"Unknown symbol in module" on module insertion despite EXPORT_SYMBOL

Question

I am trying to compile and insert the r8169 realtek ethernet driver. My kernel version is

ebin@sony:~$ uname -r 4.2.0-rc3-custom

I have the full source of the same in my local disk, which is used to install the current kernel. The module compiles successfully when I run make -C /lib/modules/uname -r/build M=pwdmodules
but when I insert the module, it shows

ebin@sony:~/linux_testing/linux-stable/drivers/net/ethernet/realtek$ sudo insmod r8169.ko insmod: ERROR: could not insert module r8169.ko: Unknown symbol in module ebin@sony:~/linux_testing/linux-stable/drivers/net/ethernet/realtek$ dmesg [16717.311216] r8169: Unknown symbol mii_ethtool_gset (err 0)

When I grepped through the source, I found

EXPORT_SYMBOL(mii_ethtool_gset);

already exported in the mii.c. So I guess it is not the problem of unexported symbol. Let me know if I have to provide any other info. Please help.

@ebin: If mii is compiled as a module, you need to insert it (sudo modprobe mii) before inserting your module. Unlike to modprobe, insmod does not load dependent modules automatically. — Tsyvarev
– Tsyvarev, Commented Sep 4, 2015 at 10:40
@Tsyvarev: I tried after loading the mii module. Now it shows the error ERROR: could not insert module r8169.ko: Invalid parameters dmesg [ 8157.140018] r8169: disagrees about version of symbol mii_ethtool_gset [ 8157.140027] r8169: Unknown symbol mii_ethtool_gset (err -22) — ebin
– ebin, Commented Sep 4, 2015 at 18:34
@VadimStupakov Thanks a lot. You made my day. It is working now. Could you please explain, why do weplace the Module.Symvers to the build directory?. Because, I think, I have already compiled this module without Module.Symvers file in another machine before — ebin
– ebin, Commented Sep 5, 2015 at 8:45

ebin · Accepted Answer · 2015-09-07 17:25:19Z

As Vadim Stupakov said in the comment, Putting the Module.symvers file in the module source directory fixed my issue. From this documentation

Module versioning is enabled by the CONFIG_MODVERSIONS tag, and is used as a simple ABI consistency check. A CRC value of the full prototype for an exported symbol is created. When a module is loaded/used, the CRC values contained in the kernel are compared with similar values in the module. if they are not equal, the kernel refuses to load the module. Module.symvers contains a list of all exported symbols from a kernel build.

As per my understanding, Module.symvers is created on make modules. I missed out that file. When I put the appropriate Module.symvers in the module build directory, the module works as I expected without any errors.

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