Re: [Qemu-devel] [PATCH v1 16/17] loader: Add data swap option to load-elf

[Peter Maydell <peter.maydell@linaro.org>]

On 18 January 2016 at 07:12, Peter Crosthwaite
<crosthwaitepeter@gmail.com> wrote:
> Some CPUs are of an opposite data-endianness to other components in the
> system. Sometimes elfs have the data sections layed out with this CPU
> data-endianess accounting for when loaded via the CPU, byte swaps
> (relative to other system components) will occur.
>
> The leading example, is ARM's BE32 mode, which is is basically LE with
> address manipulation on half-word and byte accesses to access the
> hw/byte reversed address. This means that word data is invariant
> accross LE and BE32. This also means that instructions are still LE.
> The expectation is that the elf will be loaded via the CPU in this
> endianness scheme, which means the data in the elf is reversed at
> compile time.
>
> As QEMU loads via the system memory directly, rather than the CPU, we
> need a mechanism to reverse elf data endianness to implement this
> possibility.
>
> Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>

> diff --git a/include/hw/loader.h b/include/hw/loader.h
> index 33067f8..e542575 100644
> --- a/include/hw/loader.h
> +++ b/include/hw/loader.h
> @@ -35,7 +35,7 @@ const char *load_elf_strerror(int error);
>  int load_elf(const char *filename, uint64_t (*translate_fn)(void *, uint64_t),
>               void *translate_opaque, uint64_t *pentry, uint64_t *lowaddr,
>               uint64_t *highaddr, int big_endian, int elf_machine,
> -             int clear_lsb);
> +             int clear_lsb, int data_swab);
>  void load_elf_hdr(const char *filename, void *hdr, bool *is64, Error **errp);
>  int load_aout(const char *filename, hwaddr addr, int max_sz,
>                int bswap_needed, hwaddr target_page_size);

Can we have a doc comment so we have something that defines what
values data_swab accepts? (it's not just a bool).

Otherwise
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM