Clean up SGX user memory copies #101150

jethrogb · 2022-08-29T09:28:14Z

library/std/src/sys/sgx/abi/usercalls/alloc.rs

raoulstrackx · 2022-08-29T11:04:17Z

LGTM

bors · 2022-09-24T17:29:03Z

☔ The latest upstream changes (presumably #102234) made this pull request unmergeable. Please resolve the merge conflicts.

cuviper · 2023-01-03T18:04:39Z

Sorry for the review delay, I'll try to get back to this, but can you rebase to resolve conflicts?

@rustbot label -S-waiting-on-review +S-waiting-on-author

Dylan-DPC · 2023-05-15T13:51:29Z

@jethrogb can you rebase the conflicts? we can try and push this forward after that. Thanks

rustbot · 2023-05-16T11:05:24Z

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

Stabilizing library features
Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
Changing public documentation in ways that create new stability guarantees
Changing observable runtime behavior of library APIs

workingjubilee

Is this trying for the micro-opts? That's understandable if this is called in a hot loop, of course (and it already risks maybe-painful deoptimization hits from the asm! in the middle), but then it might as well go "all the way".

workingjubilee · 2023-07-30T04:34:57Z

library/std/src/sys/sgx/abi/usercalls/alloc.rs

+/// Like `<[u8]>::align_to::<u64>`, but the the prefix and suffix are guaranteed not
+/// to straddle an alignment boundary.


It's a bit confusing to say "like align_to" if it gives some lengths instead, but somewhat understandable. However, "guaranteed not to straddle an alignment boundary" makes things even less clear since the alignment of the prefix and suffix is naturally bytes, thus 1. Yes I know the u64 will have some alignment higher than that, that's why I think this shouldn't be coy about the differences and instead just spell it out as plainly as possible.

I believe what you mean is that the first length is guaranteed to be less than mem::align_of::<u64>(), the middle length is the exact number of u64s available, and the last length is guaranteed to be less than mem::size_of::<u64>(), yes?

Updated doc comment

workingjubilee · 2023-07-30T04:51:22Z

library/std/src/sys/sgx/abi/usercalls/alloc.rs

+    const QWORD_SIZE: usize = mem::size_of::<u64>();
+
+    let offset = ptr as usize % QWORD_SIZE;
+
+    let prefix_len = if intrinsics::unlikely(offset > 0) { QWORD_SIZE - offset } else { 0 };


It's somewhat challenging to audit this code for correctness if it's handrolling is_aligned_to and the like. Is there a justification for this being written this way? If there is, it would be good to leave a comment here, so some helpful Rustacean doesn't open a PR to "clean it up".

Added comment

Thank you.

I feel like this pattern should be a stdlib function, to be honest, given how often I see it, but this is hardly the time or place to start hashing out new public API for core::ptr.

library/std/src/sys/sgx/abi/usercalls/alloc.rs

jethrogb

Is this trying for the micro-opts?

No, this is mainly trying to simplify the existing code to aid understanding and maintainability.

jethrogb · 2023-07-31T11:22:24Z

library/std/src/sys/sgx/abi/usercalls/alloc.rs

+/// Like `<[u8]>::align_to::<u64>`, but the the prefix and suffix are guaranteed not
+/// to straddle an alignment boundary.


Updated doc comment

jethrogb · 2023-07-31T11:22:32Z

library/std/src/sys/sgx/abi/usercalls/alloc.rs

+    const QWORD_SIZE: usize = mem::size_of::<u64>();
+
+    let offset = ptr as usize % QWORD_SIZE;
+
+    let prefix_len = if intrinsics::unlikely(offset > 0) { QWORD_SIZE - offset } else { 0 };


Added comment

library/std/src/sys/sgx/abi/usercalls/alloc.rs

workingjubilee · 2023-10-06T00:04:27Z

Thank you for adding the comments. This looks right to me.

@bors r+

bors · 2023-10-06T00:04:29Z

📌 Commit 905f49a has been approved by workingjubilee

It is now in the queue for this repository.

workingjubilee · 2023-10-06T00:12:09Z

library/std/src/sys/sgx/abi/usercalls/alloc.rs

+            let mut data = mem::MaybeUninit::uninit();
+            copy_from_userspace(self.0.get() as _, data.as_mut_ptr() as _, mem::size_of::<T>());
+            data.assume_init()


This alone is a necessary improvement.

bors · 2023-10-06T01:50:14Z

⌛ Testing commit 905f49a with merge 579be69...

bors · 2023-10-06T03:38:15Z

☀️ Test successful - checks-actions
Approved by: workingjubilee
Pushing 579be69 to master...

rust-timer · 2023-10-06T06:49:43Z

Finished benchmarking commit (579be69): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	5.1%	[5.1%, 5.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	1
All ❌✅ (primary)	5.1%	[5.1%, 5.1%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 624.256s -> 623.044s (-0.19%)
Artifact size: 270.63 MiB -> 270.64 MiB (0.00%)

rust-highfive assigned cuviper Aug 29, 2022

rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Aug 29, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 29, 2022

raoulstrackx reviewed Aug 29, 2022

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library/std/src/sys/sgx/abi/usercalls/alloc.rs Show resolved Hide resolved

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jethrogb force-pushed the jb/cleanup-sgx-user-memory-copies branch from 8f12d89 to 739d542 Compare August 29, 2022 10:03

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 Jan 3, 2023

raoulstrackx force-pushed the jb/cleanup-sgx-user-memory-copies branch from 739d542 to 13d72eb Compare May 16, 2023 11:05

Dylan-DPC 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 May 16, 2023

workingjubilee added the O-SGX Target: SGX label Jul 30, 2023

workingjubilee reviewed Jul 30, 2023

View reviewed changes

Clean up SGX user memory copies

905f49a

jethrogb force-pushed the jb/cleanup-sgx-user-memory-copies branch from 13d72eb to 905f49a Compare July 31, 2023 11:22

jethrogb commented Jul 31, 2023

View reviewed changes

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 Oct 6, 2023

workingjubilee reviewed Oct 6, 2023

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bors added the merged-by-bors This PR was explicitly merged by bors. label Oct 6, 2023

bors merged commit 579be69 into rust-lang:master Oct 6, 2023
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rustbot added this to the 1.75.0 milestone Oct 6, 2023

pvdrz mentioned this pull request Oct 6, 2023

Fix divergence from upstream master ferrocene/ferrocene#23

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Clean up SGX user memory copies #101150

Clean up SGX user memory copies #101150

jethrogb commented Aug 29, 2022

raoulstrackx commented Aug 29, 2022

bors commented Sep 24, 2022

cuviper commented Jan 3, 2023

Dylan-DPC commented May 15, 2023

rustbot commented May 16, 2023

workingjubilee left a comment

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rust-timer commented Oct 6, 2023

		/// Like `<[u8]>::align_to::<u64>`, but the the prefix and suffix are guaranteed not
		/// to straddle an alignment boundary.

Clean up SGX user memory copies #101150

Clean up SGX user memory copies #101150

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jethrogb commented Aug 29, 2022

raoulstrackx commented Aug 29, 2022

bors commented Sep 24, 2022

cuviper commented Jan 3, 2023

Dylan-DPC commented May 15, 2023

rustbot commented May 16, 2023

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workingjubilee commented Oct 6, 2023

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rust-timer commented Oct 6, 2023

Overall result: no relevant changes - no action needed

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