xtensa: add double exception fixup handler for fast_unaligned

fast_unaligned_fixup restores user registers and runs normal exception
handler in the current stack frame. Unaligned load/store is retried
after that.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/arch/xtensa/kernel/align.S b/arch/xtensa/kernel/align.S
index 25a65938dda8..904f32f05c09 100644
--- a/arch/xtensa/kernel/align.S
+++ b/arch/xtensa/kernel/align.S
@@ -8,6 +8,7 @@
  * this archive for more details.
  *
  * Copyright (C) 2001 - 2005 Tensilica, Inc.
+ * Copyright (C) 2014 Cadence Design Systems Inc.
  *
  * Rewritten by Chris Zankel <chris@zankel.net>
  *
@@ -174,6 +175,10 @@ ENTRY(fast_unaligned)
         s32i    a0, a2, PT_AREG2
         s32i    a3, a2, PT_AREG3
 
+        rsr     a3, excsave1
+        movi    a4, fast_unaligned_fixup
+        s32i    a4, a3, EXC_TABLE_FIXUP
+
         /* Keep value of SAR in a0 */
 
         rsr     a0, sar
@@ -430,6 +435,10 @@ ENTRY(fast_unaligned)
 .Linvalid_instruction_store:
 .Linvalid_instruction:
 
+        movi    a4, 0
+        rsr     a3, excsave1
+        s32i    a4, a3, EXC_TABLE_FIXUP
+
         /* Restore a4...a8 and SAR, set SP, and jump to default exception. */
 
         l32i    a8, a2, PT_AREG8
@@ -451,4 +460,38 @@ ENTRY(fast_unaligned)
 
 ENDPROC(fast_unaligned)
 
+ENTRY(fast_unaligned_fixup)
+
+        l32i    a2, a3, EXC_TABLE_DOUBLE_SAVE
+        wsr     a3, excsave1
+
+        l32i    a8, a2, PT_AREG8
+        l32i    a7, a2, PT_AREG7
+        l32i    a6, a2, PT_AREG6
+        l32i    a5, a2, PT_AREG5
+        l32i    a4, a2, PT_AREG4
+        l32i    a0, a2, PT_AREG2
+        xsr     a0, depc                        # restore depc and a0
+        wsr     a0, sar
+
+        rsr     a0, exccause
+        s32i    a0, a2, PT_DEPC                 # mark as a regular exception
+
+        rsr     a0, ps
+        bbsi.l  a0, PS_UM_BIT, 1f               # jump if user mode
+
+        rsr     a0, exccause
+        addx4   a0, a0, a3                      # find entry in table
+        l32i    a0, a0, EXC_TABLE_FAST_KERNEL   # load handler
+        l32i    a3, a2, PT_AREG3
+        jx      a0
+1:
+        rsr     a0, exccause
+        addx4   a0, a0, a3                      # find entry in table
+        l32i    a0, a0, EXC_TABLE_FAST_USER     # load handler
+        l32i    a3, a2, PT_AREG3
+        jx      a0
+
+ENDPROC(fast_unaligned_fixup)
+
 #endif /* XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION */