[PATCH] risu: don't do a full register compare for OP_SIGILL

[Alex Bennée]

OP_SIGILL means we have an unexpected invalid operation. If this is a
load or store the register state may be un-rectified pointing at the
memblock so would be invalid. In this case just compare the PC and
make sure the other end also faulted at the same place.

Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
---
 risu.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/risu.c b/risu.c
index 8d907d9..6d6dcf9 100644
--- a/risu.c
+++ b/risu.c
@@ -124,7 +124,6 @@ static RisuResult send_register_info(void *uc)
     switch (op) {
     case OP_TESTEND:
     case OP_COMPARE:
-    case OP_SIGILL:
         header.size = reginfo_size(&ri[MASTER]);
         extra = &ri[MASTER];
         break;
@@ -132,6 +131,7 @@ static RisuResult send_register_info(void *uc)
         header.size = MEMBLOCKLEN;
         extra = memblock;
         break;
+    case OP_SIGILL:
     case OP_SETMEMBLOCK:
     case OP_GETMEMBLOCK:
         header.size = 0;
@@ -203,7 +203,6 @@ static RisuResult recv_register_info(struct reginfo *ri)
     switch (header.risu_op) {
     case OP_COMPARE:
     case OP_TESTEND:
-    case OP_SIGILL:
         /* If we can't store the data, report invalid size. */
         if (header.size > sizeof(*ri)) {
             return RES_BAD_SIZE;
@@ -223,6 +222,7 @@ static RisuResult recv_register_info(struct reginfo *ri)
         respond(RES_OK);
         return read_buffer(other_memblock, MEMBLOCKLEN);
 
+    case OP_SIGILL:
     case OP_SETMEMBLOCK:
     case OP_GETMEMBLOCK:
         return header.size == 0 ? RES_OK : RES_BAD_SIZE;
@@ -250,7 +250,6 @@ static RisuResult recv_and_compare_register_info(void *uc)
     switch (op) {
     case OP_COMPARE:
     case OP_TESTEND:
-    case OP_SIGILL:
         /*
          * If we have nothing to compare against, report an op mismatch.
          * Otherwise allow the compare to continue, and assume that
@@ -270,7 +269,14 @@ static RisuResult recv_and_compare_register_info(void *uc)
             res = RES_END;
         }
         break;
-
+    case OP_SIGILL:
+        /* We can only check the op and PC */
+        if (header.risu_op != OP_SIGILL) {
+            res = RES_MISMATCH_OP;
+        } else if (header.pc != get_pc(&ri[APPRENTICE])) {
+            res = RES_MISMATCH_REG;
+        }
+        break;
     case OP_SETMEMBLOCK:
         if (op != header.risu_op) {
             res = RES_MISMATCH_OP;
-- 
2.20.1