From d3d30751c49cadf015c4ebb5eaebe6dcefd982b4 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sat, 31 May 2025 01:22:50 -0400
Subject: kernel: sched: Add sched_switch_to()

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/include/sys/sched.h |  2 ++
 sys/kern/kern_sched.c   | 26 +++++++++++++++++++-------
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/sys/include/sys/sched.h b/sys/include/sys/sched.h
index 80f4d1c..7d17607 100644
--- a/sys/include/sys/sched.h
+++ b/sys/include/sys/sched.h
@@ -37,6 +37,8 @@
 
 void sched_init(void);
 void sched_yield(void);
+
+void sched_switch_to(struct trapframe *tf, struct proc *td);
 void sched_detach(struct proc *td);
 
 __dead void sched_enter(void);
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index 2fe0f32..65e08d7 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -176,15 +176,31 @@ td_pri_update(struct proc *td)
     }
 }
 
+void
+sched_switch_to(struct trapframe *tf, struct proc *td)
+{
+    struct cpu_info *ci;
+    struct pcb *pcbp;
+
+    ci = this_cpu();
+
+    if (tf != NULL) {
+        memcpy(tf, &td->tf, sizeof(*tf));
+    }
+
+    ci->curtd = td;
+    pcbp = &td->pcb;
+    pmap_switch_vas(pcbp->addrsp);
+}
+
 /*
  * Perform a context switch.
  */
 void
 sched_switch(struct trapframe *tf)
 {
-    struct cpu_info *ci;
-    struct pcb *pcbp;
     struct proc *next_td, *td;
+    struct cpu_info *ci;
 
     ci = this_cpu();
     td = ci->curtd;
@@ -203,11 +219,7 @@ sched_switch(struct trapframe *tf)
         return;
     }
 
-    memcpy(tf, &next_td->tf, sizeof(*tf));
-    ci->curtd = next_td;
-    pcbp = &next_td->pcb;
-
-    pmap_switch_vas(pcbp->addrsp);
+    sched_switch_to(tf, next_td);
     sched_oneshot(false);
 }
 
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