linux-user: Add support for translation of statx() syscall

Implement support for translation of system call statx().

The implementation is based on "best effort" approach: if host
is capable of executing statx(), host statx() is used. If not,
the implementation includes invoking a more mature system call
fstatat() on the host side to achieve as close as possible
functionality.

Support for statx() in kernel and glibc was, however, introduced
at different points of time (the difference is more than a year):

  - kernel: Linux 4.11 (30 April 2017)
  - glibc: glibc 2.28 (1 Aug 2018)

In this patch, the availability of statx() support is established
via __NR_statx (if it is defined, statx() is considered available).
This coincedes with statx() introduction in kernel.

However, the structure statx definition may not be available in
any header for hosts with glibc older than 2.28 (and it is, by
design, to be defined in one of glibc headers), even though the
full statx() functionality may be supported in kernel. Hence, a
structure "target_statx" is defined in this patch, to remove that
dependency on glibc headers, and to use statx() functionality as
soon as the host kernel is capable of supporting it. Such statx
structure definition is used for both target and host structures
statx (of course, this doesn't mean the endian arrangement is
the same on target and host - the endian conversion is done in
all necessary cases).

Signed-off-by: Aleksandar Rikalo <arikalo@wavecomp.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <1561718618-20218-2-git-send-email-aleksandar.markovic@rt-rk.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

1 files changed, 114 insertions, 1 deletions

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index d2c9817938..39a37496fe 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -238,6 +238,7 @@ static type name (type1 arg1,type2 arg2,type3 arg3,type4 arg4,type5 arg5,	\
 #define __NR_sys_inotify_init __NR_inotify_init
 #define __NR_sys_inotify_add_watch __NR_inotify_add_watch
 #define __NR_sys_inotify_rm_watch __NR_inotify_rm_watch
+#define __NR_sys_statx __NR_statx
 
 #if defined(__alpha__) || defined(__x86_64__) || defined(__s390x__)
 #define __NR__llseek __NR_lseek
@@ -316,6 +317,14 @@ _syscall5(int, kcmp, pid_t, pid1, pid_t, pid2, int, type,
           unsigned long, idx1, unsigned long, idx2)
 #endif
 
+/*
+ * It is assumed that struct statx is architecture independent.
+ */
+#if defined(TARGET_NR_statx) && defined(__NR_statx)
+_syscall5(int, sys_statx, int, dirfd, const char *, pathname, int, flags,
+          unsigned int, mask, struct target_statx *, statxbuf)
+#endif
+
 static bitmask_transtbl fcntl_flags_tbl[] = {
   { TARGET_O_ACCMODE,   TARGET_O_WRONLY,    O_ACCMODE,   O_WRONLY,    },
   { TARGET_O_ACCMODE,   TARGET_O_RDWR,      O_ACCMODE,   O_RDWR,      },
@@ -6516,6 +6525,48 @@ static inline abi_long host_to_target_stat64(void *cpu_env,
 }
 #endif
 
+#if defined(TARGET_NR_statx) && defined(__NR_statx)
+static inline abi_long host_to_target_statx(struct target_statx *host_stx,
+                                            abi_ulong target_addr)
+{
+    struct target_statx *target_stx;
+
+    if (!lock_user_struct(VERIFY_WRITE, target_stx, target_addr,  0)) {
+        return -TARGET_EFAULT;
+    }
+    memset(target_stx, 0, sizeof(*target_stx));
+
+    __put_user(host_stx->stx_mask, &target_stx->stx_mask);
+    __put_user(host_stx->stx_blksize, &target_stx->stx_blksize);
+    __put_user(host_stx->stx_attributes, &target_stx->stx_attributes);
+    __put_user(host_stx->stx_nlink, &target_stx->stx_nlink);
+    __put_user(host_stx->stx_uid, &target_stx->stx_uid);
+    __put_user(host_stx->stx_gid, &target_stx->stx_gid);
+    __put_user(host_stx->stx_mode, &target_stx->stx_mode);
+    __put_user(host_stx->stx_ino, &target_stx->stx_ino);
+    __put_user(host_stx->stx_size, &target_stx->stx_size);
+    __put_user(host_stx->stx_blocks, &target_stx->stx_blocks);
+    __put_user(host_stx->stx_attributes_mask, &target_stx->stx_attributes_mask);
+    __put_user(host_stx->stx_atime.tv_sec, &target_stx->stx_atime.tv_sec);
+    __put_user(host_stx->stx_atime.tv_nsec, &target_stx->stx_atime.tv_nsec);
+    __put_user(host_stx->stx_btime.tv_sec, &target_stx->stx_atime.tv_sec);
+    __put_user(host_stx->stx_btime.tv_nsec, &target_stx->stx_atime.tv_nsec);
+    __put_user(host_stx->stx_ctime.tv_sec, &target_stx->stx_atime.tv_sec);
+    __put_user(host_stx->stx_ctime.tv_nsec, &target_stx->stx_atime.tv_nsec);
+    __put_user(host_stx->stx_mtime.tv_sec, &target_stx->stx_atime.tv_sec);
+    __put_user(host_stx->stx_mtime.tv_nsec, &target_stx->stx_atime.tv_nsec);
+    __put_user(host_stx->stx_rdev_major, &target_stx->stx_rdev_major);
+    __put_user(host_stx->stx_rdev_minor, &target_stx->stx_rdev_minor);
+    __put_user(host_stx->stx_dev_major, &target_stx->stx_dev_major);
+    __put_user(host_stx->stx_dev_minor, &target_stx->stx_dev_minor);
+
+    unlock_user_struct(target_stx, target_addr, 1);
+
+    return 0;
+}
+#endif
+
+
 /* ??? Using host futex calls even when target atomic operations
    are not really atomic probably breaks things.  However implementing
    futexes locally would make futexes shared between multiple processes
@@ -7094,7 +7145,8 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
     abi_long ret;
 #if defined(TARGET_NR_stat) || defined(TARGET_NR_stat64) \
     || defined(TARGET_NR_lstat) || defined(TARGET_NR_lstat64) \
-    || defined(TARGET_NR_fstat) || defined(TARGET_NR_fstat64)
+    || defined(TARGET_NR_fstat) || defined(TARGET_NR_fstat64) \
+    || defined(TARGET_NR_statx)
     struct stat st;
 #endif
 #if defined(TARGET_NR_statfs) || defined(TARGET_NR_statfs64) \
@@ -10172,6 +10224,67 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
             ret = host_to_target_stat64(cpu_env, arg3, &st);
         return ret;
 #endif
+#if defined(TARGET_NR_statx)
+    case TARGET_NR_statx:
+        {
+            struct target_statx *target_stx;
+            int dirfd = arg1;
+            int flags = arg3;
+
+            p = lock_user_string(arg2);
+            if (p == NULL) {
+                return -TARGET_EFAULT;
+            }
+#if defined(__NR_statx)
+            {
+                /*
+                 * It is assumed that struct statx is architecture independent.
+                 */
+                struct target_statx host_stx;
+                int mask = arg4;
+
+                ret = get_errno(sys_statx(dirfd, p, flags, mask, &host_stx));
+                if (!is_error(ret)) {
+                    if (host_to_target_statx(&host_stx, arg5) != 0) {
+                        unlock_user(p, arg2, 0);
+                        return -TARGET_EFAULT;
+                    }
+                }
+
+                if (ret != -TARGET_ENOSYS) {
+                    unlock_user(p, arg2, 0);
+                    return ret;
+                }
+            }
+#endif
+            ret = get_errno(fstatat(dirfd, path(p), &st, flags));
+            unlock_user(p, arg2, 0);
+
+            if (!is_error(ret)) {
+                if (!lock_user_struct(VERIFY_WRITE, target_stx, arg5, 0)) {
+                    return -TARGET_EFAULT;
+                }
+                memset(target_stx, 0, sizeof(*target_stx));
+                __put_user(major(st.st_dev), &target_stx->stx_dev_major);
+                __put_user(minor(st.st_dev), &target_stx->stx_dev_minor);
+                __put_user(st.st_ino, &target_stx->stx_ino);
+                __put_user(st.st_mode, &target_stx->stx_mode);
+                __put_user(st.st_uid, &target_stx->stx_uid);
+                __put_user(st.st_gid, &target_stx->stx_gid);
+                __put_user(st.st_nlink, &target_stx->stx_nlink);
+                __put_user(major(st.st_rdev), &target_stx->stx_rdev_major);
+                __put_user(minor(st.st_rdev), &target_stx->stx_rdev_minor);
+                __put_user(st.st_size, &target_stx->stx_size);
+                __put_user(st.st_blksize, &target_stx->stx_blksize);
+                __put_user(st.st_blocks, &target_stx->stx_blocks);
+                __put_user(st.st_atime, &target_stx->stx_atime.tv_sec);
+                __put_user(st.st_mtime, &target_stx->stx_mtime.tv_sec);
+                __put_user(st.st_ctime, &target_stx->stx_ctime.tv_sec);
+                unlock_user_struct(target_stx, arg5, 1);
+            }
+        }
+        return ret;
+#endif
 #ifdef TARGET_NR_lchown
     case TARGET_NR_lchown:
         if (!(p = lock_user_string(arg1)))