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[PAC] Minicore updates to support fn ptr type discriminator tests (7/8)#159086

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[PAC] Minicore updates to support fn ptr type discriminator tests (7/8)#159086
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@jchlanda jchlanda commented Jul 10, 2026 •
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This patch prepares minicore for function pointer type discriminator tests.

This is part 7 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-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
This was referenced Jul 10, 2026
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jchlanda force-pushed the jakub/pac_ty_disc_PR_7 branch from 54447d2 to 6c09f27 Compare July 10, 2026 14:39
@jchlanda jchlanda mentioned this pull request Jul 10, 2026
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jchlanda force-pushed the jakub/pac_ty_disc_PR_7 branch 2 times, most recently from a762c6a to 71a56a5 Compare July 14, 2026 07:30
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jchlanda force-pushed the jakub/pac_ty_disc_PR_7 branch from 71a56a5 to d4e180d Compare July 14, 2026 08:55
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jchlanda force-pushed the jakub/pac_ty_disc_PR_7 branch from d4e180d to efa84d7 Compare July 17, 2026 07:06
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jchlanda force-pushed the jakub/pac_ty_disc_PR_7 branch 2 times, most recently from f8bd7ba to d3e6fb9 Compare July 17, 2026 09:49
kovdan01
kovdan01 reviewed Jul 20, 2026
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Comment thread tests/auxiliary/minicore.rs

#[lang = "c_void"]
#[repr(u8)]
#[allow(non_camel_case_types)]

@kovdan01 kovdan01 Jul 20, 2026 •
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Why do we need this change? I see c_void used in tests, but I'm not sure why these naming changes are required (the enum elements do not look directly used in tests anyway)

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@jchlanda jchlanda Jul 21, 2026

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Without it tidy would fail (and it is run as part of PR CI tests).

Comment thread tests/auxiliary/minicore.rs
7
}
}
impl Add for i32 {

@kovdan01 kovdan01 Jul 20, 2026 •
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I failed to find direct uses of Add trait or add function in tests. Could you please explain why we need this new implementation for i32 here?

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@jchlanda jchlanda Jul 21, 2026 •
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Because + operator is resolved to Add, so without the code above this will fail to compile for minicore:

extern "C" fn foo(x: i32) -> i32 {
    x + 1
}

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jchlanda force-pushed the jakub/pac_ty_disc_PR_7 branch 4 times, most recently from 6ed41f8 to b4ef371 Compare July 23, 2026 08:46
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jchlanda force-pushed the jakub/pac_ty_disc_PR_7 branch from b4ef371 to 6559148 Compare July 24, 2026 15:23
jchlanda added 8 commits July 24, 2026 15:24
@jchlanda
[PAC] Introduce function pointer type encoder and hashing function
63b81b4 
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>.
@jchlanda
[PAC] Add unit tests for sip hash
8b0e0ca
@jchlanda
[PAC] Include discriminator in FnAbi, add llvm.ptrauth.resign
69e4d08 
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
06c9628 
Also remove error messages/tests that used to guarded it.
@jchlanda
[PAC] Support type discriminators in static allocations
286014f 
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
d1159e3 
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_…
67416ab 
…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
c926f3d
@jchlanda
jchlanda force-pushed the jakub/pac_ty_disc_PR_7 branch from 6559148 to c926f3d Compare July 24, 2026 16:07
@jchlanda jchlanda changed the title [WIP] 7 - Minicore updates to support fn ptr type discriminator tests [PAC] Minicore updates to support fn ptr type discriminator tests (7/8) Jul 24, 2026
@jchlanda
jchlanda marked this pull request as ready for review July 24, 2026 18:09
@rustbot

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 added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 24, 2026
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r? @mu001999

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@jchlanda

jchlanda commented Jul 24, 2026

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r? compiler

@rustbot rustbot assigned davidtwco and unassigned mu001999 Jul 24, 2026
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A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. 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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