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[PAC] Fn ptr type discrimination tests (8/8) - #159087

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[PAC] Fn ptr type discrimination tests (8/8)#159087
jchlanda wants to merge 9 commits into
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@jchlanda jchlanda commented Jul 10, 2026 •
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Adds tests for function pointer type discrimination.

Also updates the main pauthtest document to:

  • list the new tests;
  • remove the requirement to patch libc, since those changes have already landed; and
  • document that cc-rs still requires patching because compiler/rustc_llvm/Cargo.toml pins cc to the older version =1.2.16.

This is part 8 of a sequence of 8 PRs that together implement support for function pointer type discrimination:

  1. Encoder and hash
  2. FnAbi, llvm.ptrauth.resign and Session API change
  3. FPTR_TYPE_DISCR in ABI Version
  4. Static allocs
  5. Transmutes
  6. Propagate discriminator logic through remaining get_fn_ptr calls sites
  7. Minicore updates to support fn ptr type discriminator tests
  8. Fn ptr type discrimination tests

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@rustbot rustbot added A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. A-run-make Area: port run-make Makefiles to rmake.rs A-test-infra-minicore Area: `minicore` test auxiliary and `//@ add-core-stubs` S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 10, 2026
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jchlanda force-pushed the jakub/pac_ty_disc_PR_8 branch 2 times, most recently from 7527456 to 979ff1f Compare July 14, 2026 07:36
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jchlanda force-pushed the jakub/pac_ty_disc_PR_8 branch from 979ff1f to 0e9fa4d Compare July 14, 2026 08:55
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jchlanda force-pushed the jakub/pac_ty_disc_PR_8 branch from 0e9fa4d to 753b459 Compare July 17, 2026 07:08
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jchlanda force-pushed the jakub/pac_ty_disc_PR_8 branch 8 times, most recently from e07a163 to fa14e50 Compare July 23, 2026 07:48
@jchlanda
jchlanda force-pushed the jakub/pac_ty_disc_PR_8 branch from b9b8e1f to 8e11ea8 Compare July 24, 2026 16:12
@jchlanda jchlanda changed the title [WIP] 8 - Fn ptr type discrimination tests [PAC] Fn ptr type discrimination tests (8/8) Jul 24, 2026
@jchlanda
jchlanda marked this pull request as ready for review July 24, 2026 18:09
@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 24, 2026
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rustbot commented Jul 24, 2026

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rustc_codegen_gcc is developed in its own repository. If possible, consider making this change to rust-lang/rustc_codegen_gcc instead.

cc @antoyo, @GuillaumeGomez

Some changes occurred in src/doc/rustc/src/platform-support

cc @Noratrieb

@rustbot rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jul 24, 2026
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r? @oli-obk

rustbot has assigned @oli-obk.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

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Why was this reviewer chosen?

The reviewer was selected based on:

  • Owners of files modified in this PR: compiler
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jchlanda commented Jul 24, 2026

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r? compiler

@rustbot rustbot assigned JohnTitor and unassigned oli-obk Jul 24, 2026
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[PAC] Introduce function pointer type encoder and hashing function
f619018 
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>.
@davidtwco

davidtwco commented Jul 27, 2026

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r? @davidtwco

@rustbot rustbot assigned davidtwco and unassigned JohnTitor Jul 27, 2026
@jchlanda
jchlanda force-pushed the jakub/pac_ty_disc_PR_8 branch from 8e11ea8 to ff95052 Compare July 27, 2026 12:02
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This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

@jchlanda
jchlanda force-pushed the jakub/pac_ty_disc_PR_8 branch from ff95052 to 61b53fe Compare July 28, 2026 07:28
jchlanda added 8 commits July 28, 2026 07:29
@jchlanda
[PAC] Add unit tests for sip hash
43ed719
@jchlanda
[PAC] Include discriminator in FnAbi, add llvm.ptrauth.resign
e97f85c 
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.
@jchlanda
[PAC] Enable support for FPTR_TYPE_DISCR in ABI Version
76aa0dd 
Also remove error messages/tests that used to guarded it.
@jchlanda
[PAC] Support type discriminators in static allocations
0f93e37 
The codegen now walks the layout of static initializer types to find extern "C"
function pointer fields, computes their type discriminators, and applies those
discriminators when emitting authenticated function pointer relocations.

Also make sure that type discrimination is never applied to init/fini
entries.
@jchlanda
[PAC] Function pointer type discrimination for transmutes
8db5918 
Implement pointer authentication domain handling for function pointer
transmutes. When function pointer type discrimination is enabled,
transmuting between function pointer types with different authentication
domains now re-signs the pointer using the appropriate discriminator.
@jchlanda
[PAC] Propagate function pointer type discrimination through `get_fn_…
93f026b 
…addr` call sites

Fill in function pointer type discriminators logic across remaining
`get_fn_addr` call sites and explicitly avoid applying it where
discrimination is not meaningful.

Some uses of `get_fn_addr` are intentionally left unsigned, including
the EH personality function, entry wrappers, and compiler-generated Rust
ABI shims.
@jchlanda
[PAC] Minicore updates to support fn ptr type discriminator tests
a8f60e1
@jchlanda
[PAC] Function pointer type discrimination tests
5b65311 
And update to the main pauthtest document:
* list new tests
* remove the need for patching `libc` as the changes to it already went
  in. Unfortunately `cc-rs` is held back by
  `compiler/rustc_llvm/Cargo.toml` which pins to an old version:
  `cc = "=1.2.16"`
@jchlanda
jchlanda force-pushed the jakub/pac_ty_disc_PR_8 branch from 61b53fe to 5b65311 Compare July 28, 2026 08:03
@jchlanda jchlanda mentioned this pull request Jul 28, 2026
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rust-bors Bot commented Jul 28, 2026

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☔ The latest upstream changes (presumably #160102) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.

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A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. A-run-make Area: port run-make Makefiles to rmake.rs A-test-infra-minicore Area: `minicore` test auxiliary and `//@ add-core-stubs` S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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