linux-user: Allow getdents to be provided by getdents64

Newer architectures may only implement the getdents64 syscall, not
getdents. Provide an implementation of getdents in terms of getdents64
so that we can run getdents-using targets on a getdents64-only host.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Tested-by: NClaudio Fontana <claudio.fontana@huawei.com>
Message-id: 1370344377-27445-1-git-send-email-peter.maydell@linaro.org
Message-id: 1370193044-24535-1-git-send-email-peter.maydell@linaro.org

linux-user/syscall.c

@@ -223,8 +223,11 @@ static int gettid(void) {
     return -ENOSYS;
 }
 #endif
+#ifdef __NR_getdents
 _syscall3(int, sys_getdents, uint, fd, struct linux_dirent *, dirp, uint, count);
-#if defined(TARGET_NR_getdents64) && defined(__NR_getdents64)
+#endif
+#if !defined(__NR_getdents) || \
+    (defined(TARGET_NR_getdents64) && defined(__NR_getdents64))
 _syscall3(int, sys_getdents64, uint, fd, struct linux_dirent64 *, dirp, uint, count);
 #endif
 #if defined(TARGET_NR__llseek) && defined(__NR_llseek)
@@ -7123,6 +7126,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         break;
 #endif
     case TARGET_NR_getdents:
+#ifdef __NR_getdents
 #if TARGET_ABI_BITS == 32 && HOST_LONG_BITS == 64
         {
             struct target_dirent *target_dirp;
@@ -7194,6 +7198,61 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
             }
             unlock_user(dirp, arg2, ret);
         }
+#endif
+#else
+        /* Implement getdents in terms of getdents64 */
+        {
+            struct linux_dirent64 *dirp;
+            abi_long count = arg3;
+
+            dirp = lock_user(VERIFY_WRITE, arg2, count, 0);
+            if (!dirp) {
+                goto efault;
+            }
+            ret = get_errno(sys_getdents64(arg1, dirp, count));
+            if (!is_error(ret)) {
+                /* Convert the dirent64 structs to target dirent.  We do this
+                 * in-place, since we can guarantee that a target_dirent is no
+                 * larger than a dirent64; however this means we have to be
+                 * careful to read everything before writing in the new format.
+                 */
+                struct linux_dirent64 *de;
+                struct target_dirent *tde;
+                int len = ret;
+                int tlen = 0;
+
+                de = dirp;
+                tde = (struct target_dirent *)dirp;
+                while (len > 0) {
+                    int namelen, treclen;
+                    int reclen = de->d_reclen;
+                    uint64_t ino = de->d_ino;
+                    int64_t off = de->d_off;
+                    uint8_t type = de->d_type;
+
+                    namelen = strlen(de->d_name);
+                    treclen = offsetof(struct target_dirent, d_name)
+                        + namelen + 2;
+                    treclen = QEMU_ALIGN_UP(treclen, sizeof(abi_long));
+
+                    memmove(tde->d_name, de->d_name, namelen + 1);
+                    tde->d_ino = tswapal(ino);
+                    tde->d_off = tswapal(off);
+                    tde->d_reclen = tswap16(treclen);
+                    /* The target_dirent type is in what was formerly a padding
+                     * byte at the end of the structure:
+                     */
+                    *(((char *)tde) + treclen - 1) = type;
+
+                    de = (struct linux_dirent64 *)((char *)de + reclen);
+                    tde = (struct target_dirent *)((char *)tde + treclen);
+                    len -= reclen;
+                    tlen += treclen;
+                }
+                ret = tlen;
+            }
+            unlock_user(dirp, arg2, ret);
+        }
 #endif
         break;
 #if defined(TARGET_NR_getdents64) && defined(__NR_getdents64)