all: support netbsd/arm64

[coypoop]

Tracking progress of netbsd/arm64 support:

#29398 adds support, not completely functional.
A simple program (hello world) runs, getting further and trying to build Go itself fails.

[gopherbot]

Change https://golang.org/cl/155739 mentions this issue: all: add netbsd/arm64 support

[bradfitz]

What's the plan for a builder?

See https://golang.org/wiki/PortingPolicy

[bsiegert]

We can run a builder on Scaleway, with the caveat that there needs to be a working builder binary first :)

Otherwise, I could contribute a builder on real hardware; I have an arm64 machine running NetBSD.

[bradfitz]

We can run a builder on Scaleway, with the caveat that there needs to be a working builder binary first :)

Oh, does NetBSD boot on Scaleway ARM64 instances? I never had much luck with non-Linux OSes on Scaleway.

[coypoop]

I can see two problems,

(1) By code inspection, nothing seems to set TLS.
netbsd/amd64 does it with a lwp_setprivate(m->tls) syscall in lwp_tramp.
I am new to TLS so I want to see effects to my changes so I am holding onto that change until I see it affecting something.

(2) broken signal handling. if I send SIGINFO (^T), it usually segfaults,

Thread 3 received signal SIGSEGV, Segmentation fault.
0x000000000004e2b4 in runtime.sigtrampgo (sig=<optimized out>, info=0x4000449bd0, ctx=0x4000449c50) at /home/fly/go/src/runtime/signal_unix.go:307
307             if sp < g.m.gsignal.stack.lo || sp >= g.m.gsignal.stack.hi {
(gdb) bt
#0  0x000000000004e2b4 in runtime.sigtrampgo (sig=<optimized out>, info=0x4000449bd0, ctx=0x4000449c50) at /home/fly/go/src/runtime/signal_unix.go:307
#1  0x00000000000640ec in runtime.sigtramp () at /home/fly/go/src/runtime/sys_netbsd_arm64.s:297
#2  0x0000000000064060 in runtime.sigprocmask () at /home/fly/go/src/runtime/sys_netbsd_arm64.s:253
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

here g.m=NULL. I guess g is invalid.

The code for that is the runtime.sig* functions. It's probably just wrong and not exercised by other things.

[coypoop]

../cmd/vet/all/whitelist/darwin_arm.txt
5:runtime/asm_arm.s: [arm] sigreturn: function sigreturn missing Go declaration
../cmd/vet/all/whitelist/darwin_arm64.txt
3:runtime/asm_arm64.s: [arm64] sigreturn: function sigreturn missing Go declaration
../cmd/vet/all/whitelist/freebsd_arm.txt
3:runtime/asm_arm.s: [arm] sigreturn: function sigreturn missing Go declaration

let's just move this to linux?

made #31583 for this

[bsiegert]

One nit (sorry): In all the added files, can you please make the headers say "Copyright 2019"? Thanks! -- Benny

[gopherbot]

Change https://golang.org/cl/174078 mentions this issue: runtime: gofmt defs1_netbsd_arm64.go