[patch 05/96] sparc64: Fix DAX handling via userspace access from kernel.

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: David S. Miller <davem@xxxxxxxxxxxxx>

[ Upstream commit fcd26f7ae2ea5889134e8b3d60a42ce8b993c95f ]

If we do a userspace access from kernel mode, and get a
data access exception, we need to check the exception
table just like a normal fault does.

The spitfire DAX handler was doing this, but such logic
was missing from the sun4v DAX code.

Reported-by: Dennis Gilmore <dgilmore@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/sparc64/kernel/traps.c |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

--- a/arch/sparc64/kernel/traps.c
+++ b/arch/sparc64/kernel/traps.c
@@ -1,6 +1,6 @@
 /* arch/sparc64/kernel/traps.c
  *
- * Copyright (C) 1995,1997,2008 David S. Miller (davem@xxxxxxxxxxxxx)
+ * Copyright (C) 1995,1997,2008,2009 David S. Miller (davem@xxxxxxxxxxxxx)
  * Copyright (C) 1997,1999,2000 Jakub Jelinek (jakub@xxxxxxxxxx)
  */
 
@@ -262,6 +262,21 @@ void sun4v_data_access_exception(struct 
 		return;
 
 	if (regs->tstate & TSTATE_PRIV) {
+		/* Test if this comes from uaccess places. */
+		const struct exception_table_entry *entry;
+
+		entry = search_exception_tables(regs->tpc);
+		if (entry) {
+			/* Ouch, somebody is trying VM hole tricks on us... */
+#ifdef DEBUG_EXCEPTIONS
+			printk("Exception: PC<%016lx> faddr<UNKNOWN>\n", regs->tpc);
+			printk("EX_TABLE: insn<%016lx> fixup<%016lx>\n",
+			       regs->tpc, entry->fixup);
+#endif
+			regs->tpc = entry->fixup;
+			regs->tnpc = regs->tpc + 4;
+			return;
+		}
 		printk("sun4v_data_access_exception: ADDR[%016lx] "
 		       "CTX[%04x] TYPE[%04x], going.\n",
 		       addr, ctx, type);


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