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From: Greg Ungerer <gregungerer00@gmail.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "moderated list:H8/300 ARCHITECTURE"
	<uclinux-h8-devel@lists.sourceforge.jp>,
	linux-xtensa@linux-xtensa.org, Michal Simek <monstr@monstr.eu>,
	linux-c6x-dev@linux-c6x.org,
	Linux-sh list <linux-sh@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-m68k <linux-m68k@lists.linux-m68k.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	linux-riscv@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 08/17] binfmt_flat: consolidate two version of flat_v2_reloc_t
Date: Wed, 26 Jun 2019 22:14:06 +1000
Message-ID: <a2567a04-ac83-408f-51a2-53d23fcc0c36@linux-m68k.org> (raw)
In-Reply-To: <CAMuHMdXkMh+pOqPNavmYAhKXTVT12nC5gKc10CJj_CXME+uhWQ@mail.gmail.com>

Hi Geert,

On 26/6/19 6:18 pm, Geert Uytterhoeven wrote:
> Hi Greg,
> 
> On Wed, Jun 26, 2019 at 9:23 AM Greg Ungerer <gerg@linux-m68k.org> wrote:
>> On 26/6/19 8:29 am, Al Viro wrote:
>>> 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?
>>
>> I think you are right. This is much better.
>> The old mc6800 is the odd one out, the rest have it in network order,
>> and this makes that much clearer.
> 
> Is that correct for Microblaze, which can be big or little endian?

It is true for all architectures that use flat. All fields inside a
flat format binary are store in network order.

The final processing of the relocation entries in the elf2flt
converter tool:

    for (i=0; i<reloc_len; i++) reloc[i] = htonl(reloc[i]);

Regards
Greg



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Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-13  7:08 binfmt_flat cleanups and RISC-V support v2 Christoph Hellwig
2019-06-13  7:08 ` [PATCH 01/17] binfmt_flat: remove flat_reloc_valid Christoph Hellwig
2019-06-13  7:08 ` [PATCH 02/17] binfmt_flat: remove flat_set_persistent Christoph Hellwig
2019-06-13  7:08 ` [PATCH 03/17] binfmt_flat: provide a default version of flat_get_relocate_addr Christoph Hellwig
2019-06-13  7:08 ` [PATCH 04/17] binfmt_flat: remove flat_old_ram_flag Christoph Hellwig
2019-06-13  7:08 ` [PATCH 05/17] binfmt_flat: replace flat_argvp_envp_on_stack with a Kconfig variable Christoph Hellwig
2019-06-13  7:08 ` [PATCH 06/17] binfmt_flat: remove the uapi <linux/flat.h> header Christoph Hellwig
2019-06-13  7:08 ` [PATCH 07/17] binfmt_flat: remove the unused OLD_FLAT_FLAG_RAM definition Christoph Hellwig
2019-06-13  7:08 ` [PATCH 08/17] binfmt_flat: consolidate two version of flat_v2_reloc_t Christoph Hellwig
2019-06-25 22:29   ` Al Viro
2019-06-26  7:23     ` Greg Ungerer
2019-06-26  8:18       ` Geert Uytterhoeven
2019-06-26 12:14         ` Greg Ungerer [this message]
2019-06-13  7:08 ` [PATCH 09/17] binfmt_flat: use fixed size type for the on-disk format Christoph Hellwig
2019-06-13  7:08 ` [PATCH 10/17] binfmt_flat: add endianess annotations Christoph Hellwig
2019-06-13  7:08 ` [PATCH 11/17] binfmt_flat: add a ARCH_HAS_BINFMT_FLAT option Christoph Hellwig
2019-06-13  7:08 ` [PATCH 12/17] binfmt_flat: make support for old format binaries optional Christoph Hellwig
2019-06-13  7:08 ` [PATCH 13/17] binfmt_flat: provide an asm-generic/flat.h Christoph Hellwig
2019-06-13  7:09 ` [PATCH 14/17] binfmt_flat: remove the persistent argument from flat_get_addr_from_rp Christoph Hellwig
2019-06-13  7:09 ` [PATCH 15/17] binfmt_flat: move the MAX_SHARED_LIBS definition to binfmt_flat.c Christoph Hellwig
2019-06-14  8:35   ` Sergei Shtylyov
2019-06-13  7:09 ` [PATCH 16/17] binfmt_flat: don't offset the data start Christoph Hellwig
2019-06-13  7:09 ` [PATCH 17/17] riscv: add binfmt_flat support Christoph Hellwig
2019-06-13 23:38 ` binfmt_flat cleanups and RISC-V support v2 Greg Ungerer

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