Messages in this thread | | | From | Sami Tolvanen <> | Date | Mon, 23 Aug 2021 10:20:33 -0700 | Subject | Re: [PATCH v2 00/14] x86: Add support for Clang CFI |
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On Mon, Aug 23, 2021 at 10:16 AM Tom Stellard <tstellar@redhat.com> wrote: > > On 8/23/21 10:13 AM, 'Sami Tolvanen' via Clang Built Linux wrote: > > This series adds support for Clang's Control-Flow Integrity (CFI) > > checking to x86_64. With CFI, the compiler injects a runtime > > check before each indirect function call to ensure the target is > > a valid function with the correct static type. This restricts > > possible call targets and makes it more difficult for an attacker > > to exploit bugs that allow the modification of stored function > > pointers. For more details, see: > > > > https://clang.llvm.org/docs/ControlFlowIntegrity.html > > > > Version 2 depends on Clang >=14, where we fixed the issue with > > referencing static functions from inline assembly. Based on the > > feedback for v1, this version also changes the declaration of > > functions that are not callable from C to use an opaque type, > > which stops the compiler from replacing references to them. This > > avoids the need to sprinkle function_nocfi() macros in the kernel > > code. > > How invasive are the changes in clang 14 necessary to make CFI work? > Would it be possible to backport them to LLVM 13?
I'm not sure what the LLVM backport policy is, but this specific fix was quite simple:
https://reviews.llvm.org/rG7ce1c4da7726
Sami
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