1 files changed, 119 insertions, 0 deletions
diff --git a/sys/contrib/openzfs/lib/libspl/backtrace.c b/sys/contrib/openzfs/lib/libspl/backtrace.c
new file mode 100644
index 000000000000..d26d742106e2
--- /dev/null
+++ b/sys/contrib/openzfs/lib/libspl/backtrace.c
@@ -0,0 +1,119 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or https://opensource.org/licenses/CDDL-1.0.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2024, Rob Norris <robn@despairlabs.com>
+ * Copyright (c) 2024, Klara Inc.
+ */
+
+#include <sys/backtrace.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+/*
+ * libspl_backtrace() must be safe to call from inside a signal hander. This
+ * mostly means it must not allocate, and so we can't use things like printf.
+ */
+
+#if defined(HAVE_LIBUNWIND)
+#define	UNW_LOCAL_ONLY
+#include <libunwind.h>
+
+static size_t
+libspl_u64_to_hex_str(uint64_t v, size_t digits, char *buf, size_t buflen)
+{
+	static const char hexdigits[] = {
+	    '0', '1', '2', '3', '4', '5', '6', '7',
+	    '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+	};
+
+	size_t pos = 0;
+	boolean_t want = (digits == 0);
+	for (int i = 15; i >= 0; i--) {
+		const uint64_t d = v >> (i * 4) & 0xf;
+		if (!want && (d != 0 || digits > i))
+			want = B_TRUE;
+		if (want) {
+			buf[pos++] = hexdigits[d];
+			if (pos == buflen)
+				break;
+		}
+	}
+	return (pos);
+}
+
+void
+libspl_backtrace(int fd)
+{
+	ssize_t ret __attribute__((unused));
+	unw_context_t uc;
+	unw_cursor_t cp;
+	unw_word_t loc;
+	char buf[128];
+	size_t n;
+
+	ret = write(fd, "Call trace:\n", 12);
+	unw_getcontext(&uc);
+	unw_init_local(&cp, &uc);
+	while (unw_step(&cp) > 0) {
+		unw_get_reg(&cp, UNW_REG_IP, &loc);
+		ret = write(fd, "  [0x", 5);
+		n = libspl_u64_to_hex_str(loc, 10, buf, sizeof (buf));
+		ret = write(fd, buf, n);
+		ret = write(fd, "] ", 2);
+		unw_get_proc_name(&cp, buf, sizeof (buf), &loc);
+		for (n = 0; n < sizeof (buf) && buf[n] != '\0'; n++) {}
+		ret = write(fd, buf, n);
+		ret = write(fd, "+0x", 3);
+		n = libspl_u64_to_hex_str(loc, 2, buf, sizeof (buf));
+		ret = write(fd, buf, n);
+#ifdef HAVE_LIBUNWIND_ELF
+		ret = write(fd, " (in ", 5);
+		unw_get_elf_filename(&cp, buf, sizeof (buf), &loc);
+		for (n = 0; n < sizeof (buf) && buf[n] != '\0'; n++) {}
+		ret = write(fd, buf, n);
+		ret = write(fd, " +0x", 4);
+		n = libspl_u64_to_hex_str(loc, 2, buf, sizeof (buf));
+		ret = write(fd, buf, n);
+		ret = write(fd, ")", 1);
+#endif
+		ret = write(fd, "\n", 1);
+	}
+}
+#elif defined(HAVE_BACKTRACE)
+#include <execinfo.h>
+
+void
+libspl_backtrace(int fd)
+{
+	ssize_t ret __attribute__((unused));
+	void *btptrs[64];
+	size_t nptrs = backtrace(btptrs, 64);
+	ret = write(fd, "Call trace:\n", 12);
+	backtrace_symbols_fd(btptrs, nptrs, fd);
+}
+#else
+#include <sys/debug.h>
+
+void
+libspl_backtrace(int fd __maybe_unused)
+{
+}
+#endif