From 3a486d207fc948bf1d146b6071480a6ecdae41b7 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Thu, 17 Jul 2025 00:25:52 -0400
Subject: kernel: spawn: Add waitpid()

Add waitpid() in preparation of deprecating SPAWN_WAIT.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/include/sys/proc.h    |  1 +
 sys/include/sys/syscall.h |  1 +
 sys/kern/kern_spawn.c     | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 sys/kern/kern_syscall.c   |  1 +
 4 files changed, 54 insertions(+)

(limited to 'sys')

diff --git a/sys/include/sys/proc.h b/sys/include/sys/proc.h
index decc615..972d3c4 100644
--- a/sys/include/sys/proc.h
+++ b/sys/include/sys/proc.h
@@ -119,6 +119,7 @@ pid_t getppid(void);
 
 scret_t sys_getpid(struct syscall_args *scargs);
 scret_t sys_getppid(struct syscall_args *scargs);
+scret_t sys_waitpid(struct syscall_args *scargs);
 
 int md_spawn(struct proc *p, struct proc *parent, uintptr_t ip);
 
diff --git a/sys/include/sys/syscall.h b/sys/include/sys/syscall.h
index 51c2579..02629a9 100644
--- a/sys/include/sys/syscall.h
+++ b/sys/include/sys/syscall.h
@@ -58,6 +58,7 @@
 #define SYS_getppid 17
 #define SYS_setuid  18
 #define SYS_getuid  19
+#define SYS_waitpid 20
 
 #if defined(_KERNEL)
 /* Syscall return value and arg type */
diff --git a/sys/kern/kern_spawn.c b/sys/kern/kern_spawn.c
index 930c3d2..c1c0029 100644
--- a/sys/kern/kern_spawn.c
+++ b/sys/kern/kern_spawn.c
@@ -28,6 +28,7 @@
  */
 
 #include <sys/spawn.h>
+#include <sys/wait.h>
 #include <sys/proc.h>
 #include <sys/exec.h>
 #include <sys/mman.h>
@@ -96,6 +97,35 @@ spawn_thunk(void)
     __builtin_unreachable();
 }
 
+pid_t
+waitpid(pid_t pid, int *wstatus, int options)
+{
+    struct proc *child, *td;
+    pid_t ret;
+
+    td = this_td();
+    child = get_child(td, pid);
+
+    if (child == NULL) {
+        return -1;
+    }
+
+    /* Wait for it to be done */
+    while (!ISSET(child->flags, PROC_ZOMB)) {
+        sched_yield();
+    }
+
+
+    /* Give back the status */
+    if (wstatus != NULL) {
+        copyout(&child->exit_status, wstatus, sizeof(*wstatus));
+    }
+
+    ret = child->pid;
+    proc_reap(child);
+    return ret;
+}
+
 /*
  * Spawn a new process
  *
@@ -219,6 +249,27 @@ get_child(struct proc *cur, pid_t pid)
     return NULL;
 }
 
+/*
+ * arg0: PID
+ * arg1: wstatus
+ * arg2: options
+ *
+ * Returns PID of terminated child, returns
+ * -1 on failure.
+ */
+scret_t
+sys_waitpid(struct syscall_args *scargs)
+{
+    pid_t pid;
+    int *u_wstatus;
+    int options;
+
+    pid = scargs->arg0;
+    u_wstatus = (void *)scargs->arg1;
+    options = scargs->arg2;
+    return waitpid(pid, u_wstatus, options);
+}
+
 /*
  * arg0: The file /path/to/executable
  * arg1: Argv
diff --git a/sys/kern/kern_syscall.c b/sys/kern/kern_syscall.c
index a28d2dd..cb7e1d2 100644
--- a/sys/kern/kern_syscall.c
+++ b/sys/kern/kern_syscall.c
@@ -59,6 +59,7 @@ scret_t(*g_sctab[])(struct syscall_args *) = {
     sys_getppid, /* SYS_getppid */
     sys_setuid,  /* SYS_setuid */
     sys_getuid,  /* SYS_getuid */
+    sys_waitpid, /* SYS_waitpid */
 };
 
 const size_t MAX_SYSCALLS = NELEM(g_sctab);
-- 
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