svn commit: r346935 - head/sys/powerpc/powerpc

[Justin Hibbits]

Author: jhibbits
Date: Mon Apr 29 22:37:35 2019
New Revision: 346935
URL: https://svnweb.freebsd.org/changeset/base/346935

Log:
  powerpc64: Fix switch panic from cpu_throw()
  
  r18 is used to hold the old PCB flags, but cpu_throw doesn't populate r18
  with PCB flags, since the old thread is gone.  This can lead to panics on
  cores that don't have the registers guarded by these flags.

Modified:
  head/sys/powerpc/powerpc/swtch64.S

Modified: head/sys/powerpc/powerpc/swtch64.S
==============================================================================
--- head/sys/powerpc/powerpc/swtch64.S	Mon Apr 29 22:16:33 2019	(r346934)
+++ head/sys/powerpc/powerpc/swtch64.S	Mon Apr 29 22:37:35 2019	(r346935)
@@ -78,6 +78,7 @@ TOC_ENTRY(blocked_lock)
 ENTRY(cpu_throw)
 	mr	%r13, %r4
 	li	%r14,0	/* Tell cpu_switchin not to release a thread */
+	li	%r18,0	/* No old pcb flags.  The old thread is extinguished. */
 
 	b	cpu_switchin