bsd-user: Implement getdents related syscalls

Implement the following syscalls:
getdents(2)
getdirecentries(2)

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Karim Taha <kariem.taha2.7@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>

bsd-user/freebsd/os-stat.h

@@ -279,4 +279,76 @@ static inline abi_long do_freebsd_getfsstat(abi_ulong target_addr,
     return ret;
 }
 
+/* getdents(2) */
+static inline abi_long do_freebsd11_getdents(abi_long arg1,
+        abi_ulong arg2, abi_long nbytes)
+{
+    abi_long ret;
+    struct freebsd11_dirent *dirp;
+
+    dirp = lock_user(VERIFY_WRITE, arg2, nbytes, 0);
+    if (dirp == NULL) {
+        return -TARGET_EFAULT;
+    }
+    ret = get_errno(freebsd11_getdents(arg1, (char *)dirp, nbytes));
+    if (!is_error(ret)) {
+        struct freebsd11_dirent *de;
+        int len = ret;
+        int reclen;
+
+        de = dirp;
+        while (len > 0) {
+            reclen = de->d_reclen;
+            if (reclen > len) {
+                return -TARGET_EFAULT;
+            }
+            de->d_reclen = tswap16(reclen);
+            de->d_fileno = tswap32(de->d_fileno);
+            len -= reclen;
+        }
+    }
+    return ret;
+}
+
+/* getdirecentries(2) */
+static inline abi_long do_freebsd_getdirentries(abi_long arg1,
+        abi_ulong arg2, abi_long nbytes, abi_ulong arg4)
+{
+    abi_long ret;
+    struct dirent *dirp;
+    long basep;
+
+    dirp = lock_user(VERIFY_WRITE, arg2, nbytes, 0);
+    if (dirp == NULL) {
+        return -TARGET_EFAULT;
+    }
+    ret = get_errno(getdirentries(arg1, (char *)dirp, nbytes, &basep));
+    if (!is_error(ret)) {
+        struct dirent *de;
+        int len = ret;
+        int reclen;
+
+        de = dirp;
+        while (len > 0) {
+            reclen = de->d_reclen;
+            if (reclen > len) {
+                return -TARGET_EFAULT;
+            }
+            de->d_fileno = tswap64(de->d_fileno);
+            de->d_off = tswap64(de->d_off);
+            de->d_reclen = tswap16(de->d_reclen);
+            de->d_namlen = tswap16(de->d_namlen);
+            len -= reclen;
+            de = (struct dirent *)((void *)de + reclen);
+        }
+    }
+    unlock_user(dirp, arg2, ret);
+    if (arg4) {
+        if (put_user(basep, arg4, abi_ulong)) {
+            return -TARGET_EFAULT;
+        }
+    }
+    return ret;
+}
+
 #endif /* BSD_USER_FREEBSD_OS_STAT_H */