[PATCH v3 1/1] accel/tcg: Fix computing of is_write for MIPS

[Kele Huang]

Detect all MIPS store instructions in cpu_signal_handler for all available
MIPS versions, and set is_write if encountering such store instructions.

This fixed the error while dealing with self-modified code for MIPS.

Signed-off-by: Kele Huang <kele.hwang@gmail.com>
Signed-off-by: Xu Zou <iwatchnima@gmail.com>
---
 accel/tcg/user-exec.c | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index bb039eb32d..c4494c93e7 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -702,6 +702,10 @@ int cpu_signal_handler(int host_signum, void *pinfo,
 
 #elif defined(__mips__)
 
+#if defined(__misp16) || defined(__mips_micromips)
+#error "Unsupported encoding"
+#endif
+
 int cpu_signal_handler(int host_signum, void *pinfo,
                        void *puc)
 {
@@ -709,9 +713,41 @@ int cpu_signal_handler(int host_signum, void *pinfo,
     ucontext_t *uc = puc;
     greg_t pc = uc->uc_mcontext.pc;
     int is_write;
+    uint32_t insn;
 
-    /* XXX: compute is_write */
+    /* Detect all store instructions at program counter. */
     is_write = 0;
+    insn = *(uint32_t *)pc;
+    switch((insn >> 26) & 077) {
+    case 050: /* SB */
+    case 051: /* SH */
+    case 052: /* SWL */
+    case 053: /* SW */
+    case 054: /* SDL */
+    case 055: /* SDR */
+    case 056: /* SWR */
+    case 070: /* SC */
+    case 071: /* SWC1 */
+    case 074: /* SCD */
+    case 075: /* SDC1 */
+    case 077: /* SD */
+#if !defined(__mips_isa_rev) || __mips_isa_rev < 6
+    case 072: /* SWC2 */
+    case 076: /* SDC2 */
+#endif
+        is_write = 1;
+        break;
+    case 023: /* COP1X */
+        /* Required in all versions of MIPS64 since 
+           MIPS64r1 and subsequent versions of MIPS32. */
+        switch (insn & 077) {
+        case 010: /* SWXC1 */
+        case 011: /* SDXC1 */
+            is_write = 1;
+        }
+        break;
+    }
+
     return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
 }
 
-- 
2.17.1