Implement makectx(). The makectx() function is used by KDB to create

a PCB from a trapframe for purposes of unwinding the stack. The PCB
is used as the thread context and all but the thread that entered the
debugger has a valid PCB.
This function can also be used to create a context for the threads
running on the CPUs that have been stopped when the debugger got
entered. This however is not done at the time of this commit.

2 files changed, 16 insertions, 0 deletions

diff --git a/sys/sparc64/include/pcb.h b/sys/sparc64/include/pcb.h
index 38578d2..1f1e8dc 100644
--- a/sys/sparc64/include/pcb.h
+++ b/sys/sparc64/include/pcb.h
@@ -49,6 +49,7 @@ struct pcb {
 } __aligned(64);
 
 #ifdef _KERNEL
+void	makectx(struct trapframe *, struct pcb *);
 int	savectx(struct pcb *pcb);
 #endif
 
diff --git a/sys/sparc64/sparc64/machdep.c b/sys/sparc64/sparc64/machdep.c
index 3db2dd8..2bc8329 100644
--- a/sys/sparc64/sparc64/machdep.c
+++ b/sys/sparc64/sparc64/machdep.c
@@ -564,6 +564,21 @@ freebsd4_sigreturn(struct thread *td, struct freebsd4_sigreturn_args *uap)
 }
 #endif
 
+/*
+ * Construct a PCB from a trapframe. This is called from kdb_trap() where
+ * we want to start a backtrace from the function that caused us to enter
+ * the debugger. We have the context in the trapframe, but base the trace
+ * on the PCB. The PCB doesn't have to be perfect, as long as it contains
+ * enough for a backtrace.
+ */
+void
+makectx(struct trapframe *tf, struct pcb *pcb)
+{
+
+	pcb->pcb_pc = tf->tf_tpc;
+	pcb->pcb_sp = tf->tf_sp;
+}
+
 int
 get_mcontext(struct thread *td, mcontext_t *mc, int flags)
 {