Re: Dumping the checksums in a module

John Sigler
2007-05-22T08:14:36Z

Jan Engelhardt wrote:

> On May 18 2007 17:02, John Sigler wrote:
>> I'm getting "disagrees about version of symbol struct_module" messages,
>> and I'm trying to understand why.
>>
>> As far as I understand (which is not very far), if I define
>> CONFIG_MODVERSIONS, then checksums for various functions (all exported
>> functions?) and various structures (which ones?) will be included inside
>> the kernel image, and written to Module.symvers. When an out-of-tree
>> module is built, it will also include these checksums.
>>
>> How do I list the checksums within a module?
>>
>> Is there a simpler way to list all the checksums?
>
> 22:25 ichi:~ > modinfo aes
> srcversion: 8CB82B3A254D5A950FD0D14
>
> I think this one checksum is computed out of all functions that
> the module uses.

You've enabled MODULE_SRCVERSION_ALL which adds a checksum computed from
the source files used to build a given module. What I want is to list
ALL the checksums of the symbols included inside a given module.

e.g. for the kernel:

$ head Module.symvers
0x4da3749b firmware_unregister vmlinux EXPORT_SYMBOL_GPL
0xbf9d1364 generic_file_splice_write vmlinux EXPORT_SYMBOL
0x436417ac set_anon_super vmlinux EXPORT_SYMBOL
0x894bc434 kmem_cache_alloc vmlinux EXPORT_SYMBOL
0x1120b731 request_firmware vmlinux EXPORT_SYMBOL
0x0a2487e0 unblock_all_signals vmlinux EXPORT_SYMBOL
0x07d50a24 csum_partial vmlinux EXPORT_SYMBOL
0xcd6c78f9 __generic_unplug_device vmlinux EXPORT_SYMBOL
0x59ab4080 cap_bset vmlinux EXPORT_SYMBOL
0xee413334 softirq_preemption vmlinux EXPORT_SYMBOL
[...]

config MODVERSIONS
bool "Module versioning support"
depends on MODULES
help
Usually, you have to use modules compiled with your kernel.
Saying Y here makes it sometimes possible to use modules
compiled for different kernels, by adding enough information
to the modules to (hopefully) spot any changes which would
make them incompatible with the kernel you are running. If
unsure, say N.

config MODULE_SRCVERSION_ALL
bool "Source checksum for all modules"
depends on MODULES
help
Modules which contain a MODULE_VERSION get an extra "srcversion"
field inserted into their modinfo section, which contains a
sum of the source files which made it. This helps maintainers
see exactly which source was used to build a module (since
others sometimes change the module source without updating
the version). With this option, such a "srcversion" field
will be created for all modules. If unsure, say N.

Regards.