Patchwork [18/29,AARCH64] Reformat inline-asm in elf_machine_load_address.

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Submitter Andrew Pinski
Date Oct. 27, 2014, 7:59 a.m.
Message ID <1414396793-9005-19-git-send-email-apinski@cavium.com>
Download mbox | patch
Permalink /patch/3412/
State New
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Comments

Andrew Pinski - Oct. 27, 2014, 7:59 a.m.
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(-)
Will Newton - Nov. 18, 2014, 1:51 p.m.
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
>

Patch

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;
 }