arm64: 32-bit (compat) applications support

This patch adds support for 32-bit applications. The vectors page is a
binary blob mapped into the application user space at 0xffff0000 (the
AArch64 toolchain does not support compilation of AArch32 code). Full
compatibility with ARMv7 user space is supported. The use of deprecated
ARMv7 functionality (SWP, CP15 barriers) has been disabled by default on
AArch64 kernels and unaligned LDM/STM is not supported.

Please note that only the ARM 32-bit EABI is supported, so no OABI
compatibility.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>

arch/arm64/include/asm/compat.h

+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_COMPAT_H
+#define __ASM_COMPAT_H
+#ifdef __KERNEL__
+#ifdef CONFIG_COMPAT
+
+/*
+ * Architecture specific compatibility types
+ */
+#include <linux/types.h>
+#include <linux/sched.h>
+
+#define COMPAT_USER_HZ		100
+#define COMPAT_UTS_MACHINE	"armv8l\0\0"
+
+typedef u32		compat_size_t;
+typedef s32		compat_ssize_t;
+typedef s32		compat_time_t;
+typedef s32		compat_clock_t;
+typedef s32		compat_pid_t;
+typedef u32		__compat_uid_t;
+typedef u32		__compat_gid_t;
+typedef u32		__compat_uid32_t;
+typedef u32		__compat_gid32_t;
+typedef u32		compat_mode_t;
+typedef u32		compat_ino_t;
+typedef u32		compat_dev_t;
+typedef s32		compat_off_t;
+typedef s64		compat_loff_t;
+typedef s16		compat_nlink_t;
+typedef u16		compat_ipc_pid_t;
+typedef s32		compat_daddr_t;
+typedef u32		compat_caddr_t;
+typedef __kernel_fsid_t	compat_fsid_t;
+typedef s32		compat_key_t;
+typedef s32		compat_timer_t;
+
+typedef s32		compat_int_t;
+typedef s32		compat_long_t;
+typedef s64		compat_s64;
+typedef u32		compat_uint_t;
+typedef u32		compat_ulong_t;
+typedef u64		compat_u64;
+
+struct compat_timespec {
+	compat_time_t	tv_sec;
+	s32		tv_nsec;
+};
+
+struct compat_timeval {
+	compat_time_t	tv_sec;
+	s32		tv_usec;
+};
+
+struct compat_stat {
+	compat_dev_t	st_dev;
+	compat_ino_t	st_ino;
+	compat_mode_t	st_mode;
+	compat_nlink_t	st_nlink;
+	__compat_uid32_t	st_uid;
+	__compat_gid32_t	st_gid;
+	compat_dev_t	st_rdev;
+	compat_off_t	st_size;
+	compat_off_t	st_blksize;
+	compat_off_t	st_blocks;
+	compat_time_t	st_atime;
+	u32		st_atime_nsec;
+	compat_time_t	st_mtime;
+	u32		st_mtime_nsec;
+	compat_time_t	st_ctime;
+	u32		st_ctime_nsec;
+	u32		__unused4[2];
+};
+
+struct compat_flock {
+	short		l_type;
+	short		l_whence;
+	compat_off_t	l_start;
+	compat_off_t	l_len;
+	compat_pid_t	l_pid;
+};
+
+#define F_GETLK64	12	/*  using 'struct flock64' */
+#define F_SETLK64	13
+#define F_SETLKW64	14
+
+struct compat_flock64 {
+	short		l_type;
+	short		l_whence;
+	compat_loff_t	l_start;
+	compat_loff_t	l_len;
+	compat_pid_t	l_pid;
+};
+
+struct compat_statfs {
+	int		f_type;
+	int		f_bsize;
+	int		f_blocks;
+	int		f_bfree;
+	int		f_bavail;
+	int		f_files;
+	int		f_ffree;
+	compat_fsid_t	f_fsid;
+	int		f_namelen;	/* SunOS ignores this field. */
+	int		f_frsize;
+	int		f_flags;
+	int		f_spare[4];
+};
+
+#define COMPAT_RLIM_INFINITY		0xffffffff
+
+typedef u32		compat_old_sigset_t;
+
+#define _COMPAT_NSIG		64
+#define _COMPAT_NSIG_BPW	32
+
+typedef u32		compat_sigset_word;
+
+#define COMPAT_OFF_T_MAX	0x7fffffff
+#define COMPAT_LOFF_T_MAX	0x7fffffffffffffffL
+
+/*
+ * A pointer passed in from user mode. This should not
+ * be used for syscall parameters, just declare them
+ * as pointers because the syscall entry code will have
+ * appropriately converted them already.
+ */
+typedef	u32		compat_uptr_t;
+
+static inline void __user *compat_ptr(compat_uptr_t uptr)
+{
+	return (void __user *)(unsigned long)uptr;
+}
+
+static inline compat_uptr_t ptr_to_compat(void __user *uptr)
+{
+	return (u32)(unsigned long)uptr;
+}
+
+static inline void __user *arch_compat_alloc_user_space(long len)
+{
+	struct pt_regs *regs = task_pt_regs(current);
+	return (void __user *)regs->compat_sp - len;
+}
+
+struct compat_ipc64_perm {
+	compat_key_t key;
+	__compat_uid32_t uid;
+	__compat_gid32_t gid;
+	__compat_uid32_t cuid;
+	__compat_gid32_t cgid;
+	unsigned short mode;
+	unsigned short __pad1;
+	unsigned short seq;
+	unsigned short __pad2;
+	compat_ulong_t unused1;
+	compat_ulong_t unused2;
+};
+
+struct compat_semid64_ds {
+	struct compat_ipc64_perm sem_perm;
+	compat_time_t  sem_otime;
+	compat_ulong_t __unused1;
+	compat_time_t  sem_ctime;
+	compat_ulong_t __unused2;
+	compat_ulong_t sem_nsems;
+	compat_ulong_t __unused3;
+	compat_ulong_t __unused4;
+};
+
+struct compat_msqid64_ds {
+	struct compat_ipc64_perm msg_perm;
+	compat_time_t  msg_stime;
+	compat_ulong_t __unused1;
+	compat_time_t  msg_rtime;
+	compat_ulong_t __unused2;
+	compat_time_t  msg_ctime;
+	compat_ulong_t __unused3;
+	compat_ulong_t msg_cbytes;
+	compat_ulong_t msg_qnum;
+	compat_ulong_t msg_qbytes;
+	compat_pid_t   msg_lspid;
+	compat_pid_t   msg_lrpid;
+	compat_ulong_t __unused4;
+	compat_ulong_t __unused5;
+};
+
+struct compat_shmid64_ds {
+	struct compat_ipc64_perm shm_perm;
+	compat_size_t  shm_segsz;
+	compat_time_t  shm_atime;
+	compat_ulong_t __unused1;
+	compat_time_t  shm_dtime;
+	compat_ulong_t __unused2;
+	compat_time_t  shm_ctime;
+	compat_ulong_t __unused3;
+	compat_pid_t   shm_cpid;
+	compat_pid_t   shm_lpid;
+	compat_ulong_t shm_nattch;
+	compat_ulong_t __unused4;
+	compat_ulong_t __unused5;
+};
+
+static inline int is_compat_task(void)
+{
+	return test_thread_flag(TIF_32BIT);
+}
+
+static inline int is_compat_thread(struct thread_info *thread)
+{
+	return test_ti_thread_flag(thread, TIF_32BIT);
+}
+
+#else /* !CONFIG_COMPAT */
+
+static inline int is_compat_task(void)
+{
+	return 0;
+}
+
+static inline int is_compat_thread(struct thread_info *thread)
+{
+	return 0;
+}
+
+#endif /* CONFIG_COMPAT */
+#endif /* __KERNEL__ */
+#endif /* __ASM_COMPAT_H */

arch/arm64/include/asm/signal32.h

+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_SIGNAL32_H
+#define __ASM_SIGNAL32_H
+
+#ifdef __KERNEL__
+#ifdef CONFIG_COMPAT
+#include <linux/compat.h>
+
+#define AARCH32_KERN_SIGRET_CODE_OFFSET	0x500
+
+extern const compat_ulong_t aarch32_sigret_code[6];
+
+int compat_setup_frame(int usig, struct k_sigaction *ka, sigset_t *set,
+		       struct pt_regs *regs);
+int compat_setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
+			  sigset_t *set, struct pt_regs *regs);
+
+void compat_setup_restart_syscall(struct pt_regs *regs);
+#else
+
+static inline int compat_setup_frame(int usid, struct k_sigaction *ka,
+				     sigset_t *set, struct pt_regs *regs)
+{
+	return -ENOSYS;
+}
+
+static inline int compat_setup_rt_frame(int usig, struct k_sigaction *ka,
+					siginfo_t *info, sigset_t *set,
+					struct pt_regs *regs)
+{
+	return -ENOSYS;
+}
+
+static inline void compat_setup_restart_syscall(struct pt_regs *regs)
+{
+}
+#endif /* CONFIG_COMPAT */
+#endif /* __KERNEL__ */
+#endif /* __ASM_SIGNAL32_H */

arch/arm64/kernel/kuser32.S

+/*
+ * Low-level user helpers placed in the vectors page for AArch32.
+ * Based on the kuser helpers in arch/arm/kernel/entry-armv.S.
+ *
+ * Copyright (C) 2005-2011 Nicolas Pitre <nico@fluxnic.net>
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * AArch32 user helpers.
+ *
+ * Each segment is 32-byte aligned and will be moved to the top of the high
+ * vector page.  New segments (if ever needed) must be added in front of
+ * existing ones.  This mechanism should be used only for things that are
+ * really small and justified, and not be abused freely.
+ *
+ * See Documentation/arm/kernel_user_helpers.txt for formal definitions.
+ */
+	.align	5
+	.globl	__kuser_helper_start
+__kuser_helper_start:
+
+__kuser_cmpxchg64:			// 0xffff0f60
+	.inst	0xe92d00f0		//	push		{r4, r5, r6, r7}
+	.inst	0xe1c040d0		//	ldrd		r4, r5, [r0]
+	.inst	0xe1c160d0		//	ldrd		r6, r7, [r1]
+	.inst	0xf57ff05f		//	dmb		sy
+	.inst	0xe1b20f9f		// 1:	ldrexd		r0, r1, [r2]
+	.inst	0xe0303004		//	eors		r3, r0, r4
+	.inst	0x00313005		//	eoreqs		r3, r1, r5
+	.inst	0x01a23f96		//	strexdeq	r3, r6, [r2]
+	.inst	0x03330001		//	teqeq		r3, #1
+	.inst	0x0afffff9		//	beq		1b
+	.inst	0xf57ff05f		//	dmb		sy
+	.inst	0xe2730000		//	rsbs		r0, r3, #0
+	.inst	0xe8bd00f0		//	pop		{r4, r5, r6, r7}
+	.inst	0xe12fff1e		//	bx		lr
+
+	.align	5
+__kuser_memory_barrier:			// 0xffff0fa0
+	.inst	0xf57ff05f		//	dmb		sy
+	.inst	0xe12fff1e		//	bx		lr
+
+	.align	5
+__kuser_cmpxchg:			// 0xffff0fc0
+	.inst	0xf57ff05f		//	dmb		sy
+	.inst	0xe1923f9f		// 1:	ldrex		r3, [r2]
+	.inst	0xe0533000		//	subs		r3, r3, r0
+	.inst	0x01823f91		//	strexeq	r3, r1, [r2]
+	.inst	0x03330001		//	teqeq		r3, #1
+	.inst	0x0afffffa		//	beq		1b
+	.inst	0xe2730000		//	rsbs		r0, r3, #0
+	.inst	0xeaffffef		//	b		<__kuser_memory_barrier>
+
+	.align	5
+__kuser_get_tls:			// 0xffff0fe0
+	.inst	0xee1d0f70		//	mrc		p15, 0, r0, c13, c0, 3
+	.inst	0xe12fff1e		//	bx		lr
+	.rep	5
+	.word	0
+	.endr
+
+__kuser_helper_version:			// 0xffff0ffc
+	.word	((__kuser_helper_end - __kuser_helper_start) >> 5)
+	.globl	__kuser_helper_end
+__kuser_helper_end:

arch/arm64/kernel/sys32.S

+/*
+ * Compat system call wrappers
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ * Authors: Will Deacon <will.deacon@arm.com>
+ *	    Catalin Marinas <catalin.marinas@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+
+#include <asm/assembler.h>
+#include <asm/asm-offsets.h>
+
+/*
+ * System call wrappers for the AArch32 compatibility layer.
+ */
+compat_sys_fork_wrapper:
+	mov	x0, sp
+	b	compat_sys_fork
+ENDPROC(compat_sys_fork_wrapper)
+
+compat_sys_vfork_wrapper:
+	mov	x0, sp
+	b	compat_sys_vfork
+ENDPROC(compat_sys_vfork_wrapper)
+
+compat_sys_execve_wrapper:
+	mov	x3, sp
+	b	compat_sys_execve
+ENDPROC(compat_sys_execve_wrapper)
+
+compat_sys_clone_wrapper:
+	mov	x5, sp
+	b	compat_sys_clone
+ENDPROC(compat_sys_clone_wrapper)
+
+compat_sys_sigreturn_wrapper:
+	mov	x0, sp
+	mov	x27, #0		// prevent syscall restart handling (why)
+	b	compat_sys_sigreturn
+ENDPROC(compat_sys_sigreturn_wrapper)
+
+compat_sys_rt_sigreturn_wrapper:
+	mov	x0, sp
+	mov	x27, #0		// prevent syscall restart handling (why)
+	b	compat_sys_rt_sigreturn
+ENDPROC(compat_sys_rt_sigreturn_wrapper)
+
+compat_sys_sigaltstack_wrapper:
+	ldr	x2, [sp, #S_COMPAT_SP]
+	b	compat_do_sigaltstack
+ENDPROC(compat_sys_sigaltstack_wrapper)
+
+compat_sys_statfs64_wrapper:
+	mov	w3, #84
+	cmp	w1, #88
+	csel	w1, w3, w1, eq
+	b	compat_sys_statfs64
+ENDPROC(compat_sys_statfs64_wrapper)
+
+compat_sys_fstatfs64_wrapper:
+	mov	w3, #84
+	cmp	w1, #88
+	csel	w1, w3, w1, eq
+	b	compat_sys_fstatfs64
+ENDPROC(compat_sys_fstatfs64_wrapper)
+
+/*
+ * Wrappers for AArch32 syscalls that either take 64-bit parameters
+ * in registers or that take 32-bit parameters which require sign
+ * extension.
+ */
+compat_sys_lseek_wrapper:
+	sxtw	x1, w1
+	b	sys_lseek
+ENDPROC(compat_sys_lseek_wrapper)
+
+compat_sys_pread64_wrapper:
+	orr	x3, x4, x5, lsl #32
+	b	sys_pread64
+ENDPROC(compat_sys_pread64_wrapper)
+
+compat_sys_pwrite64_wrapper:
+	orr	x3, x4, x5, lsl #32
+	b	sys_pwrite64
+ENDPROC(compat_sys_pwrite64_wrapper)
+
+compat_sys_truncate64_wrapper:
+	orr	x1, x2, x3, lsl #32
+	b	sys_truncate
+ENDPROC(compat_sys_truncate64_wrapper)
+
+compat_sys_ftruncate64_wrapper:
+	orr	x1, x2, x3, lsl #32
+	b	sys_ftruncate
+ENDPROC(compat_sys_ftruncate64_wrapper)
+
+compat_sys_readahead_wrapper:
+	orr	x1, x2, x3, lsl #32
+	mov	w2, w4
+	b	sys_readahead
+ENDPROC(compat_sys_readahead_wrapper)
+
+compat_sys_lookup_dcookie:
+	orr	x0, x0, x1, lsl #32
+	mov	w1, w2
+	mov	w2, w3
+	b	sys_lookup_dcookie
+ENDPROC(compat_sys_lookup_dcookie)
+
+compat_sys_fadvise64_64_wrapper:
+	mov	w6, w1
+	orr	x1, x2, x3, lsl #32
+	orr	x2, x4, x5, lsl #32
+	mov	w3, w6
+	b	sys_fadvise64_64
+ENDPROC(compat_sys_fadvise64_64_wrapper)
+
+compat_sys_sync_file_range2_wrapper:
+	orr	x2, x2, x3, lsl #32
+	orr	x3, x4, x5, lsl #32
+	b	sys_sync_file_range2
+ENDPROC(compat_sys_sync_file_range2_wrapper)
+
+compat_sys_fallocate_wrapper:
+	orr	x2, x2, x3, lsl #32
+	orr	x3, x4, x5, lsl #32
+	b	sys_fallocate
+ENDPROC(compat_sys_fallocate_wrapper)
+
+compat_sys_fanotify_mark_wrapper:
+	orr	x2, x2, x3, lsl #32
+	mov	w3, w4
+	mov	w4, w5
+	b	sys_fanotify_mark
+ENDPROC(compat_sys_fanotify_mark_wrapper)
+
+/*
+ * Use the compat system call wrappers.
+ */
+#define sys_fork		compat_sys_fork_wrapper
+#define sys_open		compat_sys_open
+#define sys_execve		compat_sys_execve_wrapper
+#define sys_lseek		compat_sys_lseek_wrapper
+#define sys_mount		compat_sys_mount
+#define sys_ptrace		compat_sys_ptrace
+#define sys_times		compat_sys_times
+#define sys_ioctl		compat_sys_ioctl
+#define sys_fcntl		compat_sys_fcntl
+#define sys_ustat		compat_sys_ustat
+#define sys_sigaction		compat_sys_sigaction
+#define sys_sigsuspend		compat_sys_sigsuspend
+#define sys_sigpending		compat_sys_sigpending
+#define sys_setrlimit		compat_sys_setrlimit
+#define sys_getrusage		compat_sys_getrusage
+#define sys_gettimeofday	compat_sys_gettimeofday
+#define sys_settimeofday	compat_sys_settimeofday
+#define sys_statfs		compat_sys_statfs
+#define sys_fstatfs		compat_sys_fstatfs
+#define sys_setitimer		compat_sys_setitimer
+#define sys_getitimer		compat_sys_getitimer
+#define sys_newstat		compat_sys_newstat
+#define sys_newlstat		compat_sys_newlstat
+#define sys_newfstat		compat_sys_newfstat
+#define sys_wait4		compat_sys_wait4
+#define sys_sysinfo		compat_sys_sysinfo
+#define sys_sigreturn		compat_sys_sigreturn_wrapper
+#define sys_clone		compat_sys_clone_wrapper
+#define sys_adjtimex		compat_sys_adjtimex
+#define sys_sigprocmask		compat_sys_sigprocmask
+#define sys_getdents		compat_sys_getdents
+#define sys_select		compat_sys_select
+#define sys_readv		compat_sys_readv
+#define sys_writev		compat_sys_writev
+#define sys_sysctl		compat_sys_sysctl
+#define sys_sched_rr_get_interval compat_sys_sched_rr_get_interval
+#define sys_nanosleep		compat_sys_nanosleep
+#define sys_rt_sigreturn	compat_sys_rt_sigreturn_wrapper
+#define sys_rt_sigaction	compat_sys_rt_sigaction
+#define sys_rt_sigprocmask	compat_sys_rt_sigprocmask
+#define sys_rt_sigpending	compat_sys_rt_sigpending
+#define sys_rt_sigtimedwait	compat_sys_rt_sigtimedwait
+#define sys_rt_sigqueueinfo	compat_sys_rt_sigqueueinfo
+#define sys_rt_sigsuspend	compat_sys_rt_sigsuspend
+#define sys_pread64		compat_sys_pread64_wrapper
+#define sys_pwrite64		compat_sys_pwrite64_wrapper
+#define sys_sigaltstack		compat_sys_sigaltstack_wrapper
+#define sys_sendfile		compat_sys_sendfile
+#define sys_vfork		compat_sys_vfork_wrapper
+#define sys_getrlimit		compat_sys_getrlimit
+#define sys_mmap2		sys_mmap_pgoff
+#define sys_truncate64		compat_sys_truncate64_wrapper
+#define sys_ftruncate64		compat_sys_ftruncate64_wrapper
+#define sys_getdents64		compat_sys_getdents64
+#define sys_fcntl64		compat_sys_fcntl64
+#define sys_readahead		compat_sys_readahead_wrapper
+#define sys_futex		compat_sys_futex
+#define sys_sched_setaffinity	compat_sys_sched_setaffinity
+#define sys_sched_getaffinity	compat_sys_sched_getaffinity
+#define sys_io_setup		compat_sys_io_setup
+#define sys_io_getevents	compat_sys_io_getevents
+#define sys_io_submit		compat_sys_io_submit
+#define sys_lookup_dcookie	compat_sys_lookup_dcookie
+#define sys_timer_create	compat_sys_timer_create
+#define sys_timer_settime	compat_sys_timer_settime
+#define sys_timer_gettime	compat_sys_timer_gettime
+#define sys_clock_settime	compat_sys_clock_settime
+#define sys_clock_gettime	compat_sys_clock_gettime
+#define sys_clock_getres	compat_sys_clock_getres
+#define sys_clock_nanosleep	compat_sys_clock_nanosleep
+#define sys_statfs64		compat_sys_statfs64_wrapper
+#define sys_fstatfs64		compat_sys_fstatfs64_wrapper
+#define sys_utimes		compat_sys_utimes
+#define sys_fadvise64_64	compat_sys_fadvise64_64_wrapper
+#define sys_mq_open		compat_sys_mq_open
+#define sys_mq_timedsend	compat_sys_mq_timedsend
+#define sys_mq_timedreceive	compat_sys_mq_timedreceive
+#define sys_mq_notify		compat_sys_mq_notify
+#define sys_mq_getsetattr	compat_sys_mq_getsetattr
+#define sys_waitid		compat_sys_waitid
+#define sys_recv		compat_sys_recv
+#define sys_recvfrom		compat_sys_recvfrom
+#define sys_setsockopt		compat_sys_setsockopt
+#define sys_getsockopt		compat_sys_getsockopt
+#define sys_sendmsg		compat_sys_sendmsg
+#define sys_recvmsg		compat_sys_recvmsg
+#define sys_semctl		compat_sys_semctl
+#define sys_msgsnd		compat_sys_msgsnd
+#define sys_msgrcv		compat_sys_msgrcv
+#define sys_msgctl		compat_sys_msgctl
+#define sys_shmat		compat_sys_shmat
+#define sys_shmctl		compat_sys_shmctl
+#define sys_keyctl		compat_sys_keyctl
+#define sys_semtimedop		compat_sys_semtimedop
+#define sys_mbind		compat_sys_mbind
+#define sys_get_mempolicy	compat_sys_get_mempolicy
+#define sys_set_mempolicy	compat_sys_set_mempolicy
+#define sys_openat		compat_sys_openat
+#define sys_futimesat		compat_sys_futimesat
+#define sys_pselect6		compat_sys_pselect6
+#define sys_ppoll		compat_sys_ppoll
+#define sys_set_robust_list	compat_sys_set_robust_list
+#define sys_get_robust_list	compat_sys_get_robust_list
+#define sys_sync_file_range2	compat_sys_sync_file_range2_wrapper
+#define sys_vmsplice		compat_sys_vmsplice
+#define sys_move_pages		compat_sys_move_pages
+#define sys_epoll_pwait		compat_sys_epoll_pwait
+#define sys_kexec_load		compat_sys_kexec_load
+#define sys_utimensat		compat_sys_utimensat
+#define sys_signalfd		compat_sys_signalfd
+#define sys_fallocate		compat_sys_fallocate_wrapper
+#define sys_timerfd_settime	compat_sys_timerfd_settime
+#define sys_timerfd_gettime	compat_sys_timerfd_gettime
+#define sys_signalfd4		compat_sys_signalfd4
+#define sys_preadv		compat_sys_preadv
+#define sys_pwritev		compat_sys_pwritev
+#define sys_rt_tgsigqueueinfo	compat_sys_rt_tgsigqueueinfo
+#define sys_recvmmsg		compat_sys_recvmmsg
+#define sys_fanotify_mark	compat_sys_fanotify_mark_wrapper
+
+#undef __SYSCALL
+#define __SYSCALL(x, y)		.quad	y	// x
+#define __SYSCALL_COMPAT
+
+/*
+ * The system calls table must be 4KB aligned.
+ */
+	.align	12
+ENTRY(compat_sys_call_table)
+#include <asm/unistd.h>

arch/arm64/kernel/sys_compat.c

+/*
+ * Based on arch/arm/kernel/sys_arm.c
+ *
+ * Copyright (C) People who wrote linux/arch/i386/kernel/sys_i386.c
+ * Copyright (C) 1995, 1996 Russell King.
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define __SYSCALL_COMPAT
+
+#include <linux/compat.h>
+#include <linux/personality.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
+
+#include <asm/cacheflush.h>
+#include <asm/unistd.h>
+
+asmlinkage int compat_sys_fork(struct pt_regs *regs)
+{
+	return do_fork(SIGCHLD, regs->compat_sp, regs, 0, NULL, NULL);
+}
+
+asmlinkage int compat_sys_clone(unsigned long clone_flags, unsigned long newsp,
+			  int __user *parent_tidptr, int tls_val,
+			  int __user *child_tidptr, struct pt_regs *regs)
+{
+	if (!newsp)
+		newsp = regs->compat_sp;
+
+	return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
+}
+
+asmlinkage int compat_sys_vfork(struct pt_regs *regs)
+{
+	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->compat_sp,
+		       regs, 0, NULL, NULL);
+}
+
+asmlinkage int compat_sys_execve(const char __user *filenamei,
+				 compat_uptr_t argv, compat_uptr_t envp,
+				 struct pt_regs *regs)
+{
+	int error;
+	char * filename;
+
+	filename = getname(filenamei);
+	error = PTR_ERR(filename);
+	if (IS_ERR(filename))
+		goto out;
+	error = compat_do_execve(filename, compat_ptr(argv), compat_ptr(envp),
+				 regs);
+	putname(filename);
+out:
+	return error;
+}
+
+asmlinkage int compat_sys_sched_rr_get_interval(compat_pid_t pid,
+						struct compat_timespec __user *interval)
+{
+	struct timespec t;
+	int ret;
+	mm_segment_t old_fs = get_fs();
+
+	set_fs(KERNEL_DS);
+	ret = sys_sched_rr_get_interval(pid, (struct timespec __user *)&t);
+	set_fs(old_fs);
+	if (put_compat_timespec(&t, interval))
+		return -EFAULT;
+	return ret;
+}
+
+asmlinkage int compat_sys_sendfile(int out_fd, int in_fd,
+				   compat_off_t __user *offset, s32 count)
+{
+	mm_segment_t old_fs = get_fs();
+	int ret;
+	off_t of;
+
+	if (offset && get_user(of, offset))
+		return -EFAULT;
+
+	set_fs(KERNEL_DS);
+	ret = sys_sendfile(out_fd, in_fd, offset ? (off_t __user *)&of : NULL,
+			   count);
+	set_fs(old_fs);
+
+	if (offset && put_user(of, offset))
+		return -EFAULT;
+	return ret;
+}
+
+static inline void
+do_compat_cache_op(unsigned long start, unsigned long end, int flags)
+{
+	struct mm_struct *mm = current->active_mm;
+	struct vm_area_struct *vma;
+
+	if (end < start || flags)
+		return;
+
+	down_read(&mm->mmap_sem);
+	vma = find_vma(mm, start);
+	if (vma && vma->vm_start < end) {
+		if (start < vma->vm_start)
+			start = vma->vm_start;
+		if (end > vma->vm_end)
+			end = vma->vm_end;
+		up_read(&mm->mmap_sem);
+		__flush_cache_user_range(start & PAGE_MASK, PAGE_ALIGN(end));
+		return;
+	}
+	up_read(&mm->mmap_sem);
+}
+
+/*
+ * Handle all unrecognised system calls.
+ */
+long compat_arm_syscall(struct pt_regs *regs)
+{
+	unsigned int no = regs->regs[7];
+
+	switch (no) {
+	/*
+	 * Flush a region from virtual address 'r0' to virtual address 'r1'
+	 * _exclusive_.  There is no alignment requirement on either address;
+	 * user space does not need to know the hardware cache layout.
+	 *
+	 * r2 contains flags.  It should ALWAYS be passed as ZERO until it
+	 * is defined to be something else.  For now we ignore it, but may
+	 * the fires of hell burn in your belly if you break this rule. ;)
+	 *
+	 * (at a later date, we may want to allow this call to not flush
+	 * various aspects of the cache.  Passing '0' will guarantee that
+	 * everything necessary gets flushed to maintain consistency in
+	 * the specified region).
+	 */
+	case __ARM_NR_compat_cacheflush:
+		do_compat_cache_op(regs->regs[0], regs->regs[1], regs->regs[2]);
+		return 0;
+
+	case __ARM_NR_compat_set_tls:
+		current->thread.tp_value = regs->regs[0];
+		asm ("msr tpidrro_el0, %0" : : "r" (regs->regs[0]));
+		return 0;
+
+	default:
+		return -ENOSYS;
+	}
+}