attempt to support "go build -buildmode=plugin -linkshared".

[crazycomputer]

What version of Go are you using (go version)?

$ go version
go version go1.14.12 linux/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/root/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/mnt/d/wsl/01.Tools/golang/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/mnt/d/wsl/01.Tools/golang/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build174216265=/tmp/go-build -gno-record-gcc-switches"

What did you do?

first, use go install -buildmode=shared -linkshared std to build and install libstd.so
second, use go build -buildmode=plugin -linkshared plugin.go to build plugin.so
plugin.go:

package main
import "fmt"
func Print(){
	fmt.Println("plugin")
}

then, use go build -linkshared main.go to build main.go whit linkshared
main.go

package main

import (
	"log"
	"plugin"
)

func main() {
	p, err := plugin.Open("./plugin.so")
	if err != nil {
		log.Println(err)
	}
	f, err := p.Lookup("Print")
	if err != nil {
		log.Println(err)
	}
	f.(func())()
}

then I run main.

What did you expect to see?

main process run and print "plugin"

What did you see instead?

./main
SIGTRAP: trace trap
PC=0x7fb9410a81c1 m=0 sigcode=128

goroutine 0 [idle]:
runtime: unknown pc 0x7fb9410a81c1
stack: frame={sp:0x7ffe9713c240, fp:0x0} stack=[0x7ffe9693d8a0,0x7ffe9713c8e0)
00007ffe9713c140:  00007fb9410a64e0  00007ffe9713c230 
00007ffe9713c150:  0000000000000001  00007fb94383c548 
00007ffe9713c160:  0000000000000006  00000000000047a8 
00007ffe9713c170:  0000000000000ab0  0000000000000000 
00007ffe9713c180:  0000000000001000  0000000064cd305f 
00007ffe9713c190:  000056530156bc08  00007ffe9713c358 
00007ffe9713c1a0:  00007fb9410a68cc  00007ffe9713c230 
00007ffe9713c1b0:  00007ffe9713c240  00007fb9438491e9 
00007ffe9713c1c0:  0000000000000001  0000000000000000 
00007ffe9713c1d0:  0000000000000009  0000000000000000 
00007ffe9713c1e0:  0000000000000001  000056530156b8a0 
00007ffe9713c1f0:  0000000000000004  0000000000000000 
00007ffe9713c200:  000056530156b8a0  000056530156bc08 
00007ffe9713c210:  0000000000000000  0000000000000000 
00007ffe9713c220:  0000000000000000  0000000000000001 
00007ffe9713c230:  00000000ffffffff  00000000000037a8 
00007ffe9713c240: <00007fb9410a81ec  00007fb94384eb8a 
00007ffe9713c250:  0000000000000000  0000000000000001 
00007ffe9713c260:  00007ffe9713c9f8  00007ffe9713ca08 
00007ffe9713c270:  000056530156b8a0  00007fb94384ec91 
00007ffe9713c280:  78f25a33371354c3  00007ffe9713c5e0 
00007ffe9713c290:  00007ffe9713c480  fffffffffffffff0 
00007ffe9713c2a0:  0000000000000001  0000000000000006 
00007ffe9713c2b0:  000056530156b8a0  00007fb941013915 
00007ffe9713c2c0:  0000000000000000  00007ffe9713c4c0 
00007ffe9713c2d0:  00007fb9438522c0  00007ffe9713c430 
00007ffe9713c2e0:  4c576d5352587769  0000000000000000 
00007ffe9713c2f0:  0000000000000002  0000003200000008 
00007ffe9713c300:  0000000000000000  0000000000000000 
00007ffe9713c310:  0000000000000000  000000770000007c 
00007ffe9713c320:  0000005b0000006e  0000000000000000 
00007ffe9713c330:  00007fb9410a6000  0000000000000006 
runtime: unknown pc 0x7fb9410a81c1
stack: frame={sp:0x7ffe9713c240, fp:0x0} stack=[0x7ffe9693d8a0,0x7ffe9713c8e0)
00007ffe9713c140:  00007fb9410a64e0  00007ffe9713c230 
00007ffe9713c150:  0000000000000001  00007fb94383c548 
00007ffe9713c160:  0000000000000006  00000000000047a8 
00007ffe9713c170:  0000000000000ab0  0000000000000000 
00007ffe9713c180:  0000000000001000  0000000064cd305f 
00007ffe9713c190:  000056530156bc08  00007ffe9713c358 
00007ffe9713c1a0:  00007fb9410a68cc  00007ffe9713c230 
00007ffe9713c1b0:  00007ffe9713c240  00007fb9438491e9 
00007ffe9713c1c0:  0000000000000001  0000000000000000 
00007ffe9713c1d0:  0000000000000009  0000000000000000 
00007ffe9713c1e0:  0000000000000001  000056530156b8a0 
00007ffe9713c1f0:  0000000000000004  0000000000000000 
00007ffe9713c200:  000056530156b8a0  000056530156bc08 
00007ffe9713c210:  0000000000000000  0000000000000000 
00007ffe9713c220:  0000000000000000  0000000000000001 
00007ffe9713c230:  00000000ffffffff  00000000000037a8 
00007ffe9713c240: <00007fb9410a81ec  00007fb94384eb8a 
00007ffe9713c250:  0000000000000000  0000000000000001 
00007ffe9713c260:  00007ffe9713c9f8  00007ffe9713ca08 
00007ffe9713c270:  000056530156b8a0  00007fb94384ec91 
00007ffe9713c280:  78f25a33371354c3  00007ffe9713c5e0 
00007ffe9713c290:  00007ffe9713c480  fffffffffffffff0 
00007ffe9713c2a0:  0000000000000001  0000000000000006 
00007ffe9713c2b0:  000056530156b8a0  00007fb941013915 
00007ffe9713c2c0:  0000000000000000  00007ffe9713c4c0 
00007ffe9713c2d0:  00007fb9438522c0  00007ffe9713c430 
00007ffe9713c2e0:  4c576d5352587769  0000000000000000 
00007ffe9713c2f0:  0000000000000002  0000003200000008 
00007ffe9713c300:  0000000000000000  0000000000000000 
00007ffe9713c310:  0000000000000000  000000770000007c 
00007ffe9713c320:  0000005b0000006e  0000000000000000 
00007ffe9713c330:  00007fb9410a6000  0000000000000006 

goroutine 1 [syscall]:
runtime.cgocall(0x7fb9423d65f0, 0xc000362c40, 0xc000432018)
	/mnt/d/wsl/01.Tools/golang/1.16.3/go/src/runtime/cgocall.go:154 +0x65 fp=0xc000362c10 sp=0xc000362bd8 pc=0x7fb941c292c5
plugin._Cfunc_pluginOpen(0xc000438000, 0xc000432018, 0x0)
	_cgo_gotypes.go:76 +0x4e fp=0xc000362c40 sp=0xc000362c10 pc=0x7fb9423b386e
plugin.open.func1(0xc000438000, 0x1001, 0x1001, 0xc000432018, 0x7fb943832ae0)
	/mnt/d/wsl/01.Tools/golang/1.16.3/go/src/plugin/plugin_dlopen.go:64 +0x7d fp=0xc000362c70 sp=0xc000362c40 pc=0x7fb9423b4c3d
plugin.open(0x5653005ca015, 0xb, 0xc000000300, 0x300000002, 0xc000000300)
	/mnt/d/wsl/01.Tools/golang/1.16.3/go/src/plugin/plugin_dlopen.go:64 +0x34e fp=0xc000362ee8 sp=0xc000362c70 pc=0x7fb9423b3cee
plugin.Open(...)
	/mnt/d/wsl/01.Tools/golang/1.16.3/go/src/plugin/plugin.go:32
()
	/mnt/d/wsl/02.Code/01.GOPATH/src/plugindemo/main/main.go:9 +0x4a fp=0xc000362f88 sp=0xc000362ee8 pc=0x5653005c922a
runtime.main()
	/mnt/d/wsl/01.Tools/golang/1.16.3/go/src/runtime/proc.go:225 +0x2aa fp=0xc000362fe0 sp=0xc000362f88 pc=0x7fb941c72aca
runtime.goexit()
	/mnt/d/wsl/01.Tools/golang/1.16.3/go/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc000362fe8 sp=0xc000362fe0 pc=0x7fb941cb3061

rax    0x0
rbx    0x7fb9410aa7b0
rcx    0x7ffe9713ca08
rdx    0x7ffe9713ca08
rdi    0x7fb9410ab040
rsi    0x7ffe9713c9f8
rbp    0x1
rsp    0x7ffe9713c240
r8     0x0
r9     0x1
r10    0x0
r11    0x7fb94109bbe0
r12    0x7ffe9713c9f8
r13    0x7ffe9713ca08
r14    0x7fb9410aa7b8
r15    0x0
rip    0x7fb9410a81c1
rflags 0x202
cs     0x33
fs     0x0
gs     0x0

then I use objdump -D plugin.so , I found that the function runtime.addmoduledata is not in plt of plugin.so, when go.link.addmoduledata is called in dllopen, it jumped to a wrong address.

If I can add runtime.addmoduledata to plt in plugin.so, maybe I can use plugin.Open to open the plugin.so success.so,I modified the linker in toolchain. then this mistake is fixed.

Then, when I run the main. it returns an error: "plugin was built with a different version of package". I found the pkghash of the pkgs in libstd.so is blank in plugin. I modifier the linker:

It will not generate pkghash of the pkg in libstd.so to plugin.so in linktime.

After these modification，the main process runs success，and I tried some more complex plugin，it works well.
But I can't judge are there any other risk after these modification. I want to use it in production environment. Can anyone help me?

--

[crazycomputer]

@ianlancetaylor

[crazycomputer]

#18671

[cherrymui]

There is currently no plan to support plugin with linkshared.
You already found #18671 . Closing this as a dup. Thanks.

[ChenJhua]

@crazycomputer Do you get an error using plugin.so after you change it? If not I'd like to refer to your changes as I also need this functionality

[zhouguangyuan0718]

@crazycomputer Do you get an error using plugin.so after you change it? If not I'd like to refer to your changes as I also need this functionality

@ChenJhua
This is my new account in github instead of crazycomputer.
The change in this issue is based on go 1.14 and there is some bugs in it.
I had developed another two new patches for the functionality based on 1.16 and it can work on master.

The one patch is compatible with official plugin, but there is a huge modification in linker.
In the other patch, I had modified a little in official plugin library in runtime and less modification in linker. I am planing to use this patch in our producting environment.

If you can use the second one, I will try to shared it to you or open source of it.
If you can only use a patch which is compatible with official plugin (the patch one). I'm not sure I can shared the patch to you before investigation. Because it is really huge and maybe it is risky.

[ChenJhua]

@zhouguangyuan0718 If you don't mind, you can also share the code here. Thank you very much.

[zhouguangyuan0718]

@zhouguangyuan0718 If you don't mind, you can also share the code here. Thank you very much.

Communicating on github is better. I will send a CL to shared the code with you tonight. Maybe 8 hours ago.
By the way, the change in this issue can work in some situations. What error do you get with the change?

[ChenJhua]

@zhouguangyuan0718
I modified the code without recompiling golang. and then re-executed it go build -buildmode=plugin -linkshared myplugin2.go.it is ok. but i run main.go.The following error is reported

$ /data/cjh/go/goplugin # go run main.go 
SIGTRAP: trace trap
PC=0x7f97718d2741 m=0 sigcode=128

goroutine 0 [idle]:
runtime: unknown pc 0x7f97718d2741
stack: frame={sp:0x7fff049f3120, fp:0x0} stack=[0x7fff041f4638,0x7fff049f3670)
00007fff049f3020:  00007f97718d1480  00007f9771ad3fa0 
00007fff049f3030:  00007fff049f3170  00007f979ade40cf 
00007fff049f3040:  00007f9700000001  0000000000000000 
00007fff049f3050:  0000001f0000007c  00007f979afe9000 
00007fff049f3060:  00007fff049f30e0  00007fff049f30e8 
00007fff049f3070:  00007fff049f30f8  0000000000000000 
00007fff049f3080:  00007fff049f3158  0000000000000000 
00007fff049f3090:  0000000000000000  00007fff049f30f0 
00007fff049f30a0:  00007f97718d1720  00007fff049f3158 
00007fff049f30b0:  00007f97718d1000  000000000240dd88 
00007fff049f30c0:  00007f97718d1b4e  0000000000000000 
00007fff049f30d0:  00007f97718d2518  00007f97718d12d0 
00007fff049f30e0:  000000000240dff0  00007f979ade915e 
00007fff049f30f0:  0000000000429450  0000000000000005 
00007fff049f3100:  00007f97718d1bd0  0000000000000948 
00007fff049f3110:  000000000000003d  0000000000000000 
00007fff049f3120: <00007f97718d276c  00007f979ade79b3 
00007fff049f3130:  000000000240da30  0000000000000006 
00007fff049f3140:  8000000000000000  0000000000000000 
00007fff049f3150:  00007fff049f3230  0000000000000006 
00007fff049f3160:  0000000000000001  0000000000000006 
00007fff049f3170:  000000000240da30  00007f979adec58e 
00007fff049f3180:  000000000240da30  000000000240dff0 
00007fff049f3190:  00007fff049f3230  00007f979adec349 
00007fff049f31a0:  0000000000000000  0000000000000000 
00007fff049f31b0:  0000000000000001  000000000240da30 
00007fff049f31c0:  00007fff049f3180  00007fff049f31a0 
00007fff049f31d0:  0000000000000001  0000000000000006 
00007fff049f31e0:  00007f979affb120  00007fff049f3170 
00007fff049f31f0:  8000010200000001  00007fff049f3398 
00007fff049f3200:  0000000000484b2e <runtime.main+622>  00007f979afe6728 
00007fff049f3210:  0000000080000102  000000c00008a000 
runtime: unknown pc 0x7f97718d2741
stack: frame={sp:0x7fff049f3120, fp:0x0} stack=[0x7fff041f4638,0x7fff049f3670)
00007fff049f3020:  00007f97718d1480  00007f9771ad3fa0 
00007fff049f3030:  00007fff049f3170  00007f979ade40cf 
00007fff049f3040:  00007f9700000001  0000000000000000 
00007fff049f3050:  0000001f0000007c  00007f979afe9000 
00007fff049f3060:  00007fff049f30e0  00007fff049f30e8 
00007fff049f3070:  00007fff049f30f8  0000000000000000 
00007fff049f3080:  00007fff049f3158  0000000000000000 
00007fff049f3090:  0000000000000000  00007fff049f30f0 
00007fff049f30a0:  00007f97718d1720  00007fff049f3158 
00007fff049f30b0:  00007f97718d1000  000000000240dd88 
00007fff049f30c0:  00007f97718d1b4e  0000000000000000 
00007fff049f30d0:  00007f97718d2518  00007f97718d12d0 
00007fff049f30e0:  000000000240dff0  00007f979ade915e 
00007fff049f30f0:  0000000000429450  0000000000000005 
00007fff049f3100:  00007f97718d1bd0  0000000000000948 
00007fff049f3110:  000000000000003d  0000000000000000 
00007fff049f3120: <00007f97718d276c  00007f979ade79b3 
00007fff049f3130:  000000000240da30  0000000000000006 
00007fff049f3140:  8000000000000000  0000000000000000 
00007fff049f3150:  00007fff049f3230  0000000000000006 
00007fff049f3160:  0000000000000001  0000000000000006 
00007fff049f3170:  000000000240da30  00007f979adec58e 
00007fff049f3180:  000000000240da30  000000000240dff0 
00007fff049f3190:  00007fff049f3230  00007f979adec349 
00007fff049f31a0:  0000000000000000  0000000000000000 
00007fff049f31b0:  0000000000000001  000000000240da30 
00007fff049f31c0:  00007fff049f3180  00007fff049f31a0 
00007fff049f31d0:  0000000000000001  0000000000000006 
00007fff049f31e0:  00007f979affb120  00007fff049f3170 
00007fff049f31f0:  8000010200000001  00007fff049f3398 
00007fff049f3200:  0000000000484b2e <runtime.main+622>  00007f979afe6728 
00007fff049f3210:  0000000080000102  000000c00008a000 

goroutine 1 [syscall]:
runtime.cgocall(0x51ad90, 0xc00004bc40, 0xc000010028)
	/usr/local/go/src/runtime/cgocall.go:154 +0x5b fp=0xc00004bc10 sp=0xc00004bbd8 pc=0x450a5b
plugin._Cfunc_pluginOpen(0xc00008a000, 0xc000010028, 0x0)
	_cgo_gotypes.go:76 +0x45 fp=0xc00004bc40 sp=0xc00004bc10 pc=0x519765
plugin.open.func1(0xc00008a000, 0x1001, 0x1001, 0xc000010028, 0x82acc0)
	/usr/local/go/src/plugin/plugin_dlopen.go:64 +0x71 fp=0xc00004bc70 sp=0xc00004bc40 pc=0x51a911
plugin.open(0x547ae4, 0xc, 0xc000000180, 0x300000002, 0xc000000180)
	/usr/local/go/src/plugin/plugin_dlopen.go:64 +0x345 fp=0xc00004bee8 sp=0xc00004bc70 pc=0x519ba5
plugin.Open(...)
	/usr/local/go/src/plugin/plugin.go:32
main.main()
	/data/cjh/go/goplugin/main.go:6 +0x48 fp=0xc00004bf88 sp=0xc00004bee8 pc=0x51ab08
runtime.main()
	/usr/local/go/src/runtime/proc.go:225 +0x256 fp=0xc00004bfe0 sp=0xc00004bf88 pc=0x484b16
runtime.goexit()
	/usr/local/go/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc00004bfe8 sp=0xc00004bfe0 pc=0x4b54a1

rax    0x0
rbx    0x1
rcx    0x7f9771ad3dc0
rdx    0x7fff049f3788
rdi    0x7f9771ad4020
rsi    0x7fff049f3778
rbp    0x7fff049f3778
rsp    0x7fff049f3120
r8     0x7f979affb150
r9     0x7f979affb150
r10    0x0
r11    0x206
r12    0x7fff049f3788
r13    0x7f9771ad3750
r14    0x0
r15    0x7f9771ad3748
rip    0x7f97718d2741
rflags 0x283
cs     0x33
fs     0x0
gs     0x0
exit status 2

Now I'm going to recompile golang to try.

$ /data/cjh/go/goplugin # cat myplugin2.go 
package main
import "fmt"
func Hello() {
    fmt.Println("Hello, World! I am plugin 2")
}
$ /data/cjh/go/goplugin # cat main.go 
package main
import "log"
import "plugin"
func main() {
	//	加载 myplugin 库
	p, err := plugin.Open("myplugin2.so")
	if err != nil {
		log.Fatal(err)
	}
	//	取得 Hello 函数
	fn, err := p.Lookup("Hello")
	if err != nil {
		log.Fatal(err)
	}
	//	调用函数
        fn.(func())()
}

[zhouguangyuan0718]

The cmd should be rebuild, because the linker is modified.
This error is easy to resolve. For go 1.14, you can resolve by the patch in the picture of this issue.
For go 1.16, 1.17 and tips, I will send a CL tonight.