Unknown symbol reboot_mode

[Greg KH]

On Mon, Mar 23, 2020 at 11:27:50AM +0100, Tomek The Messenger wrote:
> Hi
> When I insert external kernel module which is compiled out of tree I got
> error:
> 
> root:/run# insmod ./my_module.ko
> [  137.443823] my_module: Unknown symbol reboot_mode (err 0)
> 
> I investigated that I have attached in my my_module.c file:
> #include <linux/reboot.h>
> and in this file we have:
> extern enum reboot_mode reboot_mode;
> However reboot_mode symbol is not exported with macro EXPORT_SYMBOL_GPL.
> Probably this is the reason why symbol is not seen in my module.

That is correct.

> Then why
> the same issue doesn't occur here:
> /arch/arm/kernel/setup.c
> /arch/arm64/kernel/process.c
> Those linux files also use global variable reboot_mode.

Because those files are not built as a kernel module, but rather
directly into the kernel image.

hope this helps,

greg k-h