VirtualMemory::DuplicateRX doesn't work on Fuchsia #52579
Assignees
Labels
area-vm
Use area-vm for VM related issues, including code coverage, and the AOT and JIT backends.
os-fuchsia
P3
A lower priority bug or feature request
triaged
Issue has been triaged by sub team
Comments
lrhn
added
the
area-vm
copybara-service bot
pushed a commit
that referenced
this issue
Jun 6, 2023
This reverts https://dart-review.googlesource.com/c/sdk/+/306674 Patchset 1 is a pure rollback of the rollback. Patchset 2 is https://dart-review.googlesource.com/c/sdk/+/306316 Patchset 4+ is the forward fix for the Fuchsia issues. The Fuchsia bug that we're fixing (or working around), is that VirtualMemory::DuplicateRX doesn't work on Fuchsia. A proper fix will require special casing it, like on MacOS. In the mean time we can avoid using this function by only allowing one page of trampolines on Fuchsia. Unfortunately, when I removed the BSS stuff from the original CL, it was necessary to duplicate even the first page, so I've had to add that stuff back just for Fuchsia. Change-Id: Id42de78ee5de126bcc83bfa4148f6efb4045f976 Bug: #52579 Bug: https://buganizer.corp.google.com/issues/284959841 Fixes: #52581 TEST=CI, especially vm-fuchsia-release-x64-try Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/306676 Reviewed-by: Ryan Macnak <rmacnak@google.com> Commit-Queue: Liam Appelbe <liama@google.com> Reviewed-by: Daco Harkes <dacoharkes@google.com>
a-siva
added
P3
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Specifically the call to
Protect(..., kReadExecute)(which callszx_vmar_protect) fails. This is why theFfiCallbackMetadatamigration had to be reverted.To fix this,
VirtualMemory::DuplicateRXneeds to be special cased, like it is for MacOS. In fact the implementation will be similar to the MacOS version. We'll need a call tozx_vmar_map, analogous to thevm_remapcall, which remaps our executable memory over an existing writable memory. This requires special permissions that the ordinary VMO used by the rest of virtual_memory_fuchsia.cc doesn't have.So we need the VMO that is created when the embedder loads the app's .so file in executable mode. At the moment the flutter embedder just discards this VMO, but we need to plumb it though Dart_Initialize to VirtualMemory.
cc @rmacnak-google
The text was updated successfully, but these errors were encountered: