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runtime: openbsd/arm fails when compiled with GOARM=5 #54305

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4a6f656c opened this issue Aug 5, 2022 · 2 comments
Open

runtime: openbsd/arm fails when compiled with GOARM=5 #54305

4a6f656c opened this issue Aug 5, 2022 · 2 comments
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@4a6f656c
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arch-arm Issues solely affecting the 32-bit arm architecture. compiler/runtime Issues related to the Go compiler and/or runtime. help wanted NeedsFix The path to resolution is known, but the work has not been done.
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@4a6f656c
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4a6f656c commented Aug 5, 2022

When the arm architecture is compiled with GOARM=5, the linker rewrites TLS register loads from MRC with a call to runtime.read_tls_fallback - on OpenBSD post 6.9, this fails since runtime.read_tls_fallback is still a direct system call:

https://github.com/golang/go/blob/master/src/runtime/sys_openbsd_arm.s#L90

This code path is generally never hit, since the minimum ARM CPU supported by OpenBSD is v7 and hence GOARM=7 is the default.

We should either:

  1. Revise runtime.read_tls_fallback to use a libc-based system call.

  2. Prevent GOARM < 7 from being used on openbsd/arm and remove the fallback code entirely.
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Aug 5, 2022
@seankhliao seankhliao added NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. arch-arm Issues solely affecting the 32-bit arm architecture. labels Aug 5, 2022
@cherrymui
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I think we only support GOARM=5 on Linux. On other OSes we only support GOARM=6 or 7.

I think it is okay to have a check with better error message (and remove fallback code). Thanks.

@cherrymui cherrymui added this to the Backlog milestone Aug 8, 2022
@dmitshur dmitshur added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. labels Aug 8, 2022
@4a6f656c 4a6f656c self-assigned this Aug 9, 2022
@gopherbot
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Change https://go.dev/cl/443276 mentions this issue: cmd/dist,internal/buildcfg,runtime: only allow GOARM=7 for openbsd/arm

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@4a6f656c 4a6f656c

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arch-arm Issues solely affecting the 32-bit arm architecture. compiler/runtime Issues related to the Go compiler and/or runtime. help wanted NeedsFix The path to resolution is known, but the work has not been done.
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Go Compiler / Runtime
Status: Todo
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Backlog
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@dmitshur @4a6f656c @gopherbot @seankhliao @cherrymui