FRV: Add support for emulation of userspace atomic ops [try #2]

Use traps 120-126 to emulate atomic cmpxchg32, xchg32, and XOR-, OR-, AND-, SUB-
and ADD-to-memory operations for userspace.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/frv/kernel/entry.S b/arch/frv/kernel/entry.S
index f36d7f4a7c25..b8a4b94779b1 100644
--- a/arch/frv/kernel/entry.S
+++ b/arch/frv/kernel/entry.S
@@ -656,6 +656,26 @@ __entry_debug_exception:
 
 ###############################################################################
 #
+# handle atomic operation emulation for userspace
+#
+###############################################################################
+        .globl          __entry_atomic_op
+__entry_atomic_op:
+        LEDS            0x6012
+        sethi.p         %hi(atomic_operation),gr5
+        setlo           %lo(atomic_operation),gr5
+        movsg           esfr1,gr8
+        movsg           epcr0,gr9
+        movsg           esr0,gr10
+
+        # now that we've accessed the exception regs, we can enable exceptions
+        movsg           psr,gr4
+        ori             gr4,#PSR_ET,gr4
+        movgs           gr4,psr
+        jmpl            @(gr5,gr0)      ; call atomic_operation(esfr1,epcr0,esr0)
+
+###############################################################################
+#
 # handle media exception
 #
 ###############################################################################