From 93787182312884cedf0d59b4c7a2bd7639581b17 Mon Sep 17 00:00:00 2001
From: Joshua Kriegshauser <joshuakr@nvidia.com>
Date: Mon, 23 Sep 2024 12:00:39 -0700
Subject: [PATCH] Safe copy

---
 public/client/TracyProfiler.cpp | 37 +++++++++++++---
 public/client/TracyProfiler.hpp | 77 +++++++++++++++++++++++++++++++++
 2 files changed, 107 insertions(+), 7 deletions(-)

diff --git a/public/client/TracyProfiler.cpp b/public/client/TracyProfiler.cpp
index bb0ca7c8..f7ad5c6b 100644
--- a/public/client/TracyProfiler.cpp
+++ b/public/client/TracyProfiler.cpp
@@ -111,6 +111,7 @@ extern "C" typedef char* (WINAPI *t_WineGetBuildId)();
 #else
 #  include <unistd.h>
 #  include <limits.h>
+#  include <fcntl.h>
 #endif
 #if defined __linux__
 #  include <sys/sysinfo.h>
@@ -1462,6 +1463,22 @@ Profiler::Profiler()
         m_userPort = atoi( userPort );
     }
 
+    m_safeSendBufferSize = 65536;
+    m_safeSendBuffer = (char*)tracy_malloc( m_safeSendBufferSize );
+
+#ifndef _WIN32
+    pipe(m_pipe);
+#  if defined __APPLE__ || defined BSD
+    // FreeBSD/XNU don't have F_SETPIPE_SZ, so use the default 
+    m_pipeBufSize = 16384;
+#  else
+    m_pipeBufSize = (int)(ptrdiff_t)m_safeSendBufferSize;
+    while( fcntl( m_pipe[0], F_SETPIPE_SZ, m_pipeBufSize ) == -1 && errno == EPERM )
+        m_pipeBufSize /= 2; // too big; reduce
+    m_pipeBufSize = fcntl( m_pipe[0], F_GETPIPE_SZ );
+#  endif
+#endif
+
 #if !defined(TRACY_DELAYED_INIT) || !defined(TRACY_MANUAL_LIFETIME)
     SpawnWorkerThreads();
 #endif
@@ -1487,7 +1504,7 @@ void Profiler::InstallCrashHandler()
 #endif
 
 #if defined _WIN32 && !defined TRACY_UWP && !defined TRACY_NO_CRASH_HANDLER
-    m_exceptionHandler = AddVectoredExceptionHandler( 1, CrashFilter );
+    m_exceptionHandler = AddVectoredExceptionHandler( 0, CrashFilter );
 #endif
 
 #ifndef TRACY_NO_CRASH_HANDLER
@@ -1600,6 +1617,12 @@ Profiler::~Profiler()
     tracy_free( m_kcore );
 #endif
 
+#ifndef _WIN32
+    close( m_pipe[0] );
+    close( m_pipe[1] );
+#endif
+    tracy_free( m_safeSendBuffer );
+
     tracy_free( m_lz4Buf );
     tracy_free( m_buffer );
     LZ4_freeStream( (LZ4_stream_t*)m_stream );
@@ -4017,13 +4040,13 @@ void Profiler::HandleSymbolCodeQuery( uint64_t symbol, uint32_t size )
     }
     else
     {
-        if( !EnsureReadable( symbol ) )
-        {
-            AckSymbolCodeNotAvailable();
+        // 'symbol' may have come from a module that has since unloaded, perform a safe copy before sending
+        if( withSafeCopy( (const char*)symbol, size, [this, symbol]( const char* buf, size_t size ) {
+            SendLongString( symbol, buf, size, QueueType::SymbolCode );
+        }))
             return;
-        }
-
-        SendLongString( symbol, (const char*)symbol, size, QueueType::SymbolCode );
+        
+        AckSymbolCodeNotAvailable();
     }
 }
 
diff --git a/public/client/TracyProfiler.hpp b/public/client/TracyProfiler.hpp
index 46f11f3d..b8b132ea 100644
--- a/public/client/TracyProfiler.hpp
+++ b/public/client/TracyProfiler.hpp
@@ -833,6 +833,72 @@ private:
         m_bufferOffset += int( len );
     }
 
+    template<class Callable> // must be void(const char* buf, size_t size)
+    bool withSafeCopy(const char* p, size_t size, Callable&& callable)
+    {
+        bool success = true, heap = false;
+        char* buf = m_safeSendBuffer;
+
+#ifndef NDEBUG
+        assert( !m_inUse.exchange(true) );
+#endif
+
+        if( size > m_safeSendBufferSize )
+        {
+            heap = true;
+            buf = (char*)tracy_malloc( size );
+        }
+
+#ifdef _WIN32
+        __try
+        {
+            memcpy( buf, p, size );
+        }
+        __except( 1 /*EXCEPTION_EXECUTE_HANDLER*/ )
+        {
+            success = false;
+        }
+#else
+        // Send through the pipe to ensure safe reads
+        for( size_t offset = 0; offset != size; /*in loop*/ )
+        {
+            size_t sendsize = std::min( size - offset, (size_t)(ptrdiff_t)m_pipeBufSize );
+            ssize_t result1, result2;
+            while( ( result1 = write( m_pipe[1], p + offset, sendsize ) ) < 0 && errno == EINTR )
+                /* retry */;
+            if( result1 < 0 )
+            {
+                success = false;
+                break;
+            }
+            while( ( result2 = read( m_pipe[0], buf + offset, result1 ) ) < 0 && errno == EINTR )
+                /* retry */;
+            if( result2 != result1 )
+            {
+                success = false;
+                break;
+            }
+            offset += result1;
+        }
+#endif
+
+        if( success )
+        {
+            callable( buf, size );
+        }
+
+        if( heap )
+        {
+            tracy_free( buf );
+        }
+
+#ifndef NDEBUG
+        m_inUse.store( false );
+#endif
+
+        return success;
+    }
+
     bool SendData( const char* data, size_t len );
     void SendLongString( uint64_t ptr, const char* str, size_t len, QueueType type );
     void SendSourceLocation( uint64_t ptr );
@@ -990,9 +1056,20 @@ private:
     char* m_queryData;
     char* m_queryDataPtr;
 
+#ifndef NDEBUG
+    // m_safeSendBuffer and m_pipe should only be used by the Tracy Profiler thread; this ensures that in debug builds.
+    std::atomic_bool m_inUse{ false };
+#endif
+    char* m_safeSendBuffer;
+    size_t m_safeSendBufferSize;
+
 #if defined _WIN32
     void* m_exceptionHandler;
+#else
+    int m_pipe[2];
+    int m_pipeBufSize;
 #endif
+
 #ifdef __linux__
     struct {
         struct sigaction pwr, ill, fpe, segv, pipe, bus, abrt;