[PATCH 2/2] mm: fix undefined reference to `.kernel_map_pages' on PPC builds

[Kim Phillips]

On Thu, 22 Jan 2015 10:45:51 +0900
Joonsoo Kim <iamjoonsoo.kim at lge.com> wrote:

> On Wed, Jan 21, 2015 at 09:57:59PM +0900, Akinobu Mita wrote:
> > 2015-01-21 9:07 GMT+09:00 Andrew Morton <akpm at linux-foundation.org>:
> > > On Tue, 20 Jan 2015 15:01:50 -0800 josh at joshtriplett.org wrote:
> > >
> > >> On Tue, Jan 20, 2015 at 02:02:00PM -0600, Kim Phillips wrote:
> > >> > It's possible to configure DEBUG_PAGEALLOC without PAGE_POISONING on
> > >> > ppc.  Fix building the generic kernel_map_pages() implementation in
> > >> > this case:
> > >> >
> > >> >   LD      init/built-in.o
> > >> > mm/built-in.o: In function `free_pages_prepare':
> > >> > mm/page_alloc.c:770: undefined reference to `.kernel_map_pages'
> > >> > mm/built-in.o: In function `prep_new_page':
> > >> > mm/page_alloc.c:933: undefined reference to `.kernel_map_pages'
> > >> > mm/built-in.o: In function `map_pages':
> > >> > mm/compaction.c:61: undefined reference to `.kernel_map_pages'
> > >> > make: *** [vmlinux] Error 1
> > 
> > kernel_map_pages() is static inline function since commit 031bc5743f15
> > ("mm/debug-pagealloc: make debug-pagealloc boottime configurable").
> > 
> > But there is old declaration in 'arch/powerpc/include/asm/cacheflush.h'.
> > Removing it or changing s/kernel_map_pages/__kernel_map_pages/ in this
> > header file or something can fix this problem?
> > 
> > The architecture which has ARCH_SUPPORTS_DEBUG_PAGEALLOC
> > including PPC should not build mm/debug-pagealloc.o
> 
> Yes, architecture with ARCH_SUPPORTS_DEBUG_PAGEALLOC should not build
> mm/debug-pagealloc.o. I attach the patch to remove old declaration.
> I hope it will fix Kim's problem.
> 
> -------------->8------------------
> From 7cb9d1ed8a785df152cb8934e187031c8ebd1bb2 Mon Sep 17 00:00:00 2001
> From: Joonsoo Kim <iamjoonsoo.kim at lge.com>
> Date: Thu, 22 Jan 2015 10:28:58 +0900
> Subject: [PATCH] mm/debug_pagealloc: fix build failure on ppc and some other
>  archs
> 
> Kim Phillips reported following build failure.
> 
>   LD      init/built-in.o
>   mm/built-in.o: In function `free_pages_prepare':
>   mm/page_alloc.c:770: undefined reference to `.kernel_map_pages'
>   mm/built-in.o: In function `prep_new_page':
>   mm/page_alloc.c:933: undefined reference to `.kernel_map_pages'
>   mm/built-in.o: In function `map_pages':
>   mm/compaction.c:61: undefined reference to `.kernel_map_pages'
>   make: *** [vmlinux] Error 1
> 
> Reason for this problem is that commit 031bc5743f15
> ("mm/debug-pagealloc: make debug-pagealloc boottime configurable") forgot
> to remove old declaration of kernel_map_pages() in some architectures.
> This patch removes them to fix build failure.
> 
> Reported-by: Kim Phillips <kim.phillips at freescale.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim at lge.com>
> ---

Thanks. Now I get this:

  LD      init/built-in.o
mm/built-in.o: In function `kernel_map_pages':
include/linux/mm.h:2076: undefined reference to `.__kernel_map_pages'
include/linux/mm.h:2076: undefined reference to `.__kernel_map_pages'
include/linux/mm.h:2076: undefined reference to `.__kernel_map_pages'
Makefile:925: recipe for target 'vmlinux' failed
make: *** [vmlinux] Error 1

but, AFAICT, that's not because this patch is invalid: it's because
__kernel_map_pages() isn't implemented in
arch/powerpc/mm/pgtable_64.c, i.e., for non-PPC_STD_MMU_64 PPC64
machines.

Kim