[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 <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 372 insertions, 0 deletions

diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index de94b0f3ee2a..2ce0e3a27a45 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_ARTHUR)		+= arthur.o
 obj-$(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
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index ee63ee78d84f..59ce1bcec42b 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -288,3 +288,35 @@ sys_mmap2:
                 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
+
diff --git a/arch/arm/kernel/sys_oabi-compat.c b/arch/arm/kernel/sys_oabi-compat.c
new file mode 100644
index 000000000000..eafa8e5284af
--- /dev/null
+++ b/arch/arm/kernel/sys_oabi-compat.c
@@ -0,0 +1,339 @@
+/*
+ *  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);
+        }
+}