From a6557ed0233e2193cef0ab5b4cea7f1d7f19ad5d Mon Sep 17 00:00:00 2001
From: Kimplul <kimi.h.kuparinen@gmail.com>
Date: Thu, 4 Jul 2024 23:40:37 +0300
Subject: use notification framework for orphanizing threads

---
 arch/riscv64/kernel/vmem.c |  2 +-
 include/kmi/syscalls.h     |  3 +++
 include/kmi/uapi.h         |  8 +++-----
 src/uapi/ipc.c             | 15 +++++++++------
 src/uapi/proc.c            | 26 ++++++++++++++++++--------
 5 files changed, 34 insertions(+), 20 deletions(-)

diff --git a/arch/riscv64/kernel/vmem.c b/arch/riscv64/kernel/vmem.c
index d4ae937..cc6f3ac 100644
--- a/arch/riscv64/kernel/vmem.c
+++ b/arch/riscv64/kernel/vmem.c
@@ -520,7 +520,7 @@ void setup_rpc_stack(struct tcb *t)
 void destroy_rpc_stack(struct tcb *t)
 {
 	for (size_t i = 0; i < rpc_pages; ++i) {
-		pm_t page; enum mm_order order;
+		pm_t page = 0; enum mm_order order = BASE_PAGE;
 		stat_vpage(t->rpc.vmem, RPC_STACK_BASE + BASE_PAGE_SIZE * i,
 		           &page, &order, NULL);
 		free_page(page, order);
diff --git a/include/kmi/syscalls.h b/include/kmi/syscalls.h
index 93d0ac9..4ae0f0b 100644
--- a/include/kmi/syscalls.h
+++ b/include/kmi/syscalls.h
@@ -186,6 +186,9 @@ enum notify_flag {
 
 	/** An interrupt request. */
 	NOTIFY_IRQ = (1 << 2),
+
+	/** Thread has become orphaned. */
+	NOTIFY_ORPHANED = (1 << 3),
 };
 
 /* function declarations should be somewhere else, this file could be used in
diff --git a/include/kmi/uapi.h b/include/kmi/uapi.h
index 76a759f..42d6e5b 100644
--- a/include/kmi/uapi.h
+++ b/include/kmi/uapi.h
@@ -843,18 +843,16 @@ SYSCALL_DECLARE1(exit, tid);
 
 /**
  * Request that a thread becomes orphant, i.e. eventually attached to the init
- * process. Can be used to stop threads within a process by sending an
- * appropriate signal to the troublesome thread which then detaches itself from
- * its root process.
+ * process. Can be used to stop threads within a process.
  *
  * @param t Current tcb.
- * @param a Unused.
+ * @param tid Which thread to orphanize.
  * @param b Unused.
  * @param c Unused.
  * @param d Unused.
  * @param e Unused.
  */
-SYSCALL_DECLARE0(detach);
+SYSCALL_DECLARE1(detach, tid);
 
 /** @} */
 
diff --git a/src/uapi/ipc.c b/src/uapi/ipc.c
index bc49dbb..ddc7242 100644
--- a/src/uapi/ipc.c
+++ b/src/uapi/ipc.c
@@ -138,8 +138,8 @@ static bool __enough_rpc_stack(struct tcb *t)
 /**
  * Actually run notification handler, no ifs or buts.
  *
- * @param t Previous thread.
- * @param r Next thread.
+ * @param t Current thread.
+ * @param r Process where notification handler is.
  *
  * \p t and \p r may be the same thread.
  */
@@ -148,12 +148,15 @@ static __noreturn void __run_notify(struct tcb *t, struct tcb *r)
 	use_tcb(r);
 
 	enum sys_user code = SYS_USER_NOTIFY;
-	/* if we're not in RPC, we can safely notify of a signal while we're at
-	 * it */
-	enum notify_flag flags = is_rpc(t) ? 0 : NOTIFY_SIGNAL;
+	enum notify_flag flags = 0;
+
+	/* if we're in the root process, we can safely handle signals and
+	 * becoming orphaned */
+	if (!is_rpc(t))
+		set_bits(flags, t->notify_flags & (NOTIFY_SIGNAL | NOTIFY_ORPHANED));
 
 	/* handle critical notifications with special care */
-	if (is_set(flags, NOTIFY_IRQ | NOTIFY_TIMER)) {
+	if (is_set(t->notify_flags, NOTIFY_IRQ | NOTIFY_TIMER)) {
 		set_bits(flags, t->notify_flags & (NOTIFY_IRQ | NOTIFY_TIMER));
 		disable_irqs();
 	}
diff --git a/src/uapi/proc.c b/src/uapi/proc.c
index 231cc32..5b64dce 100644
--- a/src/uapi/proc.c
+++ b/src/uapi/proc.c
@@ -92,10 +92,17 @@ SYSCALL_DEFINE0(fork)(struct tcb *t)
 SYSCALL_DEFINE2(exec)(struct tcb *t, sys_arg_t bin, sys_arg_t interp)
 {
 	/** @todo probably make sure thread is root thread of process? */
+	if (!is_proc(t))
+		return_args1(t, ERR_PERM);
+
+	/* exec is only allowed if we own all our own resources */
+	if (t->refcount)
+		return_args1(t, ERR_INVAL)
+
 	/* mark binary to be kept */
 	struct mem_region *b = find_used_region(&t->sp_r, bin);
 	if (!b)
-		return_args1(t, ERR_INVAL);
+		return_args1(t, ERR_ADDR);
 
 	set_bit(b->flags, MR_KEEP);
 
@@ -237,28 +244,31 @@ SYSCALL_DEFINE1(exit)(struct tcb *t, sys_arg_t tid)
 /**
  * Syscall handler for orphanizing a thread.
  *
- * @param t Thread that wants to make itself an orphant.
+ * @param t Current thread.
+ * @param tid Thread we want to orphanize. May be ourselves.
  * @return \ref OK on success,
  * \ref ERR_PERM if current process missing \ref CAP_PROC,
  * \ref ERR_INVAL if already an orphant.
  */
-SYSCALL_DEFINE0(detach)(struct tcb *t)
+SYSCALL_DEFINE1(detach)(struct tcb *t, sys_arg_t tid)
 {
 	struct tcb *c = get_cproc(t);
 	if (!(has_cap(c->caps, CAP_PROC)))
 		return_args1(t, ERR_PERM);
 
-	if (orphan(t))
+	struct tcb *o = get_tcb(tid);
+	if (!o || orphan(o))
 		return_args1(t, ERR_INVAL);
 
-	struct tcb *r = get_tcb(t->rid);
+	struct tcb *r = get_tcb(o->rid);
 	if (r)
 		unreference_proc(r);
 
-	orphanize(t);
+	orphanize(o);
 
-	if (!is_rpc(t))
-		unorphanize(t);
+	/* generally the thread shouldn't do anything with this information, but
+	 * it fits really nicely into the notification framework so just do it */
+	notify(o, NOTIFY_ORPHANED);
 
 	return_args1(t, OK);
 }
-- 
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