Bug 1407986 - [MIPS] Fix unwinding during the interrupt in wasm prologue/epilogue. r=bbouvier

--HG--
extra : rebase_source : 3b48f1e2efc23109e8c3c705a2ff912035c9bab7

js/src/wasm/WasmFrameIter.cpp

@@ -246,6 +246,7 @@ static const unsigned PushedFP = 5;
 static const unsigned SetFP = 8;
 static const unsigned PoppedFP = 4;
 static const unsigned PoppedExitReason = 2;
+static const unsigned PoppedTLSReg = 0;
 #elif defined(JS_CODEGEN_X86)
 static const unsigned PushedRetAddr = 0;
 static const unsigned PushedTLS = 1;
@@ -254,6 +255,7 @@ static const unsigned PushedFP = 4;
 static const unsigned SetFP = 6;
 static const unsigned PoppedFP = 2;
 static const unsigned PoppedExitReason = 1;
+static const unsigned PoppedTLSReg = 0;
 #elif defined(JS_CODEGEN_ARM)
 static const unsigned BeforePushRetAddr = 0;
 static const unsigned PushedRetAddr = 4;
@@ -263,6 +265,7 @@ static const unsigned PushedFP = 20;
 static const unsigned SetFP = 24;
 static const unsigned PoppedFP = 8;
 static const unsigned PoppedExitReason = 4;
+static const unsigned PoppedTLSReg = 0;
 #elif defined(JS_CODEGEN_ARM64)
 static const unsigned BeforePushRetAddr = 0;
 static const unsigned PushedRetAddr = 0;
@@ -272,6 +275,7 @@ static const unsigned PushedFP = 0;
 static const unsigned SetFP = 0;
 static const unsigned PoppedFP = 0;
 static const unsigned PoppedExitReason = 0;
+static const unsigned PoppedTLSReg = 0;
 #elif defined(JS_CODEGEN_MIPS32) || defined(JS_CODEGEN_MIPS64)
 static const unsigned BeforePushRetAddr = 0;
 static const unsigned PushedRetAddr = 8;
@@ -279,8 +283,9 @@ static const unsigned PushedTLS = 16;
 static const unsigned PushedExitReason = 28;
 static const unsigned PushedFP = 36;
 static const unsigned SetFP = 40;
-static const unsigned PoppedFP = 16;
-static const unsigned PoppedExitReason = 8;
+static const unsigned PoppedFP = 24;
+static const unsigned PoppedExitReason = 16;
+static const unsigned PoppedTLSReg = 8;
 #elif defined(JS_CODEGEN_NONE)
 static const unsigned PushedRetAddr = 0;
 static const unsigned PushedTLS = 1;
@@ -289,6 +294,7 @@ static const unsigned PushedFP = 0;
 static const unsigned SetFP = 0;
 static const unsigned PoppedFP = 0;
 static const unsigned PoppedExitReason = 0;
+static const unsigned PoppedTLSReg = 0;
 #else
 # error "Unknown architecture!"
 #endif
@@ -448,11 +454,20 @@ GenerateCallableEpilogue(MacroAssembler& masm, unsigned framePushed, ExitReason
     DebugOnly<uint32_t> poppedExitReason = masm.currentOffset();
 
     masm.pop(WasmTlsReg);
+    DebugOnly<uint32_t> poppedTlsReg = masm.currentOffset();
+
+#if defined(JS_CODEGEN_MIPS32) || defined(JS_CODEGEN_MIPS64)
+    masm.pop(ra);
+    *ret = masm.currentOffset();
+    masm.branch(ra);
+#else
     *ret = masm.currentOffset();
     masm.ret();
+#endif
 
     MOZ_ASSERT_IF(!masm.oom(), PoppedFP == *ret - poppedFP);
     MOZ_ASSERT_IF(!masm.oom(), PoppedExitReason == *ret - poppedExitReason);
+    MOZ_ASSERT_IF(!masm.oom(), PoppedTLSReg == *ret - poppedTlsReg);
 }
 
 void
@@ -734,7 +749,21 @@ js::wasm::StartUnwinding(const JitActivation& activation, const RegisterState& r
       case CodeRange::BuiltinThunk:
       case CodeRange::TrapExit:
       case CodeRange::DebugTrap:
-#if defined(JS_CODEGEN_ARM) || defined(JS_CODEGEN_ARM64) || defined(JS_CODEGEN_MIPS32) || defined(JS_CODEGEN_MIPS64)
+#if defined(JS_CODEGEN_MIPS32) || defined(JS_CODEGEN_MIPS64)
+        if ((offsetFromEntry >= BeforePushRetAddr && offsetFromEntry < PushedFP) || codeRange->isThunk()) {
+            // See BUG 1407986.
+            // On MIPS push is emulated by two instructions: adjusting the sp
+            // and storing the value to sp.
+            // Execution might be interrupted in between the two operation so we
+            // have to relay on register state instead of state saved on stack
+            // until the wasm::Frame is completely built.
+            // On entry the return address is in ra (registers.lr) and
+            // fp holds the caller's fp.
+            fixedPC = (uint8_t*) registers.lr;
+            fixedFP = fp;
+            AssertMatchesCallSite(activation, fixedPC, fixedFP);
+        } else
+#elif defined(JS_CODEGEN_ARM) || defined(JS_CODEGEN_ARM64)
         if (offsetFromEntry == BeforePushRetAddr || codeRange->isThunk()) {
             // The return address is still in lr and fp holds the caller's fp.
             fixedPC = (uint8_t*) registers.lr;
@@ -766,24 +795,45 @@ js::wasm::StartUnwinding(const JitActivation& activation, const RegisterState& r
             fixedPC = reinterpret_cast<Frame*>(sp)->returnAddress;
             fixedFP = fp;
             AssertMatchesCallSite(activation, fixedPC, fixedFP);
-        } else if (offsetInCode == codeRange->ret() - PoppedFP) {
+        } else if (offsetInCode >= codeRange->ret() - PoppedFP &&
+                   offsetInCode < codeRange->ret() - PoppedExitReason)
+        {
             // The fixedFP field of the Frame has been popped into fp, but the
             // exit reason hasn't been popped yet.
             fixedPC = sp[2];
             fixedFP = fp;
             AssertMatchesCallSite(activation, fixedPC, fixedFP);
-        } else if (offsetInCode == codeRange->ret() - PoppedExitReason) {
+        } else if (offsetInCode >= codeRange->ret() - PoppedExitReason &&
+                   offsetInCode < codeRange->ret() - PoppedTLSReg)
+        {
             // The fixedFP field of the Frame has been popped into fp, and the
             // exit reason has been popped.
             fixedPC = sp[1];
             fixedFP = fp;
             AssertMatchesCallSite(activation, fixedPC, fixedFP);
+#if defined(JS_CODEGEN_MIPS32) || defined(JS_CODEGEN_MIPS64)
+        } else if (offsetInCode >= codeRange->ret() - PoppedTLSReg &&
+                   offsetInCode < codeRange->ret())
+        {
+            // The fixedFP field of the Frame has been popped into fp, but the
+            // exit reason hasn't been popped yet.
+            fixedPC = sp[0];
+            fixedFP = fp;
+            AssertMatchesCallSite(activation, fixedPC, fixedFP);
+        } else if (offsetInCode == codeRange->ret()) {
+            // Both the TLS, fixedFP and ra have been popped and fp now
+            // points to the caller's frame.
+            fixedPC = (uint8_t*) registers.lr;;
+            fixedFP = fp;
+            AssertMatchesCallSite(activation, fixedPC, fixedFP);
+#else
         } else if (offsetInCode == codeRange->ret()) {
             // Both the TLS and fixedFP fields have been popped and fp now
             // points to the caller's frame.
             fixedPC = sp[0];
             fixedFP = fp;
             AssertMatchesCallSite(activation, fixedPC, fixedFP);
+#endif
         } else {
             if (codeRange->kind() == CodeRange::ImportJitExit) {
                 // The jit exit contains a range where the value of FP can't be

js/src/wasm/WasmSignalHandlers.cpp

@@ -173,6 +173,7 @@ class AutoSetHandlingSegFault
 #  define EPC_sig(p) ((p)->uc_mcontext.pc)
 #  define RFP_sig(p) ((p)->uc_mcontext.gregs[30])
 #  define RSP_sig(p) ((p)->uc_mcontext.gregs[29])
+#  define R31_sig(p) ((p)->uc_mcontext.gregs[31])
 # endif
 #elif defined(__NetBSD__)
 # define XMM_sig(p,i) (((struct fxsave64*)(p)->uc_mcontext.__fpregs)->fx_xmm[i])
@@ -418,6 +419,7 @@ struct macos_arm_context {
 # define PC_sig(p) EPC_sig(p)
 # define FP_sig(p) RFP_sig(p)
 # define SP_sig(p) RSP_sig(p)
+# define LR_sig(p) R31_sig(p)
 #endif
 
 static uint8_t**
@@ -447,7 +449,7 @@ ContextToSP(CONTEXT* context)
     return reinterpret_cast<uint8_t*>(SP_sig(context));
 }
 
-# if defined(__arm__) || defined(__aarch64__)
+# if defined(__arm__) || defined(__aarch64__) || defined(__mips__)
 static uint8_t*
 ContextToLR(CONTEXT* context)
 {
@@ -538,7 +540,7 @@ ToRegisterState(CONTEXT* context)
     state.fp = ContextToFP(context);
     state.pc = *ContextToPC(context);
     state.sp = ContextToSP(context);
-# if defined(__arm__) || defined(__aarch64__)
+# if defined(__arm__) || defined(__aarch64__) || defined(__mips__)
     state.lr = ContextToLR(context);
 # endif
     return state;