[ARM] 3109/1: old ABI compat: syscall wrappers for ABI impedance matching

Patch from Nicolas Pitre

The difference between EABI and the legacy ABI may affect either
structure member alignment and/or argument register selection.

The patch has the details.

Included are wrappers for the following syscalls:

sys_stat64
sys_lstat64
sys_fstat64
sys_fcntl64
sys_epoll_ctl
sys_epoll_wait
sys_ipc
sys_semop
sys_semtimedop
sys_pread64
sys_pwrite64
sys_truncate64
sys_ftruncate64
sys_readahead

Signed-off-by: Nicolas Pitre <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

arch/arm/kernel/Makefile

···
 obj-$(CONFIG_ISA_DMA)		+= dma-isa.o
 obj-$(CONFIG_PCI)		+= bios32.o
 obj-$(CONFIG_SMP)		+= smp.o
+obj-$(CONFIG_OABI_COMPAT)	+= sys_oabi-compat.o
 
 obj-$(CONFIG_IWMMXT)		+= iwmmxt.o
 AFLAGS_iwmmxt.o			:= -Wa,-mcpu=iwmmxt

arch/arm/kernel/entry-common.S

···
 		str	r5, [sp, #4]
 		b	do_mmap2
 #endif
+
+#ifdef CONFIG_OABI_COMPAT
+/*
+ * These are syscalls with argument register differences
+ */
+
+sys_oabi_pread64:
+		stmia	sp, {r3, r4}
+		b	sys_pread64
+
+sys_oabi_pwrite64:
+		stmia	sp, {r3, r4}
+		b	sys_pwrite64
+
+sys_oabi_truncate64:
+		mov	r3, r2
+		mov	r2, r1
+		b	sys_truncate64
+
+sys_oabi_ftruncate64:
+		mov	r3, r2
+		mov	r2, r1
+		b	sys_ftruncate64
+
+sys_oabi_readahead:
+		str	r3, [sp]
+		mov	r3, r2
+		mov	r2, r1
+		b	sys_readahead
+
+#endif
+

arch/arm/kernel/sys_oabi-compat.c

···
+/*
+ *  arch/arm/kernel/sys_oabi-compat.c
+ *
+ *  Compatibility wrappers for syscalls that are used from
+ *  old ABI user space binaries with an EABI kernel.
+ *
+ *  Author:	Nicolas Pitre
+ *  Created:	Oct 7, 2005
+ *  Copyright:	MontaVista Software, Inc.
+ *
+ *  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.
+ */
+
+/*
+ * The legacy ABI and the new ARM EABI have different rules making some
+ * syscalls incompatible especially with structure arguments.
+ * Most notably, Eabi says 64-bit members should be 64-bit aligned instead of
+ * simply word aligned.  EABI also pads structures to the size of the largest
+ * member it contains instead of the invariant 32-bit.
+ *
+ * The following syscalls are affected:
+ *
+ * sys_stat64:
+ * sys_lstat64:
+ * sys_fstat64:
+ *
+ *   struct stat64 has different sizes and some members are shifted
+ *   Compatibility wrappers are needed for them and provided below.
+ *
+ * sys_fcntl64:
+ *
+ *   struct flock64 has different sizes and some members are shifted
+ *   A compatibility wrapper is needed and provided below.
+ *
+ * sys_statfs64:
+ * sys_fstatfs64:
+ *
+ *   struct statfs64 has extra padding with EABI growing its size from
+ *   84 to 88.  This struct is now __attribute__((packed,aligned(4)))
+ *   with a small assembly wrapper to force the sz argument to 84 if it is 88
+ *   to avoid copying the extra padding over user space unexpecting it.
+ *
+ * sys_newuname:
+ *
+ *   struct new_utsname has no padding with EABI.  No problem there.
+ *
+ * sys_epoll_ctl:
+ * sys_epoll_wait:
+ *
+ *   struct epoll_event has its second member shifted also affecting the
+ *   structure size. Compatibility wrappers are needed and provided below.
+ *
+ * sys_ipc:
+ * sys_semop:
+ * sys_semtimedop:
+ *
+ *   struct sembuf loses its padding with EABI.  Since arrays of them are
+ *   used they have to be copyed to remove the padding. Compatibility wrappers
+ *   provided below.
+ */
+
+#include <linux/syscalls.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/fcntl.h>
+#include <linux/eventpoll.h>
+#include <linux/sem.h>
+#include <asm/ipc.h>
+#include <asm/uaccess.h>
+
+struct oldabi_stat64 {
+	unsigned long long st_dev;
+	unsigned int	__pad1;
+	unsigned long	__st_ino;
+	unsigned int	st_mode;
+	unsigned int	st_nlink;
+
+	unsigned long	st_uid;
+	unsigned long	st_gid;
+
+	unsigned long long st_rdev;
+	unsigned int	__pad2;
+
+	long long	st_size;
+	unsigned long	st_blksize;
+	unsigned long 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 long st_ino;
+} __attribute__ ((packed,aligned(4)));
+
+static long cp_oldabi_stat64(struct kstat *stat,
+			     struct oldabi_stat64 __user *statbuf)
+{
+	struct oldabi_stat64 tmp;
+
+	tmp.st_dev = huge_encode_dev(stat->dev);
+	tmp.__pad1 = 0;
+	tmp.__st_ino = stat->ino;
+	tmp.st_mode = stat->mode;
+	tmp.st_nlink = stat->nlink;
+	tmp.st_uid = stat->uid;
+	tmp.st_gid = stat->gid;
+	tmp.st_rdev = huge_encode_dev(stat->rdev);
+	tmp.st_size = stat->size;
+	tmp.st_blocks = stat->blocks;
+	tmp.__pad2 = 0;
+	tmp.st_blksize = stat->blksize;
+	tmp.st_atime = stat->atime.tv_sec;
+	tmp.st_atime_nsec = stat->atime.tv_nsec;
+	tmp.st_mtime = stat->mtime.tv_sec;
+	tmp.st_mtime_nsec = stat->mtime.tv_nsec;
+	tmp.st_ctime = stat->ctime.tv_sec;
+	tmp.st_ctime_nsec = stat->ctime.tv_nsec;
+	tmp.st_ino = stat->ino;
+	return copy_to_user(statbuf,&tmp,sizeof(tmp)) ? -EFAULT : 0;
+}
+
+asmlinkage long sys_oabi_stat64(char __user * filename,
+				struct oldabi_stat64 __user * statbuf)
+{
+	struct kstat stat;
+	int error = vfs_stat(filename, &stat);
+	if (!error)
+		error = cp_oldabi_stat64(&stat, statbuf);
+	return error;
+}
+
+asmlinkage long sys_oabi_lstat64(char __user * filename,
+				 struct oldabi_stat64 __user * statbuf)
+{
+	struct kstat stat;
+	int error = vfs_lstat(filename, &stat);
+	if (!error)
+		error = cp_oldabi_stat64(&stat, statbuf);
+	return error;
+}
+
+asmlinkage long sys_oabi_fstat64(unsigned long fd,
+				 struct oldabi_stat64 __user * statbuf)
+{
+	struct kstat stat;
+	int error = vfs_fstat(fd, &stat);
+	if (!error)
+		error = cp_oldabi_stat64(&stat, statbuf);
+	return error;
+}
+
+struct oabi_flock64 {
+	short	l_type;
+	short	l_whence;
+	loff_t	l_start;
+	loff_t	l_len;
+	pid_t	l_pid;
+} __attribute__ ((packed,aligned(4)));
+
+asmlinkage long sys_oabi_fcntl64(unsigned int fd, unsigned int cmd,
+				 unsigned long arg)
+{
+	struct oabi_flock64 user;
+	struct flock64 kernel;
+	mm_segment_t fs = USER_DS; /* initialized to kill a warning */
+	unsigned long local_arg = arg;
+	int ret;
+
+	switch (cmd) {
+	case F_GETLK64:
+	case F_SETLK64:
+	case F_SETLKW64:
+		if (copy_from_user(&user, (struct oabi_flock64 __user *)arg,
+				   sizeof(user)))
+			return -EFAULT;
+		kernel.l_type	= user.l_type;
+		kernel.l_whence	= user.l_whence;
+		kernel.l_start	= user.l_start;
+		kernel.l_len	= user.l_len;
+		kernel.l_pid	= user.l_pid;
+		local_arg = (unsigned long)&kernel;
+		fs = get_fs();
+		set_fs(KERNEL_DS);
+	}
+
+	ret = sys_fcntl64(fd, cmd, local_arg);
+
+	switch (cmd) {
+	case F_GETLK64:
+		if (!ret) {
+			user.l_type	= kernel.l_type;
+			user.l_whence	= kernel.l_whence;
+			user.l_start	= kernel.l_start;
+			user.l_len	= kernel.l_len;
+			user.l_pid	= kernel.l_pid;
+			if (copy_to_user((struct oabi_flock64 __user *)arg,
+					 &user, sizeof(user)))
+				ret = -EFAULT;
+		}
+	case F_SETLK64:
+	case F_SETLKW64:
+		set_fs(fs);
+	}
+
+	return ret;
+}
+
+struct oabi_epoll_event {
+	__u32 events;
+	__u64 data;
+} __attribute__ ((packed,aligned(4)));
+
+asmlinkage long sys_oabi_epoll_ctl(int epfd, int op, int fd,
+				   struct oabi_epoll_event __user *event)
+{
+	struct oabi_epoll_event user;
+	struct epoll_event kernel;
+	mm_segment_t fs;
+	long ret;
+
+	if (op == EPOLL_CTL_DEL)
+		return sys_epoll_ctl(epfd, op, fd, NULL);
+	if (copy_from_user(&user, event, sizeof(user)))
+		return -EFAULT;
+	kernel.events = user.events;
+	kernel.data   = user.data;
+	fs = get_fs();
+	set_fs(KERNEL_DS);
+	ret = sys_epoll_ctl(epfd, op, fd, &kernel);
+	set_fs(fs);
+	return ret;
+}
+
+asmlinkage long sys_oabi_epoll_wait(int epfd,
+				    struct oabi_epoll_event __user *events,
+				    int maxevents, int timeout)
+{
+	struct epoll_event *kbuf;
+	mm_segment_t fs;
+	long ret, err, i;
+
+	if (maxevents <= 0 || maxevents > (INT_MAX/sizeof(struct epoll_event)))
+		return -EINVAL;
+	kbuf = kmalloc(sizeof(*kbuf) * maxevents, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+	fs = get_fs();
+	set_fs(KERNEL_DS);
+	ret = sys_epoll_wait(epfd, kbuf, maxevents, timeout);
+	set_fs(fs);
+	err = 0;
+	for (i = 0; i < ret; i++) {
+		__put_user_error(kbuf[i].events, &events->events, err);
+		__put_user_error(kbuf[i].data,   &events->data,   err);
+		events++;
+	}
+	kfree(kbuf);
+	return err ? -EFAULT : ret;
+}
+
+struct oabi_sembuf {
+	unsigned short	sem_num;
+	short		sem_op;
+	short		sem_flg;
+	unsigned short	__pad;
+};
+
+asmlinkage long sys_oabi_semtimedop(int semid,
+				    struct oabi_sembuf __user *tsops,
+				    unsigned nsops,
+				    const struct timespec __user *timeout)
+{
+	struct sembuf *sops;
+	struct timespec local_timeout;
+	long err;
+	int i;
+
+	if (nsops < 1)
+		return -EINVAL;
+	sops = kmalloc(sizeof(*sops) * nsops, GFP_KERNEL);
+	if (!sops)
+		return -ENOMEM;
+	err = 0;
+	for (i = 0; i < nsops; i++) {
+		__get_user_error(sops[i].sem_num, &tsops->sem_num, err);
+		__get_user_error(sops[i].sem_op,  &tsops->sem_op,  err);
+		__get_user_error(sops[i].sem_flg, &tsops->sem_flg, err);
+		tsops++;
+	}
+	if (timeout) {
+		/* copy this as well before changing domain protection */
+		err |= copy_from_user(&local_timeout, timeout, sizeof(*timeout));
+		timeout = &local_timeout;
+	}
+	if (err) {
+		err = -EFAULT;
+	} else {
+		mm_segment_t fs = get_fs();
+		set_fs(KERNEL_DS);
+		err = sys_semtimedop(semid, sops, nsops, timeout);
+		set_fs(fs);
+	}
+	kfree(sops);
+	return err;
+}
+
+asmlinkage long sys_oabi_semop(int semid, struct oabi_sembuf __user *tsops,
+			       unsigned nsops)
+{
+	return sys_oabi_semtimedop(semid, tsops, nsops, NULL);
+}
+
+extern asmlinkage int sys_ipc(uint call, int first, int second, int third,
+			      void __user *ptr, long fifth);
+
+asmlinkage int sys_oabi_ipc(uint call, int first, int second, int third,
+			    void __user *ptr, long fifth)
+{
+	switch (call & 0xffff) {
+	case SEMOP:
+		return  sys_oabi_semtimedop(first,
+					    (struct oabi_sembuf __user *)ptr,
+					    second, NULL);
+	case SEMTIMEDOP:
+		return  sys_oabi_semtimedop(first,
+					    (struct oabi_sembuf __user *)ptr,
+					    second,
+					    (const struct timespec __user *)fifth);
+	default:
+		return sys_ipc(call, first, second, third, ptr, fifth);
+	}
+}