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, 24 insertions, 0 deletions

diff --git a/sys/alpha/alpha/machdep.c b/sys/alpha/alpha/machdep.c
index 005e56e..82c856d 100644
--- a/sys/alpha/alpha/machdep.c
+++ b/sys/alpha/alpha/machdep.c
@@ -1989,6 +1989,29 @@ alpha_pa_access(vm_offset_t pa)
 #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_context[0] = tf->tf_regs[FRAME_S0];
+	pcb->pcb_context[1] = tf->tf_regs[FRAME_S1];
+	pcb->pcb_context[2] = tf->tf_regs[FRAME_S2];
+	pcb->pcb_context[3] = tf->tf_regs[FRAME_S3];
+	pcb->pcb_context[4] = tf->tf_regs[FRAME_S4];
+	pcb->pcb_context[5] = tf->tf_regs[FRAME_S5];
+	pcb->pcb_context[6] = tf->tf_regs[FRAME_S6];
+	pcb->pcb_context[7] = tf->tf_regs[FRAME_PC];
+	pcb->pcb_context[8] = tf->tf_regs[FRAME_PS];
+	pcb->pcb_hw.apcb_ksp = tf->tf_regs[FRAME_SP];
+}
+
 int
 fill_regs(td, regs)
 	struct thread *td;
diff --git a/sys/alpha/include/pcb.h b/sys/alpha/include/pcb.h
index 982e97b..4375ef2 100644
--- a/sys/alpha/include/pcb.h
+++ b/sys/alpha/include/pcb.h
@@ -58,6 +58,7 @@ struct pcb {
 };
 
 #ifdef _KERNEL
+void	makectx(struct trapframe *, struct pcb *);
 void	savectx(struct pcb *);
 #endif