In W^X mode (i.e., FLAG_write_protect_code), the Dart VM allocates
code memory with is_executable==false and then later makes it
executable with Protect(kReadExecute). However, on Fuchsia, this will
require a VMO with ZX_RIGHT_EXECUTE (which soon will not be the
default).
This CL takes the approach of always adding ZX_RIGHT_EXECUTE when in
W^X mode. This is suboptimal because it means all VM allocated memory
can be changed to executable, but currently the OS-independent
VirtualMemory::Allocate API doesn't provide us a way to identify
memory that doesn't need to be executable now but will in the future.
(Note that ZX_RIGHT_EXECUTE only *allows* mapping the memory as
executable; the memory is still initially mapped by
VirtualMemory::Allocate as non-executable.)
Extending the VirtualMemory::Allocate API is tracked in FL-172.
Bug: SEC-42
Change-Id: I20555c546c5ab1798c4c36b7394f6221d3993c9e
Reviewed-on: https://dart-review.googlesource.com/c/90882
Reviewed-by: Zach Anderson <zra@google.com>
Commit-Queue: Zach Anderson <zra@google.com>
Matthew Dempsky
8e2f3ea4d6