Start CrabBIOS, implement firmware loading and push/pop/ret

Signed-off-by: AsyaTheAbove <asya@waifu.club>

Cargo.lock

@@ -19,6 +19,54 @@ version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0942ffc6dcaadf03badf6e6a2d0228460359d5e34b57ccdc720b7382dfbd5ec5"
 
+[[package]]
+name = "anstream"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2ab91ebe16eb252986481c5b62f6098f3b698a45e34b5b98200cf20dd2484a44"
+dependencies = [
+ "anstyle",
+ "anstyle-parse",
+ "anstyle-query",
+ "anstyle-wincon",
+ "colorchoice",
+ "utf8parse",
+]
+
+[[package]]
+name = "anstyle"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7079075b41f533b8c61d2a4d073c4676e1f8b249ff94a393b0595db304e0dd87"
+
+[[package]]
+name = "anstyle-parse"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "317b9a89c1868f5ea6ff1d9539a69f45dffc21ce321ac1fd1160dfa48c8e2140"
+dependencies = [
+ "utf8parse",
+]
+
+[[package]]
+name = "anstyle-query"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ca11d4be1bab0c8bc8734a9aa7bf4ee8316d462a08c6ac5052f888fef5b494b"
+dependencies = [
+ "windows-sys",
+]
+
+[[package]]
+name = "anstyle-wincon"
+version = "3.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f0699d10d2f4d628a98ee7b57b289abbc98ff3bad977cb3152709d4bf2330628"
+dependencies = [
+ "anstyle",
+ "windows-sys",
+]
+
 [[package]]
 name = "bitflags"
 version = "2.4.0"
@@ -31,11 +79,45 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "clap"
+version = "4.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d04704f56c2cde07f43e8e2c154b43f216dc5c92fc98ada720177362f953b956"
+dependencies = [
+ "clap_builder",
+]
+
+[[package]]
+name = "clap_builder"
+version = "4.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0e231faeaca65ebd1ea3c737966bf858971cd38c3849107aa3ea7de90a804e45"
+dependencies = [
+ "anstream",
+ "anstyle",
+ "clap_lex",
+ "strsim",
+]
+
+[[package]]
+name = "clap_lex"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd7cc57abe963c6d3b9d8be5b06ba7c8957a930305ca90304f24ef040aa6f961"
+
+[[package]]
+name = "colorchoice"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "acbf1af155f9b9ef647e42cdc158db4b64a1b61f743629225fde6f3e0be2a7c7"
+
 [[package]]
 name = "copycat"
 version = "0.1.0"
 dependencies = [
  "bitflags",
+ "clap",
  "hashbrown",
 ]
 
@@ -55,8 +137,86 @@ version = "1.18.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dd8b5dd2ae5ed71462c540258bedcb51965123ad7e7ccf4b9a8cafaa4a63576d"
 
+[[package]]
+name = "strsim"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
+
+[[package]]
+name = "utf8parse"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "711b9620af191e0cdc7468a8d14e709c3dcdb115b36f838e601583af800a370a"
+
 [[package]]
 name = "version_check"
 version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
+[[package]]
+name = "windows-sys"
+version = "0.48.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "677d2418bec65e3338edb076e806bc1ec15693c5d0104683f2efe857f61056a9"
+dependencies = [
+ "windows-targets",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a2fa6e2155d7247be68c096456083145c183cbbbc2764150dda45a87197940c"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc",
+ "windows_i686_gnu",
+ "windows_i686_msvc",
+ "windows_x86_64_gnu",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b38e32f0abccf9987a4e3079dfb67dcd799fb61361e53e2882c3cbaf0d905d8"
+
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc35310971f3b2dbbf3f0690a219f40e2d9afcf64f9ab7cc1be722937c26b4bc"
+
+[[package]]
+name = "windows_i686_gnu"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a75915e7def60c94dcef72200b9a8e58e5091744960da64ec734a6c6e9b3743e"
+
+[[package]]
+name = "windows_i686_msvc"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f55c233f70c4b27f66c523580f78f1004e8b5a8b659e05a4eb49d4166cca406"
+
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "53d40abd2583d23e4718fddf1ebec84dbff8381c07cae67ff7768bbf19c6718e"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b7b52767868a23d5bab768e390dc5f5c55825b6d30b86c844ff2dc7414044cc"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed94fce61571a4006852b7389a063ab983c02eb1bb37b47f8272ce92d06d9538"

Cargo.toml

@@ -7,4 +7,5 @@ edition = "2021"
 
 [dependencies]
 bitflags = "2.4.0"
+clap = { version = "4.4.6", features = ["cargo"] }
 hashbrown = "0.14.0"

build.rs

@@ -0,0 +1,13 @@
+use std::process::Command;
+
+fn main() {
+    // Tell Cargo that if the given file changes, to rerun this build script.
+    println!("cargo:rerun-if-changed=crabbios/crabbios.asm");
+    Command::new("nasm")
+        .arg("crabbios/crabbios.asm")
+        .args(["-f", "bin"])
+        .args(["-o", "roms/crabbios.bin"])
+        .args(["-I", "crabbios"])
+        .spawn()
+        .unwrap();
+}

crabbios/README.md

@@ -0,0 +1,3 @@
+# CrabBIOS
+
+BIOS implementation in x86 real mode assembly

crabbios/crabbios.asm

@@ -0,0 +1,27 @@
+bits 16     ; we're in 16 bit real mode
+org 0xfe000 ; that's where we're loaded
+
+start: ; we jump here after the entry point
+mov ax, 0xFF
+push ax
+pop bx
+hlt
+
+; fill until the reset vector
+times 4080 - ($ - start) db 0
+
+; entry point
+; we shouldn't assume any initial state here
+cli
+
+; set up stack at 0:0x7c00
+; that's just below where we'll load the boot sector
+mov ax, 0
+mov ss, ax
+mov sp, 0x7c00
+
+; jump over to start
+jmp start
+
+; fill the last bytes
+times 4096 - ($ - start) db 0

src/main.rs

@@ -4,16 +4,40 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
  */
 
+use std::fs;
+
+use clap::{command, arg};
 use copycat::memory::{Memory, KiB};
 use copycat::processor::{Instruction, Processor};
 use copycat::io::IoBus;
 
-static BIOS_ROM: &[u8; 8 * KiB as usize] = include_bytes!("../roms/BIOS_IBM5150_24APR81_5700051_U33.BIN");
+static BIOS_ROM: &[u8; 4 * KiB as usize] = include_bytes!("../roms/crabbios.bin");
 
 fn main() {
+    let matches = command!()
+        .arg(arg!(-b --bios <BIOS> "Firmware image to load"))
+        .get_matches();
+
+    let maybe_bios;
+    let bios: &[u8] = match matches.get_one::<String>("bios") {
+        Some(bios) => {
+            maybe_bios = fs::read(bios).unwrap();
+            &maybe_bios
+        },
+        None => BIOS_ROM,
+    };
+    if bios.len() == 0 {
+        panic!("firmware image empty");
+    }
+    if bios.len() % 4 * KiB as usize != 0 {
+        panic!("firmware image length not a multiple of a page");
+    }
+    let bios_len = bios.len() / (4 * KiB) as usize;
+
     let mut mem = Memory::new(64 * KiB);
-    mem.add_tlb_entry(0xfe, BIOS_ROM.as_ptr().cast_mut().cast());
+    for i in 0xff - bios_len + 1..=0xff {
-    mem.add_tlb_entry(0xff, unsafe { BIOS_ROM.as_ptr().add(4 * KiB as usize) }.cast_mut().cast());
+        mem.add_tlb_entry(i as u64, unsafe { bios.as_ptr().add((i - (0xff - bios_len + 1)) * 4 * KiB as usize) }.cast_mut().cast());
+    }
     // mem.write(0xffff0, [0x90, 0x04, 0x69, 0xF4]);
     let mut io = IoBus::default();
     let mut cpu = Processor::default();

src/processor/instruction.rs

@@ -98,6 +98,22 @@ impl Instruction {
             0x4D => (Dec, BP, NoOperand),
             0x4E => (Dec, SI, NoOperand),
             0x4F => (Dec, DI, NoOperand),
+            0x50 => (Push, AX, NoOperand),
+            0x51 => (Push, CX, NoOperand),
+            0x52 => (Push, DX, NoOperand),
+            0x53 => (Push, BX, NoOperand),
+            0x54 => (Push, SP, NoOperand),
+            0x55 => (Push, BP, NoOperand),
+            0x56 => (Push, SI, NoOperand),
+            0x57 => (Push, DI, NoOperand),
+            0x58 => (Pop, AX, NoOperand),
+            0x59 => (Pop, CX, NoOperand),
+            0x5A => (Pop, DX, NoOperand),
+            0x5B => (Pop, BX, NoOperand),
+            0x5C => (Pop, SP, NoOperand),
+            0x5D => (Pop, BP, NoOperand),
+            0x5E => (Pop, SI, NoOperand),
+            0x5F => (Pop, DI, NoOperand),
             0x70 => (Jo, Imm8, NoOperand),
             0x71 => (Jno, Imm8, NoOperand),
             0x72 => (Jc, Imm8, NoOperand),
@@ -139,6 +155,10 @@ impl Instruction {
             0xBD => (Mov, BP, Imm16),
             0xBE => (Mov, SI, Imm16),
             0xBF => (Mov, DI, Imm16),
+            0xC2 => (Retn, Imm16, NoOperand),
+            0xC3 => (Retn, NoOperand, NoOperand),
+            0xCA => (Retf, Imm16, NoOperand),
+            0xCB => (Retf, NoOperand, NoOperand),
             0xD0 => {
                 modrm = ModRM::from_bits(memory.read_u8(address + size as u64));
                 size += 1;
@@ -448,6 +468,10 @@ pub enum Mnemonic {
     Nop,
     Or,
     Out,
+    Pop,
+    Push,
+    Retf,
+    Retn,
     Sahf,
     Sbb,
     Shl,

src/processor/mod.rs

@@ -195,6 +195,14 @@ impl Processor {
 
                 self.set_operand16(value, memory, op1, instruction.segment_override);
             },
+            (Push, Operand(op1, Word), _) => {
+                let value = self.operand16(memory, op1, instruction.segment_override);
+                self.push16(value, memory);
+            },
+            (Pop, Operand(op1, Word), _) => {
+                let value = self.pop16(memory);
+                self.set_operand16(value, memory, op1, instruction.segment_override);
+            },
             (Jo, Operand(Imm8(op1), Byte), _) =>
                 if self.registers.of() { self.registers.add_ip(op1 as i8 as i16) },
             (Jno, Operand(Imm8(op1), Byte), _) =>
@@ -238,6 +246,28 @@ impl Processor {
                 self.set_operand8(self.operand8(memory, op2, instruction.segment_override), memory, op1, instruction.segment_override),
             (Mov, Operand(op1, Word), Operand(op2, Word)) =>
                 self.set_operand16(self.operand16(memory, op2, instruction.segment_override), memory, op1, instruction.segment_override),
+            (Retn, Operand(Imm16(parameters), _), _) => {
+                let ip = self.pop16(memory);
+                self.registers.set_ip(ip);
+                self.registers.set_sp(self.registers.sp() + parameters);
+            },
+            (Retn, _, _) => {
+                let ip = self.pop16(memory);
+                self.registers.set_ip(ip);
+            },
+            (Retf, Operand(Imm16(parameters), _), _) => {
+                let ip = self.pop16(memory);
+                let cs = self.pop16(memory);
+                self.registers.set_ip(ip);
+                self.registers.set_cs(cs);
+                self.registers.set_sp(self.registers.sp() + parameters);
+            },
+            (Retf, _, _) => {
+                let ip = self.pop16(memory);
+                let cs = self.pop16(memory);
+                self.registers.set_ip(ip);
+                self.registers.set_cs(cs);
+            },
             (Shl, Operand(op1, Byte), Operand(op2, Byte)) => 'shl: {
                 let dst = self.operand8(memory, op1, instruction.segment_override);
                 let shift = self.operand8(memory, op2, instruction.segment_override);
@@ -500,4 +530,16 @@ impl Processor {
             SegmentOverride::DS | SegmentOverride::None => self.registers.ds(),
         } as u64) << 4) + offset as u64
     }
+
+    fn push16(&mut self, value: u16, memory: &mut Memory) {
+        self.registers.set_sp(self.registers.sp() - 2);
+        let address = ((self.registers.ss() as u64) << 4) + self.registers.sp() as u64;
+        memory.write_u16(address, value);
+    }
+
+    fn pop16(&mut self, memory: &Memory) -> u16 {
+        let address = ((self.registers.ss() as u64) << 4) + self.registers.sp() as u64;
+        self.registers.set_sp(self.registers.sp() + 2);
+        memory.read_u16(address)
+    }
 }