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[Memory] Use randomized values for scribble_heap instead of hardcoded one

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This fixes Watchman - The End is Nigh which relay on UB on boot (OOR)

They're checking in hardcoded "game:" for '/' character.
If it doesn't exist then adds 0x7FFFFFFE to start address and start searching from that location downward
This commit is contained in:
Gliniak
2026-01-03 23:53:45 +01:00
committed by Radosław Gliński
parent 2e61df76f0
commit beb52110e3
1 changed files with 27 additions and 3 deletions
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30
src/xenia/memory.cc
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@@ -10,6 +10,7 @@
#include "xenia/memory.h"
#include <cstring>
#include <random>
#include "third_party/fmt/include/fmt/format.h"
#include "xenia/base/assert.h"
@@ -30,7 +31,12 @@ DEFINE_bool(protect_zero, true, "Protect the zero page from reads and writes.",
DEFINE_bool(protect_on_release, false,
"Protect released memory to prevent accesses.", "Memory");
DEFINE_bool(scribble_heap, false,
"Scribble 0xCD into all allocated heap memory.", "Memory");
"Scribble specific or random value into all allocated heap memory.",
"Memory");
DEFINE_int32(scribble_heap_value, 0,
"Value used to fill all allocated heap memory. 0 - Random value. "
"Valid range: [1-255]",
"Memory");
namespace xe {
uint32_t get_page_count(uint32_t value, uint32_t page_size) {
@@ -96,6 +102,24 @@ xe::memory::PageAccess ToPageAccess(uint32_t protect) {
}
}
void RandomizeMemory(void* range_start, uint32_t size) {
if (!cvars::scribble_heap) {
return;
}
if (!cvars::scribble_heap_value) {
std::random_device rd;
std::mt19937 gen(rd());
std::uniform_int_distribution<> dis(0, std::numeric_limits<uint8_t>::max());
std::generate(static_cast<char*>(range_start),
static_cast<char*>(range_start) + size,
[&]() { return dis(gen); });
} else {
std::memset(range_start, cvars::scribble_heap_value, size);
}
}
Memory::Memory() {
system_page_size_ = uint32_t(xe::memory::page_size());
system_allocation_granularity_ =
@@ -975,7 +999,7 @@ bool BaseHeap::AllocFixed(uint32_t base_address, uint32_t size,
}
if (cvars::scribble_heap && protect & kMemoryProtectWrite) {
std::memset(result, 0xCD, page_count * page_size_);
RandomizeMemory(result, page_count * page_size_);
}
}
@@ -1137,7 +1161,7 @@ bool BaseHeap::AllocRange(uint32_t low_address, uint32_t high_address,
}
if (cvars::scribble_heap && (protect & kMemoryProtectWrite)) {
std::memset(result, 0xCD, page_count << page_size_shift_);
RandomizeMemory(result, page_count << page_size_shift_);
}
}