diff options
| -rw-r--r-- | asm/start.h | 1 | ||||
| -rw-r--r-- | asm/start.s | 4 | ||||
| -rw-r--r-- | kernel/vmem.c | 2 | ||||
| -rw-r--r-- | kernel/vmem.h | 49 | ||||
| -rw-r--r-- | linker.ld | 24 |
5 files changed, 70 insertions, 10 deletions
diff --git a/asm/start.h b/asm/start.h index 7b31b76..4b2db16 100644 --- a/asm/start.h +++ b/asm/start.h @@ -4,6 +4,7 @@ * specific addresses in the final ELF kernel binary. * This is specified in the _linker.ld_ file. * + * TODO: THIS IS NOT TRUE ANYMORE (SINCE IT KILLED THE MEMORY IN BETWEEN PROABBLY) * * 0x007000 .smp - entry point for application processors (16bit code) * * 0x100000 .multiboot - the multiboot header * diff --git a/asm/start.s b/asm/start.s index 26464a7..ca99c20 100644 --- a/asm/start.s +++ b/asm/start.s @@ -15,12 +15,14 @@ .set MAGIC, 0x1BADB002 # 'magic number' lets bootloader find the header .set CHECKSUM, -(MAGIC + FLAGS) # checksum of above, to prove we are multiboot -# entry point for application processors at 0x7000 +# entry point for application processors we will copy this to 0x7000 later + .section .smp .code16 _start_smp: call smp_start # TODO: align later before going C + # Declare a header as in the Multiboot Standard. We put this into a special # section so we can force the header to be in the start of the final program. # You don't need to understand all these details as it is just magic values that 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 <stdlib.h> #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 @@ -3,19 +3,29 @@ ENTRY(_start) SECTIONS { /* 0x00000500 - 0x00007BFF : guaranteed free to use */ - . = 0x7000; - kernel_start = .; /* smp code at 0x7000*/ - .text BLOCK(4K) : ALIGN(4K) + . = 0x00007000; + kernel_start = .; + + .multiboot BLOCK(4K) : ALIGN(4K) { - *(.smp) + asm/start.o(.smp) + asm/asm_mp.o + *(.multiboot) } + + + /* + 0x00007E00 0x0007FFFF 480.5 KiB RAM (guaranteed free for use) Conventional memory + 0x00080000 0x0009FBFF approximately 120 KiB, depending on EBDA size RAM (free for use, if it exists) Conventional memory + */ + /* 0x00100000 - 0x00EFFFFF : free for use (if it exists) 14Mib */ + + . = 0x00100000; - /* 0x00100000 - 0x00EFFFFF : free for use (if it exists) */ - . = 0x100000; /* _start code as 0x100000 and rest of code*/ - .text BLOCK(4K) : ALIGN(4K) + .text BLOCK(4K): ALIGN(4K) { *(.multiboot) *(.text) |