From 6eeaa343f81f950f59a5310b0853e2da956237e0 Mon Sep 17 00:00:00 2001
From: Billy Laws <blaws05@gmail.com>
Date: Fri, 22 Oct 2021 19:00:05 +0100
Subject: [PATCH] Avoid crash when passing unallocated syncpoint IDs to
 EventWait

---
 .../skyline/services/nvdrv/core/syncpoint_manager.cpp    | 4 ++++
 .../cpp/skyline/services/nvdrv/core/syncpoint_manager.h  | 6 ++++++
 .../cpp/skyline/services/nvdrv/devices/nvhost/ctrl.cpp   | 9 +++++++++
 3 files changed, 19 insertions(+)

diff --git a/app/src/main/cpp/skyline/services/nvdrv/core/syncpoint_manager.cpp b/app/src/main/cpp/skyline/services/nvdrv/core/syncpoint_manager.cpp
index 00582dd4..7e3727fe 100644
--- a/app/src/main/cpp/skyline/services/nvdrv/core/syncpoint_manager.cpp
+++ b/app/src/main/cpp/skyline/services/nvdrv/core/syncpoint_manager.cpp
@@ -40,6 +40,10 @@ namespace skyline::service::nvdrv::core {
         return ReserveSyncpoint(FindFreeSyncpoint(), clientManaged);
     }
 
+    bool SyncpointManager::IsSyncpointAllocated(u32 id) {
+        return (id <= soc::host1x::SyncpointCount) && syncpoints[id].reserved;
+    }
+
     bool SyncpointManager::HasSyncpointExpired(u32 id, u32 threshold) {
         const SyncpointInfo &syncpoint{syncpoints.at(id)};
 
diff --git a/app/src/main/cpp/skyline/services/nvdrv/core/syncpoint_manager.h b/app/src/main/cpp/skyline/services/nvdrv/core/syncpoint_manager.h
index f40f8636..7cb8c1a1 100644
--- a/app/src/main/cpp/skyline/services/nvdrv/core/syncpoint_manager.h
+++ b/app/src/main/cpp/skyline/services/nvdrv/core/syncpoint_manager.h
@@ -23,6 +23,7 @@ namespace skyline::service::nvdrv::core {
             bool reserved;               //!< If the syncpoint is reserved or not, not to be confused with a reserved value
         };
 
+
         const DeviceState &state;
         std::array<SyncpointInfo, soc::host1x::SyncpointCount> syncpoints{};
         std::mutex reservationLock;
@@ -40,6 +41,11 @@ namespace skyline::service::nvdrv::core {
       public:
         SyncpointManager(const DeviceState &state);
 
+        /**
+         * @brief Checks if the given syncpoint is both allocated and below the number of HW syncpoints
+         */
+        bool IsSyncpointAllocated(u32 id);
+
         /**
          * @brief Finds a free syncpoint and reserves it
          * @return The ID of the reserved syncpoint
diff --git a/app/src/main/cpp/skyline/services/nvdrv/devices/nvhost/ctrl.cpp b/app/src/main/cpp/skyline/services/nvdrv/devices/nvhost/ctrl.cpp
index d672c786..25ad1076 100644
--- a/app/src/main/cpp/skyline/services/nvdrv/devices/nvhost/ctrl.cpp
+++ b/app/src/main/cpp/skyline/services/nvdrv/devices/nvhost/ctrl.cpp
@@ -76,6 +76,15 @@ namespace skyline::service::nvdrv::device::nvhost {
         if (fence.id >= soc::host1x::SyncpointCount)
             return PosixResult::InvalidArgument;
 
+        // No need to wait since syncpoints start at 0
+        if (fence.threshold == 0) {
+            // oss-nvjpg waits on syncpoint 0 during initialisation without reserving it, this is technically valid with a zero threshold but could also be a sign of a bug on our side in other cases, hence the warn
+            if (!core.syncpointManager.IsSyncpointAllocated(fence.id))
+                state.logger->Warn("Tried to wait on an unreserved syncpoint with no threshold");
+
+            return PosixResult::Success;
+        }
+
         // Check if the syncpoint has already expired using the last known values
         if (core.syncpointManager.IsFenceSignalled(fence)) {
             value.val = core.syncpointManager.ReadSyncpointMinValue(fence.id);