tools/build: Provide sys/linker_set.h when cross-building

This is needed for kldxref, which will shortly become a bootstrap tool.
Linux can use the same one as FreeBSD (provided the cross-building
sys/cdefs.h is augmented appropriately), whilst macOS needs its own
Mach-O-specific implementation.

Reviewed by:	brooks
Differential Revision:	https://reviews.freebsd.org/D43049

tools/build/Makefile

@@ -216,6 +216,10 @@ SRCS+=	progname.c
 # Stub implementations of fflagstostr/strtofflags
 SRCS+=	fflags.c
 
+# macOS has a standalone cross-build implementation, but Linux can use the same
+# ELF one as FreeBSD
+SYSINCS+=	${SRCTOP}/sys/sys/linker_set.h
+
 .endif # ${MAKE.OS} == "Linux"
 
 .if ${.MAKE.OS} == "Darwin"

tools/build/cross-build/include/common/sys/cdefs.h

@@ -121,6 +121,12 @@
 #endif
 #endif
 
+#ifndef __WEAK
+#ifdef __ELF__
+#define	__WEAK(sym)	__asm__(".weak " __XSTRING(sym))
+#endif
+#endif
+
 /* Some files built as part of the bootstrap libegacy use these macros, but
  * since we aren't actually building libc.so, we can defined them to be empty */
 #ifndef __sym_compat
@@ -249,6 +255,13 @@
 #define __DEQUALIFY(type, var) ((type)(__uintptr_t)(const volatile void *)(var))
 #endif
 
+#ifndef __nosanitizeaddress
+#if __has_attribute(no_sanitize) && defined(__clang__)
+#define __nosanitizeaddress	__attribute__((no_sanitize("address")))
+#else
+#define __nosanitizeaddress
+#endif
+#endif
 
 /* Expose all declarations when using FreeBSD headers */
 #define	__POSIX_VISIBLE		200809

tools/build/cross-build/include/mac/sys/linker_set.h

@@ -0,0 +1,140 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 1999 John D. Polstra
+ * Copyright (c) 1999,2001 Peter Wemm <[email protected]>
+ * All rights reserved.
+ * Copyright (c) 2023 Jessica Clarke <[email protected]>
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
+ */
+
+#ifndef _SYS_LINKER_SET_H_
+#define _SYS_LINKER_SET_H_
+
+#include <mach-o/dyld.h>
+#include <mach-o/getsect.h>
+
+/*
+ * The following macros are used to declare global sets of objects, which
+ * are collected by the linker into a `linker_set' as defined below.
+ * For Mach-O, this is done by constructing a separate section for each set.
+ */
+
+#define	__MAKE_SET_CONST const
+
+/*
+ * Private macros, not to be used outside this header file.
+ */
+
+/*
+ * The userspace address sanitizer inserts redzones around global variables,
+ * violating the assumption that linker set elements are packed.
+ */
+#define	__NOASAN	__nosanitizeaddress
+
+#define __MAKE_SET_QV(set, sym, qv)				\
+	static void const * qv					\
+	__NOASAN						\
+	__set_##set##_sym_##sym __section("__DATA,set_" #set)	\
+	__used = &(sym)
+#define __MAKE_SET(set, sym)	__MAKE_SET_QV(set, sym, __MAKE_SET_CONST)
+
+static inline __pure2 uint8_t *
+__set_getsectiondata(const char *segname, const char *sectname,
+    unsigned long *size)
+{
+	uint32_t image_count, image_index;
+	const struct mach_header *mh;
+	uint8_t *ret;
+
+	image_count = _dyld_image_count();
+	for (image_index = 0; image_index < image_count; ++image_index) {
+		mh = _dyld_get_image_header(image_index);
+		if (mh == NULL)
+			continue;
+
+		ret = getsectiondata((const struct mach_header_64 *)mh,
+		    segname, sectname, size);
+		if (ret != NULL)
+			return (ret);
+	}
+
+	return (NULL);
+}
+
+#define __SET_RANGE(set)	({					\
+	unsigned long __set_size;					\
+	char *__set_data;						\
+	__set_data = __set_getsectiondata("__DATA",			\
+	    "set_" #set, &__set_size);					\
+	(struct {							\
+		__CONCAT(__typeof_set_,set)	**begin;		\
+		__CONCAT(__typeof_set_,set)	**limit;		\
+	}){								\
+		.begin = (__CONCAT(__typeof_set_,set) **)__set_data,	\
+		.limit = (__CONCAT(__typeof_set_,set) **)(__set_data +	\
+		    __set_size)						\
+	};								\
+})
+
+/*
+ * Public macros.
+ */
+#define TEXT_SET(set, sym)	__MAKE_SET(set, sym)
+#define DATA_SET(set, sym)	__MAKE_SET(set, sym)
+#define DATA_WSET(set, sym)	__MAKE_SET_QV(set, sym, )
+#define BSS_SET(set, sym)	__MAKE_SET(set, sym)
+#define ABS_SET(set, sym)	__MAKE_SET(set, sym)
+#define SET_ENTRY(set, sym)	__MAKE_SET(set, sym)
+
+/*
+ * Initialize before referring to a given linker set.
+ */
+#define SET_DECLARE(set, ptype)					\
+	typedef ptype __CONCAT(__typeof_set_,set)
+
+#define SET_BEGIN(set)							\
+	(__SET_RANGE(set).begin)
+#define SET_LIMIT(set)							\
+	(__SET_RANGE(set).limit)
+
+/*
+ * Iterate over all the elements of a set.
+ *
+ * Sets always contain addresses of things, and "pvar" points to words
+ * containing those addresses.  Thus is must be declared as "type **pvar",
+ * and the address of each set item is obtained inside the loop by "*pvar".
+ */
+#define SET_FOREACH(pvar, set)						\
+	for (pvar = SET_BEGIN(set); pvar < SET_LIMIT(set); pvar++)
+
+#define SET_ITEM(set, i)						\
+	((SET_BEGIN(set))[i])
+
+/*
+ * Provide a count of the items in a set.
+ */
+#define SET_COUNT(set)							\
+	(SET_LIMIT(set) - SET_BEGIN(set))
+
+#endif	/* _SYS_LINKER_SET_H_ */