[PATCH v2] ppc: add "-z notext" flag to disable diagnostic

[Bill Wendling <morbo@google.com>]

From: Fangrui Song <maskray@google.com>

Object files used to link .tmp_vmlinux.kallsyms1 have many R_PPC64_ADDR64
relocations in non-SHF_WRITE sections. There are many text relocations (e.g. in
.rela___ksymtab_gpl+* and .rela__mcount_loc sections) in a -pie link and are
disallowed by LLD:

  ld.lld: error: can't create dynamic relocation R_PPC64_ADDR64 against local symbol 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:(__restart_table+0x10)

Newer GNU ld configured with "--enable-textrel-check=error" will report an
error as well:

  $ ld-new -EL -m elf64lppc -pie ... -o .tmp_vmlinux.kallsyms1 ...
  ld-new: read-only segment has dynamic relocations

Add "-z notext" to suppress the errors. Non-CONFIG_RELOCATABLE builds use the
default -no-pie mode and thus R_PPC64_ADDR64 relocations can be resolved at
link-time.

Link: https://github.com/ClangBuiltLinux/linux/issues/811
Signed-off-by: Fangrui Song <maskray@google.com>
Co-developed-by: Bill Wendling <morbo@google.com>
Signed-off-by: Bill Wendling <morbo@google.com>
Reported-by: Itaru Kitayama <itaru.kitayama@riken.jp>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
v2:
  - Assign "Fangrui Song" as the proper author.
  - Improve the commit message to add more context.
  - Appending tags from original patch's review.
---
 arch/powerpc/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 6505d66f1193..17a9fbf9b789 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -122,6 +122,7 @@ endif
 
 LDFLAGS_vmlinux-y := -Bstatic
 LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
+LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) += -z notext
 LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y)
 
 ifdef CONFIG_PPC64
-- 
2.33.0.rc1.237.g0d66db33f3-goog