Hello,
Thanks for your answer.
Three points to note:
- I never asked how to create an so, I already have a given so :/
- No need to provide the code because the issue is simple to describe: I
have an address of a function in a Go variable, how to call it ?
- AI is garbage (even though I use it)
I thought about using assembly with a call instruction but I hoped someone
knowledgable would tell me there is a built in Go function for that.
Regards,
Rudeus
Le jeudi 15 mai 2025 à 02:46:18 UTC+2, Kurtis Rader a écrit :
> On Wed, May 14, 2025 at 4:17 PM rudeus greyrat <rudeusqu...@gmail.com>
> wrote:
>
>> I am still a beginner in Linux internals so please bear with me.
>>
>> I have a ".so" that export "helloworld" function.
>>
>> I load the ".so" using CGO by:
>>
>> 1. Creating a file descriptor
>> 2. using ```write``` to write the so to it
>>
>> A shared library (".so" file) has a complex structure. You normally
> create one using a compiler and related tools. For example, the Go compiler
> can create a .so file from Go source code using a command like
>
> go build -buildmode=c-shared -o mylib.so
>
> It seems unlikely you are creating a valid .so file by opening an empty
> file and writing to it unless you are simply copying one .so file to
> another file.
>
>>
>> 1. Get a handle using ```dlopen```
>> 2. Get the address of ```helloworld``` symbol using ```dlsym```
>>
>> The address of "helloworld" is saved in a go variable called ```address```
>>
>> How to call ```address``` ?
>>
>> On windows I am able to call address using ```syscall.SyscallN```. On
>> Linux I tried with
>> ```
>> r1, r2, err := syscall.Syscall(address, 0, 0, 0)
>> ```
>>
>> And I get "function not implemented" error.
>>
>
> I can't speak to Windows but on Unix like operating systems, such as
> Linux, a function in a shared library is a user space function, not a
> kernel entry point. A syscall is the way you call OS kernel functions, not
> user space functions. I wouldn't expect syscall.Syscall() to work on
> Windows when passed the address of a function in a DLL. Did you actually
> confirm that it does work when passed the address of a DLL user space
> function? In any case this definitely won't work on Linux.
>
> I searched for "how to call a function in a shared library in go" in
> Chrome and the results included an AI generated example of how to do this
> along with links to many articles and other sources such as StackOverflow.
> If you're still having problems ask again but show us the source code you
> wrote and the commands you ran to compile it.
>
> --
> Kurtis Rader
> Caretaker of the exceptional canines Junior and Hank
>
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