Use the PROM provided SUNW,set-trap-table to take over the trap

table. This is required in order to set obp-control-relinquished
within the PROM, allowing to safely read the OFW translations node.
Without this, f.e. a `ofwdump -ap` triggers a fatal reset error or
worse things on machines based on USIII and beyond.
In theory this should allow to remove touching %tba in cpu_setregs(),
in practice we seem to currently face a chicken and egg problem when
doing so however.

3 files changed, 35 insertions, 0 deletions

diff --git a/sys/sparc64/include/trap.h b/sys/sparc64/include/trap.h
index e4adc78..f73340c 100644
--- a/sys/sparc64/include/trap.h
+++ b/sys/sparc64/include/trap.h
@@ -90,6 +90,7 @@
 #define	T_KERNEL			64
 
 #ifndef LOCORE
+void sun4u_set_traptable(void *tba_addr);
 extern const char *trap_msg[];
 #endif
 
diff --git a/sys/sparc64/sparc64/machdep.c b/sys/sparc64/sparc64/machdep.c
index fa173cb..cd3194b 100644
--- a/sys/sparc64/sparc64/machdep.c
+++ b/sys/sparc64/sparc64/machdep.c
@@ -437,6 +437,16 @@ sparc64_init(caddr_t mdp, u_long o1, u_long o2, u_long o3, ofw_vec_t *vec)
 	cpu_setregs(pc);
 
 	/*
+	 * Take over the trap table via the PROM.  Using the PROM for this
+	 * is necessary in order to set obp-control-relinquished to true
+	 * within the PROM so obtaining /virtual-memory/translations doesn't
+	 * trigger a fatal reset error or worse things further down the road.
+	 * XXX it should be possible to use this soley instead of writing
+	 * %tba in cpu_setregs().  Doing so causes a hang however.
+	 */
+	sun4u_set_traptable(tl0_base);
+
+	/*
 	 * It's now safe to use the real DELAY().
 	 */
 	delay_func = delay_tick;
diff --git a/sys/sparc64/sparc64/trap.c b/sys/sparc64/sparc64/trap.c
index c1a81cd..9de8e26 100644
--- a/sys/sparc64/sparc64/trap.c
+++ b/sys/sparc64/sparc64/trap.c
@@ -70,6 +70,8 @@ __FBSDID("$FreeBSD$");
 #endif
 #include <security/audit/audit.h>
 
+#include <dev/ofw/openfirm.h>
+
 #include <vm/vm.h>
 #include <vm/pmap.h>
 #include <vm/vm_extern.h>
@@ -227,6 +229,28 @@ int debugger_on_signal = 0;
 SYSCTL_INT(_debug, OID_AUTO, debugger_on_signal, CTLFLAG_RW,
     &debugger_on_signal, 0, "");
 
+/*
+ * SUNW,set-trap-table allows to take over %tba from the PROM, which
+ * will turn off interrupts and handle outstanding ones while doing so,
+ * in a safe way.
+ */
+void
+sun4u_set_traptable(void *tba_addr)
+{
+	static struct {
+		cell_t name;
+		cell_t nargs;
+		cell_t nreturns;
+		cell_t tba_addr;
+	} args = {
+		(cell_t)"SUNW,set-trap-table",
+		2,
+	};
+
+	args.tba_addr = (cell_t)tba_addr;
+	openfirmware(&args);
+}
+
 void
 trap(struct trapframe *tf)
 {