Re: [QUESTION] Compile error on ppc32 with compilation option '-fdata-sections'

[Ye Weihua <yeweihua4@huawei.com>]

On 2021/10/21 0:55, Kees Cook wrote:
> On Tue, Oct 19, 2021 at 10:14:34AM +0800, Ye Weihua wrote:
>> Hi,
>>
>>
>> When I was compiling the ppc32 kernel with the compilation option
>> '-fdata-sections', a compilation error occurred and the message was as
>> follows:
>>
>>
>>      "Inconsistent kallsyms data
>>
>>      Try make KALLSYMS_EXTRA_PASS=1 as a workaround"
>>
>>
>> After comparing the symbol tables, I found that the "_end" and "__bss_stop"
>> positions in Symtem.map and tmp_System.map are different: in Symtem.map they
>> are in the middle of the symbol table. In tmp_System.map, they are at the
>> end of the symbol table.
>>
>>
>> commit af73d78bd384aa9b add "strip-debug" to improve performance. However,
>> the addition takes effect only for tmp_vmlinux but not for vmlinux. As a
>> result, the symbol tables are different after the "-fdata-sections"
>> compilation option is enabled.
>>
>>
>> How the "strip-debug" compilation option affects symbol table order?
>>
>> Can "strip-debug" be added during vmlinux generation?
> How did you add -fdata-sections? There needs to be a lot of special
> handling to use that option...

I added "-fdata-sections" to the "CFLAGS_KERNEL" field and "-Wl,--gc-sections" to "LDFLAGS_VMLINUX" in Makefile. I've configured it this way on other architectures, but I haven't had the same problem with the exception of ppc32. Are there any other configurations or steps required?

Thanks.