Finishing PS/2 bus driver

library/runtime/system.zig

@@ -2,6 +2,7 @@
 //! stubs, one per kernel call. Numbers come from `abi.SystemCall`, the single
 //! source of truth shared with the kernel dispatcher.
 
+const std = @import("std");
 const abi = @import("abi");
 const sc = @import("system-call.zig");
 
@@ -98,6 +99,16 @@ pub fn processes(out: []abi.ProcessDescriptor) usize {
     return sc.systemCall2(.process_enumerate, @intFromPtr(out.ptr), out.len);
 }
 
+/// Whether a process spawned under `name` (its argv[0]) is currently alive.
+pub fn isProcessRunning(name: []const u8) bool {
+    var table: [32]ProcessDescriptor = undefined;
+    const total = processes(&table);
+    for (table[0..@min(total, table.len)]) |descriptor| {
+        if (std.mem.eql(u8, descriptor.name[0..descriptor.name_length], name)) return true;
+    }
+    return false;
+}
+
 /// End process `id`. Only its supervisor — the process that spawned it — may;
 /// anyone else gets false, as does a stale or unknown id (ids are never reused).
 /// Delivery is prompt but asynchronous, like a signal: a target caught running on