Merge tag 'nolibc.2023.10.23a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull nolibc updates from Paul McKenney:

 - Add stdarg.h header and a few additional system-call upgrades

 - Add support for constructors and destructors

 - Add tests to verify the ability to link multiple .o files against
   nolibc

 - Numerous string-function optimizations and improvements

 - Prevent redundant kernel relinks by avoiding embedding of initramfs
   into the kernel image

 - Allow building i386 with multiarch compiler and make ppc64le use
   qemu-system-ppc64

 - Miscellaneous fixups, including addition of -nostdinc for
   nolibc-test, avoiding -Wstringop-overflow warnings, and avoiding
   unused parameter warnings for ENOSYS fallbacks

* tag 'nolibc.2023.10.23a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  selftests/nolibc: add tests for multi-object linkage
  selftests/nolibc: use qemu-system-ppc64 for ppc64le
  tools/nolibc: add support for constructors and destructors
  tools/nolibc: drop test for getauxval(AT_PAGESZ)
  tools/nolibc: automatically detect necessity to use pselect6
  tools/nolibc: don't define new syscall number
  tools/nolibc: avoid unused parameter warnings for ENOSYS fallbacks
  selftests/nolibc: allow building i386 with multiarch compiler
  selftests/nolibc: don't embed initramfs into kernel image
  selftests/nolibc: libc-test: avoid -Wstringop-overflow warnings
  tools/nolibc: string: Remove the `_nolibc_memcpy_up()` function
  tools/nolibc: string: Remove the `_nolibc_memcpy_down()` function
  tools/nolibc: x86-64: Use `rep stosb` for `memset()`
  tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()`
  selftests/nolibc: use -nostdinc for nolibc-test
  tools/nolibc: add stdarg.h header

16 files changed, 225 insertions, 88 deletions

diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile
index 909b6eb500fe..e69c26abe1ea 100644
--- a/tools/include/nolibc/Makefile
+++ b/tools/include/nolibc/Makefile
@@ -34,6 +34,7 @@ all_files := \
 		signal.h \
 		stackprotector.h \
 		std.h \
+		stdarg.h \
 		stdint.h \
 		stdlib.h \
 		string.h \
diff --git a/tools/include/nolibc/arch-aarch64.h b/tools/include/nolibc/arch-aarch64.h
index 6c33c46848e3..b23ac1f04035 100644
--- a/tools/include/nolibc/arch-aarch64.h
+++ b/tools/include/nolibc/arch-aarch64.h
@@ -20,10 +20,7 @@
  *   - the arguments are cast to long and assigned into the target registers
  *     which are then simply passed as registers to the asm code, so that we
  *     don't have to experience issues with register constraints.
- *
- * On aarch64, select() is not implemented so we have to use pselect6().
  */
-#define __ARCH_WANT_SYS_PSELECT6
 
 #define my_syscall0(num)                                                      \
 ({                                                                            \
diff --git a/tools/include/nolibc/arch-loongarch.h b/tools/include/nolibc/arch-loongarch.h
index bf98f6220195..3f8ef8f86c0f 100644
--- a/tools/include/nolibc/arch-loongarch.h
+++ b/tools/include/nolibc/arch-loongarch.h
@@ -19,10 +19,8 @@
  *   - the arguments are cast to long and assigned into the target
  *     registers which are then simply passed as registers to the asm code,
  *     so that we don't have to experience issues with register constraints.
- *
- * On LoongArch, select() is not implemented so we have to use pselect6().
  */
-#define __ARCH_WANT_SYS_PSELECT6
+
 #define _NOLIBC_SYSCALL_CLOBBERLIST \
 	"memory", "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7", "$t8"
 
diff --git a/tools/include/nolibc/arch-riscv.h b/tools/include/nolibc/arch-riscv.h
index 950cc2283fd7..1927c643c739 100644
--- a/tools/include/nolibc/arch-riscv.h
+++ b/tools/include/nolibc/arch-riscv.h
@@ -19,10 +19,7 @@
  *   - the arguments are cast to long and assigned into the target
  *     registers which are then simply passed as registers to the asm code,
  *     so that we don't have to experience issues with register constraints.
- *
- * On riscv, select() is not implemented so we have to use pselect6().
  */
-#define __ARCH_WANT_SYS_PSELECT6
 
 #define my_syscall0(num)                                                      \
 ({                                                                            \
diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h
index e5ccb926c903..68609f421934 100644
--- a/tools/include/nolibc/arch-x86_64.h
+++ b/tools/include/nolibc/arch-x86_64.h
@@ -173,4 +173,46 @@ void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 	__builtin_unreachable();
 }
 
+#define NOLIBC_ARCH_HAS_MEMMOVE
+void *memmove(void *dst, const void *src, size_t len);
+
+#define NOLIBC_ARCH_HAS_MEMCPY
+void *memcpy(void *dst, const void *src, size_t len);
+
+#define NOLIBC_ARCH_HAS_MEMSET
+void *memset(void *dst, int c, size_t len);
+
+__asm__ (
+".section .text.nolibc_memmove_memcpy\n"
+".weak memmove\n"
+".weak memcpy\n"
+"memmove:\n"
+"memcpy:\n"
+	"movq %rdx, %rcx\n\t"
+	"movq %rdi, %rax\n\t"
+	"movq %rdi, %rdx\n\t"
+	"subq %rsi, %rdx\n\t"
+	"cmpq %rcx, %rdx\n\t"
+	"jb   .Lbackward_copy\n\t"
+	"rep movsb\n\t"
+	"retq\n"
+".Lbackward_copy:"
+	"leaq -1(%rdi, %rcx, 1), %rdi\n\t"
+	"leaq -1(%rsi, %rcx, 1), %rsi\n\t"
+	"std\n\t"
+	"rep movsb\n\t"
+	"cld\n\t"
+	"retq\n"
+
+".section .text.nolibc_memset\n"
+".weak memset\n"
+"memset:\n"
+	"xchgl %eax, %esi\n\t"
+	"movq  %rdx, %rcx\n\t"
+	"pushq %rdi\n\t"
+	"rep stosb\n\t"
+	"popq  %rax\n\t"
+	"retq\n"
+);
+
 #endif /* _NOLIBC_ARCH_X86_64_H */
diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h
index a05655b4ce1d..43b551468c2a 100644
--- a/tools/include/nolibc/crt.h
+++ b/tools/include/nolibc/crt.h
@@ -13,12 +13,23 @@ const unsigned long *_auxv __attribute__((weak));
 static void __stack_chk_init(void);
 static void exit(int);
 
+extern void (*const __preinit_array_start[])(void) __attribute__((weak));
+extern void (*const __preinit_array_end[])(void) __attribute__((weak));
+
+extern void (*const __init_array_start[])(void) __attribute__((weak));
+extern void (*const __init_array_end[])(void) __attribute__((weak));
+
+extern void (*const __fini_array_start[])(void) __attribute__((weak));
+extern void (*const __fini_array_end[])(void) __attribute__((weak));
+
 __attribute__((weak))
 void _start_c(long *sp)
 {
 	long argc;
 	char **argv;
 	char **envp;
+	int exitcode;
+	void (* const *func)(void);
 	const unsigned long *auxv;
 	/* silence potential warning: conflicting types for 'main' */
 	int _nolibc_main(int, char **, char **) __asm__ ("main");
@@ -55,8 +66,18 @@ void _start_c(long *sp)
 		;
 	_auxv = auxv;
 
+	for (func = __preinit_array_start; func < __preinit_array_end; func++)
+		(*func)();
+	for (func = __init_array_start; func < __init_array_end; func++)
+		(*func)();
+
 	/* go to application */
-	exit(_nolibc_main(argc, argv, envp));
+	exitcode = _nolibc_main(argc, argv, envp);
+
+	for (func = __fini_array_end; func > __fini_array_start;)
+		(*--func)();
+
+	exit(exitcode);
 }
 
 #endif /* _NOLIBC_CRT_H */
diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h
index 1f8d821000ac..989e707263a4 100644
--- a/tools/include/nolibc/nolibc.h
+++ b/tools/include/nolibc/nolibc.h
@@ -74,10 +74,10 @@
  *            -I../nolibc -o hello hello.c -lgcc
  *
  * The available standard (but limited) include files are:
- *   ctype.h, errno.h, signal.h, stdio.h, stdlib.h, string.h, time.h
+ *   ctype.h, errno.h, signal.h, stdarg.h, stdio.h, stdlib.h, string.h, time.h
  *
  * In addition, the following ones are expected to be provided by the compiler:
- *   float.h, stdarg.h, stddef.h
+ *   float.h, stddef.h
  *
  * The following ones which are part to the C standard are not provided:
  *   assert.h, locale.h, math.h, setjmp.h, limits.h
diff --git a/tools/include/nolibc/stdarg.h b/tools/include/nolibc/stdarg.h
new file mode 100644
index 000000000000..c628b5783da6
--- /dev/null
+++ b/tools/include/nolibc/stdarg.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * Variadic argument support for NOLIBC
+ * Copyright (C) 2005-2020 Rich Felker, et al.
+ */
+
+#ifndef _NOLIBC_STDARG_H
+#define _NOLIBC_STDARG_H
+
+typedef __builtin_va_list va_list;
+#define va_start(v, l)   __builtin_va_start(v, l)
+#define va_end(v)        __builtin_va_end(v)
+#define va_arg(v, l)     __builtin_va_arg(v, l)
+#define va_copy(d, s)    __builtin_va_copy(d, s)
+
+#endif /* _NOLIBC_STDARG_H */
diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
index cae402c11e57..d7ef43973916 100644
--- a/tools/include/nolibc/stdio.h
+++ b/tools/include/nolibc/stdio.h
@@ -7,13 +7,12 @@
 #ifndef _NOLIBC_STDIO_H
 #define _NOLIBC_STDIO_H
 
-#include <stdarg.h>
-
 #include "std.h"
 #include "arch.h"
 #include "errno.h"
 #include "types.h"
 #include "sys.h"
+#include "stdarg.h"
 #include "stdlib.h"
 #include "string.h"
 
diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h
index 0c2e06c7c477..a01c69dd495f 100644
--- a/tools/include/nolibc/string.h
+++ b/tools/include/nolibc/string.h
@@ -27,28 +27,7 @@ int memcmp(const void *s1, const void *s2, size_t n)
 	return c1;
 }
 
-static __attribute__((unused))
-void *_nolibc_memcpy_up(void *dst, const void *src, size_t len)
-{
-	size_t pos = 0;
-
-	while (pos < len) {
-		((char *)dst)[pos] = ((const char *)src)[pos];
-		pos++;
-	}
-	return dst;
-}
-
-static __attribute__((unused))
-void *_nolibc_memcpy_down(void *dst, const void *src, size_t len)
-{
-	while (len) {
-		len--;
-		((char *)dst)[len] = ((const char *)src)[len];
-	}
-	return dst;
-}
-
+#ifndef NOLIBC_ARCH_HAS_MEMMOVE
 /* might be ignored by the compiler without -ffreestanding, then found as
  * missing.
  */
@@ -72,14 +51,24 @@ void *memmove(void *dst, const void *src, size_t len)
 	}
 	return dst;
 }
+#endif /* #ifndef NOLIBC_ARCH_HAS_MEMMOVE */
 
+#ifndef NOLIBC_ARCH_HAS_MEMCPY
 /* must be exported, as it's used by libgcc on ARM */
 __attribute__((weak,unused,section(".text.nolibc_memcpy")))
 void *memcpy(void *dst, const void *src, size_t len)
 {
-	return _nolibc_memcpy_up(dst, src, len);
+	size_t pos = 0;
+
+	while (pos < len) {
+		((char *)dst)[pos] = ((const char *)src)[pos];
+		pos++;
+	}
+	return dst;
 }
+#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCPY */
 
+#ifndef NOLIBC_ARCH_HAS_MEMSET
 /* might be ignored by the compiler without -ffreestanding, then found as
  * missing.
  */
@@ -95,6 +84,7 @@ void *memset(void *dst, int b, size_t len)
 	}
 	return dst;
 }
+#endif /* #ifndef NOLIBC_ARCH_HAS_MEMSET */
 
 static __attribute__((unused))
 char *strchr(const char *s, int c)
diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index fdb6bd6c0e2f..2f359cb03d10 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -7,7 +7,6 @@
 #ifndef _NOLIBC_SYS_H
 #define _NOLIBC_SYS_H
 
-#include <stdarg.h>
 #include "std.h"
 
 /* system includes */
@@ -25,6 +24,7 @@
 
 #include "arch.h"
 #include "errno.h"
+#include "stdarg.h"
 #include "types.h"
 
 
@@ -43,6 +43,16 @@
 		: __sysret_arg;                         /* return original value */ \
 })
 
+/* Syscall ENOSYS helper: Avoids unused-parameter warnings and provides a
+ * debugging hook.
+ */
+
+static __inline__ int __nolibc_enosys(const char *syscall, ...)
+{
+	(void)syscall;
+	return -ENOSYS;
+}
+
 
 /* Functions in this file only describe syscalls. They're declared static so
  * that the compiler usually decides to inline them while still being allowed
@@ -133,7 +143,7 @@ int sys_chmod(const char *path, mode_t mode)
 #elif defined(__NR_chmod)
 	return my_syscall2(__NR_chmod, path, mode);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, mode);
 #endif
 }
 
@@ -156,7 +166,7 @@ int sys_chown(const char *path, uid_t owner, gid_t group)
 #elif defined(__NR_chown)
 	return my_syscall3(__NR_chown, path, owner, group);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, owner, group);
 #endif
 }
 
@@ -230,7 +240,7 @@ int sys_dup2(int old, int new)
 #elif defined(__NR_dup2)
 	return my_syscall2(__NR_dup2, old, new);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, old, new);
 #endif
 }
 
@@ -312,7 +322,7 @@ pid_t sys_fork(void)
 #elif defined(__NR_fork)
 	return my_syscall0(__NR_fork);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__);
 #endif
 }
 #endif
@@ -486,7 +496,7 @@ int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
 #ifdef __NR_gettimeofday
 	return my_syscall2(__NR_gettimeofday, tv, tz);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, tv, tz);
 #endif
 }
 
@@ -563,7 +573,7 @@ int sys_link(const char *old, const char *new)
 #elif defined(__NR_link)
 	return my_syscall2(__NR_link, old, new);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, old, new);
 #endif
 }
 
@@ -584,7 +594,7 @@ off_t sys_lseek(int fd, off_t offset, int whence)
 #ifdef __NR_lseek
 	return my_syscall3(__NR_lseek, fd, offset, whence);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, fd, offset, whence);
 #endif
 }
 
@@ -607,7 +617,7 @@ int sys_mkdir(const char *path, mode_t mode)
 #elif defined(__NR_mkdir)
 	return my_syscall2(__NR_mkdir, path, mode);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, mode);
 #endif
 }
 
@@ -629,7 +639,7 @@ int sys_rmdir(const char *path)
 #elif defined(__NR_unlinkat)
 	return my_syscall3(__NR_unlinkat, AT_FDCWD, path, AT_REMOVEDIR);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path);
 #endif
 }
 
@@ -652,7 +662,7 @@ long sys_mknod(const char *path, mode_t mode, dev_t dev)
 #elif defined(__NR_mknod)
 	return my_syscall3(__NR_mknod, path, mode, dev);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, mode, dev);
 #endif
 }
 
@@ -742,7 +752,7 @@ int sys_open(const char *path, int flags, mode_t mode)
 #elif defined(__NR_open)
 	return my_syscall3(__NR_open, path, flags, mode);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path, flags, mode);
 #endif
 }
 
@@ -842,7 +852,7 @@ int sys_poll(struct pollfd *fds, int nfds, int timeout)
 #elif defined(__NR_poll)
 	return my_syscall3(__NR_poll, fds, nfds, timeout);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, fds, nfds, timeout);
 #endif
 }
 
@@ -920,7 +930,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
 		struct timeval *t;
 	} arg = { .n = nfds, .r = rfds, .w = wfds, .e = efds, .t = timeout };
 	return my_syscall1(__NR_select, &arg);
-#elif defined(__ARCH_WANT_SYS_PSELECT6) && defined(__NR_pselect6)
+#elif defined(__NR__newselect)
+	return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
+#elif defined(__NR_select)
+	return my_syscall5(__NR_select, nfds, rfds, wfds, efds, timeout);
+#elif defined(__NR_pselect6)
 	struct timespec t;
 
 	if (timeout) {
@@ -928,13 +942,8 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
 		t.tv_nsec = timeout->tv_usec * 1000;
 	}
 	return my_syscall6(__NR_pselect6, nfds, rfds, wfds, efds, timeout ? &t : NULL, NULL);
-#elif defined(__NR__newselect) || defined(__NR_select)
-#ifndef __NR__newselect
-#define __NR__newselect __NR_select
-#endif
-	return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, nfds, rfds, wfds, efds, timeout);
 #endif
 }
 
@@ -989,7 +998,7 @@ int sys_statx(int fd, const char *path, int flags, unsigned int mask, struct sta
 #ifdef __NR_statx
 	return my_syscall5(__NR_statx, fd, path, flags, mask, buf);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, fd, path, flags, mask, buf);
 #endif
 }
 
@@ -1047,7 +1056,7 @@ int sys_symlink(const char *old, const char *new)
 #elif defined(__NR_symlink)
 	return my_syscall2(__NR_symlink, old, new);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, old, new);
 #endif
 }
 
@@ -1104,7 +1113,7 @@ int sys_unlink(const char *path)
 #elif defined(__NR_unlink)
 	return my_syscall1(__NR_unlink, path);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, path);
 #endif
 }
 
@@ -1127,7 +1136,7 @@ pid_t sys_wait4(pid_t pid, int *status, int options, struct rusage *rusage)
 #ifdef __NR_wait4
 	return my_syscall4(__NR_wait4, pid, status, options, rusage);
 #else
-	return -ENOSYS;
+	return __nolibc_enosys(__func__, pid, status, options, rusage);
 #endif
 }
 
diff --git a/tools/testing/selftests/nolibc/.gitignore b/tools/testing/selftests/nolibc/.gitignore
index 52f613cdad54..5119f9f7afd2 100644
--- a/tools/testing/selftests/nolibc/.gitignore
+++ b/tools/testing/selftests/nolibc/.gitignore
@@ -1,4 +1,5 @@
 /initramfs/
+/initramfs.cpio
 /libc-test
 /nolibc-test
 /run.out
diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
index dfe66776a331..a0fc07253baf 100644
--- a/tools/testing/selftests/nolibc/Makefile
+++ b/tools/testing/selftests/nolibc/Makefile
@@ -82,7 +82,7 @@ QEMU_ARCH_arm        = arm
 QEMU_ARCH_mips       = mipsel  # works with malta_defconfig
 QEMU_ARCH_ppc        = ppc
 QEMU_ARCH_ppc64      = ppc64
-QEMU_ARCH_ppc64le    = ppc64le
+QEMU_ARCH_ppc64le    = ppc64
 QEMU_ARCH_riscv      = riscv64
 QEMU_ARCH_s390       = s390x
 QEMU_ARCH_loongarch  = loongarch64
@@ -113,6 +113,7 @@ else
 Q=@
 endif
 
+CFLAGS_i386 = $(call cc-option,-m32)
 CFLAGS_ppc = -m32 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
 CFLAGS_ppc64 = -m64 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
 CFLAGS_ppc64le = -m64 -mlittle-endian -mno-vsx $(call cc-option,-mabi=elfv2)
@@ -131,18 +132,20 @@ REPORT  ?= awk '/\[OK\][\r]*$$/{p++} /\[FAIL\][\r]*$$/{if (!f) printf("\n"); f++
 
 help:
 	@echo "Supported targets under selftests/nolibc:"
-	@echo "  all          call the \"run\" target below"
-	@echo "  help         this help"
-	@echo "  sysroot      create the nolibc sysroot here (uses \$$ARCH)"
-	@echo "  nolibc-test  build the executable (uses \$$CC and \$$CROSS_COMPILE)"
-	@echo "  libc-test    build an executable using the compiler's default libc instead"
-	@echo "  run-user     runs the executable under QEMU (uses \$$XARCH, \$$TEST)"
-	@echo "  initramfs    prepare the initramfs with nolibc-test"
-	@echo "  defconfig    create a fresh new default config (uses \$$XARCH)"
-	@echo "  kernel       (re)build the kernel with the initramfs (uses \$$XARCH)"
-	@echo "  run          runs the kernel in QEMU after building it (uses \$$XARCH, \$$TEST)"
-	@echo "  rerun        runs a previously prebuilt kernel in QEMU (uses \$$XARCH, \$$TEST)"
-	@echo "  clean        clean the sysroot, initramfs, build and output files"
+	@echo "  all               call the \"run\" target below"
+	@echo "  help              this help"
+	@echo "  sysroot           create the nolibc sysroot here (uses \$$ARCH)"
+	@echo "  nolibc-test       build the executable (uses \$$CC and \$$CROSS_COMPILE)"
+	@echo "  libc-test         build an executable using the compiler's default libc instead"
+	@echo "  run-user          runs the executable under QEMU (uses \$$XARCH, \$$TEST)"
+	@echo "  initramfs.cpio    prepare the initramfs archive with nolibc-test"
+	@echo "  initramfs         prepare the initramfs tree with nolibc-test"
+	@echo "  defconfig         create a fresh new default config (uses \$$XARCH)"
+	@echo "  kernel            (re)build the kernel (uses \$$XARCH)"
+	@echo "  kernel-standalone (re)build the kernel with the initramfs (uses \$$XARCH)"
+	@echo "  run               runs the kernel in QEMU after building it (uses \$$XARCH, \$$TEST)"
+	@echo "  rerun             runs a previously prebuilt kernel in QEMU (uses \$$XARCH, \$$TEST)"
+	@echo "  clean             clean the sysroot, initramfs, build and output files"
 	@echo ""
 	@echo "The output file is \"run.out\". Test ranges may be passed using \$$TEST."
 	@echo ""
@@ -168,17 +171,17 @@ sysroot/$(ARCH)/include:
 	$(Q)mv sysroot/sysroot sysroot/$(ARCH)
 
 ifneq ($(NOLIBC_SYSROOT),0)
-nolibc-test: nolibc-test.c sysroot/$(ARCH)/include
+nolibc-test: nolibc-test.c nolibc-test-linkage.c sysroot/$(ARCH)/include
 	$(QUIET_CC)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ \
-	  -nostdlib -static -Isysroot/$(ARCH)/include $< -lgcc
+	  -nostdlib -nostdinc -static -Isysroot/$(ARCH)/include nolibc-test.c nolibc-test-linkage.c -lgcc
 else
-nolibc-test: nolibc-test.c
+nolibc-test: nolibc-test.c nolibc-test-linkage.c
 	$(QUIET_CC)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ \
-	  -nostdlib -static -include ../../../include/nolibc/nolibc.h $< -lgcc
+	  -nostdlib -static -include ../../../include/nolibc/nolibc.h nolibc-test.c nolibc-test-linkage.c -lgcc
 endif
 
-libc-test: nolibc-test.c
-	$(QUIET_CC)$(HOSTCC) -o $@ $<
+libc-test: nolibc-test.c nolibc-test-linkage.c
+	$(QUIET_CC)$(HOSTCC) -o $@ nolibc-test.c nolibc-test-linkage.c
 
 # local libc-test
 run-libc-test: libc-test
@@ -195,6 +198,9 @@ run-user: nolibc-test
 	$(Q)qemu-$(QEMU_ARCH) ./nolibc-test > "$(CURDIR)/run.out" || :
 	$(Q)$(REPORT) $(CURDIR)/run.out
 
+initramfs.cpio: kernel nolibc-test
+	$(QUIET_GEN)echo 'file /init nolibc-test 755 0 0' | $(srctree)/usr/gen_init_cpio - > initramfs.cpio
+
 initramfs: nolibc-test
 	$(QUIET_MKDIR)mkdir -p initramfs
 	$(call QUIET_INSTALL, initramfs/init)
@@ -203,17 +209,20 @@ initramfs: nolibc-test
 defconfig:
 	$(Q)$(MAKE) -C $(srctree) ARCH=$(ARCH) CC=$(CC) CROSS_COMPILE=$(CROSS_COMPILE) mrproper $(DEFCONFIG) prepare
 
-kernel: initramfs
+kernel:
+	$(Q)$(MAKE) -C $(srctree) ARCH=$(ARCH) CC=$(CC) CROSS_COMPILE=$(CROSS_COMPILE) $(IMAGE_NAME)
+
+kernel-standalone: initramfs
 	$(Q)$(MAKE) -C $(srctree) ARCH=$(ARCH) CC=$(CC) CROSS_COMPILE=$(CROSS_COMPILE) $(IMAGE_NAME) CONFIG_INITRAMFS_SOURCE=$(CURDIR)/initramfs
 
 # run the tests after building the kernel
-run: kernel
-	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(srctree)/$(IMAGE)" -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
+run: kernel initramfs.cpio
+	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(srctree)/$(IMAGE)" -initrd initramfs.cpio -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
 	$(Q)$(REPORT) $(CURDIR)/run.out
 
 # re-run the tests from an existing kernel
 rerun:
-	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(srctree)/$(IMAGE)" -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
+	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(srctree)/$(IMAGE)" -initrd initramfs.cpio -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
 	$(Q)$(REPORT) $(CURDIR)/run.out
 
 # report with existing test log
@@ -227,6 +236,8 @@ clean:
 	$(Q)rm -f nolibc-test
 	$(call QUIET_CLEAN, libc-test)
 	$(Q)rm -f libc-test
+	$(call QUIET_CLEAN, initramfs.cpio)
+	$(Q)rm -rf initramfs.cpio
 	$(call QUIET_CLEAN, initramfs)
 	$(Q)rm -rf initramfs
 	$(call QUIET_CLEAN, run.out)
diff --git a/tools/testing/selftests/nolibc/nolibc-test-linkage.c b/tools/testing/selftests/nolibc/nolibc-test-linkage.c
new file mode 100644
index 000000000000..5ff4c8a1db2a
--- /dev/null
+++ b/tools/testing/selftests/nolibc/nolibc-test-linkage.c
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include "nolibc-test-linkage.h"
+
+#ifndef NOLIBC
+#include <errno.h>
+#endif
+
+void *linkage_test_errno_addr(void)
+{
+	return &errno;
+}
+
+int linkage_test_constructor_test_value;
+
+__attribute__((constructor))
+static void constructor1(void)
+{
+	linkage_test_constructor_test_value = 2;
+}
+
+__attribute__((constructor))
+static void constructor2(void)
+{
+	linkage_test_constructor_test_value *= 3;
+}
diff --git a/tools/testing/selftests/nolibc/nolibc-test-linkage.h b/tools/testing/selftests/nolibc/nolibc-test-linkage.h
new file mode 100644
index 000000000000..c66473070d73
--- /dev/null
+++ b/tools/testing/selftests/nolibc/nolibc-test-linkage.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _NOLIBC_TEST_LINKAGE_H
+#define _NOLIBC_TEST_LINKAGE_H
+
+void *linkage_test_errno_addr(void);
+extern int linkage_test_constructor_test_value;
+
+#endif /* _NOLIBC_TEST_LINKAGE_H */
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index fb3bf91462e2..2f10541e6f38 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -41,6 +41,8 @@
 #endif
 #endif
 
+#include "nolibc-test-linkage.h"
+
 /* for the type of int_fast16_t and int_fast32_t, musl differs from glibc and nolibc */
 #define SINT_MAX_OF_TYPE(type) (((type)1 << (sizeof(type) * 8 - 2)) - (type)1 + ((type)1 << (sizeof(type) * 8 - 2)))
 #define SINT_MIN_OF_TYPE(type) (-SINT_MAX_OF_TYPE(type) - 1)
@@ -57,6 +59,9 @@ static int test_argc;
 /* will be used by some test cases as readable file, please don't write it */
 static const char *argv0;
 
+/* will be used by constructor tests */
+static int constructor_test_value;
+
 /* definition of a series of tests */
 struct test {
 	const char *name;              /* test name */
@@ -594,6 +599,19 @@ int expect_strne(const char *expr, int llen, const char *cmp)
 #define CASE_TEST(name) \
 	case __LINE__: llen += printf("%d %s", test, #name);
 
+/* constructors validate that they are executed in definition order */
+__attribute__((constructor))
+static void constructor1(void)
+{
+	constructor_test_value = 1;
+}
+
+__attribute__((constructor))
+static void constructor2(void)
+{
+	constructor_test_value *= 2;
+}
+
 int run_startup(int min, int max)
 {
 	int test;
@@ -630,7 +648,9 @@ int run_startup(int min, int max)
 		CASE_TEST(environ_HOME);     EXPECT_PTRNZ(1, getenv("HOME")); break;
 		CASE_TEST(auxv_addr);        EXPECT_PTRGT(test_auxv != (void *)-1, test_auxv, brk); break;
 		CASE_TEST(auxv_AT_UID);      EXPECT_EQ(1, getauxval(AT_UID), getuid()); break;
-		CASE_TEST(auxv_AT_PAGESZ);   EXPECT_GE(1, getauxval(AT_PAGESZ), 4096); break;
+		CASE_TEST(constructor);      EXPECT_EQ(1, constructor_test_value, 2); break;
+		CASE_TEST(linkage_errno);    EXPECT_PTREQ(1, linkage_test_errno_addr(), &errno); break;
+		CASE_TEST(linkage_constr);   EXPECT_EQ(1, linkage_test_constructor_test_value, 6); break;
 		case __LINE__:
 			return ret; /* must be last */
 		/* note: do not set any defaults so as to permit holes above */
@@ -894,14 +914,14 @@ int run_syscall(int min, int max)
 		CASE_TEST(lseek_0);           EXPECT_SYSER(1, lseek(0, 0, SEEK_SET), -1, ESPIPE); break;
 		CASE_TEST(mkdir_root);        EXPECT_SYSER(1, mkdir("/", 0755), -1, EEXIST); break;
 		CASE_TEST(mmap_bad);          EXPECT_PTRER(1, mmap(NULL, 0, PROT_READ, MAP_PRIVATE, 0, 0), MAP_FAILED, EINVAL); break;
-		CASE_TEST(munmap_bad);        EXPECT_SYSER(1, munmap((void *)1, 0), -1, EINVAL); break;
+		CASE_TEST(munmap_bad);        EXPECT_SYSER(1, munmap(NULL, 0), -1, EINVAL); break;
 		CASE_TEST(mmap_munmap_good);  EXPECT_SYSZR(1, test_mmap_munmap()); break;
 		CASE_TEST(open_tty);          EXPECT_SYSNE(1, tmp = open("/dev/null", 0), -1); if (tmp != -1) close(tmp); break;
 		CASE_TEST(open_blah);         EXPECT_SYSER(1, tmp = open("/proc/self/blah", 0), -1, ENOENT); if (tmp != -1) close(tmp); break;
 		CASE_TEST(pipe);              EXPECT_SYSZR(1, test_pipe()); break;
 		CASE_TEST(poll_null);         EXPECT_SYSZR(1, poll(NULL, 0, 0)); break;
 		CASE_TEST(poll_stdout);       EXPECT_SYSNE(1, ({ struct pollfd fds = { 1, POLLOUT, 0}; poll(&fds, 1, 0); }), -1); break;
-		CASE_TEST(poll_fault);        EXPECT_SYSER(1, poll((void *)1, 1, 0), -1, EFAULT); break;
+		CASE_TEST(poll_fault);        EXPECT_SYSER(1, poll(NULL, 1, 0), -1, EFAULT); break;
 		CASE_TEST(prctl);             EXPECT_SYSER(1, prctl(PR_SET_NAME, (unsigned long)NULL, 0, 0, 0), -1, EFAULT); break;
 		CASE_TEST(read_badf);         EXPECT_SYSER(1, read(-1, &tmp, 1), -1, EBADF); break;
 		CASE_TEST(rmdir_blah);        EXPECT_SYSER(1, rmdir("/blah"), -1, ENOENT); break;
@@ -910,7 +930,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(select_stdout);     EXPECT_SYSNE(1, ({ fd_set fds; FD_ZERO(&fds); FD_SET(1, &fds); select(2, NULL, &fds, NULL, NULL); }), -1); break;
 		CASE_TEST(select_fault);      EXPECT_SYSER(1, select(1, (void *)1, NULL, NULL, 0), -1, EFAULT); break;
 		CASE_TEST(stat_blah);         EXPECT_SYSER(1, stat("/proc/self/blah", &stat_buf), -1, ENOENT); break;
-		CASE_TEST(stat_fault);        EXPECT_SYSER(1, stat((void *)1, &stat_buf), -1, EFAULT); break;
+		CASE_TEST(stat_fault);        EXPECT_SYSER(1, stat(NULL, &stat_buf), -1, EFAULT); break;
 		CASE_TEST(stat_timestamps);   EXPECT_SYSZR(1, test_stat_timestamps()); break;
 		CASE_TEST(symlink_root);      EXPECT_SYSER(1, symlink("/", "/"), -1, EEXIST); break;
 		CASE_TEST(unlink_root);       EXPECT_SYSER(1, unlink("/"), -1, EISDIR); break;