From 9a2d5cbdc7972d1d5bfb1ea93f82f66d113faa17 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Wed, 7 Jul 2021 19:13:11 +0200
Subject: Strange implementations

---
 src/loader/impl/mb1.c | 58 +++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 47 insertions(+), 11 deletions(-)

(limited to 'src/loader/impl/mb1.c')

diff --git a/src/loader/impl/mb1.c b/src/loader/impl/mb1.c
index 765433e..5541c6e 100644
--- a/src/loader/impl/mb1.c
+++ b/src/loader/impl/mb1.c
@@ -3,9 +3,11 @@
 
 #include <elf.h>
 #include <impl/mb1.h>
+#include <lib.h>
 #include <pnc.h>
 
-#define MB1_MAGIC 0x1badb002
+// The address where data gets stored
+#define MB1_LOAD_ADDRESS 0x10000
 
 struct multiboot_entry {
 	u32 magic;
@@ -28,12 +30,43 @@ static u32 mb1_checksum(struct multiboot_entry *entry)
 	return -(entry->magic + entry->flags);
 }
 
+// Load data into memory and return address (not overlapping
+static u32 mb1_store(void *data, u32 size)
+{
+	static u32 offset = 0;
+	memcpy((void *)MB1_LOAD_ADDRESS, data, size);
+	offset += size;
+	return MB1_LOAD_ADDRESS + (size - offset);
+}
+
+// Load the mb1 structs into memory
+static void mb1_load(struct multiboot_entry *entry)
+{
+	(void)mb1_store;
+	(void)entry;
+}
+
+// Jump to kernel with correct info pointer in eax
+static void mb1_jump(u32 entry, u32 info)
+{
+	log("Jumping. So long and thanks for all the fish!\n");
+
+	// Move and jump!
+	__asm__ volatile("movl $" STRINGIFY(MB1_LOAD_MAGIC) ", %%eax\n\t"
+							    "jmpl *%%edi\n\t"
+			 :
+			 : "D"(entry), "b"(info)
+			 : "memory");
+
+	panic("Jumper returned\n");
+}
+
 // Detect and verify mb1
-u8 mb1_detect(struct dev *dev, const char *path)
+u8 mb1_detect(struct cfg_entry *cfg)
 {
 	u8 header[8192] = { 0 };
 
-	s32 ret = dev->p.disk.fs.read(path, header, 0, sizeof(header), dev);
+	s32 ret = cfg->dev->p.disk.fs.read(cfg->path, header, 0, sizeof(header), cfg->dev);
 	if (ret < 12)
 		return 0;
 
@@ -54,19 +87,22 @@ u8 mb1_detect(struct dev *dev, const char *path)
 	if (checksum != entry->checksum)
 		return 0;
 
-	dev->p.disk.impl.type = IMPL_MB1;
-	dev->p.disk.impl.start = entry;
+	cfg->impl.type = IMPL_MB1;
+	cfg->impl.start = entry;
 
 	return 1;
 }
 
+#include <pic.h>
+
 // Execute mb1 type kernel
-void mb1_exec(struct dev *dev, const char *path)
+void mb1_exec(struct cfg_entry *cfg)
 {
-	u32 entry = elf_load(dev, path);
-	void (*kernel)(void *);
-	*(void **)(&kernel) = (void *)entry;
+	u32 entry = elf_load(cfg->dev, cfg->path);
+	mb1_load(cfg->impl.start);
 
-	// TODO: Push mb1 stuff
-	kernel(dev);
+	// This is a kind of hacky parameter stack pushing thing, just disable warning :)
+#pragma GCC diagnostic ignored "-Wpedantic"
+	jmp_kernel((void *)mb1_jump, 2, entry, MB1_LOAD_ADDRESS);
+#pragma GCC diagnostic pop
 }
-- 
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