# HG changeset patch

# User Lars T Hansen <lhansen@mozilla.com>

# Date 1521449886 -3600

# Node ID 903a79a1efff18fc7cc50db09a3fe5d768adc9a8

# Parent  4d2955a9ca7e30ca4c3af9c214ccc77fb2fe7fb8

Bug 1445907 - Save x28 before clobbering it in the regex compiler. r=sstangl

Origin: upstream

Applied-upstream: 61, commit: https://hg.mozilla.org/mozilla-central/rev/903a79a1efff

---

diff --git a/js/src/irregexp/NativeRegExpMacroAssembler.cpp b/js/src/irregexp/NativeRegExpMacroAssembler.cpp

--- a/js/src/irregexp/NativeRegExpMacroAssembler.cpp

+++ b/js/src/irregexp/NativeRegExpMacroAssembler.cpp

@@ -118,17 +118,25 @@ NativeRegExpMacroAssembler::GenerateCode

     Label return_temp0;

     // Finalize code - write the entry point code now we know how many

     // registers we need.

     masm.bind(&entry_label_);

 #ifdef JS_CODEGEN_ARM64

-    // ARM64 communicates stack address via sp, but uses a pseudo-sp for addressing.

+    // ARM64 communicates stack address via SP, but uses a pseudo-sp (PSP) for

+    // addressing.  The register we use for PSP may however also be used by

+    // calling code, and it is nonvolatile, so save it.  Do this as a special

+    // case first because the generic save/restore code needs the PSP to be

+    // initialized already.

+    MOZ_ASSERT(PseudoStackPointer64.Is(masm.GetStackPointer64()));

+    masm.Str(PseudoStackPointer64, vixl::MemOperand(sp, -16, vixl::PreIndex));

+

+    // Initialize the PSP from the SP.

     masm.initStackPtr();

 #endif

     // Push non-volatile registers which might be modified by jitcode.

     size_t pushedNonVolatileRegisters = 0;

     for (GeneralRegisterForwardIterator iter(savedNonVolatileRegisters); iter.more(); ++iter) {

         masm.Push(*iter);

         pushedNonVolatileRegisters++;

@@ -416,17 +424,32 @@ NativeRegExpMacroAssembler::GenerateCode

     masm.pop(temp0);

     masm.movePtr(temp0, StackPointer);

 #endif

     // Restore non-volatile registers which were saved on entry.

     for (GeneralRegisterBackwardIterator iter(savedNonVolatileRegisters); iter.more(); ++iter)

         masm.Pop(*iter);

+#ifdef JS_CODEGEN_ARM64

+    // Now restore the value that was in the PSP register on entry, and return.

+

+    // Obtain the correct SP from the PSP.

+    masm.Mov(sp, PseudoStackPointer64);

+

+    // Restore the saved value of the PSP register, this value is whatever the

+    // caller had saved in it, not any actual SP value, and it must not be

+    // overwritten subsequently.

+    masm.Ldr(PseudoStackPointer64, vixl::MemOperand(sp, 16, vixl::PostIndex));

+

+    // Perform a plain Ret(), as abiret() will move SP <- PSP and that is wrong.

+    masm.Ret(vixl::lr);

+#else

     masm.abiret();

+#endif

     // Backtrack code (branch target for conditional backtracks).

     if (backtrack_label_.used()) {

         masm.bind(&backtrack_label_);

         Backtrack();

     }

     // Backtrack stack overflow code.

diff --git a/js/src/jit-test/tests/regexp/bug1445907.js b/js/src/jit-test/tests/regexp/bug1445907.js

new file mode 100644

--- /dev/null

+++ b/js/src/jit-test/tests/regexp/bug1445907.js

@@ -0,0 +1,15 @@

+// On ARM64, we failed to save x28 properly when generating code for the regexp

+// matcher.

+//

+// There's wasm and Debugger code here because the combination forces the use of

+// x28 and exposes the bug when running on the simulator.

+

+if (!wasmIsSupported())

+    quit();

+

+var g = newGlobal('');

+var dbg = new Debugger(g);

+g.eval(`var m = new WebAssembly.Instance(new WebAssembly.Module(wasmTextToBinary('(module (func (export "test")))')))`);

+var re = /./;

+dbg.onEnterFrame = function(frame) { re.exec("x") };

+result = g.eval("m.exports.test()");

--

2.21.0