Re: [Qemu-devel] [ARM/FDPIC v2 2/4] linux-user: ARM-FDPIC: Identify ARM FDPIC binaries

[Peter Maydell]

On 23 April 2018 at 08:51, Christophe Lyon <address@hidden> wrote:
> Define an ARM-specific version of elf_is_fdpic:
> FDPIC ELF objects are identified with e_ident[EI_OSABI] ==
> ELFOSABI_ARM_FDPIC.
>
> Co-Authored-By: Mickaël Guêné <address@hidden>
> Signed-off-by: Christophe Lyon <address@hidden>
>
> diff --git a/include/elf.h b/include/elf.h
> index c0dc9bb..934dbbd 100644
> --- a/include/elf.h
> +++ b/include/elf.h
> @@ -1483,6 +1483,7 @@ typedef struct elf64_shdr {
>  #define ELFOSABI_TRU64          10      /* Compaq TRU64 UNIX.  */
>  #define ELFOSABI_MODESTO        11      /* Novell Modesto.  */
>  #define ELFOSABI_OPENBSD        12      /* OpenBSD.  */
> +#define ELFOSABI_ARM_FDPIC      65      /* ARM FDPIC */
>  #define ELFOSABI_ARM            97      /* ARM */
>  #define ELFOSABI_STANDALONE     255     /* Standalone (embedded) application 
> */
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index bbe93b0..76d7718 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -1681,11 +1681,18 @@ static void zero_bss(abi_ulong elf_bss, abi_ulong 
> last_bss, int prot)
>      }
>  }
>
> +#ifdef TARGET_ARM
> +static int elf_is_fdpic(struct elfhdr *exec)
> +{
> +    return exec->e_ident[EI_OSABI] == ELFOSABI_ARM_FDPIC;
> +}
> +#else
>  /* Default implementation, always false.  */
>  static int elf_is_fdpic(struct elfhdr *exec)
>  {
>      return 0;
>  }
> +#endif

I have a strong dislike for per-target ifdef ladders. Can we instead
put the target's implementation of elf_is_fdpic() into
linux-user/$ARCH/target_elf.h
and also have that header do
#define TARGET_HAS_ELF_FDPIC

and then in the generic code we can protect the default elf_is_fdpic()
with #ifndef TARGET_HAS_ELF_FDPIC.

thanks
-- PMM