[WIP] 2 - FnAbi, llvm.ptrauth.resign and Session API change#159074
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[WIP] 2 - FnAbi, llvm.ptrauth.resign and Session API change#159074jchlanda wants to merge 2 commits into
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This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used in pointer authentication. Compatibility with Clang is a primary goal. The discriminator produced for a given external "C" function type must match the value computed by Clang so that function pointers can be exchanged safely between Rust and C code while preserving pointer authentication semantics. The implementation mirrors Clang's behavior in `ASTContext::encodeTypeForFunctionPointerAuth`, ensuring that identical C-compatible function types produce identical discriminators. See: <https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3>.
This patch introduces the following: * Extends `FnAbi` (`callconv`) with a `ptrauth_type_discriminator` field. This field is only used when emitting pointer authentication call bundles. It is stored in `FnAbi` because the call site is not guaranteed to have access to an `Instance`, so the discriminator cannot always be computed on demand. * Adds support for `llvm.ptrauth.resign`. This intrinsic will be used when support for semantic transmute is added. * Performs a minor API redesign as groundwork for allowing call sites to modify schemas in place.
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This patch introduces the following:
FnAbi(callconv) with aptrauth_type_discriminatorfield. This field is only used when emitting pointer authentication call bundles. It is stored inFnAbibecause the call site is not guaranteed to have access to anInstance, so the discriminator cannot always be computed on demand.llvm.ptrauth.resign. This intrinsic will be used when support for semantic transmute is added.This is part 2 of a sequence of 8 PRs, that together aim to bring function pointer type discrimination support:
Useful links:
pauthtestintroduction: Introduce aarch64-unknown-linux-pauthtest target #155722