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gets the memory map from GRUB

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This commit is contained in:
Nathan Singer
2025-06-09 17:44:50 -04:00
parent f1515ad7b5
commit 83b6a9eaf2
8 changed files with 352 additions and 7 deletions
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7
kernel/arch/boot.s
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@ -3,7 +3,7 @@
; We set up some parameters and then pass the execution to our kmain
global loader ; entry symbol for ELF
extern kmain
extern _main
MAGIC_NUMBER equ 0x1BADB002 ; magic number constant
FLAGS equ 0x3
@ -30,7 +30,10 @@ section .text
loader:
mov esp, kernel_stack + KERNEL_STACK_SIZE ; move the top of the stack into esp
call kmain ; pass execution over to our kmain function, where all of the real stuff is done
push eax
push ebx
call _main ; pass execution over to our _main function, where all of the real stuff is done
; Should the system exit, we clear the interrupt flag
; and do an infinite loop of nothing

5
kernel/arch/link.ld
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@ -19,6 +19,7 @@ SECTIONS
*/
.text BLOCK(4K) : ALIGN(4K) /* The first section we want is the text section, this is where most code is */
{
text_start = .;
*(.multiboot) /* Multiboot needs to be early in the file, required by grub */
*(.text) /* The text section */
}
@ -33,12 +34,16 @@ SECTIONS
.data BLOCK(4K) : ALIGN(4K)
{
*(.data)
end_data = .;
}
/* BSS */
.bss BLOCK(4K) : ALIGN(4K)
{
sbss = .;
*(COMMON)
*(.bss)
ebss = .;
endkernel = .;
}
}

6
kernel/arch/paging.c Normal file
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@ -0,0 +1,6 @@
#include <stdint.h>
extern uint32_t endkernel; // found in link.ld

3
kernel/include/kernel/paging.h Normal file
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@ -0,0 +1,3 @@
typedef struct {
} pageframe_t;

56
kernel/kmain.c
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@ -1,5 +1,6 @@
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <kernel/_kernel.h>
#include <kernel/tty.h>
@ -12,13 +13,61 @@
#include <kernel/x86/pci.h>
#include "multiboot.h"
void kmain(void)
void verify_memmap(multiboot_info_t* mbd, uint32_t magic)
{
if (magic != MULTIBOOT_BOOTLOADER_MAGIC)
panic("Invalid magic number!");
else
printf("%2\n", magic);
if (!(mbd->flags >> 6 & 0x1))
panic("Invalid memory map given by GRUB bootloader!");
#ifdef __TESTING__
puts("Printing available memory map...");
uint32_t i;
for (i = 0; i < mbd->mmap_length; i += sizeof(multiboot_memory_map_t)) {
multiboot_memory_map_t* mmmt = (multiboot_memory_map_t*) (mbd->mmap_addr + i);
printf("Start Addr: %4 | Length: %4 | Size: %2 | Type: ",
mmmt->addr, mmmt->len, mmmt->size);
switch (mmmt->type) {
case MULTIBOOT_MEMORY_AVAILABLE:
puts("Available");
break;
case MULTIBOOT_MEMORY_RESERVED:
puts("Reserved");
break;
case MULTIBOOT_MEMORY_ACPI_RECLAIMABLE:
puts("ACPI Reclaimable");
break;
case MULTIBOOT_MEMORY_NVS:
puts("NVS");
break;
case MULTIBOOT_MEMORY_BADRAM:
puts("Bad ram");
break;
default:
puts("Unknown");
break;
}
// if (mmmt->type == MULTIBOOT_MEMORY_AVAILABLE) -> DO SOMETHING
}
#endif
}
void _main(multiboot_info_t* mbd, uint32_t magic)
{
#ifdef __TESTING__ // important components should be declared first, but if we're testing we want to log all of that
terminal_initialize();
serial_initialize();
#endif
verify_memmap(mbd, magic);
gdt_init();
idt_init();
@ -26,14 +75,11 @@ void kmain(void)
terminal_initialize();
serial_initialize();
#endif
init_kb();
init_pit(0x36, PIT_CHANNEL_0, 0);
printf("%d\n", pci_config_read_word(0, 1, 1, 6));
printf("Entering loop...\n");
while (1) {

274
kernel/multiboot.h Normal file
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@ -0,0 +1,274 @@
/* multiboot.h - Multiboot header file. */
/* Copyright (C) 1999,2003,2007,2008,2009,2010 Free Software Foundation, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL ANY
* DEVELOPER OR DISTRIBUTOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
* IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#ifndef MULTIBOOT_HEADER
#define MULTIBOOT_HEADER 1
/* How many bytes from the start of the file we search for the header. */
#define MULTIBOOT_SEARCH 8192
#define MULTIBOOT_HEADER_ALIGN 4
/* The magic field should contain this. */
#define MULTIBOOT_HEADER_MAGIC 0x1BADB002
/* This should be in %eax. */
#define MULTIBOOT_BOOTLOADER_MAGIC 0x2BADB002
/* Alignment of multiboot modules. */
#define MULTIBOOT_MOD_ALIGN 0x00001000
/* Alignment of the multiboot info structure. */
#define MULTIBOOT_INFO_ALIGN 0x00000004
/* Flags set in the ’flags’ member of the multiboot header. */
/* Align all boot modules on i386 page (4KB) boundaries. */
#define MULTIBOOT_PAGE_ALIGN 0x00000001
/* Must pass memory information to OS. */
#define MULTIBOOT_MEMORY_INFO 0x00000002
/* Must pass video information to OS. */
#define MULTIBOOT_VIDEO_MODE 0x00000004
/* This flag indicates the use of the address fields in the header. */
#define MULTIBOOT_AOUT_KLUDGE 0x00010000
/* Flags to be set in the ’flags’ member of the multiboot info structure. */
/* is there basic lower/upper memory information? */
#define MULTIBOOT_INFO_MEMORY 0x00000001
/* is there a boot device set? */
#define MULTIBOOT_INFO_BOOTDEV 0x00000002
/* is the command-line defined? */
#define MULTIBOOT_INFO_CMDLINE 0x00000004
/* are there modules to do something with? */
#define MULTIBOOT_INFO_MODS 0x00000008
/* These next two are mutually exclusive */
/* is there a symbol table loaded? */
#define MULTIBOOT_INFO_AOUT_SYMS 0x00000010
/* is there an ELF section header table? */
#define MULTIBOOT_INFO_ELF_SHDR 0X00000020
/* is there a full memory map? */
#define MULTIBOOT_INFO_MEM_MAP 0x00000040
/* Is there drive info? */
#define MULTIBOOT_INFO_DRIVE_INFO 0x00000080
/* Is there a config table? */
#define MULTIBOOT_INFO_CONFIG_TABLE 0x00000100
/* Is there a boot loader name? */
#define MULTIBOOT_INFO_BOOT_LOADER_NAME 0x00000200
/* Is there a APM table? */
#define MULTIBOOT_INFO_APM_TABLE 0x00000400
/* Is there video information? */
#define MULTIBOOT_INFO_VBE_INFO 0x00000800
#define MULTIBOOT_INFO_FRAMEBUFFER_INFO 0x00001000
#ifndef ASM_FILE
typedef unsigned char multiboot_uint8_t;
typedef unsigned short multiboot_uint16_t;
typedef unsigned int multiboot_uint32_t;
typedef unsigned long long multiboot_uint64_t;
struct multiboot_header
{
/* Must be MULTIBOOT_MAGIC - see above. */
multiboot_uint32_t magic;
/* Feature flags. */
multiboot_uint32_t flags;
/* The above fields plus this one must equal 0 mod 2^32. */
multiboot_uint32_t checksum;
/* These are only valid if MULTIBOOT_AOUT_KLUDGE is set. */
multiboot_uint32_t header_addr;
multiboot_uint32_t load_addr;
multiboot_uint32_t load_end_addr;
multiboot_uint32_t bss_end_addr;
multiboot_uint32_t entry_addr;
/* These are only valid if MULTIBOOT_VIDEO_MODE is set. */
multiboot_uint32_t mode_type;
multiboot_uint32_t width;
multiboot_uint32_t height;
multiboot_uint32_t depth;
};
/* The symbol table for a.out. */
struct multiboot_aout_symbol_table
{
multiboot_uint32_t tabsize;
multiboot_uint32_t strsize;
multiboot_uint32_t addr;
multiboot_uint32_t reserved;
};
typedef struct multiboot_aout_symbol_table multiboot_aout_symbol_table_t;
/* The section header table for ELF. */
struct multiboot_elf_section_header_table
{
multiboot_uint32_t num;
multiboot_uint32_t size;
multiboot_uint32_t addr;
multiboot_uint32_t shndx;
};
typedef struct multiboot_elf_section_header_table multiboot_elf_section_header_table_t;
struct multiboot_info
{
/* Multiboot info version number */
multiboot_uint32_t flags;
/* Available memory from BIOS */
multiboot_uint32_t mem_lower;
multiboot_uint32_t mem_upper;
/* "root" partition */
multiboot_uint32_t boot_device;
/* Kernel command line */
multiboot_uint32_t cmdline;
/* Boot-Module list */
multiboot_uint32_t mods_count;
multiboot_uint32_t mods_addr;
union
{
multiboot_aout_symbol_table_t aout_sym;
multiboot_elf_section_header_table_t elf_sec;
} u;
/* Memory Mapping buffer */
multiboot_uint32_t mmap_length;
multiboot_uint32_t mmap_addr;
/* Drive Info buffer */
multiboot_uint32_t drives_length;
multiboot_uint32_t drives_addr;
/* ROM configuration table */
multiboot_uint32_t config_table;
/* Boot Loader Name */
multiboot_uint32_t boot_loader_name;
/* APM table */
multiboot_uint32_t apm_table;
/* Video */
multiboot_uint32_t vbe_control_info;
multiboot_uint32_t vbe_mode_info;
multiboot_uint16_t vbe_mode;
multiboot_uint16_t vbe_interface_seg;
multiboot_uint16_t vbe_interface_off;
multiboot_uint16_t vbe_interface_len;
multiboot_uint64_t framebuffer_addr;
multiboot_uint32_t framebuffer_pitch;
multiboot_uint32_t framebuffer_width;
multiboot_uint32_t framebuffer_height;
multiboot_uint8_t framebuffer_bpp;
#define MULTIBOOT_FRAMEBUFFER_TYPE_INDEXED 0
#define MULTIBOOT_FRAMEBUFFER_TYPE_RGB 1
#define MULTIBOOT_FRAMEBUFFER_TYPE_EGA_TEXT 2
multiboot_uint8_t framebuffer_type;
union
{
struct
{
multiboot_uint32_t framebuffer_palette_addr;
multiboot_uint16_t framebuffer_palette_num_colors;
};
struct
{
multiboot_uint8_t framebuffer_red_field_position;
multiboot_uint8_t framebuffer_red_mask_size;
multiboot_uint8_t framebuffer_green_field_position;
multiboot_uint8_t framebuffer_green_mask_size;
multiboot_uint8_t framebuffer_blue_field_position;
multiboot_uint8_t framebuffer_blue_mask_size;
};
};
};
typedef struct multiboot_info multiboot_info_t;
struct multiboot_color
{
multiboot_uint8_t red;
multiboot_uint8_t green;
multiboot_uint8_t blue;
};
struct multiboot_mmap_entry
{
multiboot_uint32_t size;
multiboot_uint64_t addr;
multiboot_uint64_t len;
#define MULTIBOOT_MEMORY_AVAILABLE 1
#define MULTIBOOT_MEMORY_RESERVED 2
#define MULTIBOOT_MEMORY_ACPI_RECLAIMABLE 3
#define MULTIBOOT_MEMORY_NVS 4
#define MULTIBOOT_MEMORY_BADRAM 5
multiboot_uint32_t type;
} __attribute__((packed));
typedef struct multiboot_mmap_entry multiboot_memory_map_t;
struct multiboot_mod_list
{
/* the memory used goes from bytes ’mod_start’ to ’mod_end-1’ inclusive */
multiboot_uint32_t mod_start;
multiboot_uint32_t mod_end;
/* Module command line */
multiboot_uint32_t cmdline;
/* padding to take it to 16 bytes (must be zero) */
multiboot_uint32_t pad;
};
typedef struct multiboot_mod_list multiboot_module_t;
/* APM BIOS info. */
struct multiboot_apm_info
{
multiboot_uint16_t version;
multiboot_uint16_t cseg;
multiboot_uint32_t offset;
multiboot_uint16_t cseg_16;
multiboot_uint16_t dseg;
multiboot_uint16_t flags;
multiboot_uint16_t cseg_len;
multiboot_uint16_t cseg_16_len;
multiboot_uint16_t dseg_len;
};
#endif /* ! ASM_FILE */
#endif /* ! MULTIBOOT_HEADER */

2
libc/include/stdlib.h
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@ -8,6 +8,8 @@
__attribute__((__noreturn__))
void abort(void);
void panic(const char* str);
char* s64toa(int64_t num, char* buf, int base);
char* u64toa(uint64_t num, char* buf, int base);
char* s32toa(int32_t num, char* buf, int base);

6
libc/stdlib/abort.c
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@ -13,3 +13,9 @@ void abort(void) {
while (1) { }
__builtin_unreachable();
}
void panic(const char* str)
{
printf("%s\n", str);
abort();
}