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Subject: Re: svn commit: r300257 - in head/sys/boot/i386: libi386 zfsboot
To: John Baldwin <jhb@freebsd.org>
References: <201605200141.u4K1flpV094958@repo.freebsd.org>
 <1780135.VYYOsNudFi@ralph.baldwin.cx>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org,
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From: Allan Jude <allanjude@freebsd.org>
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Date: Fri, 20 May 2016 11:00:22 -0400
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On 2016-05-20 10:48, John Baldwin wrote:
> On Friday, May 20, 2016 01:41:47 AM Allan Jude wrote:
>> Author: allanjude
>> Date: Fri May 20 01:41:47 2016
>> New Revision: 300257
>> URL: https://svnweb.freebsd.org/changeset/base/300257
>>
>> Log:
>>   Fixup the geliboot sector rounding code
>>   
>>   Replace all rounding with the round{up,down}2 macros
>>   a missing set of braces caused the previous code to be incorrect
>>   
>>   replace alloca() with malloc() because alloca() can return an allocation
>>   that is actually invalid, causing boot to fail
> 
> No, you have to revert the malloc!  malloc() can be anywhere.  The alloca
> is _on purpose_ to get a bufer below 1MB so that it will work with all
> devices.  Some BIOSes can only store data in the first 1MB.
> 

to be clear, the alloca() was something I added, not something that was
there before. And it was breaking, because ZFS was trying to allocate
too large a block of memory, that wouldn't fit below 1MB.

-- 
Allan Jude