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runtime: c-shared builds fail to load with dlopen with musllibc: initial-exec TLS resolves to dynamic definition #54805

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charleskorn opened this issue Sep 1, 2022 · 4 comments
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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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@charleskorn
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charleskorn commented Sep 1, 2022

Splitting out from #13492:

@ansiwen's comment:

For what it's worth, compiled with -buildmode=c-shared I get:

sc_dlopen failed: Error relocating ./foobar.so: (null): initial-exec TLS resolves to dynamic definition in ./foobar.so

with

$ go version
go version go1.17.5 linux/amd64
$ cat /etc/alpine-release 
3.15.0
$ apk version musl
Installed:                                Available:
musl-1.2.2-r7                           = 1.2.2-r7 

I am still seeing a similar issue today with Go 1.19.

@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Sep 1, 2022
@heschi
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heschi commented Sep 1, 2022

cc @golang/runtime

@heschi heschi added the NeedsFix The path to resolution is known, but the work has not been done. label Sep 1, 2022
@heschi heschi added this to the Backlog milestone Sep 1, 2022
@mknyszek
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mknyszek commented Sep 1, 2022

I suspect this is more compiler related (based on the other thread), so CC @golang/compiler

@charleskorn
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charleskorn commented Sep 9, 2022

@mknyszek I see you've added the help wanted label. I've never done any work in the Golang runtime or compiler, but I'm happy to have a go at fixing this if someone can give me some pointers on where to start and a reasonable approach to take - is this something you can help me with?

@richfelker
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richfelker commented Sep 21, 2022

This is happening because go is producing shared libraries with initial-exec accesses to TLS objects defined in them. As the name implies, the initial-exec access model is only valid for accessing TLS objects present at initial exec time, not ones dynamically loaded later. So shared libraries can use it only if they are loaded at program load time as a dependency or via LD_PRELOAD, not if they will be loaded (directly or indirectly as dependencies) via dlopen. My understanding is that the golang compiler does not yet implement the dynamic TLS access models, so if that's still the case, fixing this bug depends on implementing that.

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Labels
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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@mknyszek @charleskorn @gopherbot @richfelker @heschi and others