libubacktrace: Provide uClibc with backtrace functions

A new shared object, libubacktrace.so.0 is added to uClibc
to provide backtrace functions to support application self-debugging.
This set of functions requires to dynamically load libgcc_s.so so they
need to call dlopen/dlsym that are provided by libdl. For this reason
they cannot be included into libc.so.0 but are provided by a new library.

User application that wants to use backtrace needs to be compiled with
-fexceptions option and -rdynamic to get full symbols printed and must be
linked against libubacktrace.so

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

1 files changed, 105 insertions, 0 deletions

diff --git a/libubacktrace/backtracesyms.c b/libubacktrace/backtracesyms.c
new file mode 100644
index 000000000..4486fee94
--- /dev/null
+++ b/libubacktrace/backtracesyms.c
@@ -0,0 +1,105 @@
+/* Return list with names for address in backtrace.
+   Copyright (C) 1998,1999,2000,2001,2003 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
+
+   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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.
+
+   Based on glibc/sysdeps/generic/elf/backtracesyms.c
+
+   Copyright (C) 2010 STMicroelectronics Ltd
+   Author(s): Carmelo Amoroso <carmelo.amoroso@st.com>
+   * Modified to work with uClibc
+     - updated headers inclusion
+     - updated formatting and style
+     - updated to use dladdr from libdl */
+
+#include <execinfo.h>
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <dlfcn.h>
+#include <link.h>	/* required for __ELF_NATIVE_CLASS */
+
+#if __ELF_NATIVE_CLASS == 32
+# define WORD_WIDTH 8
+#else
+/* We assyme 64bits.  */
+# define WORD_WIDTH 16
+#endif
+
+
+char ** backtrace_symbols (void *const *array,  int size)
+{
+	Dl_info info[size];
+	int status[size];
+	int cnt;
+	size_t total = 0;
+	char **result;
+
+	/* Fill in the information we can get from `dladdr'.  */
+	for (cnt = 0; cnt < size; ++cnt) {
+		status[cnt] = dladdr (array[cnt], &info[cnt]);
+		if (status[cnt] && info[cnt].dli_fname &&
+			info[cnt].dli_fname[0] != '\0')
+		/*
+		 * We have some info, compute the length of the string which will be
+		 * "<file-name>(<sym-name>) [+offset].
+		 */
+		total += (strlen (info[cnt].dli_fname ?: "") +
+				  (info[cnt].dli_sname ?
+				  strlen (info[cnt].dli_sname) + 3 + WORD_WIDTH + 3 : 1)
+				  + WORD_WIDTH + 5);
+		else
+			total += 5 + WORD_WIDTH;
+	}
+
+	/* Allocate memory for the result.  */
+	result = (char **) malloc (size * sizeof (char *) + total);
+	if (result != NULL) {
+		char *last = (char *) (result + size);
+		for (cnt = 0; cnt < size; ++cnt) {
+			result[cnt] = last;
+
+			if (status[cnt] && info[cnt].dli_fname
+				&& info[cnt].dli_fname[0] != '\0') {
+
+				char buf[20];
+
+				if (array[cnt] >= (void *) info[cnt].dli_saddr)
+					sprintf (buf, "+%#lx",
+							(unsigned long)(array[cnt] - info[cnt].dli_saddr));
+				else
+					sprintf (buf, "-%#lx",
+					(unsigned long)(info[cnt].dli_saddr - array[cnt]));
+
+				last += 1 + sprintf (last, "%s%s%s%s%s[%p]",
+				info[cnt].dli_fname ?: "",
+				info[cnt].dli_sname ? "(" : "",
+				info[cnt].dli_sname ?: "",
+				info[cnt].dli_sname ? buf : "",
+				info[cnt].dli_sname ? ") " : " ",
+				array[cnt]);
+			} else
+				last += 1 + sprintf (last, "[%p]", array[cnt]);
+		}
+		assert (last <= (char *) result + size * sizeof (char *) + total);
+	}
+
+	return result;
+}