nx_emu_x86_rm16_test.nx source

1// nx_emu_x86_rm16_test.nx -- x86 full-system ladder R5 rung-3: 16-bit REAL-MODE decode. 2// The CPU boots in 16-bit real mode (operand size 16, NO REX prefix, different opcodes). This is a 3// minimal real-mode interpreter for the boot-stub subset: 4// B8+r iw mov r16, imm16 (B8=ax B9=cx BA=dx BB=bx ...) 5// 89 /r mov r/m16, r16 (mod=11 reg-reg) 6// 01 /r add r/m16, r16 (16-bit wrap) 7// F4 hlt (stop) 8// KAT: a real-mode stub computes ax = 40 + 2 = 42 then hlts. HONEST SCOPE: this minimal subset; 9// the full real-mode ISA + segment:offset addressing + the far-jump that flushes into protected mode 10// = further R5 work (then R6 paging, R7 devices, R8 kernel boot). No hardware writes (Rule 26). 11// expect_exit: 0 license_tier: ORIGINAL 12import "nx_syscalls.nx" 13 14func r16_b(c: *u8, o: i64, b: i64) -> i64 { c[o]=(b & 0xff) as u8; return o+1 } 15func r16_iw(c: *u8, o: i64, v: i64) -> i64 { c[o]=(v&0xff) as u8; c[o+1]=((v>>8)&0xff) as u8; return o+2 } 16func r16_puts(s: *u8) -> i64 { var n: i64=0; while s[n]!=(0 as u8){n=n+1} sys_write(1,s,n); return 0 } 17func r16_num(v: i64) -> i64 { let b: *u8=sys_mmap(28); var m: i64=v; if m<0{m=0-m;sys_write(1,"-" as *u8,1)} let t: *u8=sys_mmap(28); var k: i64=0; if m==0{t[0]=48 as u8;k=1} while m>0{t[k]=(48+(m%10)) as u8;m=m/10;k=k+1} var i: i64=0; while i<k{b[i]=t[k-1-i];i=i+1} sys_write(1,b,k); return 0 } 18 19// 16-bit real-mode interpreter; reg16[] = ax cx dx bx sp bp si di. returns 0 on hlt, neg on bad op. 20func emu_x86_run_16(code: *u8, len: i64, reg16: *i64) -> i64 { 21 var pc: i64 = 0 22 while pc < len { 23 let b: i64 = code[pc] as i64 24 var h: i64 = 0 25 if b == 0xF4 { return 0 } // hlt 26 if h == 0 { if b >= 0xB8 { if b <= 0xBF { reg16[b-0xB8] = (code[pc+1] as i64) | ((code[pc+2] as i64) << 8); pc=pc+3; h=1 } } } // mov r16, imm16 27 if h == 0 { if b == 0x89 { let m: i64=code[pc+1] as i64; reg16[m & 7] = reg16[(m>>3) & 7]; pc=pc+2; h=1 } } // mov r/m16, r16 28 if h == 0 { if b == 0x01 { let m: i64=code[pc+1] as i64; reg16[m & 7] = (reg16[m & 7] + reg16[(m>>3) & 7]) & 0xFFFF; pc=pc+2; h=1 } } // add r/m16, r16 29 if h == 0 { return 0 - 3 } 30 } 31 return 0 - 4 32} 33 34func main() -> i64 { 35 r16_puts("x86 full-system ladder R5 rung-3: 16-bit REAL-MODE decode\n" as *u8) 36 let c: *u8 = sys_mmap(64) 37 var o: i64 = 0 38 // mov ax, 40 (B8 iw) 39 o=r16_b(c,o,0xB8); o=r16_iw(c,o,40) 40 // mov bx, 2 (BB iw) 41 o=r16_b(c,o,0xBB); o=r16_iw(c,o,2) 42 // add ax, bx (01 D8 : r/m=ax, r=bx) 43 o=r16_b(c,o,0x01); o=r16_b(c,o,0xD8) 44 // hlt 45 o=r16_b(c,o,0xF4) 46 47 let reg16: *i64 = sys_mmap(8*8) as *i64 48 let rc: i64 = emu_x86_run_16(c, o, reg16) 49 r16_puts(" real-mode stub: ax = " as *u8); r16_num(reg16[0]); r16_puts(" (want 42), halt rc=" as *u8); r16_num(rc); r16_puts("\n" as *u8) 50 51 var pass: i64=0 52 var ttl: i64=0 53 ttl=ttl+1; r16_puts(" T1 hlt clean: " as *u8); if rc==0 { pass=pass+1; r16_puts("PASS\n" as *u8) } else { r16_puts("FAIL\n" as *u8) } 54 ttl=ttl+1; r16_puts(" T2 ax==42 (16-bit mov+add): " as *u8); if reg16[0]==42 { pass=pass+1; r16_puts("PASS\n" as *u8) } else { r16_puts("FAIL\n" as *u8) } 55 ttl=ttl+1; r16_puts(" T3 bx==2 (16-bit mov held): " as *u8); if reg16[3]==2 { pass=pass+1; r16_puts("PASS\n" as *u8) } else { r16_puts("FAIL\n" as *u8) } 56 57 r16_puts("X86-RM16-GATE passed " as *u8); r16_num(pass); r16_puts("/" as *u8); r16_num(ttl) 58 if pass==ttl { r16_puts(" verdict=GREEN (16-bit real-mode entry decodes+runs; full ISA + seg:off + far-jump-to-protected = R5 rung-4)\n" as *u8); sys_exit(0); return 0 } 59 r16_puts(" verdict=RED\n" as *u8); sys_exit(1); return 1 60}