1 files changed, 156 insertions, 0 deletions
diff --git a/src/lib/backtrace-string.c b/src/lib/backtrace-string.c
new file mode 100644
index 0000000..2ac90ec
--- /dev/null
+++ b/src/lib/backtrace-string.c
@@ -0,0 +1,156 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "backtrace-string.h"
+
+#define MAX_STACK_SIZE 30
+#define BACKTRACE_SKIP_PREFIX "backtrace_"
+
+#if defined(HAVE_LIBUNWIND)
+
+#include <libunwind.h>
+
+static int backtrace_append_unwind(string_t *str)
+{
+	size_t str_orig_size = str_len(str);
+	char proc_name[256];
+	int ret;
+	unsigned int fp = 0;
+	unw_cursor_t c;
+	unw_context_t ctx;
+	unw_proc_info_t pip;
+	bool success = FALSE;
+
+	if ((ret = unw_getcontext(&ctx)) != 0) {
+		str_printfa(str, "unw_getcontext() failed: %d", ret);
+		return -1;
+	}
+	if ((ret = unw_init_local(&c, &ctx)) != 0) {
+		str_printfa(str, "unw_init_local() failed: %d", ret);
+		return -1;
+	}
+
+	do {
+		str_printfa(str, "#%d ", fp);
+		if ((ret = unw_get_proc_info(&c, &pip)) != 0) {
+			str_printfa(str, "[unw_get_proc_info_failed(): %d]", ret);
+		} else if (pip.start_ip == 0 || pip.end_ip == 0) {
+			str_append(str, "[no start/end information]");
+		} else if ((ret = unw_get_proc_name(&c, proc_name, sizeof(proc_name), 0)) != 0 &&
+			   ret != UNW_ENOMEM) {
+			str_printfa(str, "[unw_get_proc_name() failed: %d]", ret);
+		} else if (!success && str_begins(proc_name, BACKTRACE_SKIP_PREFIX)) {
+			str_truncate(str, str_orig_size);
+			continue;
+		} else {
+			str_append_max(str, proc_name, sizeof(proc_name));
+			str_printfa(str, "[0x%08zx]", pip.start_ip);
+			success = TRUE;
+		}
+		str_append(str, " -> ");
+		fp++;
+	} while ((ret = unw_step(&c)) > 0);
+
+	/* remove ' -> ' */
+	if (str->used > 4)
+		str_truncate(str, str->used - 4);
+	return ret == 0 && success ? 0 : -1;
+}
+#endif
+
+#if defined(HAVE_BACKTRACE_SYMBOLS) && defined(HAVE_EXECINFO_H)
+/* Linux */
+#include <execinfo.h>
+
+static int backtrace_append_libc(string_t *str)
+{
+	size_t str_orig_size = str_len(str);
+	void *stack[MAX_STACK_SIZE];
+	char **strings;
+	int ret, i;
+
+	ret = backtrace(stack, N_ELEMENTS(stack));
+	if (ret <= 0)
+		return -1;
+
+	strings = backtrace_symbols(stack, ret);
+	for (i = 0; i < ret; i++) {
+		if (str_len(str) > str_orig_size)
+			str_append(str, " -> ");
+
+		if (strings == NULL) {
+			/* out of memory case */
+			str_printfa(str, "0x%p", stack[i]);
+		} else if (str_len(str) != str_orig_size ||
+			   !str_begins(strings[i], BACKTRACE_SKIP_PREFIX))
+			str_append(str, strings[i]);
+	}
+	free(strings);
+	return 0;
+}
+#elif defined(HAVE_WALKCONTEXT) && defined(HAVE_UCONTEXT_H)
+/* Solaris */
+#include <ucontext.h>
+
+struct walk_context {
+	string_t *str;
+	unsigned int pos;
+};
+
+static int walk_callback(uintptr_t ptr, int signo ATTR_UNUSED,
+			 void *context)
+{
+	struct walk_context *ctx = context;
+
+	if (ctx->pos > 0)
+		str_append(ctx->str, " -> ");
+	str_printfa(ctx->str, "0x%p", (void *)ptr);
+	ctx->pos++;
+	return 0;
+}
+
+static int backtrace_append_libc(string_t *str)
+{
+	ucontext_t uc;
+	struct walk_context ctx;
+
+	if (getcontext(&uc) < 0)
+		return -1;
+
+	ctx.str = str;
+	ctx.pos = 0;
+	walkcontext(&uc, walk_callback, &ctx);
+	return 0;
+}
+#else
+static int backtrace_append_libc(string_t *str ATTR_UNUSED)
+{
+	return -1;
+}
+#endif
+
+int backtrace_append(string_t *str)
+{
+#if defined(HAVE_LIBUNWIND)
+	size_t orig_len = str_len(str);
+	if (backtrace_append_unwind(str) == 0)
+		return 0;
+	/* failed to get useful backtrace. libc's own method is likely
+	   better. */
+	str_truncate(str, orig_len);
+#endif
+	return backtrace_append_libc(str);
+}
+
+int backtrace_get(const char **backtrace_r)
+{
+	string_t *str;
+
+	str = t_str_new(512);
+	if (backtrace_append(str) < 0)
+		return -1;
+
+	*backtrace_r = str_c(str);
+	return 0;
+}