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switch from multiboot to multiboot2

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This commit is contained in:
Josh Holtrop 2020-10-18 14:25:06 -04:00
parent 21afa93c4b
commit 412925a790
3 changed files with 52 additions and 22 deletions
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2
Rsconscript
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@ -24,7 +24,7 @@ build do
File.open("#{tmpdir}/iso/boot/grub/grub.cfg", "wb") do |fh|
fh.write(<<EOF)
menuentry "HOS" {
multiboot /hos.elf
multiboot2 /hos.elf
}
EOF
end

30
src/boot.S
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@ -1,10 +1,8 @@
/* Declare constants for the multiboot header. */
.set ALIGN, 1<<0 /* align loaded modules on page boundaries */
.set MEMINFO, 1<<1 /* provide memory map */
.set VID, 1<<2
.set FLAGS, ALIGN | MEMINFO | VID /* this is the Multiboot 'flag' field */
.set MAGIC, 0x1BADB002 /* 'magic number' lets bootloader find the header */
.set CHECKSUM, -(MAGIC + FLAGS) /* checksum of above, to prove we are multiboot */
/* Declare constants for the multiboot2 header. */
.set MAGIC, 0xE85250D6 /* 'magic number' lets bootloader find the header */
.set NTAGS, 1 /* including terminating tag */
.set LENGTH, 4 * 4 + NTAGS
.set CHECKSUM, -(MAGIC + LENGTH) /* checksum of above, to prove we are multiboot */
/*
Declare a multiboot header that marks the program as a kernel. These are magic
@ -15,18 +13,20 @@ forced to be within the first 8 KiB of the kernel file.
*/
.section .multiboot
.align 4
.long MAGIC
.long FLAGS
.long MAGIC /* magic */
.long 0 /* architecture */
.long LENGTH /* header_length */
.long CHECKSUM
.short 5
.short 0
.long 20
.long 0
.long 0
.long 0
.long 0
.long 0
.long 0
.long 0
.long 0
.long 0
.long 0 /* padding */
.short 0
.short 0
.long 8
/*
The multiboot standard does not define the value of the stack pointer register

42
src/kernel_main.c
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@ -1,12 +1,42 @@
#include <stdint.h>
void kernel_main(uint32_t mbinfo)
uint32_t * fb;
uint32_t pitch;
uint32_t width;
uint32_t height;
static uint32_t * process_mbinfo_tag(uint32_t * mbinfo)
{
volatile uint32_t * mbi = (volatile uint32_t *)mbinfo;
volatile uint32_t * fb = (volatile uint32_t *)mbi[88 / 4];
uint32_t pitch = mbi[96 / 4];
uint32_t width = mbi[100 / 4];
uint32_t height = mbi[104 / 4];
uint32_t type = mbinfo[0];
uint32_t size = mbinfo[1];
switch (type)
{
case 0u:
return 0u;
case 8u:
fb = (uint32_t *)mbinfo[2];
pitch = mbinfo[4];
width = mbinfo[5];
height = mbinfo[6];
break;
}
return (uint32_t *)(((uint32_t)mbinfo + size + 7u) & 0xFFFFFFF8u);
}
static void process_mbinfo(uint32_t * mbinfo)
{
/* Skip multiboot2 boot information header. */
mbinfo += 2u;
do
{
mbinfo = process_mbinfo_tag(mbinfo);
} while (mbinfo != (uint32_t *)0u);
}
void kernel_main(uint32_t * mbinfo)
{
process_mbinfo(mbinfo);
for (uint32_t row = 0u; row < height; row++)
{
for (uint32_t col = 0u; col < width; col++)