linux-kernel - Re: [PATCH 2/2] mm: fix undefined reference to `.kernel_map

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Message-ID: <20150122212017.4b7032d52a6c75c06d5b4728@freescale.com>
Date:	Thu, 22 Jan 2015 21:20:17 -0600
From:	Kim Phillips <kim.phillips@...escale.com>
To:	Akinobu Mita <akinobu.mita@...il.com>
CC:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<josh@...htriplett.org>, Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan@...nel.org>,
	Rik van Riel <riel@...hat.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Konstantin Khlebnikov <k.khlebnikov@...sung.com>,
	Jens Axboe <axboe@...com>, <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 2/2] mm: fix undefined reference to `.kernel_map_pages'
 on PPC builds

On Fri, 23 Jan 2015 08:49:36 +0900
Akinobu Mita <akinobu.mita@...il.com> wrote:

> 2015-01-23 5:41 GMT+09:00 Kim Phillips <kim.phillips@...escale.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.
> 
> Then, in order to use generic __kernel_map_pages() in mm/debug-pagealloc.c,
> CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC shouldn't be selected in
> arch/powerpc/Kconfig, when CONFIG_PPC_STD_MMU_64 isn't defined.

Thanks.  I'm still build-testing this now:

>From 082911ee947246ff962ef21863c45ec467455c40 Mon Sep 17 00:00:00 2001
From: Kim Phillips <kim.phillips@...escale.com>
Date: Thu, 22 Jan 2015 20:42:40 -0600
Subject: [PATCH v2] mm: fix undefined reference to  `.__kernel_map_pages' on FSL
 PPC64

arch/powerpc has __kernel_map_pages implementations in mm/pgtable_32.c, and
mm/hash_utils_64.c, of which the former is built for PPC32, and the latter
PPC64's without PPC_STD_MMU.  Fix arch/powerpc/Kconfig to not select
ARCH_SUPPORTS_DEBUG_PAGEALLOC when CONFIG_PPC_STD_MMU_64 isn't defined,
i.e., for 64-bit book3e builds to use the generic __kernel_map_pages()
in mm/debug-pagealloc.c.

  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

Signed-off-by: Kim Phillips <kim.phillips@...escale.com>
---
v2: corrected SUPPORTS_DEBUG_PAGEALLOC selection to enable
non-STD_MMU_64 builds to use the generic __kernel_map_pages().

note: depends on Joonsoo Kim's patch "mm/debug_pagealloc: fix build
failure on ppc and some other archs" published earlier in this
thread.

 arch/powerpc/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a2a168e..22b0940 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -256,6 +256,7 @@ config PPC_OF_PLATFORM_PCI
 	default n
 
 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
+	depends on PPC32 || PPC_STD_MMU_64
 	def_bool y
 
 config ARCH_SUPPORTS_UPROBES
-- 
2.2.2

Thanks,

Kim
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