Re: [Qemu-devel] [PATCH v9 1/8] loader: Allow ELF loader to auto-detect the ELF arch

[Peter Maydell]

On 14 July 2016 at 01:03, Alistair Francis <address@hidden> wrote:
> If the caller didn't specify an architecture for the ELF machine
> the load_elf() function will auto detect it based on the ELF file.
>
> Signed-off-by: Alistair Francis <address@hidden>
> ---
> V9:
>  - Update documentation
> V8:
>  - Move into load_elf64/load_elf32
> V7:
>  - Fix typo
>
>  include/hw/elf_ops.h | 5 +++++
>  include/hw/loader.h  | 3 +++
>  2 files changed, 8 insertions(+)
>
> diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
> index f510e7e..db70c11 100644
> --- a/include/hw/elf_ops.h
> +++ b/include/hw/elf_ops.h
> @@ -280,6 +280,11 @@ static int glue(load_elf, SZ)(const char *name, int fd,
>          glue(bswap_ehdr, SZ)(&ehdr);
>      }
>
> +    if (elf_machine < 1) {
> +        /* The caller didn't specify an ARCH, we can figure it out */
> +        elf_machine = ehdr.e_machine;
> +    }
> +
>      switch (elf_machine) {
>          case EM_PPC64:
>              if (ehdr.e_machine != EM_PPC64) {
> diff --git a/include/hw/loader.h b/include/hw/loader.h
> index 4879b63..fd540fc 100644
> --- a/include/hw/loader.h
> +++ b/include/hw/loader.h
> @@ -68,6 +68,9 @@ const char *load_elf_strerror(int error);
>   * load will fail if the target ELF does not match. Some architectures
>   * have some architecture-specific behaviours that come into effect when
>   * their particular values for @elf_machine are set.
> + * If no @elf_machine is provided the machine will default to the value
> + * in the ELFs header and no checks will be carried out against the
> + * machine type.
>   */

The argument is mandatory, you can't not provide it.
Should we make this "if @elf_machine is EM_NONE then the
machine type will be read from the ELF header" ? (EM_NONE is 0).

thanks
-- PMM