feat: add inherited sessions and desktop session teardown

kernel/src/Sched/Scheduler.cpp

@@ -297,6 +297,7 @@ namespace Sched {
             processTable[i].environment[0] = '\0';
             processTable[i].environmentLength = 1;
             processTable[i].user[0] = '\0';
+            processTable[i].sessionId = -1;
             processTable[i].cwd[0] = '\0';
             processTable[i].runningOnCpu = -1;
             processTable[i].killPending = false;
@@ -560,6 +561,13 @@ namespace Sched {
             }
         }
 
+        // Process sessions are explicit groups used by supervisors such as
+        // login.elf. A session leader opts in with CreateSession(); all of its
+        // subsequently spawned descendants inherit the same stable ID.
+        proc.sessionId = (parentPrimarySlot >= 0)
+            ? processTable[parentPrimarySlot].sessionId
+            : -1;
+
         {
             if (parentSlot >= 0 && processTable[parentSlot].cwd[0]) {
                 int i = 0;
@@ -1747,6 +1755,68 @@ namespace Sched {
         return 0;
     }
 
+    int CreateSession() {
+        schedLock.Acquire();
+        Process* proc = GetCurrentProcessPtr();
+        if (proc == nullptr) {
+            schedLock.Release();
+            return -1;
+        }
+        proc->sessionId = proc->pid;
+        int sessionId = proc->sessionId;
+        schedLock.Release();
+        return sessionId;
+    }
+
+    int KillSession(int sessionId) {
+        if (sessionId < 0) return -1;
+
+        int callerPid = GetCurrentPid();
+        int killed = 0;
+
+        // Mark the complete group in one scheduler-lock transaction. New
+        // children inherit sessionId, so a supervisor can repeat this call
+        // until zero is returned to close the small spawn/exit race cleanly.
+        schedLock.Acquire();
+        for (int i = 0; i < MaxProcesses; i++) {
+            Process& primary = processTable[i];
+            if (primary.primarySlot != i || primary.pid == callerPid ||
+                primary.sessionId != sessionId) {
+                continue;
+            }
+            auto state = primary.state;
+            if (state != ProcessState::Ready && state != ProcessState::Running &&
+                state != ProcessState::Blocked) {
+                continue;
+            }
+
+            primary.exitCode = 256 + 9; /* killed (SIGKILL) */
+            primary.killPending = true;
+            if (primary.state == ProcessState::Blocked) {
+                primary.state = ProcessState::Ready;
+                readyCount++;
+                primary.waitingForPid = -1;
+                primary.waitingOnObject = nullptr;
+                primary.sleepUntilTick = 0;
+            }
+
+            for (int j = 0; j < MaxProcesses; j++) {
+                if (j == i || processTable[j].primarySlot != i) continue;
+                if (processTable[j].state == ProcessState::Running) {
+                    processTable[j].killPending = true;
+                }
+            }
+            killed++;
+        }
+        schedLock.Release();
+
+        if (killed > 0) {
+            KickOneIdleCpu(Smp::GetCurrentCpuData()
+                ? Smp::GetCurrentCpuData()->cpuIndex : -1);
+        }
+        return killed;
+    }
+
     int LookupExitCode(int pid) {
         schedLock.Acquire();
         int code = 0;