tools headers: Move the nolibc header from rcutorture to tools/include/nolibc/

As suggested by Ingo, this header file might benefit other tools than
just rcutorture. For now it's quite limited, but is easy to extend, so
exposing it into tools/include/nolibc/ will make it much easier to
adopt by other tools.

The mkinitrd.sh script in rcutorture was updated to use this new location.

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

1 files changed, 2263 insertions, 0 deletions

diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h
new file mode 100644
index 000000000000..1708e9f9f8aa
--- /dev/null
+++ b/tools/include/nolibc/nolibc.h
@@ -0,0 +1,2263 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/* nolibc.h
+ * Copyright (C) 2017-2018 Willy Tarreau <w@1wt.eu>
+ */
+
+/*
+ * This file is designed to be used as a libc alternative for minimal programs
+ * with very limited requirements. It consists of a small number of syscall and
+ * type definitions, and the minimal startup code needed to call main().
+ * All syscalls are declared as static functions so that they can be optimized
+ * away by the compiler when not used.
+ *
+ * Syscalls are split into 3 levels:
+ *   - The lower level is the arch-specific syscall() definition, consisting in
+ *     assembly code in compound expressions. These are called my_syscall0() to
+ *     my_syscall6() depending on the number of arguments. The MIPS
+ *     implementation is limited to 5 arguments. All input arguments are cast
+ *     to a long stored in a register. These expressions always return the
+ *     syscall's return value as a signed long value which is often either a
+ *     pointer or the negated errno value.
+ *
+ *   - The second level is mostly architecture-independent. It is made of
+ *     static functions called sys_<name>() which rely on my_syscallN()
+ *     depending on the syscall definition. These functions are responsible
+ *     for exposing the appropriate types for the syscall arguments (int,
+ *     pointers, etc) and for setting the appropriate return type (often int).
+ *     A few of them are architecture-specific because the syscalls are not all
+ *     mapped exactly the same among architectures. For example, some archs do
+ *     not implement select() and need pselect6() instead, so the sys_select()
+ *     function will have to abstract this.
+ *
+ *   - The third level is the libc call definition. It exposes the lower raw
+ *     sys_<name>() calls in a way that looks like what a libc usually does,
+ *     takes care of specific input values, and of setting errno upon error.
+ *     There can be minor variations compared to standard libc calls. For
+ *     example the open() call always takes 3 args here.
+ *
+ * The errno variable is declared static and unused. This way it can be
+ * optimized away if not used. However this means that a program made of
+ * multiple C files may observe different errno values (one per C file). For
+ * the type of programs this project targets it usually is not a problem. The
+ * resulting program may even be reduced by defining the NOLIBC_IGNORE_ERRNO
+ * macro, in which case the errno value will never be assigned.
+ *
+ * Some stdint-like integer types are defined. These are valid on all currently
+ * supported architectures, because signs are enforced, ints are assumed to be
+ * 32 bits, longs the size of a pointer and long long 64 bits. If more
+ * architectures have to be supported, this may need to be adapted.
+ *
+ * Some macro definitions like the O_* values passed to open(), and some
+ * structures like the sys_stat struct depend on the architecture.
+ *
+ * The definitions start with the architecture-specific parts, which are picked
+ * based on what the compiler knows about the target architecture, and are
+ * completed with the generic code. Since it is the compiler which sets the
+ * target architecture, cross-compiling normally works out of the box without
+ * having to specify anything.
+ *
+ * Finally some very common libc-level functions are provided. It is the case
+ * for a few functions usually found in string.h, ctype.h, or stdlib.h. Nothing
+ * is currently provided regarding stdio emulation.
+ *
+ * The macro NOLIBC is always defined, so that it is possible for a program to
+ * check this macro to know if it is being built against and decide to disable
+ * some features or simply not to include some standard libc files.
+ *
+ * Ideally this file should be split in multiple files for easier long term
+ * maintenance, but provided as a single file as it is now, it's quite
+ * convenient to use. Maybe some variations involving a set of includes at the
+ * top could work.
+ *
+ * A simple static executable may be built this way :
+ *      $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \
+ *            -static -include nolibc.h -lgcc -o hello hello.c
+ *
+ * A very useful calling convention table may be found here :
+ *      http://man7.org/linux/man-pages/man2/syscall.2.html
+ *
+ * This doc is quite convenient though not necessarily up to date :
+ *      https://w3challs.com/syscalls/
+ *
+ */
+
+/* Some archs (at least aarch64) don't expose the regular syscalls anymore by
+ * default, either because they have an "_at" replacement, or because there are
+ * more modern alternatives. For now we'd rather still use them.
+ */
+#define __ARCH_WANT_SYSCALL_NO_AT
+#define __ARCH_WANT_SYSCALL_NO_FLAGS
+#define __ARCH_WANT_SYSCALL_DEPRECATED
+
+#include <asm/unistd.h>
+#include <asm/ioctls.h>
+#include <asm/errno.h>
+#include <linux/fs.h>
+#include <linux/loop.h>
+
+#define NOLIBC
+
+/* this way it will be removed if unused */
+static int errno;
+
+#ifndef NOLIBC_IGNORE_ERRNO
+#define SET_ERRNO(v) do { errno = (v); } while (0)
+#else
+#define SET_ERRNO(v) do { } while (0)
+#endif
+
+/* errno codes all ensure that they will not conflict with a valid pointer
+ * because they all correspond to the highest addressable memry page.
+ */
+#define MAX_ERRNO 4095
+
+/* Declare a few quite common macros and types that usually are in stdlib.h,
+ * stdint.h, ctype.h, unistd.h and a few other common locations.
+ */
+
+#define NULL ((void *)0)
+
+/* stdint types */
+typedef unsigned char       uint8_t;
+typedef   signed char        int8_t;
+typedef unsigned short     uint16_t;
+typedef   signed short      int16_t;
+typedef unsigned int       uint32_t;
+typedef   signed int        int32_t;
+typedef unsigned long long uint64_t;
+typedef   signed long long  int64_t;
+typedef unsigned long        size_t;
+typedef   signed long       ssize_t;
+typedef unsigned long     uintptr_t;
+typedef   signed long      intptr_t;
+typedef   signed long     ptrdiff_t;
+
+/* for stat() */
+typedef unsigned int          dev_t;
+typedef unsigned long         ino_t;
+typedef unsigned int         mode_t;
+typedef   signed int          pid_t;
+typedef unsigned int          uid_t;
+typedef unsigned int          gid_t;
+typedef unsigned long       nlink_t;
+typedef   signed long         off_t;
+typedef   signed long     blksize_t;
+typedef   signed long      blkcnt_t;
+typedef   signed long        time_t;
+
+/* for poll() */
+struct pollfd {
+	int fd;
+	short int events;
+	short int revents;
+};
+
+/* for select() */
+struct timeval {
+	long    tv_sec;
+	long    tv_usec;
+};
+
+/* for pselect() */
+struct timespec {
+	long    tv_sec;
+	long    tv_nsec;
+};
+
+/* for gettimeofday() */
+struct timezone {
+	int tz_minuteswest;
+	int tz_dsttime;
+};
+
+/* for getdents64() */
+struct linux_dirent64 {
+	uint64_t       d_ino;
+	int64_t        d_off;
+	unsigned short d_reclen;
+	unsigned char  d_type;
+	char           d_name[];
+};
+
+/* commonly an fd_set represents 256 FDs */
+#define FD_SETSIZE 256
+typedef struct { uint32_t fd32[FD_SETSIZE/32]; } fd_set;
+
+/* needed by wait4() */
+struct rusage {
+	struct timeval ru_utime;
+	struct timeval ru_stime;
+	long   ru_maxrss;
+	long   ru_ixrss;
+	long   ru_idrss;
+	long   ru_isrss;
+	long   ru_minflt;
+	long   ru_majflt;
+	long   ru_nswap;
+	long   ru_inblock;
+	long   ru_oublock;
+	long   ru_msgsnd;
+	long   ru_msgrcv;
+	long   ru_nsignals;
+	long   ru_nvcsw;
+	long   ru_nivcsw;
+};
+
+/* stat flags (WARNING, octal here) */
+#define S_IFDIR       0040000
+#define S_IFCHR       0020000
+#define S_IFBLK       0060000
+#define S_IFREG       0100000
+#define S_IFIFO       0010000
+#define S_IFLNK       0120000
+#define S_IFSOCK      0140000
+#define S_IFMT        0170000
+
+#define S_ISDIR(mode)  (((mode) & S_IFDIR) == S_IFDIR)
+#define S_ISCHR(mode)  (((mode) & S_IFCHR) == S_IFCHR)
+#define S_ISBLK(mode)  (((mode) & S_IFBLK) == S_IFBLK)
+#define S_ISREG(mode)  (((mode) & S_IFREG) == S_IFREG)
+#define S_ISFIFO(mode) (((mode) & S_IFIFO) == S_IFIFO)
+#define S_ISLNK(mode)  (((mode) & S_IFLNK) == S_IFLNK)
+#define S_ISSOCK(mode) (((mode) & S_IFSOCK) == S_IFSOCK)
+
+#define DT_UNKNOWN 0
+#define DT_FIFO    1
+#define DT_CHR     2
+#define DT_DIR     4
+#define DT_BLK     6
+#define DT_REG     8
+#define DT_LNK    10
+#define DT_SOCK   12
+
+/* all the *at functions */
+#ifndef AT_FDWCD
+#define AT_FDCWD             -100
+#endif
+
+/* lseek */
+#define SEEK_SET        0
+#define SEEK_CUR        1
+#define SEEK_END        2
+
+/* reboot */
+#define LINUX_REBOOT_MAGIC1         0xfee1dead
+#define LINUX_REBOOT_MAGIC2         0x28121969
+#define LINUX_REBOOT_CMD_HALT       0xcdef0123
+#define LINUX_REBOOT_CMD_POWER_OFF  0x4321fedc
+#define LINUX_REBOOT_CMD_RESTART    0x01234567
+#define LINUX_REBOOT_CMD_SW_SUSPEND 0xd000fce2
+
+
+/* The format of the struct as returned by the libc to the application, which
+ * significantly differs from the format returned by the stat() syscall flavours.
+ */
+struct stat {
+	dev_t     st_dev;     /* ID of device containing file */
+	ino_t     st_ino;     /* inode number */
+	mode_t    st_mode;    /* protection */
+	nlink_t   st_nlink;   /* number of hard links */
+	uid_t     st_uid;     /* user ID of owner */
+	gid_t     st_gid;     /* group ID of owner */
+	dev_t     st_rdev;    /* device ID (if special file) */
+	off_t     st_size;    /* total size, in bytes */
+	blksize_t st_blksize; /* blocksize for file system I/O */
+	blkcnt_t  st_blocks;  /* number of 512B blocks allocated */
+	time_t    st_atime;   /* time of last access */
+	time_t    st_mtime;   /* time of last modification */
+	time_t    st_ctime;   /* time of last status change */
+};
+
+#define WEXITSTATUS(status)   (((status) & 0xff00) >> 8)
+#define WIFEXITED(status)     (((status) & 0x7f) == 0)
+
+
+/* Below comes the architecture-specific code. For each architecture, we have
+ * the syscall declarations and the _start code definition. This is the only
+ * global part. On all architectures the kernel puts everything in the stack
+ * before jumping to _start just above us, without any return address (_start
+ * is not a function but an entry pint). So at the stack pointer we find argc.
+ * Then argv[] begins, and ends at the first NULL. Then we have envp which
+ * starts and ends with a NULL as well. So envp=argv+argc+1.
+ */
+
+#if defined(__x86_64__)
+/* Syscalls for x86_64 :
+ *   - registers are 64-bit
+ *   - syscall number is passed in rax
+ *   - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively
+ *   - the system call is performed by calling the syscall instruction
+ *   - syscall return comes in rax
+ *   - rcx and r8..r11 may be clobbered, others are preserved.
+ *   - 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.
+ *   - the syscall number is always specified last in order to allow to force
+ *     some registers before (gcc refuses a %-register at the last position).
+ */
+
+#define my_syscall0(num)                                                      \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num  asm("rax") = (num);                               \
+									      \
+	asm volatile (                                                        \
+		"syscall\n"                                                   \
+		: "=a" (_ret)                                                 \
+		: "0"(_num)                                                   \
+		: "rcx", "r8", "r9", "r10", "r11", "memory", "cc"             \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall1(num, arg1)                                                \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num  asm("rax") = (num);                               \
+	register long _arg1 asm("rdi") = (long)(arg1);                        \
+									      \
+	asm volatile (                                                        \
+		"syscall\n"                                                   \
+		: "=a" (_ret)                                                 \
+		: "r"(_arg1),                                                 \
+		  "0"(_num)                                                   \
+		: "rcx", "r8", "r9", "r10", "r11", "memory", "cc"             \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall2(num, arg1, arg2)                                          \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num  asm("rax") = (num);                               \
+	register long _arg1 asm("rdi") = (long)(arg1);                        \
+	register long _arg2 asm("rsi") = (long)(arg2);                        \
+									      \
+	asm volatile (                                                        \
+		"syscall\n"                                                   \
+		: "=a" (_ret)                                                 \
+		: "r"(_arg1), "r"(_arg2),                                     \
+		  "0"(_num)                                                   \
+		: "rcx", "r8", "r9", "r10", "r11", "memory", "cc"             \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall3(num, arg1, arg2, arg3)                                    \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num  asm("rax") = (num);                               \
+	register long _arg1 asm("rdi") = (long)(arg1);                        \
+	register long _arg2 asm("rsi") = (long)(arg2);                        \
+	register long _arg3 asm("rdx") = (long)(arg3);                        \
+									      \
+	asm volatile (                                                        \
+		"syscall\n"                                                   \
+		: "=a" (_ret)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
+		  "0"(_num)                                                   \
+		: "rcx", "r8", "r9", "r10", "r11", "memory", "cc"             \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num  asm("rax") = (num);                               \
+	register long _arg1 asm("rdi") = (long)(arg1);                        \
+	register long _arg2 asm("rsi") = (long)(arg2);                        \
+	register long _arg3 asm("rdx") = (long)(arg3);                        \
+	register long _arg4 asm("r10") = (long)(arg4);                        \
+									      \
+	asm volatile (                                                        \
+		"syscall\n"                                                   \
+		: "=a" (_ret), "=r"(_arg4)                                    \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
+		  "0"(_num)                                                   \
+		: "rcx", "r8", "r9", "r11", "memory", "cc"                    \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num  asm("rax") = (num);                               \
+	register long _arg1 asm("rdi") = (long)(arg1);                        \
+	register long _arg2 asm("rsi") = (long)(arg2);                        \
+	register long _arg3 asm("rdx") = (long)(arg3);                        \
+	register long _arg4 asm("r10") = (long)(arg4);                        \
+	register long _arg5 asm("r8")  = (long)(arg5);                        \
+									      \
+	asm volatile (                                                        \
+		"syscall\n"                                                   \
+		: "=a" (_ret), "=r"(_arg4), "=r"(_arg5)                       \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
+		  "0"(_num)                                                   \
+		: "rcx", "r9", "r11", "memory", "cc"                          \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num  asm("rax") = (num);                               \
+	register long _arg1 asm("rdi") = (long)(arg1);                        \
+	register long _arg2 asm("rsi") = (long)(arg2);                        \
+	register long _arg3 asm("rdx") = (long)(arg3);                        \
+	register long _arg4 asm("r10") = (long)(arg4);                        \
+	register long _arg5 asm("r8")  = (long)(arg5);                        \
+	register long _arg6 asm("r9")  = (long)(arg6);                        \
+									      \
+	asm volatile (                                                        \
+		"syscall\n"                                                   \
+		: "=a" (_ret), "=r"(_arg4), "=r"(_arg5)                       \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
+		  "r"(_arg6), "0"(_num)                                       \
+		: "rcx", "r11", "memory", "cc"                                \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+/* startup code */
+asm(".section .text\n"
+    ".global _start\n"
+    "_start:\n"
+    "pop %rdi\n"                // argc   (first arg, %rdi)
+    "mov %rsp, %rsi\n"          // argv[] (second arg, %rsi)
+    "lea 8(%rsi,%rdi,8),%rdx\n" // then a NULL then envp (third arg, %rdx)
+    "and $-16, %rsp\n"          // x86 ABI : esp must be 16-byte aligned when
+    "sub $8, %rsp\n"            // entering the callee
+    "call main\n"               // main() returns the status code, we'll exit with it.
+    "movzb %al, %rdi\n"         // retrieve exit code from 8 lower bits
+    "mov $60, %rax\n"           // NR_exit == 60
+    "syscall\n"                 // really exit
+    "hlt\n"                     // ensure it does not return
+    "");
+
+/* fcntl / open */
+#define O_RDONLY            0
+#define O_WRONLY            1
+#define O_RDWR              2
+#define O_CREAT          0x40
+#define O_EXCL           0x80
+#define O_NOCTTY        0x100
+#define O_TRUNC         0x200
+#define O_APPEND        0x400
+#define O_NONBLOCK      0x800
+#define O_DIRECTORY   0x10000
+
+/* The struct returned by the stat() syscall, equivalent to stat64(). The
+ * syscall returns 116 bytes and stops in the middle of __unused.
+ */
+struct sys_stat_struct {
+	unsigned long st_dev;
+	unsigned long st_ino;
+	unsigned long st_nlink;
+	unsigned int  st_mode;
+	unsigned int  st_uid;
+
+	unsigned int  st_gid;
+	unsigned int  __pad0;
+	unsigned long st_rdev;
+	long          st_size;
+	long          st_blksize;
+
+	long          st_blocks;
+	unsigned long st_atime;
+	unsigned long st_atime_nsec;
+	unsigned long st_mtime;
+
+	unsigned long st_mtime_nsec;
+	unsigned long st_ctime;
+	unsigned long st_ctime_nsec;
+	long          __unused[3];
+};
+
+#elif defined(__i386__) || defined(__i486__) || defined(__i586__) || defined(__i686__)
+/* Syscalls for i386 :
+ *   - mostly similar to x86_64
+ *   - registers are 32-bit
+ *   - syscall number is passed in eax
+ *   - arguments are in ebx, ecx, edx, esi, edi, ebp respectively
+ *   - all registers are preserved (except eax of course)
+ *   - the system call is performed by calling int $0x80
+ *   - syscall return comes in eax
+ *   - 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.
+ *   - the syscall number is always specified last in order to allow to force
+ *     some registers before (gcc refuses a %-register at the last position).
+ *
+ * Also, i386 supports the old_select syscall if newselect is not available
+ */
+#define __ARCH_WANT_SYS_OLD_SELECT
+
+#define my_syscall0(num)                                                      \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num asm("eax") = (num);                                \
+									      \
+	asm volatile (                                                        \
+		"int $0x80\n"                                                 \
+		: "=a" (_ret)                                                 \
+		: "0"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall1(num, arg1)                                                \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num asm("eax") = (num);                                \
+	register long _arg1 asm("ebx") = (long)(arg1);                        \
+									      \
+	asm volatile (                                                        \
+		"int $0x80\n"                                                 \
+		: "=a" (_ret)                                                 \
+		: "r"(_arg1),                                                 \
+		  "0"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall2(num, arg1, arg2)                                          \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num asm("eax") = (num);                                \
+	register long _arg1 asm("ebx") = (long)(arg1);                        \
+	register long _arg2 asm("ecx") = (long)(arg2);                        \
+									      \
+	asm volatile (                                                        \
+		"int $0x80\n"                                                 \
+		: "=a" (_ret)                                                 \
+		: "r"(_arg1), "r"(_arg2),                                     \
+		  "0"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall3(num, arg1, arg2, arg3)                                    \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num asm("eax") = (num);                                \
+	register long _arg1 asm("ebx") = (long)(arg1);                        \
+	register long _arg2 asm("ecx") = (long)(arg2);                        \
+	register long _arg3 asm("edx") = (long)(arg3);                        \
+									      \
+	asm volatile (                                                        \
+		"int $0x80\n"                                                 \
+		: "=a" (_ret)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
+		  "0"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num asm("eax") = (num);                                \
+	register long _arg1 asm("ebx") = (long)(arg1);                        \
+	register long _arg2 asm("ecx") = (long)(arg2);                        \
+	register long _arg3 asm("edx") = (long)(arg3);                        \
+	register long _arg4 asm("esi") = (long)(arg4);                        \
+									      \
+	asm volatile (                                                        \
+		"int $0x80\n"                                                 \
+		: "=a" (_ret)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
+		  "0"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
+({                                                                            \
+	long _ret;                                                            \
+	register long _num asm("eax") = (num);                                \
+	register long _arg1 asm("ebx") = (long)(arg1);                        \
+	register long _arg2 asm("ecx") = (long)(arg2);                        \
+	register long _arg3 asm("edx") = (long)(arg3);                        \
+	register long _arg4 asm("esi") = (long)(arg4);                        \
+	register long _arg5 asm("edi") = (long)(arg5);                        \
+									      \
+	asm volatile (                                                        \
+		"int $0x80\n"                                                 \
+		: "=a" (_ret)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
+		  "0"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_ret;                                                                 \
+})
+
+/* startup code */
+asm(".section .text\n"
+    ".global _start\n"
+    "_start:\n"
+    "pop %eax\n"                // argc   (first arg, %eax)
+    "mov %esp, %ebx\n"          // argv[] (second arg, %ebx)
+    "lea 4(%ebx,%eax,4),%ecx\n" // then a NULL then envp (third arg, %ecx)
+    "and $-16, %esp\n"          // x86 ABI : esp must be 16-byte aligned when
+    "push %ecx\n"               // push all registers on the stack so that we
+    "push %ebx\n"               // support both regparm and plain stack modes
+    "push %eax\n"
+    "call main\n"               // main() returns the status code in %eax
+    "movzbl %al, %ebx\n"        // retrieve exit code from lower 8 bits
+    "movl   $1, %eax\n"         // NR_exit == 1
+    "int    $0x80\n"            // exit now
+    "hlt\n"                     // ensure it does not
+    "");
+
+/* fcntl / open */
+#define O_RDONLY            0
+#define O_WRONLY            1
+#define O_RDWR              2
+#define O_CREAT          0x40
+#define O_EXCL           0x80
+#define O_NOCTTY        0x100
+#define O_TRUNC         0x200
+#define O_APPEND        0x400
+#define O_NONBLOCK      0x800
+#define O_DIRECTORY   0x10000
+
+/* The struct returned by the stat() syscall, 32-bit only, the syscall returns
+ * exactly 56 bytes (stops before the unused array).
+ */
+struct sys_stat_struct {
+	unsigned long  st_dev;
+	unsigned long  st_ino;
+	unsigned short st_mode;
+	unsigned short st_nlink;
+	unsigned short st_uid;
+	unsigned short st_gid;
+
+	unsigned long  st_rdev;
+	unsigned long  st_size;
+	unsigned long  st_blksize;
+	unsigned long  st_blocks;
+
+	unsigned long  st_atime;
+	unsigned long  st_atime_nsec;
+	unsigned long  st_mtime;
+	unsigned long  st_mtime_nsec;
+
+	unsigned long  st_ctime;
+	unsigned long  st_ctime_nsec;
+	unsigned long  __unused[2];
+};
+
+#elif defined(__ARM_EABI__)
+/* Syscalls for ARM in ARM or Thumb modes :
+ *   - registers are 32-bit
+ *   - stack is 8-byte aligned
+ *     ( http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka4127.html)
+ *   - syscall number is passed in r7
+ *   - arguments are in r0, r1, r2, r3, r4, r5
+ *   - the system call is performed by calling svc #0
+ *   - syscall return comes in r0.
+ *   - only lr is clobbered.
+ *   - 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.
+ *   - the syscall number is always specified last in order to allow to force
+ *     some registers before (gcc refuses a %-register at the last position).
+ *
+ * Also, ARM supports the old_select syscall if newselect is not available
+ */
+#define __ARCH_WANT_SYS_OLD_SELECT
+
+#define my_syscall0(num)                                                      \
+({                                                                            \
+	register long _num asm("r7") = (num);                                 \
+	register long _arg1 asm("r0");                                        \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_num)                                                   \
+		: "memory", "cc", "lr"                                        \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall1(num, arg1)                                                \
+({                                                                            \
+	register long _num asm("r7") = (num);                                 \
+	register long _arg1 asm("r0") = (long)(arg1);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_arg1),                                                 \
+		  "r"(_num)                                                   \
+		: "memory", "cc", "lr"                                        \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall2(num, arg1, arg2)                                          \
+({                                                                            \
+	register long _num asm("r7") = (num);                                 \
+	register long _arg1 asm("r0") = (long)(arg1);                         \
+	register long _arg2 asm("r1") = (long)(arg2);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_arg1), "r"(_arg2),                                     \
+		  "r"(_num)                                                   \
+		: "memory", "cc", "lr"                                        \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall3(num, arg1, arg2, arg3)                                    \
+({                                                                            \
+	register long _num asm("r7") = (num);                                 \
+	register long _arg1 asm("r0") = (long)(arg1);                         \
+	register long _arg2 asm("r1") = (long)(arg2);                         \
+	register long _arg3 asm("r2") = (long)(arg3);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
+		  "r"(_num)                                                   \
+		: "memory", "cc", "lr"                                        \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
+({                                                                            \
+	register long _num asm("r7") = (num);                                 \
+	register long _arg1 asm("r0") = (long)(arg1);                         \
+	register long _arg2 asm("r1") = (long)(arg2);                         \
+	register long _arg3 asm("r2") = (long)(arg3);                         \
+	register long _arg4 asm("r3") = (long)(arg4);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
+		  "r"(_num)                                                   \
+		: "memory", "cc", "lr"                                        \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
+({                                                                            \
+	register long _num asm("r7") = (num);                                 \
+	register long _arg1 asm("r0") = (long)(arg1);                         \
+	register long _arg2 asm("r1") = (long)(arg2);                         \
+	register long _arg3 asm("r2") = (long)(arg3);                         \
+	register long _arg4 asm("r3") = (long)(arg4);                         \
+	register long _arg5 asm("r4") = (long)(arg5);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r" (_arg1)                                                \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
+		  "r"(_num)                                                   \
+		: "memory", "cc", "lr"                                        \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+/* startup code */
+asm(".section .text\n"
+    ".global _start\n"
+    "_start:\n"
+#if defined(__THUMBEB__) || defined(__THUMBEL__)
+    /* We enter here in 32-bit mode but if some previous functions were in
+     * 16-bit mode, the assembler cannot know, so we need to tell it we're in
+     * 32-bit now, then switch to 16-bit (is there a better way to do it than
+     * adding 1 by hand ?) and tell the asm we're now in 16-bit mode so that
+     * it generates correct instructions. Note that we do not support thumb1.
+     */
+    ".code 32\n"
+    "add     r0, pc, #1\n"
+    "bx      r0\n"
+    ".code 16\n"
+#endif
+    "pop {%r0}\n"                 // argc was in the stack
+    "mov %r1, %sp\n"              // argv = sp
+    "add %r2, %r1, %r0, lsl #2\n" // envp = argv + 4*argc ...
+    "add %r2, %r2, $4\n"          //        ... + 4
+    "and %r3, %r1, $-8\n"         // AAPCS : sp must be 8-byte aligned in the
+    "mov %sp, %r3\n"              //         callee, an bl doesn't push (lr=pc)
+    "bl main\n"                   // main() returns the status code, we'll exit with it.
+    "and %r0, %r0, $0xff\n"       // limit exit code to 8 bits
+    "movs r7, $1\n"               // NR_exit == 1
+    "svc $0x00\n"
+    "");
+
+/* fcntl / open */
+#define O_RDONLY            0
+#define O_WRONLY            1
+#define O_RDWR              2
+#define O_CREAT          0x40
+#define O_EXCL           0x80
+#define O_NOCTTY        0x100
+#define O_TRUNC         0x200
+#define O_APPEND        0x400
+#define O_NONBLOCK      0x800
+#define O_DIRECTORY    0x4000
+
+/* The struct returned by the stat() syscall, 32-bit only, the syscall returns
+ * exactly 56 bytes (stops before the unused array). In big endian, the format
+ * differs as devices are returned as short only.
+ */
+struct sys_stat_struct {
+#if defined(__ARMEB__)
+	unsigned short st_dev;
+	unsigned short __pad1;
+#else
+	unsigned long  st_dev;
+#endif
+	unsigned long  st_ino;
+	unsigned short st_mode;
+	unsigned short st_nlink;
+	unsigned short st_uid;
+	unsigned short st_gid;
+#if defined(__ARMEB__)
+	unsigned short st_rdev;
+	unsigned short __pad2;
+#else
+	unsigned long  st_rdev;
+#endif
+	unsigned long  st_size;
+	unsigned long  st_blksize;
+	unsigned long  st_blocks;
+	unsigned long  st_atime;
+	unsigned long  st_atime_nsec;
+	unsigned long  st_mtime;
+	unsigned long  st_mtime_nsec;
+	unsigned long  st_ctime;
+	unsigned long  st_ctime_nsec;
+	unsigned long  __unused[2];
+};
+
+#elif defined(__aarch64__)
+/* Syscalls for AARCH64 :
+ *   - registers are 64-bit
+ *   - stack is 16-byte aligned
+ *   - syscall number is passed in x8
+ *   - arguments are in x0, x1, x2, x3, x4, x5
+ *   - the system call is performed by calling svc 0
+ *   - syscall return comes in x0.
+ *   - 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)                                                      \
+({                                                                            \
+	register long _num  asm("x8") = (num);                                \
+	register long _arg1 asm("x0");                                        \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall1(num, arg1)                                                \
+({                                                                            \
+	register long _num  asm("x8") = (num);                                \
+	register long _arg1 asm("x0") = (long)(arg1);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_arg1),                                                 \
+		  "r"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall2(num, arg1, arg2)                                          \
+({                                                                            \
+	register long _num  asm("x8") = (num);                                \
+	register long _arg1 asm("x0") = (long)(arg1);                         \
+	register long _arg2 asm("x1") = (long)(arg2);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_arg1), "r"(_arg2),                                     \
+		  "r"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall3(num, arg1, arg2, arg3)                                    \
+({                                                                            \
+	register long _num  asm("x8") = (num);                                \
+	register long _arg1 asm("x0") = (long)(arg1);                         \
+	register long _arg2 asm("x1") = (long)(arg2);                         \
+	register long _arg3 asm("x2") = (long)(arg3);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
+		  "r"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
+({                                                                            \
+	register long _num  asm("x8") = (num);                                \
+	register long _arg1 asm("x0") = (long)(arg1);                         \
+	register long _arg2 asm("x1") = (long)(arg2);                         \
+	register long _arg3 asm("x2") = (long)(arg3);                         \
+	register long _arg4 asm("x3") = (long)(arg4);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r"(_arg1)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
+		  "r"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
+({                                                                            \
+	register long _num  asm("x8") = (num);                                \
+	register long _arg1 asm("x0") = (long)(arg1);                         \
+	register long _arg2 asm("x1") = (long)(arg2);                         \
+	register long _arg3 asm("x2") = (long)(arg3);                         \
+	register long _arg4 asm("x3") = (long)(arg4);                         \
+	register long _arg5 asm("x4") = (long)(arg5);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r" (_arg1)                                                \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
+		  "r"(_num)                                                   \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
+({                                                                            \
+	register long _num  asm("x8") = (num);                                \
+	register long _arg1 asm("x0") = (long)(arg1);                         \
+	register long _arg2 asm("x1") = (long)(arg2);                         \
+	register long _arg3 asm("x2") = (long)(arg3);                         \
+	register long _arg4 asm("x3") = (long)(arg4);                         \
+	register long _arg5 asm("x4") = (long)(arg5);                         \
+	register long _arg6 asm("x5") = (long)(arg6);                         \
+									      \
+	asm volatile (                                                        \
+		"svc #0\n"                                                    \
+		: "=r" (_arg1)                                                \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
+		  "r"(_arg6), "r"(_num)                                       \
+		: "memory", "cc"                                              \
+	);                                                                    \
+	_arg1;                                                                \
+})
+
+/* startup code */
+asm(".section .text\n"
+    ".global _start\n"
+    "_start:\n"
+    "ldr x0, [sp]\n"              // argc (x0) was in the stack
+    "add x1, sp, 8\n"             // argv (x1) = sp
+    "lsl x2, x0, 3\n"             // envp (x2) = 8*argc ...
+    "add x2, x2, 8\n"             //           + 8 (skip null)
+    "add x2, x2, x1\n"            //           + argv
+    "and sp, x1, -16\n"           // sp must be 16-byte aligned in the callee
+    "bl main\n"                   // main() returns the status code, we'll exit with it.
+    "and x0, x0, 0xff\n"          // limit exit code to 8 bits
+    "mov x8, 93\n"                // NR_exit == 93
+    "svc #0\n"
+    "");
+
+/* fcntl / open */
+#define O_RDONLY            0
+#define O_WRONLY            1
+#define O_RDWR              2
+#define O_CREAT          0x40
+#define O_EXCL           0x80
+#define O_NOCTTY        0x100
+#define O_TRUNC         0x200
+#define O_APPEND        0x400
+#define O_NONBLOCK      0x800
+#define O_DIRECTORY    0x4000
+
+/* The struct returned by the newfstatat() syscall. Differs slightly from the
+ * x86_64's stat one by field ordering, so be careful.
+ */
+struct sys_stat_struct {
+	unsigned long   st_dev;
+	unsigned long   st_ino;
+	unsigned int    st_mode;
+	unsigned int    st_nlink;
+	unsigned int    st_uid;
+	unsigned int    st_gid;
+
+	unsigned long   st_rdev;
+	unsigned long   __pad1;
+	long            st_size;
+	int             st_blksize;
+	int             __pad2;
+
+	long            st_blocks;
+	long            st_atime;
+	unsigned long   st_atime_nsec;
+	long            st_mtime;
+
+	unsigned long   st_mtime_nsec;
+	long            st_ctime;
+	unsigned long   st_ctime_nsec;
+	unsigned int    __unused[2];
+};
+
+#elif defined(__mips__) && defined(_ABIO32)
+/* Syscalls for MIPS ABI O32 :
+ *   - WARNING! there's always a delayed slot!
+ *   - WARNING again, the syntax is different, registers take a '$' and numbers
+ *     do not.
+ *   - registers are 32-bit
+ *   - stack is 8-byte aligned
+ *   - syscall number is passed in v0 (starts at 0xfa0).
+ *   - arguments are in a0, a1, a2, a3, then the stack. The caller needs to
+ *     leave some room in the stack for the callee to save a0..a3 if needed.
+ *   - Many registers are clobbered, in fact only a0..a2 and s0..s8 are
+ *     preserved. See: https://www.linux-mips.org/wiki/Syscall as well as
+ *     scall32-o32.S in the kernel sources.
+ *   - the system call is performed by calling "syscall"
+ *   - syscall return comes in v0, and register a3 needs to be checked to know
+ *     if an error occured, in which case errno is in v0.
+ *   - 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.
+ */
+
+#define my_syscall0(num)                                                      \
+({                                                                            \
+	register long _num asm("v0") = (num);                                 \
+	register long _arg4 asm("a3");                                        \
+									      \
+	asm volatile (                                                        \
+		"addiu $sp, $sp, -32\n"                                       \
+		"syscall\n"                                                   \
+		"addiu $sp, $sp, 32\n"                                        \
+		: "=r"(_num), "=r"(_arg4)                                     \
+		: "r"(_num)                                                   \
+		: "memory", "cc", "at", "v1", "hi", "lo",                     \
+		  "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9"  \
+	);                                                                    \
+	_arg4 ? -_num : _num;                                                 \
+})
+
+#define my_syscall1(num, arg1)                                                \
+({                                                                            \
+	register long _num asm("v0") = (num);                                 \
+	register long _arg1 asm("a0") = (long)(arg1);                         \
+	register long _arg4 asm("a3");                                        \
+									      \
+	asm volatile (                                                        \
+		"addiu $sp, $sp, -32\n"                                       \
+		"syscall\n"                                                   \
+		"addiu $sp, $sp, 32\n"                                        \
+		: "=r"(_num), "=r"(_arg4)                                     \
+		: "0"(_num),                                                  \
+		  "r"(_arg1)                                                  \
+		: "memory", "cc", "at", "v1", "hi", "lo",                     \
+		  "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9"  \
+	);                                                                    \
+	_arg4 ? -_num : _num;                                                 \
+})
+
+#define my_syscall2(num, arg1, arg2)                                          \
+({                                                                            \
+	register long _num asm("v0") = (num);                                 \
+	register long _arg1 asm("a0") = (long)(arg1);                         \
+	register long _arg2 asm("a1") = (long)(arg2);                         \
+	register long _arg4 asm("a3");                                        \
+									      \
+	asm volatile (                                                        \
+		"addiu $sp, $sp, -32\n"                                       \
+		"syscall\n"                                                   \
+		"addiu $sp, $sp, 32\n"                                        \
+		: "=r"(_num), "=r"(_arg4)                                     \
+		: "0"(_num),                                                  \
+		  "r"(_arg1), "r"(_arg2)                                      \
+		: "memory", "cc", "at", "v1", "hi", "lo",                     \
+		  "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9"  \
+	);                                                                    \
+	_arg4 ? -_num : _num;                                                 \
+})
+
+#define my_syscall3(num, arg1, arg2, arg3)                                    \
+({                                                                            \
+	register long _num asm("v0")  = (num);                                \
+	register long _arg1 asm("a0") = (long)(arg1);                         \
+	register long _arg2 asm("a1") = (long)(arg2);                         \
+	register long _arg3 asm("a2") = (long)(arg3);                         \
+	register long _arg4 asm("a3");                                        \
+									      \
+	asm volatile (                                                        \
+		"addiu $sp, $sp, -32\n"                                       \
+		"syscall\n"                                                   \
+		"addiu $sp, $sp, 32\n"                                        \
+		: "=r"(_num), "=r"(_arg4)                                     \
+		: "0"(_num),                                                  \
+		  "r"(_arg1), "r"(_arg2), "r"(_arg3)                          \
+		: "memory", "cc", "at", "v1", "hi", "lo",                     \
+		  "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9"  \
+	);                                                                    \
+	_arg4 ? -_num : _num;                                                 \
+})
+
+#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
+({                                                                            \
+	register long _num asm("v0") = (num);                                 \
+	register long _arg1 asm("a0") = (long)(arg1);                         \
+	register long _arg2 asm("a1") = (long)(arg2);                         \
+	register long _arg3 asm("a2") = (long)(arg3);                         \
+	register long _arg4 asm("a3") = (long)(arg4);                         \
+									      \
+	asm volatile (                                                        \
+		"addiu $sp, $sp, -32\n"                                       \
+		"syscall\n"                                                   \
+		"addiu $sp, $sp, 32\n"                                        \
+		: "=r" (_num), "=r"(_arg4)                                    \
+		: "0"(_num),                                                  \
+		  "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4)              \
+		: "memory", "cc", "at", "v1", "hi", "lo",                     \
+		  "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9"  \
+	);                                                                    \
+	_arg4 ? -_num : _num;                                                 \
+})
+
+#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
+({                                                                            \
+	register long _num asm("v0") = (num);                                 \
+	register long _arg1 asm("a0") = (long)(arg1);                         \
+	register long _arg2 asm("a1") = (long)(arg2);                         \
+	register long _arg3 asm("a2") = (long)(arg3);                         \
+	register long _arg4 asm("a3") = (long)(arg4);                         \
+	register long _arg5 = (long)(arg5);				      \
+									      \
+	asm volatile (                                                        \
+		"addiu $sp, $sp, -32\n"                                       \
+		"sw %7, 16($sp)\n"                                            \
+		"syscall\n  "                                                 \
+		"addiu $sp, $sp, 32\n"                                        \
+		: "=r" (_num), "=r"(_arg4)                                    \
+		: "0"(_num),                                                  \
+		  "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5)  \
+		: "memory", "cc", "at", "v1", "hi", "lo",                     \
+		  "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9"  \
+	);                                                                    \
+	_arg4 ? -_num : _num;                                                 \
+})
+
+/* startup code, note that it's called __start on MIPS */
+asm(".section .text\n"
+    ".set nomips16\n"
+    ".global __start\n"
+    ".set    noreorder\n"
+    ".option pic0\n"
+    ".ent __start\n"
+    "__start:\n"
+    "lw $a0,($sp)\n"              // argc was in the stack
+    "addiu  $a1, $sp, 4\n"        // argv = sp + 4
+    "sll $a2, $a0, 2\n"           // a2 = argc * 4
+    "add   $a2, $a2, $a1\n"       // envp = argv + 4*argc ...
+    "addiu $a2, $a2, 4\n"         //        ... + 4
+    "li $t0, -8\n"
+    "and $sp, $sp, $t0\n"         // sp must be 8-byte aligned
+    "addiu $sp,$sp,-16\n"         // the callee expects to save a0..a3 there!
+    "jal main\n"                  // main() returns the status code, we'll exit with it.
+    "nop\n"                       // delayed slot
+    "and $a0, $v0, 0xff\n"        // limit exit code to 8 bits
+    "li $v0, 4001\n"              // NR_exit == 4001
+    "syscall\n"
+    ".end __start\n"
+    "");
+
+/* fcntl / open */
+#define O_RDONLY            0
+#define O_WRONLY            1
+#define O_RDWR              2
+#define O_APPEND       0x0008
+#define O_NONBLOCK     0x0080
+#define O_CREAT        0x0100
+#define O_TRUNC        0x0200
+#define O_EXCL         0x0400
+#define O_NOCTTY       0x0800
+#define O_DIRECTORY   0x10000
+
+/* The struct returned by the stat() syscall. 88 bytes are returned by the
+ * syscall.
+ */
+struct sys_stat_struct {
+	unsigned int  st_dev;
+	long          st_pad1[3];
+	unsigned long st_ino;
+	unsigned int  st_mode;
+	unsigned int  st_nlink;
+	unsigned int  st_uid;
+	unsigned int  st_gid;
+	unsigned int  st_rdev;
+	long          st_pad2[2];
+	long          st_size;
+	long          st_pad3;
+	long          st_atime;
+	long          st_atime_nsec;
+	long          st_mtime;
+	long          st_mtime_nsec;
+	long          st_ctime;
+	long          st_ctime_nsec;
+	long          st_blksize;
+	long          st_blocks;
+	long          st_pad4[14];
+};
+
+#endif
+
+
+/* Below are the C functions used to declare the raw syscalls. They try to be
+ * architecture-agnostic, and return either a success or -errno. Declaring them
+ * static will lead to them being inlined in most cases, but it's still possible
+ * to reference them by a pointer if needed.
+ */
+static __attribute__((unused))
+void *sys_brk(void *addr)
+{
+	return (void *)my_syscall1(__NR_brk, addr);
+}
+
+static __attribute__((noreturn,unused))
+void sys_exit(int status)
+{
+	my_syscall1(__NR_exit, status & 255);
+	while(1); // shut the "noreturn" warnings.
+}
+
+static __attribute__((unused))
+int sys_chdir(const char *path)
+{
+	return my_syscall1(__NR_chdir, path);
+}
+
+static __attribute__((unused))
+int sys_chmod(const char *path, mode_t mode)
+{
+#ifdef __NR_fchmodat
+	return my_syscall4(__NR_fchmodat, AT_FDCWD, path, mode, 0);
+#else
+	return my_syscall2(__NR_chmod, path, mode);
+#endif
+}
+
+static __attribute__((unused))
+int sys_chown(const char *path, uid_t owner, gid_t group)
+{
+#ifdef __NR_fchownat
+	return my_syscall5(__NR_fchownat, AT_FDCWD, path, owner, group, 0);
+#else
+	return my_syscall3(__NR_chown, path, owner, group);
+#endif
+}
+
+static __attribute__((unused))
+int sys_chroot(const char *path)
+{
+	return my_syscall1(__NR_chroot, path);
+}
+
+static __attribute__((unused))
+int sys_close(int fd)
+{
+	return my_syscall1(__NR_close, fd);
+}
+
+static __attribute__((unused))
+int sys_dup(int fd)
+{
+	return my_syscall1(__NR_dup, fd);
+}
+
+static __attribute__((unused))
+int sys_dup2(int old, int new)
+{
+	return my_syscall2(__NR_dup2, old, new);
+}
+
+static __attribute__((unused))
+int sys_execve(const char *filename, char *const argv[], char *const envp[])
+{
+	return my_syscall3(__NR_execve, filename, argv, envp);
+}
+
+static __attribute__((unused))
+pid_t sys_fork(void)
+{
+	return my_syscall0(__NR_fork);
+}
+
+static __attribute__((unused))
+int sys_fsync(int fd)
+{
+	return my_syscall1(__NR_fsync, fd);
+}
+
+static __attribute__((unused))
+int sys_getdents64(int fd, struct linux_dirent64 *dirp, int count)
+{
+	return my_syscall3(__NR_getdents64, fd, dirp, count);
+}
+
+static __attribute__((unused))
+pid_t sys_getpgrp(void)
+{
+	return my_syscall0(__NR_getpgrp);
+}
+
+static __attribute__((unused))
+pid_t sys_getpid(void)
+{
+	return my_syscall0(__NR_getpid);
+}
+
+static __attribute__((unused))
+int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+	return my_syscall2(__NR_gettimeofday, tv, tz);
+}
+
+static __attribute__((unused))
+int sys_ioctl(int fd, unsigned long req, void *value)
+{
+	return my_syscall3(__NR_ioctl, fd, req, value);
+}
+
+static __attribute__((unused))
+int sys_kill(pid_t pid, int signal)
+{
+	return my_syscall2(__NR_kill, pid, signal);
+}
+
+static __attribute__((unused))
+int sys_link(const char *old, const char *new)
+{
+#ifdef __NR_linkat
+	return my_syscall5(__NR_linkat, AT_FDCWD, old, AT_FDCWD, new, 0);
+#else
+	return my_syscall2(__NR_link, old, new);
+#endif
+}
+
+static __attribute__((unused))
+off_t sys_lseek(int fd, off_t offset, int whence)
+{
+	return my_syscall3(__NR_lseek, fd, offset, whence);
+}
+
+static __attribute__((unused))
+int sys_mkdir(const char *path, mode_t mode)
+{
+#ifdef __NR_mkdirat
+	return my_syscall3(__NR_mkdirat, AT_FDCWD, path, mode);
+#else
+	return my_syscall2(__NR_mkdir, path, mode);
+#endif
+}
+
+static __attribute__((unused))
+long sys_mknod(const char *path, mode_t mode, dev_t dev)
+{
+#ifdef __NR_mknodat
+	return my_syscall4(__NR_mknodat, AT_FDCWD, path, mode, dev);
+#else
+	return my_syscall3(__NR_mknod, path, mode, dev);
+#endif
+}
+
+static __attribute__((unused))
+int sys_mount(const char *src, const char *tgt, const char *fst,
+	      unsigned long flags, const void *data)
+{
+	return my_syscall5(__NR_mount, src, tgt, fst, flags, data);
+}
+
+static __attribute__((unused))
+int sys_open(const char *path, int flags, mode_t mode)
+{
+#ifdef __NR_openat
+	return my_syscall4(__NR_openat, AT_FDCWD, path, flags, mode);
+#else
+	return my_syscall3(__NR_open, path, flags, mode);
+#endif
+}
+
+static __attribute__((unused))
+int sys_pivot_root(const char *new, const char *old)
+{
+	return my_syscall2(__NR_pivot_root, new, old);
+}
+
+static __attribute__((unused))
+int sys_poll(struct pollfd *fds, int nfds, int timeout)
+{
+	return my_syscall3(__NR_poll, fds, nfds, timeout);
+}
+
+static __attribute__((unused))
+ssize_t sys_read(int fd, void *buf, size_t count)
+{
+	return my_syscall3(__NR_read, fd, buf, count);
+}
+
+static __attribute__((unused))
+ssize_t sys_reboot(int magic1, int magic2, int cmd, void *arg)
+{
+	return my_syscall4(__NR_reboot, magic1, magic2, cmd, arg);
+}
+
+static __attribute__((unused))
+int sys_sched_yield(void)
+{
+	return my_syscall0(__NR_sched_yield);
+}
+
+static __attribute__((unused))
+int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeval *timeout)
+{
+#if defined(__ARCH_WANT_SYS_OLD_SELECT) && !defined(__NR__newselect)
+	struct sel_arg_struct {
+		unsigned long n;
+		fd_set *r, *w, *e;
+		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)
+	struct timespec t;
+
+	if (timeout) {
+		t.tv_sec  = timeout->tv_sec;
+		t.tv_nsec = timeout->tv_usec * 1000;
+	}
+	return my_syscall6(__NR_pselect6, nfds, rfds, wfds, efds, timeout ? &t : NULL, NULL);
+#else
+#ifndef __NR__newselect
+#define __NR__newselect __NR_select
+#endif
+	return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
+#endif
+}
+
+static __attribute__((unused))
+int sys_setpgid(pid_t pid, pid_t pgid)
+{
+	return my_syscall2(__NR_setpgid, pid, pgid);
+}
+
+static __attribute__((unused))
+pid_t sys_setsid(void)
+{
+	return my_syscall0(__NR_setsid);
+}
+
+static __attribute__((unused))
+int sys_stat(const char *path, struct stat *buf)
+{
+	struct sys_stat_struct stat;
+	long ret;
+
+#ifdef __NR_newfstatat
+	/* only solution for arm64 */
+	ret = my_syscall4(__NR_newfstatat, AT_FDCWD, path, &stat, 0);
+#else
+	ret = my_syscall2(__NR_stat, path, &stat);
+#endif
+	buf->st_dev     = stat.st_dev;
+	buf->st_ino     = stat.st_ino;
+	buf->st_mode    = stat.st_mode;
+	buf->st_nlink   = stat.st_nlink;
+	buf->st_uid     = stat.st_uid;
+	buf->st_gid     = stat.st_gid;
+	buf->st_rdev    = stat.st_rdev;
+	buf->st_size    = stat.st_size;
+	buf->st_blksize = stat.st_blksize;
+	buf->st_blocks  = stat.st_blocks;
+	buf->st_atime   = stat.st_atime;
+	buf->st_mtime   = stat.st_mtime;
+	buf->st_ctime   = stat.st_ctime;
+	return ret;
+}
+
+
+static __attribute__((unused))
+int sys_symlink(const char *old, const char *new)
+{
+#ifdef __NR_symlinkat
+	return my_syscall3(__NR_symlinkat, old, AT_FDCWD, new);
+#else
+	return my_syscall2(__NR_symlink, old, new);
+#endif
+}
+
+static __attribute__((unused))
+mode_t sys_umask(mode_t mode)
+{
+	return my_syscall1(__NR_umask, mode);
+}
+
+static __attribute__((unused))
+int sys_umount2(const char *path, int flags)
+{
+	return my_syscall2(__NR_umount2, path, flags);
+}
+
+static __attribute__((unused))
+int sys_unlink(const char *path)
+{
+#ifdef __NR_unlinkat
+	return my_syscall3(__NR_unlinkat, AT_FDCWD, path, 0);
+#else
+	return my_syscall1(__NR_unlink, path);
+#endif
+}
+
+static __attribute__((unused))
+pid_t sys_wait4(pid_t pid, int *status, int options, struct rusage *rusage)
+{
+	return my_syscall4(__NR_wait4, pid, status, options, rusage);
+}
+
+static __attribute__((unused))
+pid_t sys_waitpid(pid_t pid, int *status, int options)
+{
+	return sys_wait4(pid, status, options, 0);
+}
+
+static __attribute__((unused))
+pid_t sys_wait(int *status)
+{
+	return sys_waitpid(-1, status, 0);
+}
+
+static __attribute__((unused))
+ssize_t sys_write(int fd, const void *buf, size_t count)
+{
+	return my_syscall3(__NR_write, fd, buf, count);
+}
+
+
+/* Below are the libc-compatible syscalls which return x or -1 and set errno.
+ * They rely on the functions above. Similarly they're marked static so that it
+ * is possible to assign pointers to them if needed.
+ */
+
+static __attribute__((unused))
+int brk(void *addr)
+{
+	void *ret = sys_brk(addr);
+
+	if (!ret) {
+		SET_ERRNO(ENOMEM);
+		return -1;
+	}
+	return 0;
+}
+
+static __attribute__((noreturn,unused))
+void exit(int status)
+{
+	sys_exit(status);
+}
+
+static __attribute__((unused))
+int chdir(const char *path)
+{
+	int ret = sys_chdir(path);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int chmod(const char *path, mode_t mode)
+{
+	int ret = sys_chmod(path, mode);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int chown(const char *path, uid_t owner, gid_t group)
+{
+	int ret = sys_chown(path, owner, group);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int chroot(const char *path)
+{
+	int ret = sys_chroot(path);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int close(int fd)
+{
+	int ret = sys_close(fd);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int dup2(int old, int new)
+{
+	int ret = sys_dup2(old, new);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int execve(const char *filename, char *const argv[], char *const envp[])
+{
+	int ret = sys_execve(filename, argv, envp);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+pid_t fork(void)
+{
+	pid_t ret = sys_fork();
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int fsync(int fd)
+{
+	int ret = sys_fsync(fd);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int getdents64(int fd, struct linux_dirent64 *dirp, int count)
+{
+	int ret = sys_getdents64(fd, dirp, count);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+pid_t getpgrp(void)
+{
+	pid_t ret = sys_getpgrp();
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+pid_t getpid(void)
+{
+	pid_t ret = sys_getpid();
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+	int ret = sys_gettimeofday(tv, tz);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int ioctl(int fd, unsigned long req, void *value)
+{
+	int ret = sys_ioctl(fd, req, value);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int kill(pid_t pid, int signal)
+{
+	int ret = sys_kill(pid, signal);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int link(const char *old, const char *new)
+{
+	int ret = sys_link(old, new);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+off_t lseek(int fd, off_t offset, int whence)
+{
+	off_t ret = sys_lseek(fd, offset, whence);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int mkdir(const char *path, mode_t mode)
+{
+	int ret = sys_mkdir(path, mode);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int mknod(const char *path, mode_t mode, dev_t dev)
+{
+	int ret = sys_mknod(path, mode, dev);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int mount(const char *src, const char *tgt,
+	  const char *fst, unsigned long flags,
+	  const void *data)
+{
+	int ret = sys_mount(src, tgt, fst, flags, data);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int open(const char *path, int flags, mode_t mode)
+{
+	int ret = sys_open(path, flags, mode);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int pivot_root(const char *new, const char *old)
+{
+	int ret = sys_pivot_root(new, old);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int poll(struct pollfd *fds, int nfds, int timeout)
+{
+	int ret = sys_poll(fds, nfds, timeout);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+ssize_t read(int fd, void *buf, size_t count)
+{
+	ssize_t ret = sys_read(fd, buf, count);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int reboot(int cmd)
+{
+	int ret = sys_reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, cmd, 0);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+void *sbrk(intptr_t inc)
+{
+	void *ret;
+
+	/* first call to find current end */
+	if ((ret = sys_brk(0)) && (sys_brk(ret + inc) == ret + inc))
+		return ret + inc;
+
+	SET_ERRNO(ENOMEM);
+	return (void *)-1;
+}
+
+static __attribute__((unused))
+int sched_yield(void)
+{
+	int ret = sys_sched_yield();
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeval *timeout)
+{
+	int ret = sys_select(nfds, rfds, wfds, efds, timeout);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int setpgid(pid_t pid, pid_t pgid)
+{
+	int ret = sys_setpgid(pid, pgid);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+pid_t setsid(void)
+{
+	pid_t ret = sys_setsid();
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+unsigned int sleep(unsigned int seconds)
+{
+	struct timeval my_timeval = { seconds, 0 };
+
+	if (sys_select(0, 0, 0, 0, &my_timeval) < 0)
+		return my_timeval.tv_sec + !!my_timeval.tv_usec;
+	else
+		return 0;
+}
+
+static __attribute__((unused))
+int stat(const char *path, struct stat *buf)
+{
+	int ret = sys_stat(path, buf);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int symlink(const char *old, const char *new)
+{
+	int ret = sys_symlink(old, new);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int tcsetpgrp(int fd, pid_t pid)
+{
+	return ioctl(fd, TIOCSPGRP, &pid);
+}
+
+static __attribute__((unused))
+mode_t umask(mode_t mode)
+{
+	return sys_umask(mode);
+}
+
+static __attribute__((unused))
+int umount2(const char *path, int flags)
+{
+	int ret = sys_umount2(path, flags);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+int unlink(const char *path)
+{
+	int ret = sys_unlink(path);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+pid_t wait4(pid_t pid, int *status, int options, struct rusage *rusage)
+{
+	pid_t ret = sys_wait4(pid, status, options, rusage);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+pid_t waitpid(pid_t pid, int *status, int options)
+{
+	pid_t ret = sys_waitpid(pid, status, options);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+pid_t wait(int *status)
+{
+	pid_t ret = sys_wait(status);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+ssize_t write(int fd, const void *buf, size_t count)
+{
+	ssize_t ret = sys_write(fd, buf, count);
+
+	if (ret < 0) {
+		SET_ERRNO(-ret);
+		ret = -1;
+	}
+	return ret;
+}
+
+/* some size-optimized reimplementations of a few common str* and mem*
+ * functions. They're marked static, except memcpy() and raise() which are used
+ * by libgcc on ARM, so they are marked weak instead in order not to cause an
+ * error when building a program made of multiple files (not recommended).
+ */
+
+static __attribute__((unused))
+void *memmove(void *dst, const void *src, size_t len)
+{
+	ssize_t pos = (dst <= src) ? -1 : (long)len;
+	void *ret = dst;
+
+	while (len--) {
+		pos += (dst <= src) ? 1 : -1;
+		((char *)dst)[pos] = ((char *)src)[pos];
+	}
+	return ret;
+}
+
+static __attribute__((unused))
+void *memset(void *dst, int b, size_t len)
+{
+	char *p = dst;
+
+	while (len--)
+		*(p++) = b;
+	return dst;
+}
+
+static __attribute__((unused))
+int memcmp(const void *s1, const void *s2, size_t n)
+{
+	size_t ofs = 0;
+	char c1 = 0;
+
+	while (ofs < n && !(c1 = ((char *)s1)[ofs] - ((char *)s2)[ofs])) {
+		ofs++;
+	}
+	return c1;
+}
+
+static __attribute__((unused))
+char *strcpy(char *dst, const char *src)
+{
+	char *ret = dst;
+
+	while ((*dst++ = *src++));
+	return ret;
+}
+
+static __attribute__((unused))
+char *strchr(const char *s, int c)
+{
+	while (*s) {
+		if (*s == (char)c)
+			return (char *)s;
+		s++;
+	}
+	return NULL;
+}
+
+static __attribute__((unused))
+char *strrchr(const char *s, int c)
+{
+	const char *ret = NULL;
+
+	while (*s) {
+		if (*s == (char)c)
+			ret = s;
+		s++;
+	}
+	return (char *)ret;
+}
+
+static __attribute__((unused))
+size_t nolibc_strlen(const char *str)
+{
+	size_t len;
+
+	for (len = 0; str[len]; len++);
+	return len;
+}
+
+#define strlen(str) ({                          \
+	__builtin_constant_p((str)) ?           \
+		__builtin_strlen((str)) :       \
+		nolibc_strlen((str));           \
+})
+
+static __attribute__((unused))
+int isdigit(int c)
+{
+	return (unsigned int)(c - '0') <= 9;
+}
+
+static __attribute__((unused))
+long atol(const char *s)
+{
+	unsigned long ret = 0;
+	unsigned long d;
+	int neg = 0;
+
+	if (*s == '-') {
+		neg = 1;
+		s++;
+	}
+
+	while (1) {
+		d = (*s++) - '0';
+		if (d > 9)
+			break;
+		ret *= 10;
+		ret += d;
+	}
+
+	return neg ? -ret : ret;
+}
+
+static __attribute__((unused))
+int atoi(const char *s)
+{
+	return atol(s);
+}
+
+static __attribute__((unused))
+const char *ltoa(long in)
+{
+	/* large enough for -9223372036854775808 */
+	static char buffer[21];
+	char       *pos = buffer + sizeof(buffer) - 1;
+	int         neg = in < 0;
+	unsigned long n = neg ? -in : in;
+
+	*pos-- = '\0';
+	do {
+		*pos-- = '0' + n % 10;
+		n /= 10;
+		if (pos < buffer)
+			return pos + 1;
+	} while (n);
+
+	if (neg)
+		*pos-- = '-';
+	return pos + 1;
+}
+
+__attribute__((weak,unused))
+void *memcpy(void *dst, const void *src, size_t len)
+{
+	return memmove(dst, src, len);
+}
+
+/* needed by libgcc for divide by zero */
+__attribute__((weak,unused))
+int raise(int signal)
+{
+	return kill(getpid(), signal);
+}
+
+/* Here come a few helper functions */
+
+static __attribute__((unused))
+void FD_ZERO(fd_set *set)
+{
+	memset(set, 0, sizeof(*set));
+}
+
+static __attribute__((unused))
+void FD_SET(int fd, fd_set *set)
+{
+	if (fd < 0 || fd >= FD_SETSIZE)
+		return;
+	set->fd32[fd / 32] |= 1 << (fd & 31);
+}
+
+/* WARNING, it only deals with the 4096 first majors and 256 first minors */
+static __attribute__((unused))
+dev_t makedev(unsigned int major, unsigned int minor)
+{
+	return ((major & 0xfff) << 8) | (minor & 0xff);
+}