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// MIT License, Copyright (c) 2021 Marvin Borner
// Everything according to spec
#include <impl/mb1.h>
#include <pnc.h>
#define MB1_MAGIC 0x1badb002
struct multiboot_entry {
u32 magic;
u32 flags;
u32 checksum; // Everything after that is optional
u32 header_addr;
u32 load_addr;
u32 load_end_addr;
u32 bss_end_addr;
u32 entry_addr;
u32 mode_type;
u32 width;
u32 height;
u32 depth;
};
// The (really simple) multiboot checksum algorithm
static u32 mb1_checksum(struct multiboot_entry *entry)
{
return -(entry->magic + entry->flags);
}
// Detect and verify mb1
u8 mb1_detect(struct dev *dev, const char *path)
{
u8 header[8192] = { 0 };
s32 ret = dev->p.disk.fs.read(path, header, 0, sizeof(header), dev);
if (ret < 12)
return 0;
// Find start of multiboot entry by searching for magic
struct multiboot_entry *entry = 0;
for (u32 i = 0; i < sizeof(header); i++) {
u32 *p = (u32 *)&header[i];
if (*p == MB1_MAGIC) {
entry = (void *)p;
break;
}
}
if (!entry)
return 0;
u32 checksum = mb1_checksum(entry);
if (checksum != entry->checksum)
return 0;
dev->p.disk.impl.type = IMPL_MB1;
dev->p.disk.impl.start = entry;
return 1;
}
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