &arg);
+
+  /* _Unwind_Backtrace seems to put NULL address above
+   * _start.  Fix it up here.
+   */
+
+  if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
+    {
+      --arg.cnt;
+    }
+
+  return arg.cnt != -1 ? arg.cnt : 0;
+}