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SubjectRe: [PATCH 08/17] binfmt_flat: consolidate two version of flat_v2_reloc_t
On Thu, Jun 13, 2019 at 09:08:54AM +0200, Christoph Hellwig wrote:
> Two branches of the ifdef maze actually have the same content, so merge
> them.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> include/linux/flat.h | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/flat.h b/include/linux/flat.h
> index 2b7cda6e9c1b..19c586b74b99 100644
> --- a/include/linux/flat.h
> +++ b/include/linux/flat.h
> @@ -69,15 +69,13 @@ struct flat_hdr {
> typedef union {
> unsigned long value;
> struct {
> -# if defined(mc68000) && !defined(CONFIG_COLDFIRE)
> +#if defined(__LITTLE_ENDIAN_BITFIELD) || \
> + (defined(mc68000) && !defined(CONFIG_COLDFIRE))
> signed long offset : 30;
> unsigned long type : 2;
> # elif defined(__BIG_ENDIAN_BITFIELD)
> unsigned long type : 2;
> signed long offset : 30;
> -# elif defined(__LITTLE_ENDIAN_BITFIELD)
> - signed long offset : 30;
> - unsigned long type : 2;
> # else
> # error "Unknown bitfield order for flat files."
> # endif
> --
> 2.20.1
>

FWIW, I wonder if keeping that type is worth bothering.
Something like
old_reloc(__be32 reloc)
{
u32 v = be32_to_cpu(reloc);
int offset, type;

#if (defined(mc68000) && !defined(CONFIG_COLDFIRE))
/* old m68k uses unusual format - type is in lower bits of octet 3 */
type = v % 4;
offset = (int)v / 4;
#else
/* everything else (including coldfire) has it in upper bits of octet 0 */
type = v >> 30;
offset = (int)(v << 2) >> 2; /* or (v & 0x1fffffff) - (v & 0x20000000) * 4 */
#endif
...

and to hell with bitfields, aliasing unions, etc. Unless I'm misreading
the whole thing, that is... Greg?

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