Date: Tue, 29 Apr 1997 15:43:17 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: hackers@freebsd.org Subject: mapping memory inside the kernel? Message-ID: <199704290613.PAA20132@genesis.atrad.adelaide.edu.au>
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A question for those familiar with the workings of the kernel wrt.
load-time and mappings;
If I want to load extra data after the kernel, and not have it clobbered
by the bss clearing in locore.s, how should this be done?
As I see it I can :
- put the data after _edata, and copy it somewhere before the bss is
cleared. (Yuck, requires a static buffer in the data segment).
- put the data after _end, and copy it into a buffer in the bss
(still yuck for a static buffer ripe for overflowing).
- put the data after _end and adjust _end after the bss is cleared,
saving the old _end value as a reference to this data.
- put the data somewhere else (first meg somewhere?) and advertise
its location in some fashion. Perhaps the kernel flags should
become a physical address reference to a parameter block instead.
This could be done in a backwards-compatible fashion I think.
Of these, I obviously like the third, although it requires some more
structure on the part of the data (ie. more work on the part of the
bootstrap loader). I don't know how well this would work in conjunction
with compressed kernels though.
--
]] Mike Smith, Software Engineer msmith@gsoft.com.au [[
]] Genesis Software genesis@gsoft.com.au [[
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