Because you want to write a simple operating system, you need to install a virtual machine to simulate the hardware. VMware is not suitable for this scenario, because you will use hardware level virtualization, and bochs, the open-source virtual machine, uses software to virtualize all the hardware, so debugging can be very fine-grained. For example, every time the cpu executes a command, we can pause and look at the register State, look at the memory state, which is too much help for operating system development and debugging. So we use bochs as a virtual machine.
mac install bochs
My current environment is Mac version 10.15.3. Record the installation process and the steps.
Steps:
- Install sdl library, which will be used in subsequent compilation
brew install sdl
- Download the source code and extract it
Download address: https://sourceforge.net/projects/bochs/files/latest/download
# Download decompression tar -xvf bochs-2.6.tar.gz # Parameters required for configure ./configure --enable-ne2000 \ --enable-all-optimizations \ --enable-cpu-level=6 \ --enable-x86-64 \ --enable-vmx=2 \ --enable-pci \ --enable-usb \ --enable-usb-ohci \ --enable-e1000 \ --enable-debugger \ --enable-disasm \ --disable-debugger-gui \ --with-sdl \ --prefix=$HOME/opt/bochs
The prefix parameter here specifies the installation location and changes it to the desired address.
Here comes the first question:
Question 1
Report this error
cdrom_osx.cc:194:18: error: assigning to 'char ' from incompatible type 'const ch
So I checked it on the Internet. There is a patch for this error report[ https://raw.githubusercontent.com/Homebrew/formula-patches/e9b520dd4c/bochs/xcode9.patch ], we find this file and modify the source code. This file is in bochs-2.6/iodev/hdimage/cdrom_osx.cc. We open and modify line 193
if ((devname = strrchr(devpath, '/')) != NULL) { //Changed to: if ((devname = (char *) strrchr(devpath, '/')) != NULL) {
The problem is solved. Let's compile.
make && make install
Question two
Report this mistake at this time
config.cc:3261:55: error: ordered comparison between pointer and zero ('char *' and 'int') if (SIM->get_param_string("model", base)->getptr()>0) { ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~ 1 error generated.
We open config.cc, find line 3621, and change it to
modify config.cc The 3621 line if (SIM->get_param_string("model", base)->getptr()>0) { //by if (SIM->get_param_string("model", base)->getptr()>(char *)0) {
Yes.
And then we compile it again
make && make install
At this time, the normal compilation is successful.
We can add bochs to the environment variable to use:
export BXSHARE="$HOME/workplace/os/bochs/share/bochs" export PATH="$PATH:$HOME/workplace/os/bochs/bin"
Bochs use
bochs/share/doc/bochs/bochsrc-sample.txt in the installation directory of bochs is the template of the configuration file. We write a simple configuration file to run:
# Set virtual machine memory to 32MB megs: 32 # Set BIOS image romimage: file=$BXSHARE/BIOS-bochs-latest # Set VGA BIOS image vgaromimage: file=$BXSHARE/VGABIOS-lgpl-latest # Set boot from hard disk boot: disk # Set log file log: bochsout.txt # Close mouse mouse: enabled=0 # Open keyboard keyboard: type=mf, serial_delay=250 # Set up hard disk ata0: enabled=1, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14 # Add gdb remote debugging support gdbstub: enabled=1, port=1234, text_base=0, data_base=0, bss_base=0
Save as bochsrc. Run command execution in this directory:
➜ my_src git:(master) ✗ bochs ======================================================================== Bochs x86 Emulator 2.6 Built from SVN snapshot on September 2nd, 2012 Compiled on Feb 11 2020 at 14:52:19 ======================================================================== 00000000000i[ ] reading configuration from bochsrc 00000000000p[ ] >>PANIC<< bochsrc:26: Bochs is not compiled with gdbstub support ======================================================================== Bochs is exiting with the following message: [ ] bochsrc:26: Bochs is not compiled with gdbstub support ======================================================================== 00000000000i[CPU0 ] CPU is in real mode (active) 00000000000i[CPU0 ] CS.mode = 16 bit 00000000000i[CPU0 ] SS.mode = 16 bit 00000000000i[CPU0 ] EFER = 0x00000000 00000000000i[CPU0 ] | EAX=00000000 EBX=00000000 ECX=00000000 EDX=00000000 00000000000i[CPU0 ] | ESP=00000000 EBP=00000000 ESI=00000000 EDI=00000000 00000000000i[CPU0 ] | IOPL=0 id vip vif ac vm rf nt of df if tf sf ZF af PF cf 00000000000i[CPU0 ] | SEG sltr(index|ti|rpl) base limit G D 00000000000i[CPU0 ] | CS:0000( 0000| 0| 0) 00000000 00000000 0 0 00000000000i[CPU0 ] | DS:0000( 0000| 0| 0) 00000000 00000000 0 0 00000000000i[CPU0 ] | SS:0000( 0000| 0| 0) 00000000 00000000 0 0 00000000000i[CPU0 ] | ES:0000( 0000| 0| 0) 00000000 00000000 0 0 00000000000i[CPU0 ] | FS:0000( 0000| 0| 0) 00000000 00000000 0 0 00000000000i[CPU0 ] | GS:0000( 0000| 0| 0) 00000000 00000000 0 0 00000000000i[CPU0 ] | EIP=00000000 (00000000) 00000000000i[CPU0 ] | CR0=0x00000000 CR2=0x00000000 00000000000i[CPU0 ] | CR3=0x00000000 CR4=0x00000000 bx_dbg_read_linear: physical memory read error (phy=0x0000000000000000, lin=0x0000000000000000) 00000000000i[CTRL ] quit_sim called with exit code 1
At this point, we successfully run a virtual machine.
Analog hard disk
bochs provides a tool to create a virtual hard disk, bximage, which provides an interactive way to create a virtual hard disk. Let's do the following:
➜ my_src git:(master) ✗ bximage ======================================================================== bximage Disk Image Creation Tool for Bochs $Id: bximage.c 11315 2012-08-05 18:13:38Z vruppert $ ======================================================================== Do you want to create a floppy disk image or a hard disk image? Please type hd or fd. [hd] // Enter, new hard disk What kind of image should I create? Please type flat, sparse or growing. [flat] // Enter, flat hard disk Enter the hard disk size in megabytes, between 1 and 8257535 [10] 10 // 10MB hard disk I will create a 'flat' hard disk image with cyl=20 heads=16 sectors per track=63 total sectors=20160 total size=9.84 megabytes What should I name the image? [c.img] hd10m.img // Name Writing: [] Done. I wrote 10321920 bytes to hd10m.img. The following line should appear in your bochsrc: ata0-master: type=disk, path="hd10m.img", mode=flat, cylinders=20, heads=16, spt=63 ➜ my_src git:(master) ✗ ls bochsrc hd10m.img
Now, that's the end of the environment configuration, and we'll learn how to write the startup information later.
Welcome to my Blog And github( https://github.com/veeupup)!