Modify go to use Gem5 m5ops: go tool dist displays import message and then exits

php editor Apple is here to introduce to you a method of modifying the Go language to use Gem5 m5ops. Gem5 is a widely used emulator, and m5ops is a set of operating system interfaces in Gem5. By modifying the Go language, we can use Gem5's m5ops interface for performance analysis and debugging. The specific steps are to add support for m5ops to the Go tool chain, and then use the functions provided by m5ops for performance monitoring and debugging operations. In this way, we can better understand how the Go language is running in the simulation environment and perform corresponding optimization and debugging work.

Question content

I am still new to golang.

I'm trying to insert some c function calls (specifically m5ops) into golang's runtime (specifically src/proc.go).

I tried using cgo, which resulted in adding this import to the beginning of proc.go:

// #cgo cflags: -i$(gem5_path)/include -static
// #cgo ldflags: -l$(gem5_path)/util/m5/build/x86/out -lm5
// #include <gem5/m5ops.h>
import "c"

But when I try to rebuild using ./all.bash the script outputs and then exits:

./all.bash
building go cmd/dist using /usr/local/go. (go1.20.5 linux/amd64)
building go toolchain1 using /usr/local/go.
building go bootstrap cmd/go (go_bootstrap) using go toolchain1.
go tool dist: /home/landerx/goroot/src/runtime/proc.go imports c

A more detailed version of the above output:

./all.bash -v
Building Go cmd/dist using /usr/local/go. (go1.20.5 linux/amd64)
cmd/dist

Building Go toolchain1 using /usr/local/go.
internal/goarch
internal/coverage/rtcov
internal/goos
internal/race
internal/unsafeheader
internal/goexperiment
unicode
runtime/internal/syscall
sync/atomic
runtime/internal/atomic
internal/cpu
unicode/utf8
internal/itoa
math/bits
internal/abi
runtime/internal/math
runtime/internal/sys
bootstrap/internal/goarch
bootstrap/internal/goexperiment
bootstrap/math/bits
encoding
bootstrap/internal/unsafeheader
bootstrap/internal/platform
bootstrap/internal/coverage
internal/bytealg
bootstrap/internal/abi
math
unicode/utf16
bootstrap/internal/goversion
internal/goversion
bootstrap/internal/race
bootstrap/cmd/compile/internal/test
runtime
internal/reflectlite
runtime/metrics
sync
internal/testlog
internal/godebug
bootstrap/internal/bisect
math/rand
errors
sort
bootstrap/sort
io
internal/oserror
internal/safefilepath
path
strconv
bootstrap/strconv
syscall
bootstrap/container/heap
hash
text/tabwriter
bytes
strings
hash/adler32
hash/fnv
hash/crc32
crypto
reflect
bootstrap/internal/types/errors
go/build/constraint
bootstrap/go/build/constraint
bufio
regexp/syntax
html
internal/syscall/execenv
internal/syscall/unix
time
regexp
context
io/fs
internal/poll
internal/fmtsort
bootstrap/internal/saferio
encoding/binary
os
bootstrap/cmd/internal/notsha256
encoding/base64
bootstrap/cmd/internal/sys
crypto/md5
bootstrap/internal/lazyregexp
internal/lazyregexp
path/filepath
fmt
os/exec
log
bootstrap/internal/buildcfg
flag
bootstrap/cmd/internal/src
text/scanner
bootstrap/cmd/internal/edit
bootstrap/cmd/internal/pkgpath
go/token
bootstrap/compress/flate
bootstrap/internal/zstd
go/doc/comment
bootstrap/debug/dwarf
encoding/json
runtime/debug
bootstrap/math/big
bootstrap/cmd/internal/bio
net/url
go/scanner
bootstrap/cmd/internal/objabi
bootstrap/cmd/compile/internal/abt
bootstrap/cmd/internal/goobj
bootstrap/cmd/internal/gcprog
bootstrap/cmd/internal/quoted
bootstrap/compress/zlib
encoding/hex
compress/flate
go/ast
internal/buildcfg
internal/goroot
bootstrap/cmd/internal/dwarf
runtime/trace
bootstrap/cmd/internal/archive
bootstrap/cmd/internal/obj
bootstrap/debug/macho
bootstrap/debug/elf
bootstrap/debug/pe
bootstrap/internal/xcoff
bootstrap/cmd/link/internal/dwtest
compress/gzip
bootstrap/internal/profile
runtime/pprof
go/doc
go/printer
go/internal/typeparams
go/parser
bootstrap/cmd/internal/codesign
bootstrap/go/constant
bootstrap/internal/pkgbits
bootstrap/cmd/compile/internal/syntax
bootstrap/cmd/link/internal/benchmark
bootstrap/cmd/compile/internal/pgo/internal/graph
go/build
go/format
bootstrap/cmd/cgo
bootstrap/cmd/internal/obj/loong64
bootstrap/cmd/internal/obj/mips
bootstrap/cmd/internal/obj/wasm
bootstrap/cmd/internal/obj/arm
bootstrap/cmd/internal/obj/arm64
bootstrap/cmd/internal/obj/s390x
bootstrap/cmd/internal/obj/riscv
bootstrap/cmd/internal/obj/ppc64
bootstrap/cmd/internal/obj/x86
bootstrap/cmd/asm/internal/flags
bootstrap/cmd/compile/internal/base
bootstrap/cmd/compile/internal/logopt
bootstrap/cmd/asm/internal/lex
bootstrap/cmd/link/internal/sym
bootstrap/cmd/link/internal/loader
bootstrap/cmd/compile/internal/bitvec
bootstrap/cmd/compile/internal/types
bootstrap/cmd/compile/internal/types2
bootstrap/cmd/link/internal/loadelf
bootstrap/cmd/link/internal/loadmacho
bootstrap/cmd/link/internal/loadpe
bootstrap/cmd/link/internal/loadxcoff
bootstrap/cmd/compile/internal/typebits
bootstrap/cmd/compile/internal/ir
bootstrap/cmd/asm/internal/arch
bootstrap/cmd/link/internal/ld
bootstrap/cmd/asm/internal/asm
bootstrap/cmd/asm
bootstrap/cmd/compile/internal/abi
bootstrap/cmd/compile/internal/deadcode
bootstrap/cmd/compile/internal/typecheck
bootstrap/cmd/compile/internal/objw
bootstrap/cmd/compile/internal/staticdata
bootstrap/cmd/compile/internal/compare
bootstrap/cmd/compile/internal/pgo
bootstrap/cmd/compile/internal/coverage
bootstrap/cmd/compile/internal/loopvar
bootstrap/cmd/compile/internal/importer
bootstrap/cmd/compile/internal/escape
bootstrap/cmd/compile/internal/inline
bootstrap/cmd/compile/internal/reflectdata
bootstrap/cmd/compile/internal/devirtualize
bootstrap/cmd/compile/internal/staticinit
bootstrap/cmd/compile/internal/ssa
bootstrap/cmd/link/internal/amd64
bootstrap/cmd/link/internal/loong64
bootstrap/cmd/link/internal/arm
bootstrap/cmd/link/internal/mips
bootstrap/cmd/link/internal/mips64
bootstrap/cmd/link/internal/arm64
bootstrap/cmd/link/internal/ppc64
bootstrap/cmd/link/internal/riscv64
bootstrap/cmd/link/internal/s390x
bootstrap/cmd/link/internal/wasm
bootstrap/cmd/link/internal/x86
bootstrap/cmd/link
bootstrap/cmd/compile/internal/liveness
bootstrap/cmd/compile/internal/ssagen
bootstrap/cmd/compile/internal/amd64
bootstrap/cmd/compile/internal/arm
bootstrap/cmd/compile/internal/arm64
bootstrap/cmd/compile/internal/dwarfgen
bootstrap/cmd/compile/internal/loong64
bootstrap/cmd/compile/internal/mips
bootstrap/cmd/compile/internal/mips64
bootstrap/cmd/compile/internal/wasm
bootstrap/cmd/compile/internal/s390x
bootstrap/cmd/compile/internal/riscv64
bootstrap/cmd/compile/internal/ppc64
bootstrap/cmd/compile/internal/walk
bootstrap/cmd/compile/internal/x86
bootstrap/cmd/compile/internal/noder
bootstrap/cmd/compile/internal/pkginit
bootstrap/cmd/compile/internal/gc
bootstrap/cmd/compile

Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1.
runtime
go tool dist: /home/landerx/goroot/src/runtime/proc.go imports C

Tried the cgo_enabled=1 flag, doesn't seem to make any difference.

Tried just running make.bash, it didn't seem to make any difference.

I was wondering if it was a dependency issue, but I didn't see any messages related to the fake package cgo, nor did I see any errors with my vscode.

Solution

Okay... Finally, let me answer this question.

Why doesn’t it work

After quite some in-depth investigation, I found that it seems that Go (tools dist) does not allow source files in most go internals (Link)

Solution

There are still some workarounds to achieve this effect, namely using m5ops in go.

1. Pass function pointer through global variable

You can define global function pointers in proc.go and import cgo in your go application and assign these global function pointers to your functions that perform m5ops. Does not support calling C function pointers, so it needs to be wrapped with golang functions.

2. Go to assembly

Go uses a lot of Go Asm in its internal source files to handle stack switching etc.

On the other hand, m5ops will eventually be inlined as a single directive.

So following Go Asm's syntax and function bindings, which happens in asm_amd64.s and stubs.go a>, one can write an asm function that contains the m5ops directive, and then # Call it anywhere in the ##runtime. go should be good.

other information

It seems that in
• runtime.go when it switches to the system stack it can no longer execute functions outside of the file (or package?), so if you try to insert these function calls, method 1 Writing code that will run on the system stack does not work. So I finally discovered the second method.

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