clang/ld.lld build fails with `can't create dynamic relocation R_PPC64_ADDR64 against local symbol in readonly segment`

[Christophe Leroy]

Le 10/08/2021 à 20:38, Paul Menzel a écrit :
> Dear Linux folks,
> 
> 
> Am 29.07.21 um 10:23 schrieb Paul Menzel:
> 
>> I just wanted to make you aware that building Linux for ppc64le with clang/lld.ld fails with [1]:
>>
>>      ld.lld: error: can't create dynamic relocation R_PPC64_ADDR64 against symbol: empty_zero_page 
>> in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text 
>> relocations in the output
>>      >>> defined in arch/powerpc/kernel/head_64.o
>>      >>> referenced by arch/powerpc/kernel/head_64.o:(___ksymtab+empty_zero_page+0x0)
>>
>> The patch below from one of the comments [2] fixes it.
>>
>> --- i/arch/powerpc/Makefile
>> +++ w/arch/powerpc/Makefile
>> @@ -122,7 +122,7 @@ cflags-$(CONFIG_STACKPROTECTOR)     += -mstack-protector-guard-reg=r2
>>   endif
>>
>>   LDFLAGS_vmlinux-y := -Bstatic
>> -LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
>> +LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie -z notext
>>   LDFLAGS_vmlinux        := $(LDFLAGS_vmlinux-y)
>>   LDFLAGS_vmlinux += $(call ld-option,--orphan-handling=warn)
> 
> Any comments, if this is the right fix? Current Linux master branch still fails to build with 
> `LLVM=1` on Ubuntu 21.04 without this change.

Which kernel version are you building ?

Since https://github.com/linuxppc/linux/commit/45b30fafe528601f1a4449c9d68d8ebe7bbc39ad , 
empty_zero_page[] is in arch/powerpc/mm/mem.c not in arch/powerpc/kernel/head_64.o

Do you still have the issue with kernel 5.14 ?

Christophe