sparc64: Add global register dumping facility.

When a cpu really is stuck in the kernel, it can be often
impossible to figure out which cpu is stuck where.  The
worst case is when the stuck cpu has interrupts disabled.

Therefore, implement a global cpu state capture that uses
SMP message interrupts which are not disabled by the
normal IRQ enable/disable APIs of the kernel.

As long as we can get a sysrq 'y' to the kernel, we can
get a dump.  Even if the console interrupt cpu is wedged,
we can trigger it from userspace using /proc/sysrq-trigger

The output is made compact so that this facility is more
useful on high cpu count systems, which is where this
facility will likely find itself the most useful :)

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 1 deletions

diff --git a/arch/sparc64/mm/ultra.S b/arch/sparc64/mm/ultra.S
index 15d124963f68..9bb2d90a9df6 100644
--- a/arch/sparc64/mm/ultra.S
+++ b/arch/sparc64/mm/ultra.S
@@ -1,7 +1,7 @@
 /*
  * ultra.S: Don't expand these all over the place...
  *
- * Copyright (C) 1997, 2000 David S. Miller (davem@redhat.com)
+ * Copyright (C) 1997, 2000, 2008 David S. Miller (davem@davemloft.net)
  */
 
 #include <asm/asi.h>
@@ -15,6 +15,7 @@
 #include <asm/thread_info.h>
 #include <asm/cacheflush.h>
 #include <asm/hypervisor.h>
+#include <asm/cpudata.h>
 
         /* Basically, most of the Spitfire vs. Cheetah madness
          * has to do with the fact that Cheetah does not support
@@ -514,6 +515,32 @@ xcall_report_regs:
         b               rtrap_xcall
          ldx            [%sp + PTREGS_OFF + PT_V9_TSTATE], %l1
 
+#ifdef CONFIG_MAGIC_SYSRQ
+        .globl          xcall_fetch_glob_regs
+xcall_fetch_glob_regs:
+        sethi           %hi(global_reg_snapshot), %g1
+        or              %g1, %lo(global_reg_snapshot), %g1
+        __GET_CPUID(%g2)
+        sllx            %g2, 6, %g3
+        add             %g1, %g3, %g1
+        rdpr            %tstate, %g7
+        stx             %g7, [%g1 + GR_SNAP_TSTATE]
+        rdpr            %tpc, %g7
+        stx             %g7, [%g1 + GR_SNAP_TPC]
+        rdpr            %tnpc, %g7
+        stx             %g7, [%g1 + GR_SNAP_TNPC]
+        stx             %o7, [%g1 + GR_SNAP_O7]
+        stx             %i7, [%g1 + GR_SNAP_I7]
+        sethi           %hi(trap_block), %g7
+        or              %g7, %lo(trap_block), %g7
+        sllx            %g2, TRAP_BLOCK_SZ_SHIFT, %g2
+        add             %g7, %g2, %g7
+        ldx             [%g7 + TRAP_PER_CPU_THREAD], %g3
+        membar          #StoreStore
+        stx             %g3, [%g1 + GR_SNAP_THREAD]
+        retry
+#endif /* CONFIG_MAGIC_SYSRQ */
+
 #ifdef DCACHE_ALIASING_POSSIBLE
         .align          32
         .globl          xcall_flush_dcache_page_cheetah