exo2: implement through end of random cache init

exosphere2/program/source/smc/secmon_random_cache.cpp

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2018-2020 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <exosphere.hpp>
+#include "secmon_smc_common.hpp"
+#include "secmon_random_cache.hpp"
+
+namespace ams::secmon::smc {
+
+    namespace {
+
+        constexpr inline size_t MaxRandomBytes  = sizeof(SmcArguments) - sizeof(SmcArguments{}.r[0]);
+
+        constinit int g_random_offset_low  = 0;
+        constinit int g_random_offset_high = 0;
+
+        void FillRandomCache(int offset, int size) {
+            /* Get the cache. */
+            u8 * const random_cache_loc = GetRandomBytesCache() + offset;
+
+            /* Flush the region we're about to fill to ensure consistency with the SE. */
+            hw::FlushDataCache(random_cache_loc, size);
+            hw::DataSynchronizationBarrierInnerShareable();
+
+            /* Generate random bytes. */
+            se::GenerateRandomBytes(random_cache_loc, size);
+            hw::DataSynchronizationBarrierInnerShareable();
+
+            /* Flush to ensure the CPU sees consistent data for the region. */
+            hw::FlushDataCache(random_cache_loc, size);
+            hw::DataSynchronizationBarrierInnerShareable();
+        }
+
+    }
+
+    void FillRandomCache() {
+        /* Fill the cache. */
+        FillRandomCache(0, GetRandomBytesCacheSize());
+
+        /* Set the extents. */
+        g_random_offset_low  = 0;
+        g_random_offset_high = GetRandomBytesCacheSize() - 1;
+    }
+
+    void RefillRandomCache() {
+        /* Check that we need to do any refilling. */
+        if (const int used_start = (g_random_offset_high + 1) % GetRandomBytesCacheSize(); used_start != g_random_offset_low) {
+            if (used_start < g_random_offset_low) {
+                /* The region we need to fill is after used_start but before g_random_offset_low. */
+                const auto size = g_random_offset_low - used_start;
+                FillRandomCache(used_start, size);
+                g_random_offset_high += size;
+            } else {
+                /* We need to fill the space from high to the end and from low to start. */
+                const int high_size = GetRandomBytesCacheSize() - used_start;
+                if (high_size > 0) {
+                    FillRandomCache(used_start, high_size);
+                    g_random_offset_high += high_size;
+                }
+
+                const int low_size  = g_random_offset_low;
+                if (low_size > 0) {
+                    FillRandomCache(0, low_size);
+                    g_random_offset_high += low_size;
+                }
+
+            }
+
+            g_random_offset_high %= GetRandomBytesCacheSize();
+        }
+    }
+
+    void GetRandomFromCache(void *dst, size_t size) {
+        u8 * const cache = GetRandomBytesCache();
+        u8 * cur_dst     = static_cast<u8 *>(dst);
+
+        /* NOTE: Nintendo does not do bounds checking here, and does not do multiple reads when the get would wrap around. */
+        while (size > 0) {
+            const size_t copy_size = std::min(size, static_cast<size_t>(GetRandomBytesCacheSize() - g_random_offset_low));
+            std::memcpy(cur_dst, cache + g_random_offset_low, copy_size);
+
+            cur_dst += copy_size;
+            size    -= copy_size;
+
+            if (g_random_offset_low + copy_size >= GetRandomBytesCacheSize()) {
+                g_random_offset_low = 0;
+            }
+        }
+    }
+
+}