nx_emu_x86_paging_test.nx source

1// nx_emu_x86_paging_test.nx -- x86 full-system ladder R6: PAGING (long-mode 4-level page walk). 2// Long mode translates a 48-bit virtual address through 4 tables (512 entries each, 8-byte entries): 3// VA[47:39]=PML4 idx -> VA[38:30]=PDPT idx -> VA[29:21]=PD idx -> VA[20:12]=PT idx -> +VA[11:0] off 4// Each entry holds the next table's (or the page's) 4KB-aligned base in bits[63:12] + flags (bit0=present). 5// This models that walk over an in-RAM page-table tree (the x86 twin of the rv64 SV39 MMU we have). 6// KAT: tables mapping VA 0x1000->PA 0x40000 and 0x2000->0x50000; translate + offset; unmapped -> fault. 7// HONEST SCOPE: 4KB pages, present bit; large pages / A-D bits / TLB / permission faults = refinements. 8// R7 = device models (16550 UART/timer/disk). No hardware writes (Rule 26). expect_exit: 0 license_tier: ORIGINAL 9import "nx_syscalls.nx" 10 11func pg_puts(s: *u8) -> i64 { var n: i64=0; while s[n]!=(0 as u8){n=n+1} sys_write(1,s,n); return 0 } 12func pg_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 } 13 14func pg_wr(mem: *u8, addr: i64, v: i64) -> i64 { var i: i64=0; while i<8 { mem[addr+i]=((v>>(i*8)) & 0xff) as u8; i=i+1 } return 0 } 15func pg_rd(mem: *u8, addr: i64) -> i64 { var v: i64=0; var i: i64=0; while i<8 { v = v | ((mem[addr+i] as i64) << (i*8)); i=i+1 } return v } 16 17// 4-level long-mode page walk; returns physical addr, or (0-1) on a not-present fault. 18func pg_walk(mem: *u8, cr3: i64, va: i64) -> i64 { 19 let i1: i64 = (va >> 39) & 0x1FF 20 let e1: i64 = pg_rd(mem, cr3 + i1*8) 21 if (e1 & 1)==0 { return 0 - 1 } 22 let b2: i64 = (e1 >> 12) << 12 23 let i2: i64 = (va >> 30) & 0x1FF 24 let e2: i64 = pg_rd(mem, b2 + i2*8) 25 if (e2 & 1)==0 { return 0 - 1 } 26 let b3: i64 = (e2 >> 12) << 12 27 let i3: i64 = (va >> 21) & 0x1FF 28 let e3: i64 = pg_rd(mem, b3 + i3*8) 29 if (e3 & 1)==0 { return 0 - 1 } 30 let b4: i64 = (e3 >> 12) << 12 31 let i4: i64 = (va >> 12) & 0x1FF 32 let e4: i64 = pg_rd(mem, b4 + i4*8) 33 if (e4 & 1)==0 { return 0 - 1 } 34 let page: i64 = (e4 >> 12) << 12 35 return page + (va & 0xFFF) 36} 37 38func main() -> i64 { 39 pg_puts("x86 full-system ladder R6: PAGING (long-mode 4-level page walk)\n" as *u8) 40 let mem: *u8 = sys_mmap(2097152) 41 let cr3: i64 = 0x1000 42 // PML4[0]->PDPT@0x2000, PDPT[0]->PD@0x3000, PD[0]->PT@0x4000, PT[1]->page 0x40000, PT[2]->page 0x50000 43 pg_wr(mem, cr3 + 0*8, 0x2000 | 1) 44 pg_wr(mem, 0x2000 + 0*8, 0x3000 | 1) 45 pg_wr(mem, 0x3000 + 0*8, 0x4000 | 1) 46 pg_wr(mem, 0x4000 + 1*8, 0x40000 | 1) 47 pg_wr(mem, 0x4000 + 2*8, 0x50000 | 1) 48 49 var pass: i64=0 50 var ttl: i64=0 51 52 let p1: i64 = pg_walk(mem, cr3, 0x1000) 53 ttl=ttl+1; pg_puts(" T1 VA 0x1000 -> PA " as *u8); pg_num(p1); pg_puts(" (want 262144=0x40000): " as *u8); if p1==0x40000 { pass=pass+1; pg_puts("PASS\n" as *u8) } else { pg_puts("FAIL\n" as *u8) } 54 55 let p2: i64 = pg_walk(mem, cr3, 0x1123) 56 ttl=ttl+1; pg_puts(" T2 VA 0x1123 -> PA " as *u8); pg_num(p2); pg_puts(" (want 0x40123, offset preserved): " as *u8); if p2==0x40123 { pass=pass+1; pg_puts("PASS\n" as *u8) } else { pg_puts("FAIL\n" as *u8) } 57 58 let p3: i64 = pg_walk(mem, cr3, 0x2000) 59 ttl=ttl+1; pg_puts(" T3 VA 0x2000 -> PA " as *u8); pg_num(p3); pg_puts(" (want 0x50000, second PT entry): " as *u8); if p3==0x50000 { pass=pass+1; pg_puts("PASS\n" as *u8) } else { pg_puts("FAIL\n" as *u8) } 60 61 let p4: i64 = pg_walk(mem, cr3, 0x3000) 62 ttl=ttl+1; pg_puts(" T4 neg: unmapped VA 0x3000 -> " as *u8); pg_num(p4); pg_puts(" (want -1 page-fault): " as *u8); if p4 < 0 { pass=pass+1; pg_puts("PASS\n" as *u8) } else { pg_puts("FAIL\n" as *u8) } 63 64 ttl=ttl+1; pg_puts(" T5 PT index extraction (VA 0x1000 -> idx 1): " as *u8); if ((0x1000 >> 12) & 0x1FF)==1 { pass=pass+1; pg_puts("PASS\n" as *u8) } else { pg_puts("FAIL\n" as *u8) } 65 66 pg_puts("X86-PAGING-GATE passed " as *u8); pg_num(pass); pg_puts("/" as *u8); pg_num(ttl) 67 if pass==ttl { pg_puts(" verdict=GREEN (long-mode 4-level paging; device models 16550/timer/disk = R7)\n" as *u8); sys_exit(0); return 0 } 68 pg_puts(" verdict=RED\n" as *u8); sys_exit(1); return 1 69}