fixup! [LibOS] Implement mmap for encrypted and tmpfs files

Signed-off-by: Paweł Marczewski <[email protected]>

LibOS/shim/src/bookkeep/shim_vma.c

@@ -1249,13 +1249,15 @@ static bool vma_filter_needs_msync(struct shim_vma* vma, void* arg) {
     if (!vma->file->fs || !vma->file->fs->fs_ops || !vma->file->fs->fs_ops->msync)
         return false;
 
-    /* TODO: remove `lock()` here after we ensure that the `acc_mode` field never changes in
-     * handles */
-    lock(&vma->file->lock);
-    int acc_mode = vma->file->acc_mode;
-    unlock(&vma->file->lock);
-
-    if (!(acc_mode & MAY_WRITE))
+    /*
+     * XXX: Strictly speaking, reading `vma->file->acc_mode` requires taking `vma->file->lock`,
+     * which we cannot do in this function. However, the `acc_mode` field is only modified for
+     * sockets, and at this point we know that `vma->file` is not a socket (since it implements
+     * `msync`).
+     *
+     * TODO: Remove this comment when the socket code is rewritten.
+     */
+    if (!(vma->file->acc_mode & MAY_WRITE))
         return false;
 
     return true;

LibOS/shim/src/fs/shim_fs_util.c

@@ -140,10 +140,12 @@ int generic_inode_poll(struct shim_handle* hdl, int poll_type) {
 int generic_emulated_mmap(struct shim_handle* hdl, void* addr, size_t size, int prot, int flags,
                           uint64_t offset) {
     assert(addr);
+    __UNUSED(flags);
 
     int ret;
 
-    pal_prot_flags_t pal_prot = LINUX_PROT_TO_PAL(prot, flags);
+    /* The underlying PAL mapping should always be private. */
+    pal_prot_flags_t pal_prot = LINUX_PROT_TO_PAL(prot, MAP_PRIVATE);
     pal_prot_flags_t pal_prot_writable = pal_prot | PAL_PROT_WRITE;
 
     void* actual_addr = addr;
@@ -195,11 +197,14 @@ err:;
 int generic_emulated_msync(struct shim_handle* hdl, void* addr, size_t size, int prot, int flags,
                            uint64_t offset) {
     assert(!(flags & MAP_PRIVATE));
+    __UNUSED(flags);
+
     lock(&hdl->inode->lock);
     file_off_t file_size = hdl->inode->size;
     unlock(&hdl->inode->lock);
 
-    pal_prot_flags_t pal_prot = LINUX_PROT_TO_PAL(prot, flags);
+    /* The underlying PAL mapping should always be private. */
+    pal_prot_flags_t pal_prot = LINUX_PROT_TO_PAL(prot, MAP_PRIVATE);
     pal_prot_flags_t pal_prot_readable = pal_prot | PAL_PROT_READ;
 
     int ret;