linux-kernel - Re: [PATCH] MIPS: boot: Fix unaligned access with?? CONFIG_MIPS_RAW_APPENDED

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Message-Id: <GL54MQ.XG61RLIPAFCV@crapouillou.net>
Date:   Tue, 29 Dec 2020 18:20:04 +0000
From:   Paul Cercueil <paul@...pouillou.net>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>, od@...c.me,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com, stable@...r.kernel.org
Subject: Re: [PATCH] MIPS: boot: Fix unaligned access
 with??
 CONFIG_MIPS_RAW_APPENDED_DTB

Hi Thomas,

Le mar. 29 déc. 2020 à 16:08, Thomas Bogendoerfer 
<tsbogend@...ha.franken.de> a écrit :
> On Mon, Dec 28, 2020 at 10:30:36PM +0000, Paul Cercueil wrote:
>>  Le lun. 28 déc. 2020 à 23:25, Thomas Bogendoerfer
>>  <tsbogend@...ha.franken.de> a écrit :
>>  > On Wed, Dec 16, 2020 at 11:39:56PM +0000, Paul Cercueil wrote:
>>  > >  The compressed payload is not necesarily 4-byte aligned, at 
>> least
>>  > > when
>>  > >  compiling with Clang. In that case, the 4-byte value appended 
>> to the
>>  > >  compressed payload that corresponds to the uncompressed kernel 
>> image
>>  > >  size must be read using get_unaligned_le().
>>  > >
>>  > >  This fixes Clang-built kernels not booting on MIPS (tested on a
>>  > > Ingenic
>>  > >  JZ4770 board).
>>  > >
>>  > >  Fixes: b8f54f2cde78 ("MIPS: ZBOOT: copy appended dtb to the 
>> end of
>>  > > the kernel")
>>  > >  Cc: <stable@...r.kernel.org> # v4.7
>>  > >  Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>>  > >  ---
>>  > >   arch/mips/boot/compressed/decompress.c | 2 +-
>>  > >   1 file changed, 1 insertion(+), 1 deletion(-)
>>  > >
>>  > >  diff --git a/arch/mips/boot/compressed/decompress.c
>>  > > b/arch/mips/boot/compressed/decompress.c
>>  > >  index c61c641674e6..47c07990432b 100644
>>  > >  --- a/arch/mips/boot/compressed/decompress.c
>>  > >  +++ b/arch/mips/boot/compressed/decompress.c
>>  > >  @@ -117,7 +117,7 @@ void decompress_kernel(unsigned long
>>  > > boot_heap_start)
>>  > >   		dtb_size = fdt_totalsize((void *)&__appended_dtb);
>>  > >
>>  > >   		/* last four bytes is always image size in little endian */
>>  > >  -		image_size = le32_to_cpup((void *)&__image_end - 4);
>>  > >  +		image_size = get_unaligned_le32((void *)&__image_end - 4);
>>  >
>>  > gives me following error
>>  >
>>  > arch/mips/boot/compressed/decompress.c:120:16: error: implicit
>>  > declaration of function ‘get_unaligned_le32’
>>  > [-Werror=implicit-function-declaration]
>>  >    image_size = get_unaligned_le32((void *)&__image_end - 4);
>>  >
>>  > I've added
>>  >
>>  > #include <asm/unaligned.h>
>>  >
>>  > which fixes the compile error, but I'm wondering why the patch 
>> compiled
>>  > for you ?
>> 
>>  No idea - but it does compile fine without the include here. 
>> Probably a
>>  defconfig difference.
> 
> # CONFIG_KERNEL_LZO is not set
> # CONFIG_KERNEL_LZ4 is not set
> 
> this makes the difference. Both decompress.c files include 
> asm/unaligned.h.
> 
> I've added the #include, fixed the get_unaligned_le32 in the 
> description
> and applied it to mips-fixes.

Alright, great! Thanks!

Cheers,
-Paul