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plugin: Incorrect Symbol Table generation #19748

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slightnerd opened this issue Mar 28, 2017 · 4 comments
Closed

plugin: Incorrect Symbol Table generation #19748

slightnerd opened this issue Mar 28, 2017 · 4 comments
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@slightnerd
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Please answer these questions before submitting your issue. Thanks!

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

go version go1.8 linux/amd64

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/export/home/sll2/go"
GORACE=""
GOROOT="/usr/local/sll2/go18src/go"
GOTOOLDIR="/usr/local/sll2/go18src/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build859461664=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

When using a 10 different functions in a plugin the plugin_open process confuses dot notated names after trying to delete entry in symbol table build in plugin_dlopen.go

    for symName, sym := range syms {
            fmt.Println("symName : ", string(symName))
            isFunc := symName[0] == '.'
            if isFunc {

error --> delete(syms, symName) <- error deleting from list while processing list
symName = symName[1:]
}

            cname := C.CString(pluginpath + "." + symName)
            p := C.pluginLookup(h, cname, &cErr)
            C.free(unsafe.Pointer(cname))
            if p == nil {
                    return nil, errors.New("plugin.Open: could not find symbol " + symName + ": " + C.GoString(cErr))
            }
            valp := (*[2]unsafe.Pointer)(unsafe.Pointer(&sym))
            if isFunc {
                    (*valp)[1] = unsafe.Pointer(&p)
            } else {
                    (*valp)[1] = p
            }             
           syms[symName] = sym
    }

What did you expect to see?

syms : map[.AX_Init: .AX_Print: .AX_Init.func1: .AX_Apply.func1: .AX_Apply.func2: .AX_Release: .AX_Apply: .AX_Message: .AX_ClearMessage: .AX_Trace: AZ_ITEM:]
symslen : 11 But looped 13 times. because delete in loop changed loop.
symName : AZ_ITEM
symName : .AX_Apply
symName : .AX_Message
symName : .AX_ClearMessage
symName : .AX_Trace
symName : .AX_Apply.func2
symName : AX_ClearMessage
symName : AX_Trace
symName : .AX_Release
symName : .AX_Init
symName : .AX_Print
symName : .AX_Init.func1
symName : .AX_Apply.func1

** Notice bad addresses in AX_INIT, and AX_PRINT because they were double processed and thought to be data the second time. Can cause a panic sometimes.

map[AX_Init:0x640029af090d8b48 AX_Print:0x640029aae90d8b48 AX_Message:0x7efcb073d7c0 AX_ClearMessage:0x7efcb073d820 AX_Trace:0x7efcb073d8a0 AX_Apply.func1:0x7efcb073d960 AX_Init.func1:0x7efcb073d8e0 AX_Apply.func2:0x7efcb073d9e0 AZ_ITEM:0x7efcb09dd920 AX_Release:0x7efcb073d050 AX_Apply:0x7efcb073d500]

What did you see instead?

syms : map[.AX_Init: .AX_Print: .AX_Init.func1: .AX_Apply.func1: .AX_Apply.func2: .AX_Release: .AX_Apply: .AX_Message: .AX_ClearMessage: .AX_Trace: AZ_ITEM:]
symslen : 11
symName : AZ_ITEM
symName : .AX_Apply
symName : .AX_Message
symName : .AX_ClearMessage
symName : .AX_Trace
symName : .AX_Apply.func2
symName : .AX_Release
symName : .AX_Init
symName : .AX_Print
symName : .AX_Init.func1
symName : .AX_Apply.func1
@slightnerd
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Map delete and map add both cause processing problems with newly created symbol map

@slightnerd
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Here is a simple fix I use until it can be refactored by development team.

symshold := make(map[string]interface{}, len(syms))

// Fill out the value of each plugin symbol.
for symName, sym := range syms {
	isFunc := symName[0] == '.'
	if isFunc {
		delete(syms, symName)
		symName = symName[1:]
	}  

	cname := C.CString(pluginpath + "." + symName)
	p := C.pluginLookup(h, cname, &cErr)
	C.free(unsafe.Pointer(cname))
	if p == nil {
		return nil, errors.New("plugin.Open: could not find symbol " + symName + ": " + C.GoString(cErr))
	}
	valp := (*[2]unsafe.Pointer)(unsafe.Pointer(&sym))
	if isFunc {
		(*valp)[1] = unsafe.Pointer(&p)
	} else {
		(*valp)[1] = p
	}
	symshold[symName] = sym
}
for symName, sym := range symshold {
	syms[symName] = sym
}

@tzneal
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tzneal commented Apr 11, 2017

Dupe of #19269

@tzneal
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tzneal commented Apr 17, 2017

Dupe, verified fixed in tip.

@tzneal tzneal closed this as completed Apr 17, 2017
@golang golang locked and limited conversation to collaborators Apr 17, 2018
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@tzneal @gopherbot @slightnerd