unwind: split unwind code into front-end and back-end

This opens the way for alternative unwinder back-ends.

* unwind.h: New file, defines the unwinder back-end interface.
* unwind.c: Move all libunwind related code ...
* unwind-libunwind.c: ... here.
* Makefile.am [USE_LIBUNWIND] (strace_SOURCES): Add unwind.h
and unwind-libunwind.c.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>

1 files changed, 174 insertions, 0 deletions

diff --git a/unwind-libunwind.c b/unwind-libunwind.c
new file mode 100644
index 000000000..38b3e2c59
--- /dev/null
+++ b/unwind-libunwind.c
@@ -0,0 +1,174 @@
+/*
+ * Copyright (c) 2013 Luca Clementi <luca.clementi@gmail.com>
+ * Copyright (c) 2013-2018 The strace developers.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "defs.h"
+#include "unwind.h"
+
+#include "mmap_cache.h"
+#include <libunwind-ptrace.h>
+
+static unw_addr_space_t libunwind_as;
+
+static void
+init(void)
+{
+	libunwind_as = unw_create_addr_space(&_UPT_accessors, 0);
+	if (!libunwind_as)
+		error_msg_and_die("failed to create address space"
+				  " for stack tracing");
+	unw_set_caching_policy(libunwind_as, UNW_CACHE_GLOBAL);
+}
+
+static void *
+tcb_init(struct tcb *tcp)
+{
+	void *r = _UPT_create(tcp->pid);
+
+	if (!r)
+		perror_msg_and_die("_UPT_create");
+	return r;
+}
+
+static void
+tcb_fin(struct tcb *tcp)
+{
+	_UPT_destroy(tcp->unwind_ctx);
+}
+
+static void
+get_symbol_name(unw_cursor_t *cursor, char **name,
+		size_t *size, unw_word_t *offset)
+{
+	for (;;) {
+		int rc = unw_get_proc_name(cursor, *name, *size, offset);
+
+		if (rc == 0)
+			break;
+		if (rc != -UNW_ENOMEM) {
+			**name = '\0';
+			*offset = 0;
+			break;
+		}
+		*name = xgrowarray(*name, size, 1);
+	}
+}
+
+static int
+print_stack_frame(struct tcb *tcp,
+		  unwind_call_action_fn call_action,
+		  unwind_error_action_fn error_action,
+		  void *data,
+		  unw_cursor_t *cursor,
+		  char **symbol_name,
+		  size_t *symbol_name_size)
+{
+	unw_word_t ip;
+	struct mmap_cache_t *cur_mmap_cache;
+
+	if (unw_get_reg(cursor, UNW_REG_IP, &ip) < 0) {
+		perror_msg("cannot walk the stack of process %d", tcp->pid);
+		return -1;
+	}
+
+	cur_mmap_cache = mmap_cache_search(tcp, ip);
+	if (cur_mmap_cache
+	    /* ignore mappings that have no PROT_EXEC bit set */
+	    && (cur_mmap_cache->protections & MMAP_CACHE_PROT_EXECUTABLE)) {
+		unsigned long true_offset;
+		unw_word_t function_offset;
+
+		get_symbol_name(cursor, symbol_name, symbol_name_size,
+				&function_offset);
+		true_offset = ip - cur_mmap_cache->start_addr +
+			cur_mmap_cache->mmap_offset;
+		call_action(data,
+			    cur_mmap_cache->binary_filename,
+			    *symbol_name,
+			    function_offset,
+			    true_offset);
+
+		return 0;
+	}
+
+	/*
+	 * there is a bug in libunwind >= 1.0
+	 * after a set_tid_address syscall
+	 * unw_get_reg returns IP == 0
+	 */
+	if (ip)
+		error_action(data, "unexpected_backtracing_error", ip);
+	return -1;
+}
+
+static void
+tcb_walk(struct tcb *tcp,
+	 unwind_call_action_fn call_action,
+	 unwind_error_action_fn error_action,
+	 void *data)
+{
+	char *symbol_name;
+	size_t symbol_name_size = 40;
+	unw_cursor_t cursor;
+	int stack_depth;
+
+	if (!tcp->mmap_cache)
+		error_func_msg_and_die("mmap_cache is NULL");
+	if (tcp->mmap_cache_size == 0)
+		error_func_msg_and_die("mmap_cache is empty");
+
+	symbol_name = xmalloc(symbol_name_size);
+
+	if (unw_init_remote(&cursor, libunwind_as, tcp->unwind_ctx) < 0)
+		perror_func_msg_and_die("cannot initialize libunwind");
+
+	for (stack_depth = 0; stack_depth < 256; ++stack_depth) {
+		if (print_stack_frame(tcp, call_action, error_action, data,
+				&cursor, &symbol_name, &symbol_name_size) < 0)
+			break;
+		if (unw_step(&cursor) <= 0)
+			break;
+	}
+	if (stack_depth >= 256)
+		error_action(data, "too many stack frames", 0);
+
+	free(symbol_name);
+}
+
+static void
+tcb_flush_cache(struct tcb *tcp)
+{
+	unw_flush_cache(libunwind_as, 0, 0);
+}
+
+const struct unwind_unwinder_t unwinder = {
+	.name = "libunwind",
+	.init = init,
+	.tcb_init = tcb_init,
+	.tcb_fin = tcb_fin,
+	.tcb_walk = tcb_walk,
+	.tcb_flush_cache = tcb_flush_cache,
+};