nx_exclprobe.nx source

1// nx_exclprobe.nx -- DOES O_CREAT|O_EXCL VIA __syscall ACTUALLY WORK HERE? (2026-08-07) 2// 3// WHY THIS EXISTS. The async job lane assigns ids by probing whether `_jobs/job_<id>.done` EXISTS, but a 4// RUNNING job has no `.done`, so two tools/call in the same second get the IDENTICAL id and the loser's 5// receipt is overwritten (observed live: two nx_debt add both returned id=1786110674). 6// The correct fix is an ATOMIC reservation, and `dl_lock` in nx_dispatch_lease already does exactly that 7// with __syscall(SYS_OPENAT, AT_FDCWD, path, 193, 420, 0, 0). But banked memory warns that LITERAL 8// __syscall numbers are rv64->x86 TRANSLATED, which would make 257 mean something else entirely -- and I 9// am not shipping that into the daemon that serves /mcp on a guess after two outages today. 10// ★ VERIFY A PRIMITIVE IN A THROWAWAY BEFORE PUTTING IT IN THE THING EVERYTHING ELSE DEPENDS ON. 11// This organ answers it decisively and touches nothing but /tmp. 12// nx_exclprobe -> JSON {first_create, second_create, verdict} 13// EXPECTED IF THE PRIMITIVE IS SOUND: first >= 0 (we created it), second < 0 (EEXIST refused us). 14// If BOTH succeed, O_EXCL is not being honoured and the whole approach is unusable. 15// If BOTH fail, the syscall number is being translated and 257 is not openat here. 16// license_tier: ORIGINAL No hw writes (Rule 26). expect_exit: 0 17import "nx_syscalls.nx" 18 19const XP_SYS_OPENAT: i64 = 257 20const XP_AT_FDCWD: i64 = 0 - 100 21const XP_OEXCL: i64 = 193 // O_CREAT(0x40)|O_EXCL(0x80)|O_WRONLY(0x1) 22const XP_MODE: i64 = 420 // 0644 23const XP_PATH: *u8 = "/tmp/nx_exclprobe.claim" as *u8 24 25func xw(s: *u8) -> i64 { var n: i64 = 0; while s[n] != (0 as u8) { n = n + 1 } sys_write(1, s, n); return 0 } 26func xn(v: i64) -> i64 { 27 let b: *u8 = sys_mmap(32) 28 var x: i64 = v 29 var neg: i64 = 0 30 if x < 0 { neg = 1; x = 0 - x } 31 var i: i64 = 31 32 if x == 0 { b[i] = 48 as u8; i = i - 1 } 33 while x > 0 { b[i] = ((48 + (x - ((x / 10) * 10))) as u8); x = x / 10; i = i - 1 } 34 if neg == 1 { b[i] = 45 as u8; i = i - 1 } 35 sys_write(1, ((b as i64) + i + 1) as *u8, 31 - i) 36 return 0 37} 38 39func main() -> i64 { 40 sys_unlinkat(XP_PATH) 41 let a: i64 = __syscall(XP_SYS_OPENAT, XP_AT_FDCWD, XP_PATH as i64, XP_OEXCL, XP_MODE, 0, 0) 42 if a >= 0 { sys_close(a) } 43 let b: i64 = __syscall(XP_SYS_OPENAT, XP_AT_FDCWD, XP_PATH as i64, XP_OEXCL, XP_MODE, 0, 0) 44 if b >= 0 { sys_close(b) } 45 // control: the file must now EXIST and be readable, proving the first call really created it 46 let r: i64 = sys_openat_rd(XP_PATH) 47 var exists: i64 = 0 48 if r >= 0 { exists = 1; sys_close(r) } 49 sys_unlinkat(XP_PATH) 50 xw("{\"organ\":\"nx_exclprobe\",\"first_create\":" as *u8); xn(a) 51 xw(",\"second_create\":" as *u8); xn(b) 52 xw(",\"file_existed_after_first\":" as *u8); xn(exists) 53 xw(",\"verdict\":\"" as *u8) 54 var ok: i64 = 0 55 if a >= 0 { if b < 0 { if exists == 1 { ok = 1 } } } 56 if ok == 1 { xw("SOUND -- O_EXCL refuses the second creator; atomic reservation is usable" as *u8) } else { 57 if a < 0 { xw("UNUSABLE -- even the FIRST create failed; the syscall number is not openat here" as *u8) } else { 58 xw("UNSAFE -- both creates succeeded; O_EXCL is NOT being honoured" as *u8) 59 } 60 } 61 xw("\"}\n" as *u8) 62 sys_exit(0) 63 return 0 64}