tests: Test pac-ret flag merging on clang with LTO by mrkajetanp · Pull Request #133045 · rust-lang/rust

mrkajetanp · 2024-11-14T18:33:52Z

Extend the test for pac-ret with clang and LTO by checking that different branch protection flags are preserved after the LTO step. There was an issue in older LLVM versions that was causing this to behave incorrectly.

try-job: aarch64-gnu-debug

rustbot · 2024-11-14T18:34:00Z

r? @jieyouxu

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rustbot · 2024-11-14T18:34:02Z

This PR modifies tests/run-make/. If this PR is trying to port a Makefile
run-make test to use rmake.rs, please update the
run-make port tracking issue
so we can track our progress. You can either modify the tracking issue
directly, or you can comment on the tracking issue and link this PR.

cc @jieyouxu

jieyouxu · 2024-11-15T09:17:19Z

@bors try

jieyouxu · 2024-11-15T09:18:02Z

 .output("test.bin")
 .run();
+
+ // Check that both a-key and b-key pac-ret survived LTO


Question: is there any background / links for this? I'm fine with the change, but it's even better if there's any kind of context to read.

For sure, this is the context:
llvm/llvm-project@1782810
TLDR: there was a bug in LLVM where during the LTO step instructions like "pacibsp" would get replaced with "paciasp" due to LLVM module flag merging behaviour. As currently written the assembly output should have no PAuth on library functions, paciasp at the start of main and pacibsp at the start of foo.
It is worrying that the test is failing, I'll try to reproduce it locally.

Thanks for the context. And I agree, the test failing is... suspicious lol. Can you please include your reply as a test comment to help a $FUTURE_READER not have to find this PR to understand the context?

Also it might help if you do something like let clang_version = clang().arg("-v").run(); and then print that to double-check what clang version CI has.

Okay this is very funny
00000000000677a4 <test::main>: 677a4: d503233f paciasp 677a8: d50323bf autiasp 677ac: d65f03c0 ret
The test fails because the compiler optimises away the entire call to foo and its pac instructions along with it. I'll fix it..

Right... That can explain it lol. black_box to the rescue.

bors · 2024-11-15T09:18:30Z

⌛ Trying commit ab13be7 with merge bc93078...

…-merge, r=<try> tests: Test pac-ret flag merging on clang with LTO Extend the test for pac-ret with clang and LTO by checking that different branch protection flags are preserved after the LTO step. There was an issue in older LLVM versions that was causing this to behave incorrectly. try-job: aarch64-gnu-debug

bors · 2024-11-15T10:24:15Z

💔 Test failed - checks-actions

Extend the test for pac-ret with clang and LTO by checking that different branch protection flags are preserved after the LTO step. There was an issue in older LLVM versions that was causing this to behave incorrectly. Tests the LLVM behaviour added in: llvm/llvm-project@1782810

mrkajetanp · 2024-11-15T14:48:35Z

Dropping that opt flag makes it work for me, could you have bors try it again?

jieyouxu · 2024-11-15T15:05:07Z

Sure. @bors try

bors · 2024-11-15T15:11:30Z

⌛ Trying commit 194471c with merge 9002bfd...

…-merge, r=<try> tests: Test pac-ret flag merging on clang with LTO Extend the test for pac-ret with clang and LTO by checking that different branch protection flags are preserved after the LTO step. There was an issue in older LLVM versions that was causing this to behave incorrectly. try-job: aarch64-gnu-debug

bors · 2024-11-15T16:26:33Z

☀️ Try build successful - checks-actions
Build commit: 9002bfd (9002bfd553268869bd638084c35ca9946b301b7f)

jieyouxu

So it turns out not optimizing out the function that we want to check makes it easier to test for assembly inside said function 😆. Thanks!

jieyouxu · 2024-11-15T16:32:41Z

@bors r+ rollup (only runs in one CI job that was tested here).

bors · 2024-11-15T16:32:45Z

📌 Commit 194471c has been approved by jieyouxu

It is now in the queue for this repository.

…iaskrgr Rollup of 4 pull requests Successful merges: - rust-lang#132817 (Recurse into APITs in `impl_trait_overcaptures`) - rust-lang#133021 (Refactor `configure_annotatable`) - rust-lang#133045 (tests: Test pac-ret flag merging on clang with LTO) - rust-lang#133049 (Change Visitor::visit_precise_capturing_arg so it returns a Visitor::Result) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#133045 - mrkajetanp:pauth-test-clang-lto-flag-merge, r=jieyouxu tests: Test pac-ret flag merging on clang with LTO Extend the test for pac-ret with clang and LTO by checking that different branch protection flags are preserved after the LTO step. There was an issue in older LLVM versions that was causing this to behave incorrectly. try-job: aarch64-gnu-debug

rustbot assigned jieyouxu Nov 14, 2024

rustbot added A-run-make Area: port run-make Makefiles to rmake.rs S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 14, 2024

jieyouxu reviewed Nov 15, 2024
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bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 15, 2024

mrkajetanp force-pushed the pauth-test-clang-lto-flag-merge branch from ab13be7 to 194471cCompare November 15, 2024 14:47

jieyouxu approved these changes Nov 15, 2024
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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 15, 2024

matthiaskrgr mentioned this pull request Nov 15, 2024
Rollup of 4 pull requests #133079
Merged

bors merged commit 249a910 into rust-lang:masterNov 15, 2024

rustbot added this to the 1.84.0 milestone Nov 15, 2024

davidtwco mentioned this pull request Mar 25, 2026
Tracking Issue for stabilisation of -Z branch-protection#113369
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mrkajetanp commented Nov 14, 2024•
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