Re: [x32] Allow R_X86_64_64

["Jan Beulich" <JBeulich at novell dot com>]

>>> On 12.08.11 at 06:37, "H.J. Lu" <hjl.tools@gmail.com> wrote:
> On Mon, Aug 1, 2011 at 3:15 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> Hi,
>>
>> It turns out that x32 needs R_X86_64_64.  One major reason is
>> the displacement range of x32 is -2G to +2G.  It isn't a problem
>> for compiler since only small model is required for x32.
>>
>> However, to address 0 to 4G directly in assembly code, we have
>> to use R_X86_64_64 with movabs.  I am checking the follow patch
>> into x32 psABI to allow R_X86_64_64.
>>
>>
> 
> X32  Linker should treats R_X86_64_64 as R_X86_64_32
> zero-extended to 64bit for output.  I will update x32 psABI with

I'm sorry to say that, but the situation about x32 seems to be
getting worse with each change you do, every time again
revolving around mixing up ABI specification and a particular
implementation thereof.

Here, if you need something zero-extended (though I can't see
why you would), then you should use a new relocation type. As
pointed out before, there are valid possible uses of R_X86_64_64
that would require the semantics of x86-64.

Jan

> ---
> diff --git a/object-files.tex b/object-files.tex
> index 7f0fd14..d1543b5 100644
> --- a/object-files.tex
> +++ b/object-files.tex
> @@ -451,7 +451,7 @@ or \texttt{Elf32_Rel} relocation.
>        \multicolumn{1}{c}{Calculation} \\
>        \hline
>        \texttt{R_X86_64_NONE}  & 0 & none & none \\
> -      \texttt{R_X86_64_64} & 1 & \textit{word64} & \texttt{S + A} \\
> +      \texttt{R_X86_64_64} $^{\dagger\dagger}$ & 1 & \textit{word64}
> & \texttt{S + A} \\
>        \texttt{R_X86_64_PC32}  & 2 & \textit{word32} & \texttt{S + A - P} \\
>        \texttt{R_X86_64_GOT32} & 3 & \textit{word32} & \texttt{G + A} \\
>        \texttt{R_X86_64_PLT32} & 4 & \textit{word32} & \texttt{L + A - P} \\
> @@ -487,6 +487,8 @@ or \texttt{Elf32_Rel} relocation.
>  %      \texttt{R_X86_64_PLT64} & 17 & \textit{word64} & \texttt{L + A - P} \\
>       \cline{1-4}
>      \multicolumn{3}{l}{\small $^\dagger$ This relocation is used only
> for LP64.}\\
> +    \multicolumn{3}{l}{\small $^{\dagger\dagger}$ This relocation only
> +    appears in relocatable files for X32.}\\
>      \end{tabular}
>    \end{center}
>  \Hrule
> ----
> 
> I opened:
> 
> http://sourceware.org/bugzilla/show_bug.cgi?id=13082 
> 
> and will fix it.
>