Re: [ISSUE] [CLOSED] cross-built kernel cannot load externally-built modules

[classabbyamp <classabbyamp@users.noreply.github.com>]

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Closed issue by classabbyamp on void-packages repository

https://github.com/void-linux/void-packages/issues/51005

Description:
### System Info

Void 6.8.12_2 aarch64-glibc

### Package(s) Affected

linux6.8 at minimum, probably other `linux6.*` kernels (rpi-kernel is *not* affected)

if the kernel is built natively, this issue does not occur

### Expected behaviour

externally-built (dkms or other mechanism) modules load successfully

```
nm --print-size --size-sort hello.ko | grep __this_module       
0000000000000000 0000000000000500 D __this_module
```

### Actual behaviour

```
# modprobe ./hello.ko
modprobe: ERROR: could not insert 'hello': Exec format error
```
dmesg:
```
[...] module hello: .gnu.linkonce.this_module section size must match the kernel's built struct module size at run time
```

```
nm --print-size --size-sort hello.ko | grep __this_module
0000000000000000 00000000000004c0 D __this_module
```

### Steps to reproduce

```sh
mkdir -p hello-mod && cd hello-mod

cat <<EOF > Makefile 
obj-m += hello.o

PWD := $(CURDIR)

all:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
EOF

cat <<EOF > hello.c
#include <linux/module.h>
#include <linux/printk.h>

int init_module(void) {
    pr_info("hello");
    return 0;
}

void cleanup_module(void) {
    pr_info("goodbye");
}

MODULE_LICENSE("GPL");
EOF

make
sudo modprobe ./hello.ko
```

### Notes

Error message introduced by https://lore.kernel.org/lkml/ZBuShv1hx03WmzH4@bombadil.infradead.org/T/