rcutorture: Import a copy of nolibc

This is a definition of the most common syscalls needed in minimalist
init executables, allowing to statically build them with no external
dependencies. It is sufficient in its current form to build rcutorture's
init on x86_64, i386, arm, and arm64. Others have not been ported or
tested. Updates may be found here :

     http://git.formilux.org/?p=people/willy/nolibc.git

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 2197 insertions, 0 deletions

diff --git a/tools/testing/selftests/rcutorture/bin/nolibc.h b/tools/testing/selftests/rcutorture/bin/nolibc.h
new file mode 100644
index 000000000000..f98f5b92d3eb
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/nolibc.h
@@ -0,0 +1,2197 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/* nolibc.h
+ * Copyright (C) 2017-2018 Willy Tarreau <w@1wt.eu>
+ */
+
+/* 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
+
+/* Build a static executable this way :
+ *      $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \
+ *            -static -include nolibc.h -lgcc -o hello hello.c
+ *
+ * Useful calling convention table found here :
+ *      http://man7.org/linux/man-pages/man2/syscall.2.html
+ *
+ * This doc is even better :
+ *      https://w3challs.com/syscalls/
+ */
+
+
+/* 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",                     \
+									      \
+	);                                                                    \
+	_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",                     \
+									      \
+	);                                                                    \
+	_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",                     \
+									      \
+	);                                                                    \
+	_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",                     \
+									      \
+	);                                                                    \
+	_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",                     \
+									      \
+	);                                                                    \
+	_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",                     \
+									      \
+	);                                                                    \
+	_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);
+}