[LLVMdev] elf linking problem

[Sinha, Prokash]

So what I'm looking for is that if some sums are defined in the kernel
namespace by some kernel component, it should be visible by other kernel
module at load time fix/resolve those references, which is what the gcc on
freebsd 7.2 seem to be doing. For freebsd 10.1 using the clang front, this
could be broken.

Can anyone point me to some document along the line of freebsd ko
linking/loading.

I used objdump, but I'm particularly looking for some internals related
document, so that I can see the linker actually trying to pull in and
fix/resolve ref from the kernel name space.

Thanks,
-prokash

On 1/16/15 8:15 AM, "Sinha, Prokash" <psinha at panasas.com> wrote:

>Has anyone seen this , when clang is being used for 10.1 compilation ?
>
>Thanks,
>-prokash
>
>
>On 1/15/15 7:30 PM, "Sinha, Prokash" <psinha at panasas.com> wrote:
>
>>Hello,
>>
>>I'm trying to find out what could be the cause of a kldload problem I'm
>>facing. Here is the context detail --
>>
>>
>>1. I'm building two ko module. And it has a dependency order, so when I
>>load the first module, it loads, and a function symbol ( F ) is defined
>>into kernel variable space sysctl -b kern.function_list | tr '\0' '\n' |
>>grep symname.
>>2. Now trying to load the 2nd module, and link_elf_obj flags error and
>>symbol undefined when freebsd10.1 is being used.
>>3. If I probe using the same sysctl as in step 1, I still the symbol is
>>defined.
>>
>>/var/log/messages shows -
>>kernel: link_elf_obj: symbol pan_sys_once undefined
>>kernel: linker_load_file: Unsupported file type
>>
>>The same two modules when complied using freebsd7.2, we don't see the
>>problem.
>>
>>
>>The question is - Is there changes along the elf formats ( in both case
>>it
>>64bit), also is there any changes
>>In the API between those two OS version, that I need to aware of ( and
>>possible flags I need to set).
>>
>>Using objdump -t  modone.ko
>>00000000000fb940 g     F .text	0000000000000062 pan_sys_once
>>
>>
>>
>>In modtwo.ko it is undefined
>>0000000000000000         *UND*	0000000000000000 pan_sys_once
>>
>>
>>Note the objdump on freebsd 7.2, is identical. So it is defined in the
>>module1 as F(function), and undefined(UND) in module two.
>>
>>Any suggestion, please ?
>>
>>Thanks,
>>-prokash
>>
>>
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>