On Tue, Jan 14, 2025 at 6:27 PM Wei Yang [off-list ref] wrote:

On Fri, Jan 10, 2025 at 08:26:03PM -0800, Suren Baghdasaryan wrote:

quoted

diff --git a/kernel/fork.c b/kernel/fork.c
index 9d9275783cf8..151b40627c14 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c

@@ -449,6 +449,42 @@ struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
      return vma;

}

+static void vm_area_init_from(const struct vm_area_struct *src,
+                            struct vm_area_struct *dest)
+{
+      dest->vm_mm = src->vm_mm;
+      dest->vm_ops = src->vm_ops;
+      dest->vm_start = src->vm_start;
+      dest->vm_end = src->vm_end;
+      dest->anon_vma = src->anon_vma;
+      dest->vm_pgoff = src->vm_pgoff;
+      dest->vm_file = src->vm_file;
+      dest->vm_private_data = src->vm_private_data;
+      vm_flags_init(dest, src->vm_flags);
+      memcpy(&dest->vm_page_prot, &src->vm_page_prot,
+             sizeof(dest->vm_page_prot));
+      /*
+       * src->shared.rb may be modified concurrently when called from
+       * dup_mmap(), but the clone will reinitialize it.
+       */
+      data_race(memcpy(&dest->shared, &src->shared, sizeof(dest->shared)));
+      memcpy(&dest->vm_userfaultfd_ctx, &src->vm_userfaultfd_ctx,
+             sizeof(dest->vm_userfaultfd_ctx));
+#ifdef CONFIG_ANON_VMA_NAME
+      dest->anon_name = src->anon_name;
+#endif
+#ifdef CONFIG_SWAP
+      memcpy(&dest->swap_readahead_info, &src->swap_readahead_info,
+             sizeof(dest->swap_readahead_info));
+#endif
+#ifndef CONFIG_MMU
+      dest->vm_region = src->vm_region;
+#endif
+#ifdef CONFIG_NUMA
+      dest->vm_policy = src->vm_policy;
+#endif
+}

Would this be difficult to maintain? We should make sure not miss or overwrite
anything.

Yeah, it is less maintainable than a simple memcpy() but I did not
find a better alternative. I added a warning above the struct
vm_area_struct definition to update this function every time we change
that structure. Not sure if there is anything else I can do to help
with this.

--
Wei Yang
Help you, Help me