[wasm] Add guard regions to end of WebAssembly.Memory buffers

src/flag-definitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines all of the flags.  It is separated into different section,
 // for Debug, Release, Logging and Profiling, etc.  To add a new flag, find the
 // correct section, and use one of the DEFINE_ macros, without a trailing ';'.
 //
 // This include does not have a guard, because it is a template-style include,
 // which can be included multiple times in different modes.  It expects to have
@@ skipping 507 matching lines @@
             "enable prototype simd opcodes for wasm")
 DEFINE_BOOL(wasm_eh_prototype, false,
             "enable prototype exception handling opcodes for wasm")
 DEFINE_BOOL(wasm_mv_prototype, false,
             "enable prototype multi-value support for wasm")
 DEFINE_BOOL(wasm_atomics_prototype, false,
             "enable prototype atomic opcodes for wasm")
 
 DEFINE_BOOL(wasm_trap_handler, false,
             "use signal handlers to catch out of bounds memory access in wasm"
-            " (currently Linux x86_64 only)")
+            " (experimental, currently Linux x86_64 only)")
+DEFINE_BOOL(wasm_guard_pages, false,
+            "add guard pages to the end of WebWassembly memory (experimental)")
 

[titzer, 2016/11/07 19:54:52]

I think you should just be able to do a DEFINE_IMPLICATION(wasm_trap_handler,
wasm_guard_pages) here.

[Eric Holk, 2016/11/08 23:58:15]

Oh awesome, this is exactly what I wanted.

done.

 // Profiler flags.
 DEFINE_INT(frame_count, 1, "number of stack frames inspected by the profiler")
 // 0x1800 fits in the immediate field of an ARM instruction.
 DEFINE_INT(interrupt_budget, 0x1800,
            "execution budget before interrupt is triggered")
 DEFINE_INT(type_info_threshold, 25,
            "percentage of ICs that must have type info to allow optimization")
 DEFINE_INT(generic_ic_threshold, 30,
            "max percentage of megamorphic/generic ICs to allow optimization")
 DEFINE_INT(self_opt_count, 130, "call count before self-optimization")
@@ skipping 683 matching lines @@
 #undef DEFINE_ALIAS_FLOAT
 #undef DEFINE_ALIAS_ARGS
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS
 
 #undef COMMA