x/tools/go/analysis/passes/asmdecl: allow syscall write registers implicitly

[mengzhuo]

Go version

master

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/root/.cache/go-build'
GOENV='/root/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/root/go/pkg/mod'
GONOPROXY=''
GONOSUMDB='*'
GOOS='linux'
GOPATH='/root/go'
GOPRIVATE=''
GOPROXY='https://goproxy.cn,direct'
GOROOT='/root/godev'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/root/godev/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='devel go1.24-2707d42966 Thu Sep 5 01:59:23 2024 +0000'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/root/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build1468563689=/tmp/go-build -gno-record-gcc-switches'

What did you do?

Consider compile this fucntion with syscall only src/runtime/sys_linux_riscv64.s

 // func rtsigprocmask(how int32, new, old *sigset, size int32)
-TEXT runtime·rtsigprocmask(SB),NOSPLIT|NOFRAME,$0-28
-       MOVW    how+0(FP), A0
-       MOV     new+8(FP), A1
-       MOV     old+16(FP), A2
-       MOVW    size+24(FP), A3
+TEXT runtime·rtsigprocmask<ABIInternal>(SB),NOSPLIT|NOFRAME,$0
        MOV     $SYS_rt_sigprocmask, A7
        ECALL
        MOV     $-4096, T0

What did you see happen?

./sys_linux_riscv64.s:395:1: [riscv64] rt_sigaction: RET without writing to result register

What did you expect to see?

Build complete.

ECALL changed A0 (result register)
I think we should allow all syscall that changed result register implicitly.

[gabyhelp]

Related Issues and Documentation

• syscall: ptrace weird behaviour #50920 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[gopherbot]

Change https://go.dev/cl/611815 mentions this issue: go/analysis/passes/asmdecl: allow syscall write registers implicitly

[timothy-king]

CC @golang/compiler, @cherrymui as cmd/asm owners.

This seems like the relevant expertise to me.