unwinder: generate backtrace using SFrame format

[Changes in V4]
  - Renamed ESFRAME_* enum error code names to SFRAME_ERR_*.
  - Addressed review comments by Mike.
    - Use AC_CACHE_CHECK macro in sframe.m4
    - Delete config/sframe.m4. Add into libsframe/acinclude.m4.
    - Code fixups.
[End of changes in V4]

[Changes in V3]
  - Use the updated APIs from libsframe.
  - Use sframe_decoder_get_fixed_ra_offset on AMD64 instead of magic
    number -8.
[End of changes in V3]

[Changes in V2]
  - Minor formatting fixes.
[End of changes in V2]

A simple unwinder based on SFrame format.

The unwinder is made available via libsframebt library.

Buildsystem changes have been made to build libsframebt only when
--gsframe support is available in the assembler. These buildsystem
changes are necessary because the SFrame based unwinder the SFrame
unwind info for itself to work.

include/ChangeLog:

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

ChangeLog:

	* libsframe/acinclude.m4: New file.
	* libsframe/Makefile.am: Build backtrace functionality in its
	own library.  Install libsframebt conditionally.
	* libsframe/Makefile.in: Regenerate.
	* libsframe/aclocal.m4: Regenerate.
	* libsframe/configure: Regenerate.
	* libsframe/configure.ac: Check if gas supports --gsframe
	command line option.
	* libsframe/sframe-backtrace-err.c: New file.
	* libsframe/sframe-backtrace.c: New file.

1 files changed, 60 insertions, 0 deletions

diff --git a/include/sframe-backtrace-api.h b/include/sframe-backtrace-api.h
new file mode 100644
index 0000000..b9537bf
--- /dev/null
+++ b/include/sframe-backtrace-api.h
@@ -0,0 +1,60 @@
+/* Public API to SFrame backtrace.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of libsframebt.
+
+   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	_SFRAME_BACKTRACE_API_H
+#define	_SFRAME_BACKTRACE_API_H
+
+#ifdef	__cplusplus
+extern "C"
+{
+#endif
+
+enum sframe_bt_errcode
+{
+  SFRAME_BT_OK,
+  SFRAME_BT_ERR_NOTPRESENT,
+  SFRAME_BT_ERR_ARG,
+  SFRAME_BT_ERR_MALLOC,
+  SFRAME_BT_ERR_REALLOC,
+  SFRAME_BT_ERR_OPEN,
+  SFRAME_BT_ERR_READLINK,
+  SFRAME_BT_ERR_LSEEK,
+  SFRAME_BT_ERR_READ,
+  SFRAME_BT_ERR_GETCONTEXT,
+  SFRAME_BT_ERR_DECODE,
+  SFRAME_BT_ERR_CFA_OFFSET,
+};
+
+#define NUM_OF_DSOS	32			/* Number of DSOs.  */
+
+#define ENUM_ARRAY_SIZE(a) (sizeof (a) / sizeof ((a)[0]))
+
+/* 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 sframe_backtrace (void **buffer, int size, int *errp);
+
+extern const char *sframe_bt_errmsg (enum sframe_bt_errcode ecode);
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif				/* _SFRAME_BACKTRACE_API_H */