On Wed, May 14, 2025 at 4:17 PM rudeus greyrat <rudeusquagmir...@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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