libspl: lift backtrace into a separate file

If it's going to be used directly by zdb/ztest, then it sort of doesn't
make sense to carry it with the assert code.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes #16181

lib/libspl/Makefile.am

@@ -7,7 +7,8 @@ noinst_LTLIBRARIES += libspl_assert.la libspl.la
 CPPCHECKTARGETS    += libspl_assert.la libspl.la
 
 libspl_assert_la_SOURCES = \
-	%D%/assert.c
+	%D%/assert.c \
+	%D%/backtrace.c
 
 libspl_la_SOURCES = \
 	%D%/libspl_impl.h \

lib/libspl/assert.c

@@ -28,6 +28,7 @@
 
 #include <assert.h>
 #include <pthread.h>
+#include <sys/backtrace.h>
 
 #if defined(__linux__)
 #include <errno.h>
@@ -51,58 +52,6 @@
 	pthread_getname_np(pthread_self(), buf, len);
 #endif
 
-#if defined(HAVE_LIBUNWIND)
-#define	UNW_LOCAL_ONLY
-#include <libunwind.h>
-
-void
-libspl_dump_backtrace(void)
-{
-	unw_context_t uc;
-	unw_cursor_t cp;
-	unw_word_t ip, off;
-	char funcname[128];
-#ifdef HAVE_LIBUNWIND_ELF
-	char objname[128];
-	unw_word_t objoff;
-#endif
-
-	fprintf(stderr, "Call trace:\n");
-	unw_getcontext(&uc);
-	unw_init_local(&cp, &uc);
-	while (unw_step(&cp) > 0) {
-		unw_get_reg(&cp, UNW_REG_IP, &ip);
-		unw_get_proc_name(&cp, funcname, sizeof (funcname), &off);
-#ifdef HAVE_LIBUNWIND_ELF
-		unw_get_elf_filename(&cp, objname, sizeof (objname), &objoff);
-		fprintf(stderr, "  [0x%08lx] %s+0x%2lx (in %s +0x%2lx)\n",
-		    ip, funcname, off, objname, objoff);
-#else
-		fprintf(stderr, "  [0x%08lx] %s+0x%2lx\n", ip, funcname, off);
-#endif
-	}
-}
-#elif defined(HAVE_BACKTRACE)
-#include <execinfo.h>
-
-void
-libspl_dump_backtrace(void)
-{
-	void *btptrs[100];
-	size_t nptrs = backtrace(btptrs, 100);
-	char **bt = backtrace_symbols(btptrs, nptrs);
-	fprintf(stderr, "Call trace:\n");
-	for (size_t i = 0; i < nptrs; i++)
-		fprintf(stderr, "  %s\n", bt[i]);
-	free(bt);
-}
-#else
-void
-libspl_dump_backtrace(void)
-{
-}
-#endif
-
 #if defined(__APPLE__)
 static inline uint64_t
 libspl_gettid(void)
@@ -154,7 +103,7 @@ libspl_assertf(const char *file, const char *func, int line,
 	    getpid(), libspl_getprogname(),
 	    libspl_gettid(), tname);
 
-	libspl_dump_backtrace();
+	libspl_backtrace();
 
 #if !__has_feature(attribute_analyzer_noreturn) && !defined(__COVERITY__)
 	if (libspl_assert_ok) {

lib/libspl/backtrace.c

@@ -0,0 +1,80 @@
+/*
+ * 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 <stdio.h>
+
+#if defined(HAVE_LIBUNWIND)
+#define	UNW_LOCAL_ONLY
+#include <libunwind.h>
+
+void
+libspl_backtrace(void)
+{
+	unw_context_t uc;
+	unw_cursor_t cp;
+	unw_word_t ip, off;
+	char funcname[128];
+#ifdef HAVE_LIBUNWIND_ELF
+	char objname[128];
+	unw_word_t objoff;
+#endif
+
+	fprintf(stderr, "Call trace:\n");
+	unw_getcontext(&uc);
+	unw_init_local(&cp, &uc);
+	while (unw_step(&cp) > 0) {
+		unw_get_reg(&cp, UNW_REG_IP, &ip);
+		unw_get_proc_name(&cp, funcname, sizeof (funcname), &off);
+#ifdef HAVE_LIBUNWIND_ELF
+		unw_get_elf_filename(&cp, objname, sizeof (objname), &objoff);
+		fprintf(stderr, "  [0x%08lx] %s+0x%2lx (in %s +0x%2lx)\n",
+		    ip, funcname, off, objname, objoff);
+#else
+		fprintf(stderr, "  [0x%08lx] %s+0x%2lx\n", ip, funcname, off);
+#endif
+	}
+}
+#elif defined(HAVE_BACKTRACE)
+#include <execinfo.h>
+
+void
+libspl_backtrace(void)
+{
+	void *btptrs[100];
+	size_t nptrs = backtrace(btptrs, 100);
+	char **bt = backtrace_symbols(btptrs, nptrs);
+	fprintf(stderr, "Call trace:\n");
+	for (size_t i = 0; i < nptrs; i++)
+		fprintf(stderr, "  %s\n", bt[i]);
+	free(bt);
+}
+#else
+void
+libspl_backtrace(void)
+{
+}
+#endif
+

lib/libspl/include/Makefile.am

@@ -27,6 +27,7 @@ libspl_sys_HEADERS = \
 	%D%/sys/acl.h \
 	%D%/sys/acl_impl.h \
 	%D%/sys/asm_linkage.h \
+	%D%/sys/backtrace.h \
 	%D%/sys/callb.h \
 	%D%/sys/cmn_err.h \
 	%D%/sys/cred.h \

lib/libspl/include/assert.h

@@ -60,8 +60,6 @@ libspl_assert(const char *buf, const char *file, const char *func, int line)
 	return (0);
 }
 
-extern void libspl_dump_backtrace(void);
-
 #ifdef verify
 #undef verify
 #endif

lib/libspl/include/sys/backtrace.h

@@ -0,0 +1,32 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License, Version 1.0 only
+ * (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.
+ */
+
+#ifndef _LIBSPL_SYS_BACKTRACE_H
+#define	_LIBSPL_SYS_BACKTRACE_H
+
+void libspl_backtrace(void);
+
+#endif