linux-kernel - New ORC unwinder in 4.14 broke cross-compilation?

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Date:   Mon, 13 Nov 2017 21:33:23 +0300
From:   Andrew Randrianasulu <randrianasulu@...il.com>
To:     linux-kernel@...r.kernel.org
Subject: New ORC unwinder in 4.14 broke cross-compilation?

Hello!

I was building my new 4.14 kernel, and on first instance I got working kernel + 
modules, booted ok, found my fb console was missing, recompiled kernel with 
framebuffer console built-in (it resetted itself from M to N, because I was 
using menuconfig on .config from 4.12 where I had fbcon = M). After reboot into 
new kernel everything works, so far. But if I select new ORC unwinder under 
kernel hacking submenu - I get compilation error early:

guest@...x:/dev/shm/src/linux-2.6$ LANG=C make ARCH=x86_64 
CROSS_COMPILE=x86_64-unknown-linux-gnu-
  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CHK     include/generated/bounds.h
  CHK     include/generated/timeconst.h
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  DESCEND  objtool
  CC       /dev/shm/src/linux-2.6/tools/objtool/orc_dump.o
orc_dump.c: In function 'orc_dump':
orc_dump.c:105:2: error: passing argument 2 of 'elf_getshdrnum' from 
incompatible pointer type [-Werror]
  if (elf_getshdrnum(elf, &nr_sections)) {
  ^
In file included from /usr/include/gelf.h:32:0,
                 from elf.h:22,
                 from warn.h:26,
                 from orc_dump.c:20:
/usr/include/libelf.h:244:12: note: expected 'size_t *' but argument is of 
type 'long unsigned int *'
 extern int elf_getshdrnum (Elf *__elf, size_t *__dst);
            ^
orc_dump.c:190:4: error: format '%lx' expects argument of type 'long unsigned 
int', but argument 3 has type 'Elf64_Sxword' [-Werror=format=]
    printf("%s+%lx:", name, rela.r_addend);
    ^
cc1: all warnings being treated as errors
mv: cannot stat '/dev/shm/src/linux-2.6/tools/objtool/.orc_dump.o.tmp': No such 
file or directory
make[3]: *** [/dev/shm/src/linux-2.6/tools/objtool/orc_dump.o] Error 1
make[2]: *** [/dev/shm/src/linux-2.6/tools/objtool/objtool-in.o] Error 2
make[1]: *** [objtool] Error 2
make: *** [tools/objtool] Error 2

--------------

I try to cross-compile from 32-bit slackware with self-built minimal 
cross-compiler:

LANG=C /opt/kgcc64/bin/x86_64-unknown-linux-gnu-gcc --version
x86_64-unknown-linux-gnu-gcc (GCC) 4.9.2
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

I basically just followed steps from https://www.linux-mips.org/wiki/Toolchains 
but replaced mips with x86_64 . It worked on many kernels for long time. This 
new kernel first complained about missing gelf.h include, and after installing 
elfutils-0.163-i586-1 (compiled on 32-bit slackware) I now have this error. 
Problem is, even if I unselect ORC unwinder and choose Frame-pointer based 
unwinder again - error remain, at least after make clean.

I usually monitor LKML via web-interface, but please CC me just in case I miss 
my answers. Attached .config after changing unwinder back to frame-pointer 
based.

View attachment ".config" of type "text/plain" (197348 bytes)