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Re: [PATCH] Mach-O: Remove ambiguity of mach-o-le and mach-o-x86-64

From: Tristan Gingold <gingold at adacore dot com>
To: shinichiro hamaji <shinichiro dot hamaji at gmail dot com>
Cc: binutils Development <binutils at sourceware dot org>
Date: Fri, 16 Dec 2011 13:37:43 +0100
Subject: Re: [PATCH] Mach-O: Remove ambiguity of mach-o-le and mach-o-x86-64
References: <CALOyH=++wnGQePk8YVFHsoE5pfF7H7==yjw75Xk8yAHp2TjW-A@mail.gmail.com> <E02AA568-29D0-4358-BCDC-C105765E2123@adacore.com> <CALOyH=+tr=+RPtXM7aZ6Wj36mkbuJTNpHS4pR+6M7dOjVuW=MA@mail.gmail.com>

On Dec 16, 2011, at 1:19 PM, shinichiro hamaji wrote:

> Hi,
> 
> On Fri, Dec 16, 2011 at 5:28 PM, Tristan Gingold <gingold@adacore.com> wrote:
>> 
>> On Dec 15, 2011, at 7:26 PM, shinichiro hamaji wrote:
>> 
>>> Hi,
>>> 
>>> When we use objdump for x86-64 mach-o files without explicit -b flag,
>>> it says "File format is ambiguous" because there are two matching
>>> formats (mach-o-le and mach-o-x86-64). It's especially not useful when
>>> we run objdump for a fat binary which contains x86-64. Actually, I
>>> couldn't find any way to dump contents of x86-64 part of a fat binary.
>>> It seems i386 is OK as i386 mach-o doesn't match mach-o-le. This tiny
>>> patch does the same thing for x86-64:
>>> http://shinh.skr.jp/t/mach-o-64-le.patch
>> 
>> How did you configure binutils ?  It worked for me.
> 
> Ah, I've forgot to notice I'm using binutils from linux, where the
> bfd_default_vector[0] is elf64. I guess it work for you because you
> are working on Mac? I could confirm it just worked on Mac.

Ah, ok.  It explains why I have never noticed this issue.

>> 
>> I think it would be better to use the match_priority field.
> 
> Got it. I've found this field while investigating the matching
> algorithm in format.c, but I didn't use it because 1) I thought it is
> used only by binary.c due to lack of my grep-fu (I was clearly wrong
> here. ELF is using this field at least) and 2) mach-o.c is already
> using this way for i386.
> 
> I've rewritten my patch using match_priority field:
> http://shinh.skr.jp/t/mach-o-64-le-2.patch
> 
> I removed the special handling for i386 as I think it's unnecessary
> anymore. Of course, I'm happy to revert this change if we still should
> have it. I ran objdump -S and objdump -x on linux and mac for
> mach-o-i386, mach-o-x86-64, and mach-o-fat with my patch. Their
> outputs look good to me.

Nice.
I will commit that soon.

Thanks,
Tristan.

> 
> Thanks!
> 
> bfd/
> 2011-12-16  Shinichiro Hamaji  <shinichiro.hamaji@gmail.com>
> 
> 	* mach-o-i386.c (TARGET_PRIORITY): Define as 0 (top priority)
> 	* mach-o-target.c (TARGET_NAME): Use TARGET_PRIORITY
> 	* mach-o-x86-64.c (TARGET_PRIORITY): Define as 0 (top priority)
> 	* mach-o.c (bfd_mach_o_header_p): Remove special handling for
> 	mach-o-i386.
> 	(TARGET_PRIORITY) Set 1 for mach-o-be and mach-o-le, and set 0 for
> 	mach-o-fat.
> diff --git a/bfd/mach-o-i386.c b/bfd/mach-o-i386.c
> index c5e3884..3dadcb8 100644
> --- a/bfd/mach-o-i386.c
> +++ b/bfd/mach-o-i386.c
> @@ -347,4 +347,5 @@ const mach_o_segment_name_xlat
> mach_o_i386_segsec_names_xlat[] =
> #define TARGET_ARCHITECTURE	bfd_arch_i386
> #define TARGET_BIG_ENDIAN 	0
> #define TARGET_ARCHIVE 		0
> +#define TARGET_PRIORITY		0
> #include "mach-o-target.c"
> diff --git a/bfd/mach-o-target.c b/bfd/mach-o-target.c
> index c91584c..4aeb920 100644
> --- a/bfd/mach-o-target.c
> +++ b/bfd/mach-o-target.c
> @@ -118,7 +118,7 @@ const bfd_target TARGET_NAME =
>   '_',				/* symbol_leading_char.  */
>   ' ',				/* ar_pad_char.  */
>   16,				/* ar_max_namelen.  */
> -  0,				/* match priority.  */
> +  TARGET_PRIORITY,	/* match priority.  */
> 
> #if TARGET_BIG_ENDIAN
>   bfd_getb64, bfd_getb_signed_64, bfd_putb64,
> diff --git a/bfd/mach-o-x86-64.c b/bfd/mach-o-x86-64.c
> index 1bc3bf8..c86efb7 100644
> --- a/bfd/mach-o-x86-64.c
> +++ b/bfd/mach-o-x86-64.c
> @@ -294,4 +294,5 @@ bfd_mach_o_x86_64_bfd_reloc_name_lookup (bfd *abfd
> ATTRIBUTE_UNUSED,
> #define TARGET_ARCHITECTURE	bfd_arch_i386
> #define TARGET_BIG_ENDIAN 	0
> #define TARGET_ARCHIVE 		0
> +#define TARGET_PRIORITY		0
> #include "mach-o-target.c"
> diff --git a/bfd/mach-o.c b/bfd/mach-o.c
> index 325cf61..dca8601 100644
> --- a/bfd/mach-o.c
> +++ b/bfd/mach-o.c
> @@ -3261,17 +3261,6 @@ bfd_mach_o_header_p (bfd *abfd,
>       if (header.cputype != cputype)
>         goto wrong;
>     }
> -  else
> -    {
> -      switch (header.cputype)
> -        {
> -        case BFD_MACH_O_CPU_TYPE_I386:
> -          /* Handled by mach-o-i386 */
> -          goto wrong;
> -        default:
> -          break;
> -        }
> -    }
>   if (filetype)
>     {
>       if (header.filetype != filetype)
> @@ -3802,6 +3791,7 @@ bfd_boolean bfd_mach_o_free_cached_info (bfd *abfd)
> #define TARGET_ARCHITECTURE	bfd_arch_unknown
> #define TARGET_BIG_ENDIAN 	1
> #define TARGET_ARCHIVE 		0
> +#define TARGET_PRIORITY		1
> #include "mach-o-target.c"
> 
> #undef TARGET_NAME
> @@ -3809,12 +3799,14 @@ bfd_boolean bfd_mach_o_free_cached_info (bfd *abfd)
> #undef TARGET_ARCHITECTURE
> #undef TARGET_BIG_ENDIAN
> #undef TARGET_ARCHIVE
> +#undef TARGET_PRIORITY
> 
> #define TARGET_NAME 		mach_o_le_vec
> #define TARGET_STRING 		"mach-o-le"
> #define TARGET_ARCHITECTURE	bfd_arch_unknown
> #define TARGET_BIG_ENDIAN 	0
> #define TARGET_ARCHIVE 		0
> +#define TARGET_PRIORITY		1
> 
> #include "mach-o-target.c"
> 
> @@ -3823,6 +3815,7 @@ bfd_boolean bfd_mach_o_free_cached_info (bfd *abfd)
> #undef TARGET_ARCHITECTURE
> #undef TARGET_BIG_ENDIAN
> #undef TARGET_ARCHIVE
> +#undef TARGET_PRIORITY
> 
> /* Not yet handled: creating an archive.  */
> #define bfd_mach_o_mkarchive                      _bfd_noarchive_mkarchive
> @@ -3844,6 +3837,7 @@ bfd_boolean bfd_mach_o_free_cached_info (bfd *abfd)
> #define TARGET_ARCHITECTURE	bfd_arch_unknown
> #define TARGET_BIG_ENDIAN 	1
> #define TARGET_ARCHIVE 		1
> +#define TARGET_PRIORITY		0
> 
> #include "mach-o-target.c"
> 
> @@ -3852,3 +3846,4 @@ bfd_boolean bfd_mach_o_free_cached_info (bfd *abfd)
> #undef TARGET_ARCHITECTURE
> #undef TARGET_BIG_ENDIAN
> #undef TARGET_ARCHIVE
> +#undef TARGET_PRIORITY
> 
> 
>> 
>> Tristan.
>> 
>>> 
>>> bfd/
>>> 2011-12-16  Shinichiro Hamaji  <shinichiro.hamaji@gmail.com>
>>> 
>>>       * mach-o.c (bfd_mach_o_header_p): Don't handle x86-64 mach-o
>>>       when cputype is not specified. This case should be handled by
>>>       mach-o-x86-64.c.
>>> diff --git a/bfd/mach-o.c b/bfd/mach-o.c
>>> index 325cf61..a455b09 100644
>>> --- a/bfd/mach-o.c
>>> +++ b/bfd/mach-o.c
>>> @@ -3266,7 +3266,8 @@ bfd_mach_o_header_p (bfd *abfd,
>>>       switch (header.cputype)
>>>         {
>>>         case BFD_MACH_O_CPU_TYPE_I386:
>>> -          /* Handled by mach-o-i386 */
>>> +        case BFD_MACH_O_CPU_TYPE_X86_64:
>>> +          /* Handled by mach-o-i386 or mach-o-x86-64 */
>>>           goto wrong;
>>>         default:
>>>           break;
>>

References:
- [PATCH] Mach-O: Remove ambiguity of mach-o-le and mach-o-x86-64
  - From: shinichiro hamaji
- Re: [PATCH] Mach-O: Remove ambiguity of mach-o-le and mach-o-x86-64
  - From: Tristan Gingold
- Re: [PATCH] Mach-O: Remove ambiguity of mach-o-le and mach-o-x86-64
  - From: shinichiro hamaji

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