svn commit: r316367 - stable/11/sys/powerpc/ofw

[Justin Hibbits]

Author: jhibbits
Date: Sat Apr  1 18:52:48 2017
New Revision: 316367
URL: https://svnweb.freebsd.org/changeset/base/316367

Log:
  MFC r314885:
  
    Fix booting with >4GB RAM on PowerMac G5 hardware
  
    ===
    From Nathan Whitehorn:
  
    Open Firmware runs in virtual mode on the Powermac G5. This runs inside
    the
    kernel page table, which preserves all address translations made by OF
    before
    the kernel starts; as a result, the kernel address space is a strict
    superset of
    OF's.
  
    Where this explodes is if OF uses an unmapped SLB entry. The SLB
    fault handler
    runs in real mode and refers to the PCPU pointer in SPRG0,
    which blows up the
    kernel. Having a value of SPRG0 that works for the kernel is
    less fatal than
    preserving OF's value in this case.
  
    ===
  
    The result of this is seemingly random panics from
    NULL dereferences, or hangs
    immediately upon boot.  By not restoring SPRG0 for
    Open Firmware entry the
    kernel PCPU pointer is preserved and SLB faults
    are successful, resulting in a
    stable kernel.
  
  PR:		205458

Modified:
  stable/11/sys/powerpc/ofw/ofw_machdep.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/powerpc/ofw/ofw_machdep.c
==============================================================================
--- stable/11/sys/powerpc/ofw/ofw_machdep.c	Sat Apr  1 17:15:53 2017	(r316366)
+++ stable/11/sys/powerpc/ofw/ofw_machdep.c	Sat Apr  1 18:52:48 2017	(r316367)
@@ -111,6 +111,15 @@ ofw_sprg_prepare(void)
 	 * Assume that interrupt are disabled at this point, or
 	 * SPRG1-3 could be trashed
 	 */
+#ifdef __powerpc64__
+	__asm __volatile("mtsprg1 %0\n\t"
+	    		 "mtsprg2 %1\n\t"
+			 "mtsprg3 %2\n\t"
+			 :
+			 : "r"(ofmsr[2]),
+			 "r"(ofmsr[3]),
+			 "r"(ofmsr[4]));
+#else
 	__asm __volatile("mfsprg0 %0\n\t"
 			 "mtsprg0 %1\n\t"
 	    		 "mtsprg1 %2\n\t"
@@ -121,6 +130,7 @@ ofw_sprg_prepare(void)
 			 "r"(ofmsr[2]),
 			 "r"(ofmsr[3]),
 			 "r"(ofmsr[4]));
+#endif
 }
 
 static __inline void
@@ -136,7 +146,9 @@ ofw_sprg_restore(void)
 	 *
 	 * PCPU data cannot be used until this routine is called !
 	 */
+#ifndef __powerpc64__
 	__asm __volatile("mtsprg0 %0" :: "r"(ofw_sprg0_save));
+#endif
 }
 #endif
 
@@ -344,8 +356,9 @@ OF_initial_setup(void *fdt_ptr, void *ju
 	ofmsr[0] = mfmsr();
 	#ifdef __powerpc64__
 	ofmsr[0] &= ~PSL_SF;
-	#endif
+	#else
 	__asm __volatile("mfsprg0 %0" : "=&r"(ofmsr[1]));
+	#endif
 	__asm __volatile("mfsprg1 %0" : "=&r"(ofmsr[2]));
 	__asm __volatile("mfsprg2 %0" : "=&r"(ofmsr[3]));
 	__asm __volatile("mfsprg3 %0" : "=&r"(ofmsr[4]));