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, 116 insertions, 0 deletions

diff --git a/libubacktrace/backtracesymsfd.c b/libubacktrace/backtracesymsfd.c
new file mode 100644
index 000000000..66d7687ca
--- /dev/null
+++ b/libubacktrace/backtracesymsfd.c
@@ -0,0 +1,116 @@
+/* Write formatted list with names for addresses in backtrace to a file.
+   Copyright (C) 1998, 2000, 2003, 2005 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/backtracesymsfd.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
+     - updated to use snprintf instead of _itoa_word */
+
+#include <execinfo.h>
+#include <string.h>
+#include <sys/uio.h>
+#include <dlfcn.h>
+#include <stdio.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
+
+#define BUF_SIZE (WORD_WIDTH + 1)
+
+void backtrace_symbols_fd (void *const *array, int size, int fd)
+{
+	struct iovec iov[9];
+	int cnt;
+
+	for (cnt = 0; cnt < size; ++cnt) {
+		char buf[BUF_SIZE];
+		Dl_info info;
+		size_t last = 0;
+		size_t len = 0;
+
+		memset(buf, 0, sizeof(buf));
+		if (dladdr (array[cnt], &info)
+			&& info.dli_fname && info.dli_fname[0] != '\0')	{
+			/* Name of the file.  */
+			iov[0].iov_base = (void *) info.dli_fname;
+			iov[0].iov_len = strlen (info.dli_fname);
+			last = 1;
+
+			/* Symbol name.  */
+			if (info.dli_sname != NULL) {
+				char buf2[BUF_SIZE];
+				memset(buf2, 0, sizeof(buf2));
+				size_t diff;
+
+				iov[1].iov_base = (void *) "(";
+				iov[1].iov_len = 1;
+				iov[2].iov_base = (void *) info.dli_sname;
+				iov[2].iov_len = strlen (info.dli_sname);
+
+				if (array[cnt] >= (void *) info.dli_saddr) {
+					iov[3].iov_base = (void *) "+0x";
+					diff = array[cnt] - info.dli_saddr;
+				} else {
+					iov[3].iov_base = (void *) "-0x";
+					diff = info.dli_saddr - array[cnt];
+				}
+
+				iov[3].iov_len = 3;
+
+				/* convert diff to a string in hex format */
+				len = snprintf(buf2, sizeof(buf2), "%lx", (unsigned long) diff);
+				iov[4].iov_base = buf2;
+				iov[4].iov_len = len;
+
+				iov[5].iov_base = (void *) ")";
+				iov[5].iov_len = 1;
+
+				last = 6;
+			}
+		}
+
+		iov[last].iov_base = (void *) "[0x";
+		iov[last].iov_len = 3;
+		++last;
+
+		/* convert array[cnt] to a string in hex format */
+		len = snprintf(buf, sizeof(buf), "%lx", (unsigned long) array[cnt]);
+		iov[last].iov_base = buf;
+		iov[last].iov_len = len;
+
+		++last;
+
+		iov[last].iov_base = (void *) "]\n";
+		iov[last].iov_len = 2;
+		++last;
+
+		writev (fd, iov, last);
+	}
+}