Re: [PATCH] MIPS: boot: Fix unaligned access with CONFIG_MIPS_RAW_APPENDED_DTB

[Paul Cercueil]

Hi Thomas,

Le lun. 28 déc. 2020 à 23:25, Thomas Bogendoerfer 
<tsbogend@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx> # v4.7
> >  Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  ---
> >   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.

Cheers,
-Paul