cmd/compile/internal/ssa: SIGSEGV building 1.16 toolchain2 on openbsd/mips64

[fuhry]

===>  Building for go-1.16
Building Go cmd/dist using /usr/ports/pobj/go-1.16/go-openbsd-mips64-bootstrap. (go1.16 openbsd/mips64)
Building Go toolchain1 using /usr/ports/pobj/go-1.16/go-openbsd-mips64-bootstrap.
Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1.
Building Go toolchain2 using go_bootstrap and Go toolchain1.
# cmd/compile/internal/ssa
unexpected fault address 0xc00b209d87
fatal error: fault
[signal SIGSEGV: segmentation violation code=0x2 addr=0xc00b209d87 pc=0x19e78]

goroutine 1 [running]:
runtime.throw(0x610916, 0x5)
        /usr/local/go/src/runtime/panic.go:1117 +0x6c fp=0xc00b206a08 sp=0xc00b2069e0 pc=0x50c34
runtime.sigpanic()
        /usr/local/go/src/runtime/signal_unix.go:741 +0x368 fp=0xc00b206a38 sp=0xc00b206a08 pc=0x6e3d8
runtime.readUnaligned64(...)
        /usr/local/go/src/runtime/alg.go:366
runtime.memhashFallback(0xc00b209d80, 0x91e36743, 0x1f, 0x1)
        /usr/local/go/src/runtime/hash64.go:43 +0x308 fp=0xc00b206a40 sp=0xc00b206a40 pc=0x19e78
runtime.strhashFallback(0xc00b581888, 0x91e36743, 0xc00b5818f0)
        /usr/local/go/src/runtime/alg.go:54 +0x50 fp=0xc00b206a68 sp=0xc00b206a40 pc=0x12858
runtime.evacuate_faststr(0x5abec0, 0xc00006ee10, 0x1e)
        /usr/local/go/src/runtime/map_faststr.go:437 +0x308 fp=0xc00b206b10 sp=0xc00b206a68 pc=0x26d78
runtime.growWork_faststr(0x5abec0, 0xc00006ee10, 0x41e)
        /usr/local/go/src/runtime/map_faststr.go:390 +0x8c fp=0xc00b206b30 sp=0xc00b206b10 pc=0x26a1c
runtime.mapassign_faststr(0x5abec0, 0xc00006ee10, 0xc0108dc7e0, 0x19, 0x98f560)
        /usr/local/go/src/runtime/map_faststr.go:226 +0x434 fp=0xc00b206b90 sp=0xc00b206b30 pc=0x2689c
bootstrap/cmd/internal/obj.(*Link).LookupInit(0xc0003bc000, 0xc0108dc7e0, 0x19, 0xc00b206c08, 0x48f158)
        /usr/ports/pobj/go-1.16/go/src/cmd/internal/obj/sym.go:128 +0x128 fp=0xc00b206bd0 sp=0xc00b206b90 pc=0x13f698
bootstrap/cmd/compile/internal/types.(*Sym).Linksym(0xc0108e4540, 0xc0108e4540)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/types/sym.go:94 +0xec fp=0xc00b206c18 sp=0xc00b206bd0 pc=0x14aea4
bootstrap/cmd/compile/internal/gc.dtypesym(0xc0108802a0, 0xc0108dbc80)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:1152 +0x84 fp=0xc00b206dd0 sp=0xc00b206c18 pc=0x48f16c
bootstrap/cmd/compile/internal/gc.dextratype(0xc0107dfa00, 0x38, 0xc0099efb00, 0x0, 0x38)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:660 +0xe0 fp=0xc00b206e80 sp=0xc00b206dd0 pc=0x48cb60
bootstrap/cmd/compile/internal/gc.dtypesym(0xc0099efb00, 0xc0099efb00)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:1352 +0x98c fp=0xc00b207038 sp=0xc00b206e80 pc=0x48fa74
bootstrap/cmd/compile/internal/gc.dtypesym(0xc0099efb60, 0xc010730f00)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:1210 +0x9c0 fp=0xc00b2071f0 sp=0xc00b207038 pc=0x48faa8
bootstrap/cmd/compile/internal/gc.dtypesym(0xc0099ef980, 0xc0099ef980)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:1359 +0xbe0 fp=0xc00b2073a8 sp=0xc00b2071f0 pc=0x48fcc8
bootstrap/cmd/compile/internal/gc.dtypesym(0xc0099f64e0, 0xc0001707e0)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:1199 +0xa50 fp=0xc00b207560 sp=0xc00b2073a8 pc=0x48fb38
bootstrap/cmd/compile/internal/gc.dtypesym(0xc0099f6420, 0xc0099f6420)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:1359 +0xbe0 fp=0xc00b207718 sp=0xc00b207560 pc=0x48fcc8
bootstrap/cmd/compile/internal/gc.dtypesym(0xc0099fb560, 0xc0107c4080)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:1348 +0x924 fp=0xc00b2078d0 sp=0xc00b207718 pc=0x48fa0c
bootstrap/cmd/compile/internal/gc.dtypesym(0xc010745bc0, 0x10000c000ecbc40)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/reflect.go:1359 +0xbe0 fp=0xc00b207a88 sp=0xc00b2078d0 pc=0x48fcc8
bootstrap/cmd/compile/internal/gc.compile(0xc00122e160)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/pgen.go:266 +0x31c fp=0xc00b207b00 sp=0xc00b207a88 pc=0x476824
bootstrap/cmd/compile/internal/gc.funccompile(0xc00122e160)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/pgen.go:220 +0x114 fp=0xc00b207b50 sp=0xc00b207b00 pc=0x4763bc
bootstrap/cmd/compile/internal/gc.Main(0x63e7e8)
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/internal/gc/main.go:762 +0x2f90 fp=0xc00b207f10 sp=0xc00b207b50 pc=0x4504b0
main.main()
        /usr/ports/pobj/go-1.16/go/src/cmd/compile/main.go:52 +0xc0 fp=0xc00b207f80 sp=0xc00b207f10 pc=0x56ea88
runtime.main()
        /usr/local/go/src/runtime/proc.go:225 +0x30c fp=0xc00b207fd8 sp=0xc00b207f80 pc=0x53be4
runtime.goexit()
        /usr/local/go/src/runtime/asm_mips64x.s:631 +0x4 fp=0xc00b207fd8 sp=0xc00b207fd8 pc=0x904b4
go tool dist: FAILED: /usr/ports/pobj/go-1.16/go/pkg/tool/openbsd_mips64/go_bootstrap install -gcflags=all= -ldflags=all= -i cmd/asm cmd/cgo cmd/compile cmd/link: exit status 2
*** Error 2 in . (Makefile:101 'do-build': @cd /usr/ports/pobj/go-1.16/go/src &&  ulimit -d $(ulimit -H -d) &&  /usr/bin/env -i GO386=387 PO...)
*** Error 2 in . (/usr/ports/infrastructure/mk/bsd.port.mk:2921 '/usr/ports/pobj/go-1.16/build-mips64/.build_done': @cd /usr/ports/lang/go &...)
*** Error 2 in /usr/ports/lang/go (/usr/ports/infrastructure/mk/bsd.port.mk:2584 'build': @lock=go-1.16;  export _LOCKS_HELD=" go-1.16";   /...)

Caveat: this is a seriously underpowered octeon (mips64) machine with only 512MB of RAM and 2 cores.

I cross built a mips64 go1.16 bootstrap toolchain on an amd64 system without issues, and modified the port to use this bootstrap.

cc @4a6f656c (maintainer of openbsd lang/go port)

[randall77]

Can you disassemble the compiler and see what instruction caused that fault? The address it faulted on looks ok.

Are there any issues with unaligned reads on your machine?

[4a6f656c]

OpenBSD on mips64 is a strict alignment architecture, however that should not be the issue here - runtime.memhashFallback (which has runtime.readUnaligned64 inlined) uses lbu instructions. For what it is worth, I do not see the issue on an Octeon machine here (which runs the openbsd-mips64 builder for https://build.golang.org/). Does it always fail with the same traceback?

[gopherbot]

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)