fix the fragment_in_dst_padding_gets_overwritten test on s390x by fneddy · Pull Request #149056 · rust-lang/rust

fneddy · 2025-11-18T10:44:50Z

on s390x 128bit types have a smaller alignment then on x86¹. This leads to smaller structs (24 instead of 32 bytes) and therefore the write_unaligned will write outside of the structs boundary.

To fix the test, change the trailing u32 into a u8. This will generate 7 trailing padding bytes on s390x and 15 on x86_64. Also change the start of the garbage data so it will span over x,y and padding:

s390x:   XXXXXXXXXXXXXXXXY-------
x86_64:  XXXXXXXXXXXXXXXXY---------------
                      GGGGGGGG

s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi ↩

rustbot · 2025-11-18T10:44:55Z

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fneddy · 2025-11-18T10:49:14Z

tagging @RalfJung who introduced the test in #148259

RalfJung · 2025-11-18T12:58:54Z

Given that what we are testing here is entirely target-independent code (the handling of provenance in the interpreter), I think I'd prefer just skipping the test on s390x over the risk of making the test not test the right thing any more.

RalfJung · 2025-11-18T12:59:57Z

This leads to smaller structs (24 instead of 32 bytes) and therefore the write_unaligned will write outside of the structs boundary.

If you add align(16) to the struct Pair, does that suffice? That should make it 32 bytes large, right?

RalfJung · 2025-11-18T13:03:53Z

Actually never mind that, repr(align) would make this not be a ScalarPair any more.

fneddy · 2025-11-18T13:38:48Z

ok for me. I'll revert the test and disable the test on s390x.

on s390x 128bit types have a smaller alignment then on x86[^1]. This leads to smaller structs and therefore the write_unaligned will write outside of the structs boundary. For now disable the tests on s390x. [^2] [^1]: s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi [^2]: rust-lang#149056 (comment)

tests/ui/consts/const-eval/ptr_fragments.rs

RalfJung · 2025-11-19T08:00:30Z

This looks great, thanks! Please squash the commits, then we can land this. Please use the --keep-base flag when squashing so that the force-push diff is easier to review; do not rebase on the latest master branch. Then write @rustbot ready after you force-pushed the squashed PR.

@rustbot author

rustbot · 2025-11-19T08:00:35Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

on s390x 128bit types have a smaller alignment then on x86[^1]. This leads to smaller structs and therefore the write_unaligned will write outside of the structs boundary. For now disable the tests on s390x. [^2] [^1]: s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi [^2]: rust-lang#149056 (comment) Co-authored-by: Ralf Jung <post@ralfj.de>

fneddy · 2025-11-19T08:50:42Z

@rustbot ready

RalfJung · 2025-11-19T09:05:24Z

Thanks!

@bors r+ rollup

bors · 2025-11-19T09:05:27Z

📌 Commit 10172d1 has been approved by RalfJung

It is now in the queue for this repository.

…rite, r=RalfJung fix the fragment_in_dst_padding_gets_overwritten test on s390x on s390x 128bit types have a smaller alignment then on x86[^1]. This leads to smaller structs (24 instead of 32 bytes) and therefore the write_unaligned will write outside of the structs boundary. To fix the test, change the trailing u32 into a u8. This will generate 7 trailing padding bytes on s390x and 15 on x86_64. Also change the start of the garbage data so it will span over x,y and padding: ``` s390x: XXXXXXXXXXXXXXXXY------- x86_64: XXXXXXXXXXXXXXXXY--------------- GGGGGGGG ``` [^1]: s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi

Rollup of 7 pull requests Successful merges: - #146341 (minimal dirfd implementation (1/4)) - #146925 (Add doc for va_list APIs) - #147035 (alloc: fix `Debug` implementation of `ExtractIf`) - #147173 (Add support for hexagon-unknown-qurt target) - #149041 (ignore unsized types in mips64 and sparc64 callconvs) - #149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - #149095 (rustc-dev-guide subtree update) r? `@ghost` `@rustbot` modify labels: rollup

…rite, r=RalfJung fix the fragment_in_dst_padding_gets_overwritten test on s390x on s390x 128bit types have a smaller alignment then on x86[^1]. This leads to smaller structs (24 instead of 32 bytes) and therefore the write_unaligned will write outside of the structs boundary. To fix the test, change the trailing u32 into a u8. This will generate 7 trailing padding bytes on s390x and 15 on x86_64. Also change the start of the garbage data so it will span over x,y and padding: ``` s390x: XXXXXXXXXXXXXXXXY------- x86_64: XXXXXXXXXXXXXXXXY--------------- GGGGGGGG ``` [^1]: s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi

Rollup of 6 pull requests Successful merges: - #146925 (Add doc for va_list APIs) - #147035 (alloc: fix `Debug` implementation of `ExtractIf`) - #147173 (Add support for hexagon-unknown-qurt target) - #149041 (ignore unsized types in mips64 and sparc64 callconvs) - #149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - #149095 (rustc-dev-guide subtree update) r? `@ghost` `@rustbot` modify labels: rollup

…rite, r=RalfJung fix the fragment_in_dst_padding_gets_overwritten test on s390x on s390x 128bit types have a smaller alignment then on x86[^1]. This leads to smaller structs (24 instead of 32 bytes) and therefore the write_unaligned will write outside of the structs boundary. To fix the test, change the trailing u32 into a u8. This will generate 7 trailing padding bytes on s390x and 15 on x86_64. Also change the start of the garbage data so it will span over x,y and padding: ``` s390x: XXXXXXXXXXXXXXXXY------- x86_64: XXXXXXXXXXXXXXXXY--------------- GGGGGGGG ``` [^1]: s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi

Rollup of 9 pull requests Successful merges: - #146925 (Add doc for va_list APIs) - #147035 (alloc: fix `Debug` implementation of `ExtractIf`) - #147173 (Add support for hexagon-unknown-qurt target) - #148261 (rustc_public: Make Id types !Send / !Sync) - #149041 (ignore unsized types in mips64 and sparc64 callconvs) - #149043 ( rustdoc-json: add rlib path to ExternalCrate to enable robust crate resolution) - #149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - #149095 (rustc-dev-guide subtree update) - #149108 ([AIX][ppc64le-linux-gnu] Add Amy Kwan to target maintainers) r? `@ghost` `@rustbot` modify labels: rollup

…rite, r=RalfJung fix the fragment_in_dst_padding_gets_overwritten test on s390x on s390x 128bit types have a smaller alignment then on x86[^1]. This leads to smaller structs (24 instead of 32 bytes) and therefore the write_unaligned will write outside of the structs boundary. To fix the test, change the trailing u32 into a u8. This will generate 7 trailing padding bytes on s390x and 15 on x86_64. Also change the start of the garbage data so it will span over x,y and padding: ``` s390x: XXXXXXXXXXXXXXXXY------- x86_64: XXXXXXXXXXXXXXXXY--------------- GGGGGGGG ``` [^1]: s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi

Rollup of 10 pull requests Successful merges: - #146925 (Add doc for va_list APIs) - #147035 (alloc: fix `Debug` implementation of `ExtractIf`) - #147173 (Add support for hexagon-unknown-qurt target) - #148261 (rustc_public: Make Id types !Send / !Sync) - #148831 (Bump compiler dependencies) - #149041 (ignore unsized types in mips64 and sparc64 callconvs) - #149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - #149071 (Add test scaffolding for the `remote-test-client`) - #149095 (rustc-dev-guide subtree update) - #149108 ([AIX][ppc64le-linux-gnu] Add Amy Kwan to target maintainers) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 9 pull requests Successful merges: - #146925 (Add doc for va_list APIs) - #147035 (alloc: fix `Debug` implementation of `ExtractIf`) - #147173 (Add support for hexagon-unknown-qurt target) - #148261 (rustc_public: Make Id types !Send / !Sync) - #149041 (ignore unsized types in mips64 and sparc64 callconvs) - #149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - #149071 (Add test scaffolding for the `remote-test-client`) - #149095 (rustc-dev-guide subtree update) - #149108 ([AIX][ppc64le-linux-gnu] Add Amy Kwan to target maintainers) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #149056 - fneddy:fix_s390_test_padding_overwrite, r=RalfJung fix the fragment_in_dst_padding_gets_overwritten test on s390x on s390x 128bit types have a smaller alignment then on x86[^1]. This leads to smaller structs (24 instead of 32 bytes) and therefore the write_unaligned will write outside of the structs boundary. To fix the test, change the trailing u32 into a u8. This will generate 7 trailing padding bytes on s390x and 15 on x86_64. Also change the start of the garbage data so it will span over x,y and padding: ``` s390x: XXXXXXXXXXXXXXXXY------- x86_64: XXXXXXXXXXXXXXXXY--------------- GGGGGGGG ``` [^1]: s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi

Rollup of 9 pull requests Successful merges: - rust-lang/rust#146925 (Add doc for va_list APIs) - rust-lang/rust#147035 (alloc: fix `Debug` implementation of `ExtractIf`) - rust-lang/rust#147173 (Add support for hexagon-unknown-qurt target) - rust-lang/rust#148261 (rustc_public: Make Id types !Send / !Sync) - rust-lang/rust#149041 (ignore unsized types in mips64 and sparc64 callconvs) - rust-lang/rust#149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - rust-lang/rust#149071 (Add test scaffolding for the `remote-test-client`) - rust-lang/rust#149095 (rustc-dev-guide subtree update) - rust-lang/rust#149108 ([AIX][ppc64le-linux-gnu] Add Amy Kwan to target maintainers) r? `@ghost` `@rustbot` modify labels: rollup

…rite, r=RalfJung fix the fragment_in_dst_padding_gets_overwritten test on s390x on s390x 128bit types have a smaller alignment then on x86[^1]. This leads to smaller structs (24 instead of 32 bytes) and therefore the write_unaligned will write outside of the structs boundary. To fix the test, change the trailing u32 into a u8. This will generate 7 trailing padding bytes on s390x and 15 on x86_64. Also change the start of the garbage data so it will span over x,y and padding: ``` s390x: XXXXXXXXXXXXXXXXY------- x86_64: XXXXXXXXXXXXXXXXY--------------- GGGGGGGG ``` [^1]: s390x ELF ABI Table 1.1, Page 12 https://github.com/IBM/s390x-abi

…iaskrgr Rollup of 9 pull requests Successful merges: - rust-lang#146925 (Add doc for va_list APIs) - rust-lang#147035 (alloc: fix `Debug` implementation of `ExtractIf`) - rust-lang#147173 (Add support for hexagon-unknown-qurt target) - rust-lang#148261 (rustc_public: Make Id types !Send / !Sync) - rust-lang#149041 (ignore unsized types in mips64 and sparc64 callconvs) - rust-lang#149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - rust-lang#149071 (Add test scaffolding for the `remote-test-client`) - rust-lang#149095 (rustc-dev-guide subtree update) - rust-lang#149108 ([AIX][ppc64le-linux-gnu] Add Amy Kwan to target maintainers) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 9 pull requests Successful merges: - rust-lang/rust#146925 (Add doc for va_list APIs) - rust-lang/rust#147035 (alloc: fix `Debug` implementation of `ExtractIf`) - rust-lang/rust#147173 (Add support for hexagon-unknown-qurt target) - rust-lang/rust#148261 (rustc_public: Make Id types !Send / !Sync) - rust-lang/rust#149041 (ignore unsized types in mips64 and sparc64 callconvs) - rust-lang/rust#149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - rust-lang/rust#149071 (Add test scaffolding for the `remote-test-client`) - rust-lang/rust#149095 (rustc-dev-guide subtree update) - rust-lang/rust#149108 ([AIX][ppc64le-linux-gnu] Add Amy Kwan to target maintainers) r? `@ghost` `@rustbot` modify labels: rollup

…iaskrgr Rollup of 9 pull requests Successful merges: - rust-lang#146925 (Add doc for va_list APIs) - rust-lang#147035 (alloc: fix `Debug` implementation of `ExtractIf`) - rust-lang#147173 (Add support for hexagon-unknown-qurt target) - rust-lang#148261 (rustc_public: Make Id types !Send / !Sync) - rust-lang#149041 (ignore unsized types in mips64 and sparc64 callconvs) - rust-lang#149056 (fix the fragment_in_dst_padding_gets_overwritten test on s390x) - rust-lang#149071 (Add test scaffolding for the `remote-test-client`) - rust-lang#149095 (rustc-dev-guide subtree update) - rust-lang#149108 ([AIX][ppc64le-linux-gnu] Add Amy Kwan to target maintainers) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned madsmtm Nov 18, 2025

rustbot added 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. labels Nov 18, 2025

fneddy force-pushed the fix_s390_test_padding_overwrite branch from eae45d8 to e58572b Compare November 18, 2025 14:02

RalfJung reviewed Nov 18, 2025

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rustbot 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 19, 2025

fneddy force-pushed the fix_s390_test_padding_overwrite branch from 425b450 to 10172d1 Compare November 19, 2025 08:49

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 Nov 19, 2025

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-review Status: Awaiting review from the assignee but also interested parties. labels Nov 19, 2025

madsmtm assigned RalfJung and unassigned madsmtm Nov 19, 2025

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bors merged commit 5172159 into rust-lang:main Nov 20, 2025
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fix the fragment_in_dst_padding_gets_overwritten test on s390x#149056

fix the fragment_in_dst_padding_gets_overwritten test on s390x#149056
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