[PAC] FnAbi, llvm.ptrauth.resign and Session API change (2/8) - #159074
Open
jchlanda wants to merge 2 commits into
Open
[PAC] FnAbi, llvm.ptrauth.resign and Session API change (2/8)#159074jchlanda wants to merge 2 commits into
jchlanda wants to merge 2 commits into
Conversation
rustbot
added
A-LLVM
jchlanda
changed the title
This was referenced Jul 10, 2026
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
2 times, most recently
from
July 14, 2026 07:27
8f37395 to
0792cdd
Compare
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
July 14, 2026 08:51
0792cdd to
281565d
Compare
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
July 17, 2026 07:01
281565d to
360a700
Compare
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
2 times, most recently
from
July 17, 2026 09:47
089232b to
d85aa6b
Compare
kovdan01
reviewed
Jul 20, 2026
| let discriminator = if self.sess().pointer_authentication_fn_ptr_type_discrimination() { | ||
| fn_abi?.ptrauth_type_discriminator | ||
| } else { | ||
| 0 |
Contributor
There was a problem hiding this comment.
Do we need this check here? As far as I can see, we already conditionally set ptrauth_type_discriminator to 0 if pointer_authentication_fn_ptr_type_discrimination() is false in compiler/rustc_ty_utils/src/abi.rs. Maybe we can even rename ptrauth_type_discriminator field in FnAbi to smth like just ptrauth_discriminator and assume it's storing the "effective" discriminator (either 0 or type discriminator)?
Just loudly thinking, I might easily miss smth - I would appreciate your explanation if I've got smth wrong
Contributor
Author
There was a problem hiding this comment.
You are right, we don't need it here, added comment about it though.
Also renaming to ptrauth_discriminator.
| ), | ||
| ptrauth_type_discriminator: if tcx.sess.pointer_authentication_fn_ptr_type_discrimination() | ||
| { | ||
| compute_fn_ptr_type_discriminator_for(tcx, sig).unwrap_or(0).into() |
Contributor
There was a problem hiding this comment.
Just in case: do I get it correct that the sequence of PRs is not about "at each point we are expected to have a successful build", it's about ease of review only?
I'm just not seeing compute_fn_ptr_type_discriminator_for defined at this point - was it intentional or should PR content split decisions be reconsidered?
Contributor
Author
There was a problem hiding this comment.
No, you do not. It is intended to be buildable at each stage.
The split is twofold: logical, to show the progression of the implementation, and functional, since each commit is expected to be independently buildable. They are not exactly atomic in the sense that the functionality will not be complete, so if you check out a commit in the middle of the sequence, it should build, but the generated code might not be fully correct.
The function you are referring to was added in the first PR of the series:
https://github.com/rust-lang/rust/pull/159071/changes#diff-40f6b89998ba7d54d3f76fde93944eab9b8ba5a16eb1d763c598e2802a180af7R166
| /// Indicates if an unwind may happen across a call to this function. | ||
| pub can_unwind: bool, | ||
| /// Computed type discriminator for pointer authentication purpose. | ||
| pub ptrauth_type_discriminator: u64, |
Contributor
There was a problem hiding this comment.
Just a future note: when submitting as final non-draft PR for mainline review, it might be worth to provide a summary why a new field in FnAbi is considered at this point the proper solution for our problem and why we really need that. The summary could be placed somewhere in the PR description/PR comments/elsewhere if a more appropriate place exists.
Contributor
Author
There was a problem hiding this comment.
Done, in the PR description.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
July 20, 2026 12:44
d85aa6b to
7708e94
Compare
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
3 times, most recently
from
July 24, 2026 15:34
5d74d74 to
69e4d08
Compare
jchlanda
changed the title
jchlanda
marked this pull request as ready for review
July 24, 2026 18:07
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
August 3, 2026 07:51
6a4ad09 to
5818ee3
Compare
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
August 10, 2026 08:05
5818ee3 to
e051d93
Compare
rustbot
added
the
A-meta
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
August 12, 2026 06:20
e051d93 to
65cfc9f
Compare
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
August 17, 2026 08:40
65cfc9f to
a574613
Compare
This comment has been minimized.
This comment has been minimized.
davidtwco
approved these changes
Aug 19, 2026
| /// Indicates if an unwind may happen across a call to this function. | ||
| pub can_unwind: bool, | ||
| /// Computed type discriminator for pointer authentication purpose. | ||
| pub ptrauth_discriminator: u64, |
Member
There was a problem hiding this comment.
Can you use an Option or introduce an enum here instead of using 0 as a default value? You can add a method that does an unwrap_or(0) for when you actually need the value.
JonathanBrouwer
added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Aug 19, 2026
…=davidtwco [PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](rust-lang#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](rust-lang#159074) 3. [FPTR_TYPE_DISCR in ABI Version](rust-lang#159075) 4. [Static allocs](rust-lang#159081) 5. [Transmutes](rust-lang#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](rust-lang#159084) 7. [Minicore updates to support fn ptr type discriminator tests](rust-lang#159086) 8. [Fn ptr type discrimination tests](rust-lang#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: rust-lang#155722 * Library support follow up: rust-lang#156548 * Config follow up: rust-lang#156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
JonathanBrouwer
added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Aug 19, 2026
…=davidtwco [PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](rust-lang#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](rust-lang#159074) 3. [FPTR_TYPE_DISCR in ABI Version](rust-lang#159075) 4. [Static allocs](rust-lang#159081) 5. [Transmutes](rust-lang#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](rust-lang#159084) 7. [Minicore updates to support fn ptr type discriminator tests](rust-lang#159086) 8. [Fn ptr type discrimination tests](rust-lang#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: rust-lang#155722 * Library support follow up: rust-lang#156548 * Config follow up: rust-lang#156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
JonathanBrouwer
added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Aug 19, 2026
…=davidtwco [PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](rust-lang#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](rust-lang#159074) 3. [FPTR_TYPE_DISCR in ABI Version](rust-lang#159075) 4. [Static allocs](rust-lang#159081) 5. [Transmutes](rust-lang#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](rust-lang#159084) 7. [Minicore updates to support fn ptr type discriminator tests](rust-lang#159086) 8. [Fn ptr type discrimination tests](rust-lang#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: rust-lang#155722 * Library support follow up: rust-lang#156548 * Config follow up: rust-lang#156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
rust-bors Bot
pushed a commit
that referenced
this pull request
Aug 19, 2026
[PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](#159074) 3. [FPTR_TYPE_DISCR in ABI Version](#159075) 4. [Static allocs](#159081) 5. [Transmutes](#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](#159084) 7. [Minicore updates to support fn ptr type discriminator tests](#159086) 8. [Fn ptr type discrimination tests](#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: #155722 * Library support follow up: #156548 * Config follow up: #156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
JonathanBrouwer
added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Aug 19, 2026
…=davidtwco [PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](rust-lang#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](rust-lang#159074) 3. [FPTR_TYPE_DISCR in ABI Version](rust-lang#159075) 4. [Static allocs](rust-lang#159081) 5. [Transmutes](rust-lang#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](rust-lang#159084) 7. [Minicore updates to support fn ptr type discriminator tests](rust-lang#159086) 8. [Fn ptr type discrimination tests](rust-lang#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: rust-lang#155722 * Library support follow up: rust-lang#156548 * Config follow up: rust-lang#156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
JonathanBrouwer
added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Aug 20, 2026
…=davidtwco [PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](rust-lang#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](rust-lang#159074) 3. [FPTR_TYPE_DISCR in ABI Version](rust-lang#159075) 4. [Static allocs](rust-lang#159081) 5. [Transmutes](rust-lang#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](rust-lang#159084) 7. [Minicore updates to support fn ptr type discriminator tests](rust-lang#159086) 8. [Fn ptr type discrimination tests](rust-lang#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: rust-lang#155722 * Library support follow up: rust-lang#156548 * Config follow up: rust-lang#156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
August 20, 2026 07:07
5b1bb41 to
4c55733
Compare
This comment has been minimized.
This comment has been minimized.
jchlanda
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
August 20, 2026 08:01
4c55733 to
96a2710
Compare
JonathanBrouwer
added a commit
to JonathanBrouwer/rust
that referenced
this pull request
Aug 20, 2026
…=davidtwco [PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](rust-lang#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](rust-lang#159074) 3. [FPTR_TYPE_DISCR in ABI Version](rust-lang#159075) 4. [Static allocs](rust-lang#159081) 5. [Transmutes](rust-lang#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](rust-lang#159084) 7. [Minicore updates to support fn ptr type discriminator tests](rust-lang#159086) 8. [Fn ptr type discrimination tests](rust-lang#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: rust-lang#155722 * Library support follow up: rust-lang#156548 * Config follow up: rust-lang#156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
rust-bors Bot
pushed a commit
that referenced
this pull request
Aug 20, 2026
Rollup merge of #159071 - jchlanda:jakub/pac_ty_disc_PR_1, r=davidtwco [PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](#159074) 3. [FPTR_TYPE_DISCR in ABI Version](#159075) 4. [Static allocs](#159081) 5. [Transmutes](#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](#159084) 7. [Minicore updates to support fn ptr type discriminator tests](#159086) 8. [Fn ptr type discrimination tests](#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: #155722 * Library support follow up: #156548 * Config follow up: #156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
pull Bot
pushed a commit
to LeeeeeeM/miri
that referenced
this pull request
Aug 21, 2026
[PAC] Encoder and hash (1/8) This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used for pointer authentication. Compatibility with Clang is a primary design goal. For a given extern "C" function type, the discriminator produced by Rust 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 is part 1 of a sequence of 8 PRs that together implement support for function pointer type discrimination: 1. [Encoder and hash](rust-lang/rust#159071) 2. [FnAbi, llvm.ptrauth.resign and Session API change](rust-lang/rust#159074) 3. [FPTR_TYPE_DISCR in ABI Version](rust-lang/rust#159075) 4. [Static allocs](rust-lang/rust#159081) 5. [Transmutes](rust-lang/rust#159082) 6. [Propagate discriminator logic through remaining get_fn_ptr calls sites](rust-lang/rust#159084) 7. [Minicore updates to support fn ptr type discriminator tests](rust-lang/rust#159086) 8. [Fn ptr type discrimination tests](rust-lang/rust#159087) --- Useful links: * Previous PAC work: * `pauthtest` introduction: rust-lang/rust#155722 * Library support follow up: rust-lang/rust#156548 * Config follow up: rust-lang/rust#156712 * [Project goal](https://rust-lang.github.io/rust-project-goals/2026/aarch64_pointer_authentication_pauthtest.html) and [tracking issue](rust-lang/goals#618) * Clang's implementation of [ASTContext::encodeTypeForFunctionPointerAuth](https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3) * LLVM's [SpiHash](https://github.com/llvm/llvm-project/blob/main/third-party/siphash/include/siphash/SipHash.h)
Contributor
Author
|
This should be ready to land @davidtwco @JonathanBrouwer. Thank you! |
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
force-pushed
the
jakub/pac_ty_disc_PR_2
branch
from
September 1, 2026 11:50
96a2710 to
5ebe84b
Compare
Collaborator
|
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. |
Collaborator
|
The job Click to see the possible cause of the failure (guessed by this bot) |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
7 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
View all comments
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.The use of an extended
FnAbiis dictated by the need to issue a ptrauth bundle for call-like instructions. At that point, we only have access to theFnAbistruct (Instanceis not guaranteed to be available).Fundamentally, the discriminator originates from the source-level function type. Deriving it at the codegen stage would introduce a layering violation: it would require relying on
FnAbi'sArgAbi(for both return values and arguments) to preserve source-level type information. This is not a guarantee provided by these abstractions (and in code comments), asFnAbirepresents a lowered calling convention rather than the original function signature.Computing the discriminator at this stage would therefore create a hard dependency on type information being available where it is not intended to be preserved. Carrying the value explicitly avoids reconstructing source-level information from lowered ABI data and keeps the abstraction boundaries intact.
This is part 2 of a sequence of 8 PRs that together implement support for function pointer type discrimination:
Useful links:
pauthtestintroduction: Introduce aarch64-unknown-linux-pauthtest target #155722