Clean slate; Bochs + IPXE boot

.gitignore

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+*.o
+boot.bin
+boot.elf

Makefile

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+-include config.mk
+
+.PHONY: all clean
+
+all: boot.bin
+
+clean:
+	rm -f *.o boot.elf boot.bin
+
+config.mk: | config.default.mk
+	cp config.default.mk $@
+
+boot.bin: boot.elf
+	objcopy -O binary -j .text -j .data boot.elf $@
+	wc -c $@
+
+boot.elf: Rnbp.o Ptftp.o Qcommon.o fernlader.ld
+	$(LD) $(LDFLAGS) -o $@ Rnbp.o Ptftp.o Qcommon.o
+
+%.o: %.S
+	$(CC) $(CFLAGS) -c -o $@ $(@:.o=.S)
+
+%.o: %.c
+	$(CC) $(CFLAGS) -O0 -c -o $@ $(@:.o=.c)

Qcommon.c

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+#include <stdint.h>
+
+#define COM1_BASE_PORT 0x3F8
+
+static inline uint8_t
+inb(uint16_t port)
+{
+	uint8_t data;
+	__asm__ ("inb %%dx, %%al" : "=a"(data) : "d"(port));
+	return data;
+}
+
+static inline void
+outb(uint16_t port, uint8_t data)
+{
+	__asm__ ("outb %%al, %%dx" :: "a"(data), "d"(port));
+}
+
+void serial_write_char(char c)
+{
+	while (1) {
+		int line_status = inb(COM1_BASE_PORT + 5);
+		if (line_status & 0x20) {
+			break;
+		}
+	}
+	outb(COM1_BASE_PORT, c);
+}
+
+void
+main()
+{
+	outb(0xE9, 'X');
+	serial_write_char('X');
+	for (;;) {
+		__asm__ ("hlt" :);
+	}
+}

Rnbp.S

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+            // vim: et:sw=12:ts=12:sts=12
+
+            .global     _start
+            .text
+            .code16
+
+            .set        SS_CODE16,  0x08
+            .set        SS_DATA16,  0x10
+            .set        SS_CODE32,  0x18
+            .set        SS_DATA32,  0x20
+
+            
+
+            // _start: entry point
+_start:     cli
+            cld
+            mov         %sp, %bp
+            xor         %ax, %ax
+            mov         %ax, %ds
+            mov         %ax, %es
+
+            push        $msg_start
+            call        dbgmsg
+            add         $2, %sp
+
+            // initialize our own BSS section
+            mov         $_bss_start, %di
+            mov         $_bss_end, %cx
+            sub         %di, %cx
+            xor         %al, %al
+            rep         stosb
+
+            // a20_enable: Allow use of 'high' (>1Mb) memory
+a20_enable: // Of all the ways to toggle A20, we only try the Fast A20 Gate.
+            // This is known to cause problems on some ancient systems,
+            // but as our bootloader exclusively runs on 64-bit machines,
+            // we should not run into any of those systems.
+            // Modern machines apparently don't even have the A20 line anymore.
+            push        $msg_a20
+            call        dbgmsg
+            add         $2, %sp
+
+            inb         $0x92, %al
+            or          $2, %al
+            outb        %al, $0x92
+
+            // prot_enter: Set up GDT, switch into 32-bit protected mode.
+prot_enter: 
+            push        $msg_prot
+            call        dbgmsg
+            add         $2, %sp
+
+            lgdt        GDT_PTR
+
+            // Set Protection Enable (PE) bit
+            mov         %cr0, %eax
+            or          $1, %al
+            mov         %eax, %cr0
+
+            ljmp        $SS_CODE32, $prot_trampo
+
+            .code32
+prot_trampo:
+            mov         $SS_DATA32, %eax
+            mov         %eax, %ds
+            mov         %eax, %es
+            mov         %eax, %fs
+            mov         %eax, %gs
+            mov         %eax, %ss
+
+            mov         'Y', %al
+            outb        %al, $0xE9
+
+            // TODO load proper stack pointer
+            mov         $0x90000, %ebp
+            mov         %ebp, %esp
+
+            jmp         main
+
+            .code16
+dbgmsg:     push        %bp
+            mov         %sp, %bp
+            push        %ax
+            push        %si
+            mov         4(%bp), %si
+            
+1:          lodsb
+            test        %al, %al
+            jz          2f
+            outb        %al, $0xE9
+            jmp         1b
+
+2:          pop         %si
+            pop         %ax
+            pop         %bp
+            ret
+
+            .data
+
+            .global     GDT
+
+GDT:        // entry 0: null descriptor
+            .space      8, 0
+            // entry 1: 16-bit code segment
+            .byte       0xFF, 0xFF, 0, 0, 0, 0b10011010, 0x8F, 0
+            // entry 2: 16-bit data segment
+            .byte       0xFF, 0xFF, 0, 0, 0, 0b10010010, 0x8F, 0
+            // entry 3: 32-bit code segment
+            .byte       0xFF, 0xFF, 0, 0, 0, 0b10011010, 0xCF, 0
+            // entry 4: 32-bit data segment
+            .byte       0xFF, 0xFF, 0, 0, 0, 0b10010010, 0xCF, 0
+            // TODO: 32-bit TSS
+            .set        GDT_SIZE, . - GDT
+GDT_PTR:    .word       GDT_SIZE - 1
+            .quad       GDT
+
+msg_start:  .asciz      "Netboot via fernlader v2 ...\r\n"
+msg_a20:    .asciz      " * Enabling A20 Gate\r\n"
+msg_prot:   .asciz      " * Protected Mode\r\n"

bochsrc.txt

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+cpu: model=tigerlake, count=1
+
+floppya: 1_44=ipxe.dsk, status=inserted, write_protected=1
+boot: floppy
+
+e1000: mac=b0:c4:20:00:00:00, ethmod=tuntap, ethdev=/dev/net/tun, script=tunconfig.sh
+
+keyboard: keymap=de
+port_e9_hack: enabled=1

boot.ipxe

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+#!ipxe
+ifopen net0
+
+set net0/ip 10.0.0.2
+set net0/netmask 255.255.255.0
+set net0/dns 10.0.0.1
+set net0/gateway ${net0/dns}
+set net0/next-server ${net0/dns}
+set net0/filename boot.bin
+
+# Verify settings with user
+# config net0
+
+chain ${net0/filename}

bootboot.h

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+/*
+ * bootboot.h
+ * https://gitlab.com/bztsrc/bootboot
+ *
+ * Copyright (C) 2017 - 2021 bzt (bztsrc@gitlab)
+ *
+ * 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 THE AUTHORS OR COPYRIGHT
+ * HOLDERS 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.
+ *
+ * This file is part of the BOOTBOOT Protocol package.
+ * @brief The BOOTBOOT structure
+ *
+ */
+
+#ifndef _BOOTBOOT_H_
+#define _BOOTBOOT_H_
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+#ifndef _MSC_VER
+#define _pack __attribute__((packed))
+#else
+#define _pack
+#pragma pack(push)
+#pragma pack(1)
+#endif
+
+#define BOOTBOOT_MAGIC "BOOT"
+
+/* default virtual addresses for level 0 and 1 static loaders */
+#define BOOTBOOT_MMIO   0xfffffffff8000000  /* memory mapped IO virtual address */
+#define BOOTBOOT_FB     0xfffffffffc000000  /* frame buffer virtual address */
+#define BOOTBOOT_INFO   0xffffffffffe00000  /* bootboot struct virtual address */
+#define BOOTBOOT_ENV    0xffffffffffe01000  /* environment string virtual address */
+#define BOOTBOOT_CORE   0xffffffffffe02000  /* core loadable segment start */
+
+/* minimum protocol level:
+ *  hardcoded kernel name, static kernel memory addresses */
+#define PROTOCOL_MINIMAL 0
+/* static protocol level:
+ *  kernel name parsed from environment, static kernel memory addresses */
+#define PROTOCOL_STATIC  1
+/* dynamic protocol level:
+ *  kernel name parsed, kernel memory addresses from ELF or PE symbols */
+#define PROTOCOL_DYNAMIC 2
+/* big-endian flag */
+#define PROTOCOL_BIGENDIAN 0x80
+
+/* loader types, just informational */
+#define LOADER_BIOS     (0<<2)
+#define LOADER_UEFI     (1<<2)
+#define LOADER_RPI      (2<<2)
+#define LOADER_COREBOOT (3<<2)
+
+/* framebuffer pixel format, only 32 bits supported */
+#define FB_ARGB   0
+#define FB_RGBA   1
+#define FB_ABGR   2
+#define FB_BGRA   3
+
+/* mmap entry, type is stored in least significant tetrad (half byte) of size
+ * this means size described in 16 byte units (not a problem, most modern
+ * firmware report memory in pages, 4096 byte units anyway). */
+typedef struct {
+  uint64_t   ptr;
+  uint64_t   size;
+} _pack MMapEnt;
+#define MMapEnt_Ptr(a)  ((a)->ptr)
+#define MMapEnt_Size(a) ((a)->size & 0xFFFFFFFFFFFFFFF0)
+#define MMapEnt_Type(a) ((a)->size & 0xF)
+#define MMapEnt_IsFree(a) (((a)->size&0xF)==1)
+
+#define MMAP_USED     0   /* don't use. Reserved or unknown regions */
+#define MMAP_FREE     1   /* usable memory */
+#define MMAP_ACPI     2   /* acpi memory, volatile and non-volatile as well */
+#define MMAP_MMIO     3   /* memory mapped IO region */
+
+#define INITRD_MAXSIZE 16 /* Mb */
+
+typedef struct {
+  /* first 64 bytes is platform independent */
+  uint8_t    magic[4];    /* 'BOOT' magic */
+  uint32_t   size;        /* length of bootboot structure, minimum 128 */
+  uint8_t    protocol;    /* 1, static addresses, see PROTOCOL_* and LOADER_* above */
+  uint8_t    fb_type;     /* framebuffer type, see FB_* above */
+  uint16_t   numcores;    /* number of processor cores */
+  uint16_t   bspid;       /* Bootsrap processor ID (Local APIC Id on x86_64) */
+  int16_t    timezone;    /* in minutes -1440..1440 */
+  uint8_t    datetime[8]; /* in BCD yyyymmddhhiiss UTC (independent to timezone) */
+  uint64_t   initrd_ptr;  /* ramdisk image position and size */
+  uint64_t   initrd_size;
+  uint64_t   fb_ptr;      /* framebuffer pointer and dimensions */
+  uint32_t   fb_size;
+  uint32_t   fb_width;
+  uint32_t   fb_height;
+  uint32_t   fb_scanline;
+
+  /* the rest (64 bytes) is platform specific */
+  union {
+    struct {
+      uint64_t acpi_ptr;
+      uint64_t smbi_ptr;
+      uint64_t efi_ptr;
+      uint64_t mp_ptr;
+      uint64_t unused0;
+      uint64_t unused1;
+      uint64_t unused2;
+      uint64_t unused3;
+    } x86_64;
+    struct {
+      uint64_t acpi_ptr;
+      uint64_t mmio_ptr;
+      uint64_t efi_ptr;
+      uint64_t unused0;
+      uint64_t unused1;
+      uint64_t unused2;
+      uint64_t unused3;
+      uint64_t unused4;
+    } aarch64;
+  } arch;
+
+  /* from 128th byte, MMapEnt[], more records may follow */
+  MMapEnt    mmap;
+  /* use like this:
+   * MMapEnt *mmap_ent = &bootboot.mmap; mmap_ent++;
+   * until you reach bootboot->size, while(mmap_ent < bootboot + bootboot->size) */
+} _pack BOOTBOOT;
+
+#ifdef _MSC_VER
+#pragma pack(pop)
+#endif
+
+#ifdef  __cplusplus
+}
+#endif
+
+#endif

config.default.mk

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+CC = cc
+LD = ld
+
+CFLAGS = -no-pie -fno-pic
+LDFLAGS = -Tfernlader.ld

config.mk

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+CC = cc
+LD = ld
+
+CFLAGS = -no-pie -fno-pic -fno-stack-protector
+LDFLAGS = -Tfernlader.ld

dnsmasq.conf

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+listen-address=10.0.0.1
+bind-dynamic
+#bind-interfaces
+#except-interface=lo
+
+log-async
+
+# Disable DNS server
+port=0
+
+enable-tftp
+tftp-root=/home/thomas/karlos/fernlader2/serve
+

fernlader.ld

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+ENTRY(_start)
+PHDRS {
+    all PT_LOAD;
+}
+SECTIONS {
+    .text 0x7C00: {
+        Rnbp.o(.text)
+        *(.text*, .rodata*)
+    } :all
+    .data : {
+        *(.data*)
+    } :all
+    .bss (NOLOAD) : {
+        _bss_start = .;
+        *(COMMON)
+        *(.bss)
+        . = ALIGN(4K);
+        *(.bootboot)
+        _bss_end = .;
+    } :all
+}

run-qemu.sh

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+#!/bin/sh
+qemu-system-x86_64 -netdev user,id=n1,net=10.0.0.5/24,tftp=.,bootfile=/boot.bin -device virtio-net-pci,netdev=n1,bootindex=0 "$@"

tunconfig.sh

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+#!/bin/bash
+DEV="${1##/*/}"
+HOST_IP="10.0.0.1/24"
+ip addr add "$HOST_IP" dev "$DEV"
+ip link set up dev "$DEV"