[MIPS] Add support for thread_suspension test

src/trusted/service_runtime/thread_suspension_unwind.c

 /*
  * Copyright (c) 2013 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "native_client/src/trusted/service_runtime/thread_suspension_unwind.h"
 
 #include "native_client/src/trusted/cpu_features/arch/x86/cpu_x86.h"
 #include "native_client/src/trusted/service_runtime/arch/arm/tramp_arm.h"
 #include "native_client/src/trusted/service_runtime/arch/x86_64/tramp_64.h"
 #include "native_client/src/trusted/service_runtime/nacl_app_thread.h"
 #include "native_client/src/trusted/service_runtime/nacl_config.h"
 #include "native_client/src/trusted/service_runtime/nacl_copy.h"
 #include "native_client/src/trusted/service_runtime/sel_ldr.h"
 
 
-#if NACL_ARCH(NACL_BUILD_ARCH) == NACL_x86 || \
-    NACL_ARCH(NACL_BUILD_ARCH) == NACL_arm
-
 static void GetNaClSyscallSeg(struct NaClApp *nap,
                               uintptr_t *nacl_syscall_seg,
                               uintptr_t *nacl_syscall_seg_regs_saved) {
 #if NACL_ARCH(NACL_BUILD_ARCH) == NACL_x86 && NACL_BUILD_SUBARCH == 32
   NaClCPUFeaturesX86 *features = (NaClCPUFeaturesX86 *) nap->cpu_features;
   if (NaClGetCPUFeatureX86(features, NaClCPUFeatureX86_SSE)) {
     *nacl_syscall_seg = (uintptr_t) &NaClSyscallSegSSE;
     *nacl_syscall_seg_regs_saved = (uintptr_t) &NaClSyscallSegRegsSavedSSE;
   } else {
     *nacl_syscall_seg = (uintptr_t) &NaClSyscallSegNoSSE;
@@ skipping 40 matching lines @@
     regs->stack_ptr += 8;  /* Pop user return address */
     return 1;
   }
 #elif NACL_ARCH(NACL_BUILD_ARCH) == NACL_arm
   if (regs->prog_ctr >= NACL_TRAMPOLINE_START &&
       regs->prog_ctr < NACL_TRAMPOLINE_END) {
     *unwind_case = NACL_UNWIND_in_trampoline;
     regs->prog_ctr = NaClSandboxCodeAddr(nap, regs->lr);
     return 1;
   }
+#elif NACL_ARCH(NACL_BUILD_ARCH) == NACL_mips
+  if (regs->prog_ctr >= NACL_TRAMPOLINE_START &&
+      regs->prog_ctr < NACL_TRAMPOLINE_END) {
+    *unwind_case = NACL_UNWIND_in_trampoline;
+    regs->prog_ctr = NaClSandboxCodeAddr(nap, regs->return_addr);
+    return 1;
+  }
 #endif
 
 #if NACL_ARCH(NACL_BUILD_ARCH) == NACL_x86 && NACL_BUILD_SUBARCH == 32
   if (regs->cs == NaClGetGlobalCs() &&
       regs->prog_ctr >= nap->pcrel_thunk &&
       regs->prog_ctr < nap->pcrel_thunk_end) {
     *unwind_case = NACL_UNWIND_in_pcrel_thunk;
     regs->stack_ptr += 4 + 8;  /* Pop user + trampoline return addresses */
     return 1;
   }
@@ skipping 15 matching lines @@
       regs->stack_ptr += 8;  /* Pop user return address */
     }
     return 1;
   }
 #endif
 
   GetNaClSyscallSeg(nap, &nacl_syscall_seg, &nacl_syscall_seg_regs_saved);
   if (regs->prog_ctr >= nacl_syscall_seg &&
       regs->prog_ctr < nacl_syscall_seg_regs_saved) {
     *unwind_case = NACL_UNWIND_in_syscallseg;
-    if (NACL_ARCH(NACL_BUILD_ARCH) == NACL_x86) {
-      if (NACL_BUILD_SUBARCH == 32) {
-        /* Pop user + trampoline return addresses */
-        regs->stack_ptr += 4 + 8;
-      } else {
-        /* Pop user return address. */
-        regs->stack_ptr += 8;
-      }
-    }
+#if NACL_ARCH(NACL_BUILD_ARCH) == NACL_x86 && NACL_BUILD_SUBARCH == 32
+    /* Pop user + trampoline return addresses */
+    regs->stack_ptr += 4 + 8;
+#elif NACL_ARCH(NACL_BUILD_ARCH) == NACL_x86 && NACL_BUILD_SUBARCH == 64
+    /* Pop user return address. */
+    regs->stack_ptr += 8;
+#elif NACL_ARCH(NACL_BUILD_ARCH) == NACL_mips
+    /*
+     * On MIPS, $ra is not modified from the start of the trampoline to the
+     * point where registers are saved.
+     */
+    regs->prog_ctr = NaClSandboxCodeAddr(nap, regs->return_addr);
+#endif
     return 1;
   }
 
   *unwind_case = NACL_UNWIND_after_saving_regs;
   return 0;
 }
 
 /*
  * Given that thread |natp| has been suspended during a
  * trusted/untrusted context switch and has trusted register state
  * |regs|, this modifies |regs| to contain untrusted register state
  * (that is, the state the syscall will return with).
  */
 void NaClGetRegistersForContextSwitch(struct NaClAppThread *natp,
                                       struct NaClSignalContext *regs,
                                       enum NaClUnwindCase *unwind_case) {
   if (Unwind(natp, regs, unwind_case)) {
     NaClSignalContextUnsetClobberedRegisters(regs);
   } else {
     NaClThreadContextToSignalContext(&natp->user, regs);
   }
 
   if (NACL_ARCH(NACL_BUILD_ARCH) == NACL_x86 ||
       (NACL_ARCH(NACL_BUILD_ARCH) == NACL_arm &&
-       *unwind_case != NACL_UNWIND_in_trampoline)) {
+       *unwind_case != NACL_UNWIND_in_trampoline) ||
+      (NACL_ARCH(NACL_BUILD_ARCH) == NACL_mips &&
+       *unwind_case != NACL_UNWIND_in_trampoline &&
+       *unwind_case != NACL_UNWIND_in_syscallseg)) {
     /*
      * Read the return address from the untrusted stack.
      * NaClCopyInFromUser() can fault or return an error here, but only
      * if the thread was suspended just before it was about to crash.
      * This can happen if untrusted code JMP'd to the trampoline with a
      * bad stack pointer or if the thread was racing with an munmap().
      */
     nacl_reg_t user_ret = 0;
     if (!NaClCopyInFromUser(natp->nap, &user_ret,
                             (uint32_t) (regs->stack_ptr + NACL_USERRET_FIX),
                             sizeof(user_ret))) {
       NaClLog(LOG_WARNING, "NaClGetRegistersForContextSwitch: "
               "Failed to read return address; using dummy value\n");
     }
     regs->prog_ctr = NaClSandboxCodeAddr(natp->nap, user_ret);
   }
 }
-
-#else
-
-/* TODO(mseaborn): Extend this to handle MIPS. */
-void NaClGetRegistersForContextSwitch(struct NaClAppThread *natp,
-                                      struct NaClSignalContext *regs,
-                                      enum NaClUnwindCase *unwind_case) {
-  UNREFERENCED_PARAMETER(natp);
-  UNREFERENCED_PARAMETER(regs);
-  *unwind_case = 0;
-}
-
-#endif