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

Dear Christophe,


Am 11.08.21 um 16:10 schrieb Christophe Leroy:

Le 10/08/2021 à 20:38, Paul Menzel a écrit :

quoted

Am 29.07.21 um 10:23 schrieb Paul Menzel:

quoted

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 ?

Yes, before sending the message, I reproduced it with

     $ git describe
     v5.14-rc5-2-g9a73fa375d58

containing the commit you mentioned.


Kind regards,

Paul