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git: kern build: Tweak ldscripts for gold linker

From: John Marino <marino@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 23 Feb 2012 22:52:21 -0800 (PST)

commit e19c755caea4d4761617e54c6d5ae1919cbf2765
Author: John Marino <draco@marino.st>
Date:   Thu Feb 23 19:03:04 2012 +0100

    kern build: Tweak ldscripts for gold linker
    The gold linker v2.21 was able to link a working kernel although its
    modules were unloadable.  The gold linker v2.22 could build loadable
    modules, but the kernel wouldn't boot!  It's not clear why the modules
    started to work -- my guess is that the ancient ldscripts used during
    the 2.21 trial were the culprit.
    The gold linker changed its ELF program header handling defaults for
    version 2.22, and this resulted in an extra LOAD segment reserved only
    for the program headers.  The DragonFly loader wasn't expecting that
    and instantly rebooted when trying to load a gold kernel.
    The solution was to add a PHDRS section to the ldscripts to specify
    exactly the section to segment mapping, and prevent gold from putting
    the elf headers in their own load segment.  Now gold matches gnu ld
    linker in having only two LOAD segments, text and data.
    As a curiousity, gold sets the LOAD segment alignment value at 0x1000
    for both i386 and x86_64, where gnu ld sets the segment alignment at
    0x1000 for i386 and 0x200000 for x86_64.  This seems to have no impact
    on the loading of the kernel.

Summary of changes:
 sys/platform/pc32/conf/ldscript.i386        |   20 +++++++++++++++-----
 sys/platform/pc64/conf/ldscript.x86_64      |   20 +++++++++++++++-----
 sys/platform/vkernel/conf/ldscript.i386     |   20 +++++++++++++++-----
 sys/platform/vkernel64/conf/ldscript.x86_64 |   20 +++++++++++++++-----
 4 files changed, 60 insertions(+), 20 deletions(-)


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