Messages in this thread | | | Date | Tue, 26 Oct 2021 22:16:22 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v5 00/15] x86: Add support for Clang CFI |
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On Wed, Oct 13, 2021 at 11:16:43AM -0700, Sami Tolvanen 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
So, if I understand this right, the compiler emits, for every function two things: 1) the actual funcion and 2) a jump-table entry.
Then, every time the address of a function is taken, 2) is given instead of the expected 1), right?
But how does this work with things like static_call(), which we give a function address (now a jump-table entry) and use that to write direct call instructions?
Should not this jump-table thingy get converted to an actual function address somewhere around arch_static_call_transform() ? This also seems relevant for arm64 (which already has CLANG_CFI supported) given:
https://lkml.kernel.org/r/20211025122102.46089-3-frederic@kernel.org
Or am I still not understanding this CFI thing?
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