Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

cmd/compile: R12 can be clobbered for write barrier call on PPC64 [1.15 backport] #40868

Closed
gopherbot opened this issue Aug 18, 2020 · 4 comments
Closed

cmd/compile: R12 can be clobbered for write barrier call on PPC64 [1.15 backport] #40868

gopherbot opened this issue Aug 18, 2020 · 4 comments
Labels
CherryPickApproved Used during the release process for point releases FrozenDueToAge
Milestone
Go1.15.2

Comments

@gopherbot
Copy link
Contributor

@cherrymui requested issue #40851 to be considered for backport to the next 1.15 minor release.

@gopherbot please consider backporting this to Go 1.15. Thanks.
@gopherbot gopherbot added the CherryPickCandidate Used during the release process for point releases label Aug 18, 2020
@gopherbot gopherbot mentioned this issue Aug 18, 2020
Closed
@gopherbot gopherbot added this to the Go1.15.1 milestone Aug 18, 2020
@cherrymui
Copy link
Member

(Copied from the original issue)
I think we may want to back port, as this could cause runtime crash or data corruption without workaround.

@gopherbot
Copy link
Contributor Author

Change https://golang.org/cl/249019 mentions this issue: [release-branch.go1.15] cmd/compile, runtime: mark R12 clobbered for write barrier call on PPC64

@dmitshur dmitshur modified the milestones: Go1.15.1, Go1.15.2 Sep 1, 2020
@dmitshur
Copy link
Contributor

dmitshur commented Sep 2, 2020

Approving per discussion in a release meeting. This backport applies to both 1.15 (this issue) and 1.14 (#40938).

@dmitshur dmitshur mentioned this issue Sep 2, 2020
Closed
@dmitshur dmitshur added CherryPickApproved Used during the release process for point releases and removed CherryPickCandidate Used during the release process for point releases labels Sep 2, 2020
@gopherbot
Copy link
Contributor Author

Closed by merging f50cde9 to release-branch.go1.15.

gopherbot pushed a commit that referenced this issue Sep 3, 2020
@cherrymui @dmitshur
[release-branch.go1.15] cmd/compile, runtime: mark R12 clobbered for …
f50cde9 
…write barrier call on PPC64

When external linking, for large binaries, the external linker
may insert a trampoline for the write barrier call, which looks

0000000005a98cc8 <__long_branch_runtime.gcWriteBarrier>:
 5a98cc8:       86 01 82 3d     addis   r12,r2,390
 5a98ccc:       d8 bd 8c e9     ld      r12,-16936(r12)
 5a98cd0:       a6 03 89 7d     mtctr   r12
 5a98cd4:       20 04 80 4e     bctr

It clobbers R12 (and CTR, which is never live across a call).

As at compile time we don't know whether the binary is big and
what link mode will be used, I think we need to mark R12 as
clobbered for write barrier call. For extra safety (future-proof)
we mark caller-saved register that cannot be used for function
arguments, which includes R11, as potentially clobbered as well.

Updates #40851.
Fixes #40868.

Change-Id: Iedd901c5072f1127cc59b0a48cfeb4aaec81b519
Reviewed-on: https://go-review.googlesource.com/c/go/+/248917
Run-TryBot: Cherry Zhang <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
(cherry picked from commit b58d297)
Reviewed-on: https://go-review.googlesource.com/c/go/+/249019
claucece pushed a commit to claucece/go that referenced this issue Oct 22, 2020
@cherrymui @claucece
[release-branch.go1.15] cmd/compile, runtime: mark R12 clobbered for …
d22de4b 
…write barrier call on PPC64

When external linking, for large binaries, the external linker
may insert a trampoline for the write barrier call, which looks

0000000005a98cc8 <__long_branch_runtime.gcWriteBarrier>:
 5a98cc8:       86 01 82 3d     addis   r12,r2,390
 5a98ccc:       d8 bd 8c e9     ld      r12,-16936(r12)
 5a98cd0:       a6 03 89 7d     mtctr   r12
 5a98cd4:       20 04 80 4e     bctr

It clobbers R12 (and CTR, which is never live across a call).

As at compile time we don't know whether the binary is big and
what link mode will be used, I think we need to mark R12 as
clobbered for write barrier call. For extra safety (future-proof)
we mark caller-saved register that cannot be used for function
arguments, which includes R11, as potentially clobbered as well.

Updates golang#40851.
Fixes golang#40868.

Change-Id: Iedd901c5072f1127cc59b0a48cfeb4aaec81b519
Reviewed-on: https://go-review.googlesource.com/c/go/+/248917
Run-TryBot: Cherry Zhang <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
(cherry picked from commit b58d297)
Reviewed-on: https://go-review.googlesource.com/c/go/+/249019
@golang golang locked and limited conversation to collaborators Sep 3, 2021
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
Assignees
No one assigned
Labels
CherryPickApproved Used during the release process for point releases FrozenDueToAge
Projects
None yet
Milestone
Go1.15.2
Development

No branches or pull requests
3 participants
@dmitshur @gopherbot @cherrymui