Re: [PATCH 18/29] [AARCH64] Reformat inline-asm in elf_machine_load_address.

[Will Newton <will.newton@linaro.org>]

On 27 October 2014 07:59, Andrew Pinski <apinski@cavium.com> wrote:
> This patch reformats the inline-asm in elf_machine_load_address so it is
> easier to change only part of the inline-asm.  That is using string
> concating instead of string continueing.
>
> Also document on why this inline-asm works, it depends on the 32bit
> relocation being resolved at link time.
>
> * sysdeps/aarch64/dl-machine.h (elf_machine_load_address):
> Refactor inline-asm.  Also add comment.
> ---
>  sysdeps/aarch64/dl-machine.h |   21 ++++++++++++---------
>  1 files changed, 12 insertions(+), 9 deletions(-)

This looks ok to me.

> diff --git a/sysdeps/aarch64/dl-machine.h b/sysdeps/aarch64/dl-machine.h
> index 6e041b1..121b178 100644
> --- a/sysdeps/aarch64/dl-machine.h
> +++ b/sysdeps/aarch64/dl-machine.h
> @@ -53,19 +53,22 @@ elf_machine_load_address (void)
>       The choice of symbol is arbitrary. The static address we obtain
>       by constructing a non GOT reference to the symbol, the dynamic
>       address of the symbol we compute using adrp/add to compute the
> -     symbol's address relative to the PC. */
> +     symbol's address relative to the PC.
> +     This depends on 32bit relocations being resolved at link time
> +     and that the static address fits in the 32bits.  */
>
>    ElfW(Addr) static_addr;
>    ElfW(Addr) dynamic_addr;
>
> -  asm ("                                       \n\
> -       adrp    %1, _dl_start;                  \n\
> -        add    %1, %1, #:lo12:_dl_start        \n\
> -        ldr    %w0, 1f                         \n\
> -       b       2f                              \n\
> -1:     .word   _dl_start                       \n\
> -2:                                             \n\
> -       " : "=r" (static_addr),  "=r" (dynamic_addr));
> +  asm ("                                       \n"
> +"      adrp    %1, _dl_start;                  \n"
> +"       add    %1, %1, #:lo12:_dl_start        \n"
> +"       ldr    %w0, 1f                         \n"
> +"      b       2f                              \n"
> +"1:                                            \n"
> +"      .word   _dl_start                       \n"
> +"2:                                            \n"
> +    : "=r" (static_addr),  "=r" (dynamic_addr));
>    return dynamic_addr - static_addr;
>  }
>
> --
> 1.7.2.5
>

-- 
Will Newton
Toolchain Working Group, Linaro