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Unified Diff: src/v8.cc

Issue 5143004: Split out the random number state between JavaScript and private API... (Closed) Base URL: http://v8.googlecode.com/svn/branches/bleeding_edge/
Patch Set: Created 10 years, 1 month ago
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Index: src/v8.cc
===================================================================
--- src/v8.cc (revision 5844)
+++ src/v8.cc (working copy)
@@ -176,26 +176,40 @@
return FLAG_random_seed;
}
+typedef struct {
+ uint32_t hi;
+ uint32_t lo;
+} random_state;
-uint32_t V8::Random() {
- // Random number generator using George Marsaglia's MWC algorithm.
- static uint32_t hi = 0;
- static uint32_t lo = 0;
-
+// Random number generator using George Marsaglia's MWC algorithm.
+static uint32_t random_base(random_state *state) {
// Initialize seed using the system random(). If one of the seeds
// should ever become zero again, or if random() returns zero, we
// avoid getting stuck with zero bits in hi or lo by re-initializing
// them on demand.
- if (hi == 0) hi = random_seed();
- if (lo == 0) lo = random_seed();
+ if (state->hi == 0) state->hi = random_seed();
+ if (state->lo == 0) state->lo = random_seed();
// Mix the bits.
- hi = 36969 * (hi & 0xFFFF) + (hi >> 16);
- lo = 18273 * (lo & 0xFFFF) + (lo >> 16);
- return (hi << 16) + (lo & 0xFFFF);
+ state->hi = 36969 * (state->hi & 0xFFFF) + (state->hi >> 16);
+ state->lo = 18273 * (state->lo & 0xFFFF) + (state->lo >> 16);
+ return (state->hi << 16) + (state->lo & 0xFFFF);
}
+// Used by JavaScript APIs
+uint32_t V8::Random() {
+ static random_state state = {0, 0};
+ return random_base(&state);
+}
+// Used internally by the JIT for security purposes. So, we keep a different
+// state to prevent informations leaks that could be used in an exploit.
+uint32_t V8::RandomPrivate() {
+ static random_state state = {0, 0};
+ return random_base(&state);
+}
+
+
bool V8::IdleNotification() {
// Returning true tells the caller that there is no need to call
// IdleNotification again.
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