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-Zharden-sls flag (target modifier) added to enable mitigation against straight line speculation (SLS) #136597

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@azhogin azhogin commented Feb 5, 2025 •
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Flag (target modifier) to mitigate against straight line speculation (SLS).
-Zharden-sls=[none|all|return|indirect-jmp].

The flag enables the related features: +harden-sls-ijmp,+harden-sls-ret.
The flag is tracked as a target modifier to be equal between linked crates.

Tracking issue: #116851

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rustbot commented Feb 5, 2025

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@rustbot 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 Feb 5, 2025
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@azhogin azhogin mentioned this pull request Feb 13, 2025
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@Darksonn Darksonn mentioned this pull request Feb 13, 2025
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@ojeda ojeda mentioned this pull request Feb 13, 2025
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@azhogin azhogin marked this pull request as ready for review February 25, 2025 17:35
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rustbot commented Feb 25, 2025

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

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klensy commented Feb 25, 2025

First commit adds retpoline feature, but PR descriptions says about sls.

@azhogin azhogin marked this pull request as draft February 25, 2025 18:23
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azhogin commented Feb 25, 2025

First commit adds retpoline feature, but PR descriptions says about sls.

Yes, first commit is in another PR #135927.
This one depends on.

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Marking this as blocked on #135927

@Dylan-DPC Dylan-DPC added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 22, 2025
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I filed an MCP for this flag: rust-lang/compiler-team#869

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bors commented May 18, 2025

☔ The latest upstream changes (presumably #141232) made this pull request unmergeable. Please resolve the merge conflicts.

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tests/ui/target-feature/retpoline-target-feature-flag.by_feature.stderr
Comment on lines 1 to 6
warning: target feature `retpoline-external-thunk` cannot be enabled with `-Ctarget-feature`: use `x86-retpoline` target modifier flag instead
|
= note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>

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Why is this possible at all?

tests/ui/target-feature/harden-sls-target-feature-flag.rs
//@ compile-flags: --target=x86_64-unknown-linux-gnu --crate-type=lib
//@ needs-llvm-components: x86
//@ [by_flag]compile-flags: -Zharden-sls=all
//@ [by_feature]compile-flags: -Ctarget-feature=+harden-sls-ijmp,+harden-sls-ret
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These should not be set by -Ctarget-feature.

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@azhogin it would be great if we could make these hard errors now instead of an FCW

@workingjubilee workingjubilee self-assigned this Jun 14, 2025
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ojeda commented Jul 16, 2025 •
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@azhogin Since #135927 is merged now, should this be rebased and unblocked now?

Thanks!

@Darksonn Darksonn added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-blocked Status: Blocked on something else such as an RFC or other implementation work. labels Jul 16, 2025
@rustbot rustbot added the A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. label Jul 20, 2025
@azhogin azhogin marked this pull request as ready for review July 20, 2025 11:25
@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 20, 2025
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rustbot commented Jul 20, 2025

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

@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 20, 2025
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azhogin commented Jul 20, 2025

Converted to "Ready for review" because retpoline PR was merged.

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Adding myself to review as part of the RfL project goal I signed up for 🙂

r? wesleywiser

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ojeda commented Aug 21, 2025

Thanks Wesley! Much appreciated.

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ojeda commented Aug 22, 2025

By the way, @azhogin, I think we should have an assembly test for this one too, even if small/trivial, to double-check LLVM is actually doing something, like in the other flags.

(Another rebase is needed, given the recent renaming of the folders)

Thanks!

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rustbot commented Aug 27, 2025

This PR was rebased onto a different master 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.

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azhogin commented Aug 27, 2025

By the way, @azhogin, I think we should have an assembly test for this one too, even if small/trivial, to double-check LLVM is actually doing something, like in the other flags.

(Another rebase is needed, given the recent renaming of the folders)

Thanks!

Added tests/assembly-llvm/x86_64-sls.rs test for x86 asm codegen

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ojeda commented Aug 27, 2025

Added tests/assembly-llvm/x86_64-sls.rs test for x86 asm codegen

Thanks!

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@wesleywiser wesleywiser 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 Oct 15, 2025
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