09d44b1ef5
I was in the middle of one of these "projects" when I started on the next, so they wound up all intermixed) Move the mailing list entities from authors.sgml to the new file lists.sgml. Add an entity for majordomo at the same time. Avoid the use of contractions. This revealed some grammer problems, and also has the benefit of helping make things clearer for those people who do make speak English as a their first language.
51 lines
2.3 KiB
Plaintext
51 lines
2.3 KiB
Plaintext
<!-- $Id: memoryuse.sgml,v 1.6 1996/01/31 19:02:59 mpp Exp $ -->
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<!-- The FreeBSD Documentation Project -->
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<sect><heading>PC memory utilization<label id="memoryuse"></heading>
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<p><em>Contributed by &a.joerg;.<newline>
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16 Apr 1995.</em>
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<em>A short description of how FreeBSD uses the memory on the i386
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platform</em>
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The boot sector will be loaded at <tt>0:0x7c00</tt>, and relocates itself
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immediately to <tt>0x7c0:0</tt>. (This is nothing magic, just an adjustment
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for the <tt>%cs</tt> selector, done by an <tt>ljmp</tt>.)
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It then loads the first 15 sectors at <tt>0x10000</tt> (segment BOOTSEG in the
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biosboot Makefile), and sets up the stack to work below <tt>0x1fff0</tt>.
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After this, it jumps to the entry of boot2 within that code. I.e., it
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jumps over itself and the (dummy) partition table, and it is going to
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adjust the %cs selector---we are still in 16-bit mode there.
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boot2 asks for the boot file, and examines the <tt>a.out</tt> header. It masks
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the file entry point (usually <tt>0xf0100000</tt>) by <tt>0x00ffffff</tt>, and loads the
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file there. Hence the usual load point is 1 MB (<tt>0x00100000</tt>). During
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load, the boot code toggles back and forth between real and protected
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mode, to use the BIOS in real mode.
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The boot code itself uses segment selectors <tt>0x18</tt> and <tt>0x20</tt> for <tt>%cs</tt> and
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<tt>%ds/%es</tt> in protected mode, and <tt>0x28</tt> to jump back into real mode. The
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kernel is finally started with <tt>%cs</tt> <tt>0x08</tt> and <tt>%ds/%es/%ss</tt> <tt>0x10</tt>, which
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refer to dummy descriptors covering the entire address space.
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The kernel will be started at its load point. Since it has been linked
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for another (high) address, it will have to execute PIC until the page
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table and page directory stuff is setup properly, at which point
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paging will be enabled and the kernel will finally run at the address
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for which it was linked.
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<em>Contributed by &a.davidg;.<newline>
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16 Apr 1995.</em>
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The physical pages immediately following the kernel BSS contain
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proc0's page directory, page tables, and upages. Some time later
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when the VM system is initialized, the physical memory between
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<tt>0x1000-0x9ffff</tt> and the physical memory after the kernel
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(text+data+bss+proc0 stuff+other misc) is made available in the
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form of general VM pages and added to the global free page list.
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