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Date:      Tue, 28 Nov 2017 08:13:53 -0800
From:      Nathan Whitehorn <nwhitehorn@freebsd.org>
To:        Justin Hibbits <jrh29@alumni.cwru.edu>
Cc:        src-committers <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>
Subject:   Re: svn commit: r326203 - head/sys/conf
Message-ID:  <5831ba86-742d-7019-e1c9-4b6563d2cdcc@freebsd.org>
In-Reply-To: <CAHSQbTA7c9VpZpYcB1%2BuW62yW%2BFoscnV8K9AL9txMKO43wcQpg@mail.gmail.com>
References:  <201711252145.vAPLjpV6051703@repo.freebsd.org> <CAHSQbTA7c9VpZpYcB1%2BuW62yW%2BFoscnV8K9AL9txMKO43wcQpg@mail.gmail.com>

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On 11/28/17 07:27, Justin Hibbits wrote:
> On Sat, Nov 25, 2017 at 3:45 PM, Nathan Whitehorn
> <nwhitehorn@freebsd.org> wrote:
>> Author: nwhitehorn
>> Date: Sat Nov 25 21:45:51 2017
>> New Revision: 326203
>> URL: https://svnweb.freebsd.org/changeset/base/326203
>>
>> Log:
>>    Avoid emitting a PT_INTERP section for powerpc64 kernels and arrange for
>>    the first instruction to be at the start of the text segment. This allows
>>    the kernel to be booted correctly by stock kexec-lite.
>>
>>    MFC after:    2 weeks
>>
>> Modified:
>>    head/sys/conf/ldscript.powerpc64
>>
>> Modified: head/sys/conf/ldscript.powerpc64
>> ==============================================================================
>> --- head/sys/conf/ldscript.powerpc64    Sat Nov 25 21:44:23 2017        (r326202)
>> +++ head/sys/conf/ldscript.powerpc64    Sat Nov 25 21:45:51 2017        (r326203)
>> @@ -10,7 +10,7 @@ SECTIONS
>>   {
>>     /* Read-only sections, merged into text segment: */
>>
>> -  . = kernbase + SIZEOF_HEADERS;
>> +  . = kernbase;
>>     PROVIDE (begin = . - SIZEOF_HEADERS);
>>
>>     .text      :
>> @@ -24,7 +24,10 @@ SECTIONS
>>     _etext = .;
>>     PROVIDE (etext = .);
>>
>> -  .interp     : { *(.interp)   }
>> +  /* Do not emit PT_INTERP section, which confuses some loaders (kexec-lite) */
>> +  .interpX    : { *(.interp)   } : NONE
>> +  /DISCARD/   : { *(.interp)   }
>> +
>>     .hash          : { *(.hash)          }
>>     .dynsym        : { *(.dynsym)                }
>>     .dynstr        : { *(.dynstr)                }
>>
> This broke powerpc64 Book-E kernels.  It now puts a 1MB blank space
> ahead of the kernel data (ELF header + 1MB - sizeof(header) of 0's),
> meaning that now the kernel needs to be loaded by uboot 1MB earlier in
> memory, rather than straight on the 64MB boundary as it has been.
>
> - Justin
>

How on Earth? It doesn't do that on my system. What binutils are you using?
-Nathan



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