Re: Help needed to track down bug: linking Linux kernel with gold creates unbootable kernel

[Suresh Siddha <suresh dot b dot siddha at intel dot com>]

On Thu, 2010-04-22 at 14:21 -0700, H.J. Lu wrote:
> On Thu, Apr 22, 2010 at 2:10 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> > On Mon, Apr 12, 2010 at 10:27 PM, Ian Lance Taylor <iant@google.com>
> wrote:
> >> John Reiser <jreiser@bitwagon.com> writes:
> >>
> >>> The differing .p_align values of 0x1000 vs 0x200000 indicate that
> >>> gold has a bug interpreting the commands from the linker script
> >>> for alignment of Elf64_Phdr.
> >>
> >> It is perhaps worth noting that for x86_64 gold by default uses -z
> >> max-page-size 0x1000 whereas the default for GNU ld is -z
> >> max-page-size 0x200000.  While I haven't looked at the Linux linker
> >> script, perhaps it is assuming the latter.
> >>
> >
> > Linux kernel linker scripts needs to align .rodata section to 2MB:
> >
> > . = ALIGN((1 << 21));
> >
> > Since gold can only align to 4K, gold can't be used on Linux
> > kernel.
> >
> 
> Hi Ian,
> 
> If gold should be compatible with ld, this patch should be applied.
> 

We can also workaround in the kernel by overriding the value with "-z
max-page-size=0x200000" if this is supported.

thanks,
suresh

> 
> -- 
> H.J.
> ---
> diff --git a/gold/x86_64.cc b/gold/x86_64.cc
> index 9110278..99be4de 100644
> --- a/gold/x86_64.cc
> +++ b/gold/x86_64.cc
> @@ -516,7 +516,7 @@ const Target::Target_info
> Target_x86_64::x86_64_info =
>    '\0',       // wrap_char
>    "/lib/ld64.so.1",     // program interpreter
>    0x400000,      // default_text_segment_address
> -  0x1000,     // abi_pagesize (overridable by -z max-page-size)
> +  0x200000,      // abi_pagesize (overridable by -z max-page-size)
>    0x1000,     // common_pagesize (overridable by -z common-page-size)
>    elfcpp::SHN_UNDEF,   // small_common_shndx
>    elfcpp::SHN_X86_64_LCOMMON,   // large_common_shndx