From 76b3da6022310dd8edbbbfdf4f73f1696a559853 Mon Sep 17 00:00:00 2001 From: Miguel Date: Mon, 3 Sep 2018 03:08:43 +0200 Subject: thinking about memory layout --- kernel/vmem.c | 2 -- kernel/vmem.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/vmem.c b/kernel/vmem.c index 2d3a5e4..542b3a2 100644 --- a/kernel/vmem.c +++ b/kernel/vmem.c @@ -1,5 +1,3 @@ -// http://www.brokenthorn.com/Resources/OSDev18.html -// #include #include "kernel.h" diff --git a/kernel/vmem.h b/kernel/vmem.h index b7e9cd3..8e538bb 100644 --- a/kernel/vmem.h +++ b/kernel/vmem.h @@ -1,3 +1,52 @@ +/** + * @file + * http://www.brokenthorn.com/Resources/OSDev18.html + * https://wiki.osdev.org/Memory_Map_(x86) + * + * Paging + * ====== + * + * The Smallest Managable Unit is a Page containing 4096 (0x1000) bytes. + * + * A Page Directory holds 1024 tables each mapping 1024 pages, totaling + * in 0x100000000 bytes of addressable space (4gigs). + * + * The first 32megs will get ALWAYS identity mapped (hold kernel code/kernel stack etc) + * This are the first 8 page-tables + * + * Layout + * ====== + * + * We are aiming for the following layout: + * + * 0xFFFFFFFF + * 0xC0000000 RESERVED + * + * 0xB0000000 User Stack TOP (Grows down) | + * env, argc, argv ... | + * | alltogether ~2.5gigs + * .......... User Heap (brk()) | + * 0x08000000 User Code | + * | + * | almost 100 megs (in kernel alloc/free?) + * | + * 0x02000000 FoolOS TSS Stack TOP (max ~8mb) GROWS DOWN + * leave few empty pages under stack as guard. + * + * 0x01800000 FoolOS Stack TOP (max ~8mb) GROWS DOWN + * leave few empty pages under stack as guard. + * + * 0x01000000 + * 0x00EFFFFF RESERVED + * 0x00100000 FoolOS Kernel (max ~14mb) + * 0x00007BFF RESERVED + * 0x00007000 16-bit SMP entry (max ~3kb) + * 0x00000500 + * 0x00000000 RESERVED + * + */ + + //! i86 architecture defines 1024 entries per table--do not change #define PAGES_PER_TABLE 1024 #define PAGES_PER_DIR 1024 -- cgit v1.2.3